Room: 315B
Session Chairperson: J.K. Hirvonen, Metals Research Branch, U.S. Army Research Laboratory, AMSRL-WM-ME, APG, MD 21005-5069
THE DARPA PROGRAM IN ADVANCED THIN FILM COATING TECHNOLOGY: Lawrence H. Dubois, Thomas J. Moran, Defense Sciences Office, Defense Advanced Research Projects Agency, Arlington, VA
Corrosion and wear of mechanical and structural components and systems cost U.S. Industry and the military millions of dollars every year and leads to excess waste, decreased product reliability, and poor worker safety. Unfortunately, the surface preparation, application and use of most coatings to protect to protect these components leads to the generation of significant quantities of hazardous wastes which are subsequently released to the air, water and land. Through the development of new, more advanced corrosion and wear resistant coating systems and/or surface preparation techniques, the DoD and its suppliers can not only minimize the environmental impact of these materials, but improve performance and decrease costs. The DARPA program in advanced thin film coatings is developing innovative technologies to eliminate volatile organic compounds, heavy metals and other hazardous waste materials in the manufacture, application and maintenance of high performance wear, fatigue and corrosion resistant coatings of utility to the DoD.
9:10 am
ADVANCES IN SURFACE TECHNOLOGY IN RUSSIA: Anthony J. Perry, ISM Technologies, San Diego, CA; Jesse N. Matossian, Hughes Research Labs, Malibu, CA; Michael O. Thompson, Cornell University, Ithaca, NY
Since the removal of the Berlin Wall and the changes in the relationships between the former Soviet Union with the rest of the world, a great deal of information has become available on their technology. Developments in some areas appear to have outpaced those in the West, specifically in the application of ion beams to surface modification. The present authors have had the opportunity to attend workshops in Russia and to visit laboratories. In the present work, a report is given on some of the technologies reviewed there and which are now becoming available to the West. These include novel designs in the fields of cathodic arc sources and gas ion sources, and intense ion and electron beams. These technologies will be presented.
9:45 am
THE JET DEPOSITION PROCESS: NEW TECHNIQUES AND APPLICATIONS: Brett Halpern, Jet Process Corporation, 24 Science Park, New Haven, CT 06511
Development of the "sonic jet sources in low vacuum" theme enables the Jet Vapor DepositionTM process (JVDTM) to make a wide range of thin film materials. Thus, we have developed jet sources, driven in the 0.1-10 torr range by mechanical pumps, for deposition of metals, semiconductors, oxides, nitrides, alloys and guest-host materials in multicomponent and multilayer form. These sources combine high rate, high efficiency, and low temperature operation with excellent control of microstructure. For example, we recently described and patented an "electron-jet, or e-jetTM "source, which combines metal thermal vaporization with an intense thermionic plasma and allows high rate deposition of metals, oxides and nitrides coupled with simultaneous ion bombardment at high flux and low energy. JVD's versatility opens new approaches to problems in electronic, automotive, aerospace, corrosion resistance and optical applications. In this talk we review the principles of JVD, new jet source developments, JVD's advantages over conventional CVD and PVD and recent commercial applications.
10:20 am BREAK
10:30 am
DoD ACTIVITIES IN ION BEAM PROCESSING: James K. Hirvonen, Metals Research Branch, U.S. Army Research Laboratory, AMSRL-WM-ME, APG, MD 21005-5069
The use of energetic ion beams for beneficially modifying the surface sensitive properties of critical military material has been pursued within DoD now for almost two decades demonstrating improved material properties including increased wear-, fatigue-, corrosion-, and oxidation-resistance. High dose ion implantation has been demonstrated to be technically suitable for extending the lifetime of precision aerospace bearings (U.S. Navy) and specific cutting tools (U.S. Army). Ion beam assisted deposition (IBAD) processing has increased both the number and the variety of DoD applications, including robust optical coatings and coatings for wear, corrosion and fatigue improvements. A DoD program exploring these benign, dry, ion beam techniques for supplanting the wet Cr/Cd electroplating processing is currently underway at the National Defense Center for Environmental Excellence in Johnstown, PA. This program includes the scheduled installation, (Fall 96) of a large ion beam system for the processing of selected DoD components. The status of this program and other recent DoD ion beam efforts will be discussed.
11:05 am
SURFACE PROCESSING BY GAS CLUSTER ION BEAMS: Allen Kirkpatrick, Epion Corporation, Bedford, MA 01730
Clusters consisting of hundreds or thousands of weakly bound atoms can be formed from various gases by expanding the gas through a small nozzle into high vacuum. The clusters can be ionized and subjected to acceleration potentials so as to produce beams of cluster ions which possess high total energy, mass and momentum in combination with low energy per constituent atom. Cluster ion beams have been shown to be capable of producing processing effects which have not been available with monomer ions. A number of prospective applications for gas cluster ions have been identified and commercial gas cluster ion beam equipment is now being developed. This paper will review the current status of gas cluster ion technology and will include discussion of methods for generation of the gas cluster beams, kinetics of the interactions of cluster ions with solid materials, anticipated applications and available equipment.
11:40 am
COMPARISON OF DEPOSITION TECHNOLOGIES FOR ION ASSISTED COATINGS A.J. Armini, S.N. Bunker, L.A. Stelmack, Implant Sciences Corporation
The current ion assisted coating methods and the corresponding equipment are compared, for depositing a variety of wear and/or corrosion resistant coatings. Ion beam assisted deposition (IBAD), unbalanced magnetron sputtering, and cathodic arc processes were used to deposit coatings of amorphous diamond, chromium, and noble metals for various applications in the aerospace, biomedical, and industrial markets. The three techniques were compared with respect to coating uniformity, deposition rate, adhesion, and microstructure. Coatings were evaluated for hardness, adhesion, smoothness, sliding wear, and friction coefficient. Coating-substrate adhesion was measured using the diamond scratch test. Wear and friction were measured against several opposing materials, using a high speed, high temperature pin-on-disk instrument. Scale-up issues and the suitability of each technology for various production applications will be discussed.
Room: 340B
Session Chairperson: S. Jin, Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974
8:30 am INVITED
ELECTRODE MATERIALS FOR LITHIUM BATTERIES AND FUEL CELLS: A. Manthiram, Center for Materials Science and Engineering, ETC 9.104, The University of Texas at Austin, Austin, TX 78712
Electrically conducting metal oxides find potential applications in electrochemical systems such as batteries and fuel cells. For example, several lithium insertion compounds are used as cathodes in rechargeable lithium batteries. However, the battery performance and cyclability of the cathodes are controlled partly by the microstructure and morphology, which in turn are influenced by the methods of synthesis and processing used. A novel approach involving the reduction of aqueous metallate solutions with aqueous alkali metal borohydrides at ambient temperatures to obtain amorphous or nanocrystalline transition metal oxide electrodes will be presented. The electrode performance of, for example, amorphous or nanocrystalline VO2, CrO2, MoO2, and LiMn2O4 will be discussed. In addition, the design and synthesis of perovskite-based metal oxides that exhibit mixed electronic and ionic conductivity will be presented. These mixed conductors are attractive not only as electrode materials for solid oxide fuel cells but also for oxygen separation membranes and catalysts.
9:00 am INVITED
EPITAXIAL THIN FILMS AND HETEROSTRUCTURES OF METALLIC OXIDES FOR DEVICE APPLICATIONS: C.B. Eom, Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708
For many electronic device applications, it is necessary to have epitaxial growth of metallic oxide thin films in a single heterostructure. We have grown epitaxial thin films of Sr1-xCaxRuO3 and La6.4Sr1.6Cu8O20 in-situ by 90 degree off-axis sputtering. These metallic oxides are pseudo-cubic perovskites, which could be ideal electrodes for ferroelectric devices, and normal metal barriers for SNS junctions in integrated superconducting devices. However, the properties of epitaxial thin films of the metallic oxides may be quite different from the corresponding bulk materials because of the existence of strain and cation disorder in the films. We have observed a strain stabilized metal-insulator transition in epitaxial Sr1-xCaxRuO3 thin films deposited on (100) SrTiO3 substrates that differed in crystalline quality. The growth mechanisms of the films and their correlation with the crystalline quality of the substrates is discussed. We have also grown epitaxial planar SNS heterostructures YBCO/La6.4Sr1.6Cu8O20/YBCO. We will discuss the microstructures, junction properties and the origin of the interface resistance between YBCO and La6.4Sr1.6Cu8O20.
9:30 am INVITED
FUNDAMENTAL INVESTIGATIONS OF CADMIUM STANNATE THIN FILMS: T.J. Coutts, W.P. Mulligan, X. Wu, National Renewable Energy Laboratory, Golden, CO 80215
We are investigating a variety of novel transparent conductive oxides, including cadmium stannate (Cd2SnO4), cadmium indate (CdIn2O4), zinc stannate (Zn2SnO4 and ZnSnO3), and zinc indium oxide (Zn2In2O5). To date, the cadmium stannate films have shown the highest conductivity, with resistivities as low as 1.3X10-4 ohm-cm. Films have been fabricated with sheet resistances as low 2 ohm/sq., while maintaining approximately 80% transmittance across the visible and near infrared. The conductivity of the films is high because of both high electron concentration and relatively high electron mobility. One possible explanation for the high mobility is that the electron effective mass is unusually low. Direct measurement of the effective mass by cyclotron resonance is not feasible due to the extremely short electron scattering times characteristic of these highly defective materials. Instead, we have estimated effective mass by Drude modelling of optical reflectance and transmittance data, and by analysis of a combination of electron transport measurements, including resistivity, Hall effect, thermopower, and transverse Nernst-Ettingshausen effect. Cadmium stannate films with a range of carrier concentrations were fabricated, and their optical and transport properties were measured. We will present the results of our comparative analysis of carrier effective mass by these two independent methods. Possible conduction band curvature, and carrier scattering time and mechanisms will also be reported. The implications for design of novel transparent conductive oxides will be discussed.
10:00 am BREAK
10:20 am INVITED
ELECTRICALLY ACTIVE POLYMERS: M. E. Galvin, Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974
It has been known for two decades that polymers with extended conjugation could be rendered highly conductive by doping, that is, by oxidizing or reducing the polymer chain. The commercialization of these polymers has, however, been limited by their poor chemical stability in the doped form. More recently these polymers have shown promise when used in their undoped forms in LEDs, light emitting diodes, or in thin film transistors. This talk will cover the recent developments in these two areas and describe the scientific challenges which still remain.
10:50 am INVITED
NOVEL ANISOTROPIC CONDUCTORS THROUGH THE DESIGN OF COMPOSITE STRUCTURES: S. Jin, Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974
Anisotropic electrical conductivity with many orders of magnitude change along different directions can be obtained by the design of novel, composite structures. Materials with such characteristics are useful for a variety of electronic applications including ultra-high density circuit interconnections, 3-D packaging, and solder-free interconnection. Optically transparent but electrically conductive medium can also be made via composite route. Novel composite structures with vertically aligned metal elements in ceramic or polymer sheets will be described. Materials fabrication process, electrical properties and reliability issues will also be discussed.
11:20 am
OPTICAL STUDIES FOR THE CHARACTERIZATION OF CONDUCTING POLYMERS:L.M. Abrantes, CECUL, Dept. Qumica, FCUL, Bloco C1-5 piso, 1700 Lisboa, Portugal; J.P. Correia, INETI, Dept. de Energias Renovaveis, 1699 Lisboa Codex, Portugal
The properties of conducting polymers have stimulated much interest in many fields of research and considerable effort has been directed towards reliable characterization of the envisaged properties for commercial applications. Apart from polyacetylene (PA) the major existing conducting polymers can be electrochemically synthesized and this encouraged the use of conventional electrochemical methods coupled to other techniques to study the electropolymerization and insulator/conductor conversion of these new materials. The purpose of this paper is to give an overview of the ability of optical methods to provide useful information on the properties of electronically conducting polymers. Three techniques will be focused and their contribution illustrated considering different systems: 1. The principles of the Probe Beam Deflection (also known as Mirage Effect) and respective data for polyaniline (PANI) systems discussed. 2. Recent applications of Photocurrent Spectroscopy are reviewed and photoeffects displayed by poly-3-methylthiophene (P3MeTh) analysed. 3. The information on structural changes during electropolymerization and doping processes, which can be provided by ellipsometry evidenced by the study of PANI, P3MeTh and polypyrrole.
11:40 am
HYDROSTATICALLY EXTRUDED COPPER-NIOBIUM SPARK ERODED POWDER: M.A. Hill, J.F. Bingert, F.E. Spada, A.E. Berkowitz, S.A. Bingert, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, Center for Magnetic Recording Research, University of California at San Diego, La Jolla, CA 92093
High strength, high conductivity copper-niobium wire is a promising conductor wire for use in pulsed high field magnets. Due to the high melting point of niobium, it is difficult to produce an ingot with a fine, homogeneous structure. One possibility for reducing the scale of the cast structure, improving the homogeneity of the ingot, and enhancing the strength at a given level of deformation strain is to use rapid solidification techniques, such as powder processing, to fabricate the Cu-Nb ingot. Both melt spinning and gas atomization of Cu-Nb are difficult due to problems associated with thermal shock of components, such as crucibles and stopper rods. Spark erosion provides a method for powder production without the use of components which may crack under thermal stresses. Furthermore, in the spark erosion process quench rates exceeding 106 K/s from temperatures above 104 K promote formation of fine particles with homogeneous composition. Spark eroded Cu-10 vol % Nb powder has been consolidated by cold pressing and subsequently hydrostatically extruded to form 2.5 cm diameter rod with a yield strength of 500 MPa and a conductivity of 85% IACS at a reduction of 
=2.6.
Room: 230A
Session Chairperson: Michel Reverdy, Aluminium Pechiney, Pechiney-Balzac, France
8:30 am
CELL HOODING EFFICIENCY MEASUREMENTS FOR HS SØDERBERG CELLS: Alton T. Tabereaux, Jim Brown, Ivan Eldridge, Reynolds Metals Company, Manufacturing Technology Laboratory, 3326 East 2nd Street, Muscle Shoals, AL 35661
A method has been developed for measuring the gas capture efficiency of volatile gas emissions for the cell hooding system of HS Søderberg cells. No prior method for measuring the gas capture efficiency for HS Søderberg cells has been reported to date. This paper presents the newly developed procedures, techniques and results measured during plant tests for the gas capture efficiency of 92 kA HS Søderberg cells equipped with an improved cell hooding system to reduce plant emissions. The dependency of the gas capture efficiency upon the duct exhaust velocity was determined for the HS Søderberg cells using this method.
8:55 am
COS, CS2 AND SO2 EMISSIONS FROM PRE-BAKED HALL HEROULT CELLS: Frank M. Kimmerle, Luc Noël, Alcan International Ltd., Arvida Research and Development Centre, P.O. Box 1250, Jonquiere, QC, G7S-4K8, Canada; John T. Pisano, Unisearch Ass. Inc., 222 Snidercroft Rd., Concord, ONT, L4K 1B5, Canada
Measurements of CO2, CO, COS and CS2 emissions in collected gas samples by GC-MS and of SO2 by ion chromatography of scrubber solutions allowed us to complete a carbon and sulphur mass balance for P155 pre-bake electrolysis cells. COS and CS2 emissions were confirmed by continuous analysis using tunable diode laser absorption spectrometry of the flue cases from 64 cells over a two day period. While the volume mixing ratios of COS and CS2 of the flue gases agree with those reported recently for a German prebake smelter, the specific emissions were found to be considerably lower.
9:20 am
PERFLUOROCARBON (PFC) GENERATION IN LABORATORY-SCALE ALUMINUM REDUCTION CELLS: Steen Nissen, Donald R. Sadoway, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307
The generation of CF4 and C2F6 is being studied in a laboratory-scale aluminum reduction cell. During electrolysis in well behaved cells and in cells on anode effect, anode gases have been analyzed by gas chromatography (GC) on-line. Process parameters have been systematically varied to determine how PFC generation depends upon anode material (industrial pre-bake and Søderberg), bath ratio (1.45, 1.15 and 0.56), LiF concentration (0 and 2.7%), current density (0.7 A cm-2 and higher), and temperature (970 and 800°C). Measurements agree with those reported for industrial cells with respect to total PFC level as well as the ratio of CF4 to C2F6. The main factor determining PFC concentration appears to be the anodic overvoltage. The functional relationship between the rate of PFC generation and anodic overvoltage is derived from the current-overpotential equation. Research sponsor: U.S. Environmental Protection Agency, Atmospheric Pollution Prevention Division.
9:45 am
REDUCTION OF THE CF4 EMISSIONS FROM PRE-BAKED HALL HEROULT CELLS: Frank M. Kimmerle, Gilles Potvin, Alcan International Ltd., Arvida Research and Development Centre, P.O. Box 1250, Jonquiere, QC, G7S-4K8, Canada; John T. Pisano, Unisearch Ass. Inc., 222 Snidercroft Rd., Concord, ONT, L4K 1B5, Canada
It has been established that CF4 and C2F6 are given off from the Hall-Heroult electrolysis cells during so-called anode effects. The introduction of a novel alumina feeding and cell operation algorithm in the Grande Baie smelter operating with P155 pre-bake electrolysis cells, has dramatically reduced the anode effect duration and anode effect frequency. The implementation of the new cell control logic constituted a unique opportunity to compare data from some two hundred events before and after commissioning on identical cells. Using tunable diode laser absorption spectrometry we measured PFC emissions from individual anode effects with a temporal resolutions of as little as 8 seconds. This communication will describe the experimental set-up, present the decrease in PFC emissions attained, discuss the CF4/C2F6 ratios observed and compare the data observed with model predictions.
10:10 am BREAK
10:30 am
POTROOM COMPARISON TRIAL OF A LASER HF MEASURING INSTRUMENT AND AN INTENSIVE AIR SAMPLING ARRAY OVER A 400 M PATH: D.L. Death, J.E. Eberhardt, R.P. Read, C.A. Rogers, CSIRO Division of Minerals, Private Mail Bag #5, Menai, NSW, 2234 Australia; M. Atkinson, Comalco Research Center, P.O. Box 316, Thomastown, Vic. 3074, Australia; D. Collins, Alcoa of Australia Ltd., Point Henry Works, P.O. Box 460, Geelong, VIC. 3220, Australia; K. Whiteley, Tomago Aluminium Co. Ltd., P.O. Box 405, Raymond terrace NSW, 2324, Australia
The laser hydrogen fluoride measuring instrument described at TMS '95 was compared with an optimised eighty-fold array of air sampling cassettes over a 400m path in a potroom of the Tomago (NSW) aluminium smelter. Thirteen one-hour comparison trials were performed at average HF concentrations over the range 0.07-3.7 mg/Nm3. For the twelve concentrations up to 2.0 mg/Nm3 the cassette array average and the laser average correlated with a slope of 0.93 and a regression coefficient r2=0.98. For the nine points up to 1.5 mg/Nm3 the slope was 1.02 and the regression coefficient r2=0.99. As configured during the comparison trial the laser instrument did not correctly indicate the 3.7 mg/Nm3 HF concentration due to insufficient signal to noise ratio. The correlation between array and laser was considered very good. The technique is being commercialised. The contributions of Frank Fleer of AirWaterNoise Ltd to this work are gratefully acknowledged. This work was partly supported by the Australian Aluminium Council.
10:55 am
THE MEASUREMENT OF GASEOUS FLUORIDE IN THE ALUMINIUM INDUSTRY: John M. Jones, Anglesey Aluminium Metal Ltd., Penrhos Works, P.O. Box 4, Holyhead, Gwynedd, LL65-2UJ, United Kingdom
The introduction of integrated Pollution Control (IPC) by means of the Environmental Protection Act (EPA 90), has brought with it regulatory requirements for operators of industrial processes in the U.K. to undertake continuous monitoring of gaseous atmospheric releases. In response to these changes Anglesey Aluminium Metal Limited (AAM) has chosen to install Tunable Diode Laser Spectroscopy (TDLAS). This method, operating in the Middle Infra Red region (MIR), is gaining increased acceptance as the choice for trace gas measurement where sensitivity, specificity, and fast response are required. This paper focuses on this change to the gaseous fluoride monitoring activities at AAM with particular attention to stack monitoring.
11:20 am
IMPROVED EFFICIENCIES IN THE DRY SCRUBBING PROCESS: Geir Wedde, ABB Environmental, P.O. Box 6260 Etterstad, 0603 Oslo, Norway
An advanced process for removal and recovery of fluorides and particulates from the aluminium reduction pot gas has been developed and tested in pilot plant prior to full scale installation. The dry scrubbing process is arranged in two stages with a counter-current flow of the alumina allowing for the reactive fresh alumina at the tail end of the process. The benefits and features of this concept include high process flexibility with stable and improved performance on removal of fluorides, reduced pressure drop and low particulate emission by optimized filter design and operating performance, and improved compactness through design and equipment developments.
11:45 am
TGT RI - A NOVEL REACTOR / FILTER CONCEPT FOR DRY SCRUBBING: B. Cloutier, Procedair Industries Inc., 625 President Kennedy, Montreal, Quebec, Canada H3A 1K2; Ph. Dumortier, B. Caratge, Procedair SA, 25-27 Boulevard de la Paix, 78951 St. Germain en Laye Cedex, France
The fluorine emissions from modern PFPB pots have led to a requirement to further improve gas scrubbing efficiency. This improvement has been achieved without any detrimental effect on scaling or attrition of alumina. Economic factors create a further technical challenge of reducing capital cost and lowering energy consumption. A novel process called the TGT-RI which combines an innovative reactor concept integrated in a new generation of fabric filter fully responds to the new requirements of aluminium producers. Several years of exhaustive tests have been conducted on gases emitted by large pots to develop the TGT filter and then the TGT-RI concept of integrating the reactor within the filter unit. The paper will incorporate a comprehensive set of test results. A descriptive of the first industrial applications on pot gases and baking furnaces is presented.
Room: 232A
Session Chairs: R.G. Reddy, Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487; D.J. Fray, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ, United Kingdom
8:30 am
STABILITY ANALYSIS OF MICROSTRUCTURE EVOLUTION PROCESSES: W.M. Mullins, Wright Laboratory, WL/MLIM-TMCI, Bldg. 653, 2977 P St., WPAFB, OH 45433-7746; R.D. Irwin, E.A. Medina, Department of Electrical and Computer Engineering, Stocker Center, Ohio University, Athens, OH 45701
Various stability criteria are introduced and thermo-kinetic models for metallurgical processes are used as concrete examples for evaluation. Kinetic criteria for the process of dynamic recrystallization are proposed. These criteria are compared to the non-equilibrium thermodynamic approaches discussed in the literature. The application of macroscopic stability criteria to materials processing is then discussed.
8:55 am
STATISTICAL ANALYSIS OF INTERFACE DYNAMICS IN NON-SPHERICAL MORPHOLOGIES: S.P. Marsh, Code 6325, Naval Research Laboratory, Washington, D.C. 20375-5000; M.E. Glicksman, Rensselaer Polytechnic Institute, Troy, NY
Complex interfaces can be described as a distribution of interfacial patches, each having a differential area. The patches are fully characterized by a mean curvature, a dimensionless shape factor, and an extensive variable such as solid angle or area. Using this approach, a statistical theory of Ostwald ripening has been extended to describe the diffusion-limited coarsening of non-spherical convex interfaces. Coarsening rate constants are calculated as a function of both the precipitate volume fraction and the geometric shape factor. Application of these results to ripening of ellipsoidal precipitates and other morphologies will be discussed.
9:20 am
ULTRA FINE PRECIPITATES IN REACTOR PRESSURE VESSEL STEELS INVESTIGATED BY MONTE CARLO SIMULATIONS: STRUCTURE, COMPOSITION, AND MORPHOLOGY: C.L. Liu, G.R. Odette, B.D. Wirth, and G.E. Lucas, Dept. of Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106
Ultra fine scale precipitates are the leading cause to the irradiation embrittlement of reactor pressure vessel (RPV) steels and may limit the continued operation or extended life of a number of nuclear power plants around the world. Tremendous effort in studying these precipitates has been made using various experimental techniques such as small angle neutron scattering (SANS) and atom probe field ion microscope (APFIM). However, detailed identity and characteristic of the precipitates o atomic scale are not well known. We propose a self-consistent model, combining advanced thermodynamics, small angle neutron scattering measurements, and Lattice Monte Carlo simulations, to examine detailed identity and characteristic of the ultra fine precipitates on atomic scale in Fe-based multicomponent systems Fe-Cu-Ni-Mn and Fe-Cu-Ni-Mn-Si. A systematic parametric study using both the metallurgical and simulation variables is carried out. Interaction parameters in an extended regular solution treatment, composition, and temperature as the metallurgical variables, and starting configurations, sizes of simulation cells, and simulation duration as the simulation variables, are exercised. The results from the simulations are in good agreement with those from SANS and APFIM.
9:45 am
OBSERVATION AND CALCULATION OF MARANGONI CONVECTION INDUCED THERMALLY IN A MOLTEN SALT: T. Takasu, J.M. Toguri, Dept of Metallurgy and Materials Science, University of Toronto, 184 College Street, Toronto, Ontario, Canada, M5S 1A4; H. Itou, T. Nakamura, Dept of Materials Science & Engineering, Kyushu Institute of Technology, Secsui-cho 1-1, Tobata-ku, Kitakyushu, 804 Japan
Marangoni convection has a large effect on materials processing since it remarkably promotes heat and mass transport near the free interface. In order to clarify the behavior of marangoni convection in a molten salt, observation and calculation of the thermal convection in a column held between a pair of Pt disks (2mm in diameter) which were fixed to hot thermocouples, were carried out. Calculated flow patterns and absolute values of fluid velocity agreed well with the observed results. When the temperatures of both disks were set equal and the height of liquid bridge was 2.4mm, four vortexes were generated on the longitudinal plane and typical velocity was 15mm/s. From the calculated isothermal lines the behavior of promotion of heat transport is obvious; fluid heated at the disks was conveyed to the free surface and fluid cooled at the surface was conveyed to the inner region. Increase in the height of column and/or increase in the absolute value of applied temperature difference lead to increase in fluid velocity lineally in this calculation range.
10:10 am BREAK
10:20 am
MIXING PHENOMENA PERTINENT TO FERROALLOY REFINING USING WATER MODELS: G. Akdogan, R.H. Eric, School of Process and Materials Engineering, University of the Witwatersraind, Johannesburg, Private Bag 3, Wits 2050 South Africa
Mixing phenomena in a bottom blown air-stirred one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor was studied using three different configurations of straight circular nozzles fitted axially at the bottom of the vessel. The mixing time has been experimentally determined utilizing acid injection and pH measurements at various gas flow rates, bath heights and nozzle orientations in the presence and in the absence of a second phase. High air flow rates were utilized usually above the range of ordinary flow meters. During experiments the air flow rates varied from 0.00599m3/sec to 0.01465m3/sec. An integral orifice plate assembly, which is coupled to two pressure transmitters, was constructed to calculate gas flow rates from pressure readings. Experimental results reveal that the mixing time decreases with increasing gas flow rate. A critical gas flow rate exists after which the mixing time tends to increase for all tuyere configurations studied. For a given gas flow rate the mixing time increases non-linearly with increasing bath height. Off-center configuration gives slightly lower mixing times as compared to center configuration. The presence of an upper oil layer increases the mixing time significantly for all configurations showing its resistance to the recirculatory velocity of fluid near the surface of the bath. Under the very high flow rates employed in this investigation, it is found that the contribution of buoyancy to the total stirring energy density is very small, but its contribution increases with increasing bath height.
10:45 am
DIMENSIONAL ANALYSIS FOR PREDICTING THE STRESSES IN FORGING: T. Robert N., Congreso 128-A204, Col. La Joya, Del. Tlalpan, Mexico, D.F., 14090; J. Navarrete M., J. Ramirez V., G. Salas B., M. Noguez A., Departamento de Ing. Metalurgica, Facultad de Quimica, Universidad Nal. Autonoma de Mexico, Cuidad Universitaria, 04510 Mexico, D.F.
The stresses required in an axial closed die forging are determined by the geometry of the blank and that of the die, the yield stress of the working material and the process variables like temperature, strain, strain rate, friction, etc. Five adimensional groups of the mentioned parameters are proposed. Like the Reynolds number, they permit the characterization and evaluation of almost any axial forging process. A wide data base is experimentally obtained, which validates the model. This dimensional analysis is an alternative to the traditional methods for calculating the stresses in metal forming.
11:10 am
MODELING OF LIQUIDUS TEMPERATURE AND ELECTRICAL CONDUCTIVITIES OF MANGANESE SMELTING SLAGS BY THE USE OF NEURAL NETS: M.A. Reuter, Faculty of Mining and Petroleum Engineering, Delft University of Technology, Delft, The Netherlands, R H. Eric, A.A. Hejja, School of Process and Materials Engineering, University of the Witwatersrand, Johannesburg, Private Bag 3, WITS 2050, South Africa
Liquidus temperature and electrical conductivity data measured on synthetic slags were modeled by the use of neural nets(NN). In this work the applied multilayer feedforward NNs were trained by a conjugate-gradient optimization for which a three layer formulation was used. Very good fits were obtained for both the liquidus temperature and the conductivity data. The synthetic slags were prepared from pure oxides to represent a wide range of compositions likely to be encountered in ferromanganese and silicomanganese smelting. The slag constituents were in the following range: MnO, 5-30%; CaO, 20-35%; MgO, 5-15%; SiO2, 27-58%; and Al2O3, 5%. Liquidus temperatures varied from 1300°C to 1380°C and increased with increasing basicity ratio. The electrical resistivity of slags decreased with the increase of basicity ratio from 0.55 to 1.1 but above 1.1 basicity ratio the resistivity tended to increase depending upon the MnO content.
Room: 231A
Session Chairperson: Mrs. S. Young, BHP Copper Inc., 2400 Oracle Road, Suite 200, Tucson, AZ 85704
8:30 am
EFFECTS OF FLUID VELOCITY OF ELECTROLYTE ON COPPER ELECTROREFINING: A. Tsubouchi, T. Nakamura, F. Noguchi, I. Iakasu, Kyushu Institute of Technology, Department of Materials Science and Engineering, Kitakyushu, Japan 804
A high current density operation is desired to improve the productivity in copper electrorefining. However, a lot of problems still remain such as passivation of anode, dendritic deposition of cathode and contamination of impurity elements during the high current density electrorefining of copper. To clear the problems mentioned above, effects of the fluid velocity of the electrolyte on the morphology of copper deposition on cathode and the passivation behaviour of anode have been investigated at various current densities in the present study. Although a granular appearance of the copper deposition was obtained with increasing the current density, it was depressed by an increase of the fluid velocity of the electrolyte. Then an uniform deposition on the cathode was also observed when the fluid velocity of it became higher. Further more, no passivation behaviour of anode could be found by high speed circulating the electrolyte even in the high current density operation.
8:55 am
ENERGY SAVING IN COPPER ELECTROWINNING: C. Lupi, D. Pilone, Dip. ICMMPM, Università di Roma "La Sapienza", V. Eudossiana, 18, 00184 Roma, Italy
The energy consumption, in the electrowinning step of copper production by hydrometallurgical traditional process, generally represents more than 1/4 of the total energy requirement. The considerable saving can be achieved just in this step that requires about 8 GJ/tonne of the produced copper. To save energy the cell voltage, or more appropriately its anodic component, can be reduced: that is because the anodic voltage represents the main component of cell voltage and so it is responsible for the actual energy consumption in the copper sulphate electrowinning. In this work some ways are studied to lower the anodic voltage. First the cobalt ions were added to the sulphate solution in order to study the catalytic effect on oxygen discharge. Then lead alloys anodes (Pb-Ag, Pb-Sb-Ag and Pb-Ca) were used to promote a better oxygen evolution as a result of a different anodic surface. Their behaviour was compared with the Pb-Sb traditional ones. Finally, as already pointed out by several authors for zinc electrowinning, ethylene glycol was employed as anodic depolarizer in order to verify its effectiveness in the case of copper electrowinning. Combining all the above-mentioned ways energy saving ranging from 20% to 27% is achieved. All the tests were carried out on a laboratory pilot-plant for long time to simulate the industrial conditions. The obtained copper deposits were observed by SEM to highlight their morphology and were also analyzed by spectrometer to verify their purity.
9:20 am
RECENT IMPROVEMENTS IN THE STRIPPER SECTION OF ONAHAMA TANKHOUSE: Kiyotaka Abe, Fumihiko Shimizu, Onahama Smelter and Refinery, Onahama Smelting & Refining Co., Ltd., 1-1, Nagisa, Onahama, Iwaki-City, Fukushima, 971, Japan
Auto-stripping machine was developed and installed in 1971. Major modifications were performed in 1981 such as relocating conveyor lines, changing the stripping devise and stacking unit of stripped sheets and others. In 1988 stainless steel blanks with Edge Wise Protector which is highly efficient edge masking plastics were introduced from Mitsubishi Materials Corporation. Then the blank polishing machine and durable plastics for EWP were developed to improve stripability. Not only tremendous cost savings of labors, maintenance, supplies and others but also good quality of the starting sheets were attained and the capacity of cathode production was increased. According to the recent results of operation, the speed and the sheet production rate of stripping machine are 5.5 seconds per blank and 7,000 sheets per day respectively. The operation of commercial tanks is also satisfactory, of which current efficiency is keeping 98-99% at the tankhouses #1 &2 and 95-97% at the tankhouse #3.
9:45 am
INFLUENCE OF THE ELECTROCRYSTALLIZATION INHIBITORS DURING COPPER ELECTROREFINING: A NEW EXPERIMENTAL APPROACH: J.-L. Delplancke, M. Degrez, C. Temmerman, R. Winand, Université Libre de Bruxelles, Metallurgy, CP165, 50 Av. F.D. Roosevelt, B1050 Brussels, Belgium
The influence of the copper electrocrystallization inhibitors (mainly thiourea, gelatin and chloride ions) is studied in a new fully automatic pilot plan. This paper describes the conception and the building of this plan. The plan is in hydrodynamic similitude with an industrial copper electrorefining plan. Three cells with forced electrolyte flow may be connected in parallel or in series on order to model the copper production cells. The electrolyte is characterized chemically and electrochemically before and after electrolysis. One day and one week long experiments are performed. The structure of the deposits is characterized by SEM, EDX and metallographic cross-sections. The new approach for the study of these inhibitors is firstly to reproduce the experimental conditions observed in the industry with the three additives present simultaneously in the electrolyte and secondly to study the influence of a slight modification of the concentration of one inhibitor, the others being present in the electrolyte with their industrial nominal concentrations.
10:10 am
THE CHARACTERIZATION OF PASSIVATING FILMS ON COMMERCIAL COPPER ANODES USING IMPEDANCE SPECTROSCOPY: M.S. Moats, J.B. Hiskey, S.C. Campin, University of Arizona, Copper Research Center, Material Science and Engineering Department, College of Engineering and Mines, Tucson, AZ
Electrochemical techniques are a valuable means of analyzing the passivation of commercial copper anodes. Electrochemical impedance spectroscopy (EIS) provides information concerning transport and reaction phenomena occurring at an electrode surface. Commercial copper anodes of varying compositions have been examined using EIS. Experiments were conducted in a flat cell with an electrolyte of 40 g/l Cu2+ and 160 g/l H2SP4 maintained at 65°C. Impedance spectra were obtained at the potentials characteristic of the open circuit voltage and the passive region for each anode. The spectra of the passivating films exhibited a flattened resistive/capacitive loop at middle to high frequencies and an inductive loop at low frequencies. An equivalent circuit utilizing an inductor-resistor series in parallel with the double layer capacitance and charge transfer resistance was adequate in modeling the impedance data. The influence of anodes impurities on the components of the equivalent circuit is discussed and correlated with a bilayer passivation model.
10:30 am
SURFACE ROUGHENING OF ELECTROWON COPPER IN THE PRESENCE OF CHLORIDE IONS: E. Ilgar, P. Yu, T.J. O'Keefe, University of Missouri-Rolla, Department of Metallurgical Engineering and Graduate Center for Materials Research, Rolla, MO 65409-1170
A statistically designed screening test was carried out in the absence and presence of 20 ppm Cl- ions using a three factor, two-level factorial design in an electrolyte containing 36 gl-1 Cu2+ and 150 gl-1 sulfuric acid. The independent variables evaluated were agitation, current density and temperature; their influence on surface roughness was determined. Using the data generated, a model expression was developed to allow estimation of surface roughness of the copper deposits. X-ray diffraction, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and profilometer techniques were used in the evaluation. The copper deposited at current densities where activation was the primary control mechanism appeared similar in morphology whether stirring was used or not. The addition of 20 ppm Cl- ions to the electrolyte gave rougher deposits under the same conditions. In the mixed control regions, where mass transfer effects were initiated, considerably rougher and more dendritic deposits were obtained when Cl- ions were present. Agitation was effective in reducing the copper surface roughness both in the apparent activation and mixed control regions in the presence of Cl- ions. The results of this study showed that 20 ppm Cl- polarized the copper deposition at low overpotentials but caused depolarization at higher overpotentials, and promoted roughening even where Cu2+ mass transfer was not a factor.
10:55 am
THREE-DIMENSIONAL CALCULATION OF CURRENT DISTRIBUTION IN ELECTRODEPOSITION OF COPPER: Y.S. Choi, N.S. Kim, S.H. Jeon, T. Kang, Seoul National University, Department of Metallurgical Engineering, Seoul, Korea; H.J. Sohn, Seoul National University, Department of Mineral and Petroleum Engineering, Seoul, Korea
The thickness uniformity of electrodeposits depends largely on the current density distribution over the cathode. The current distribution is determined by the geometrical characteristics of the electrodes and the cell, the polarization at the electrode surface and the mass transfer in the electrolyte. The calculation of the current distribution is possible by various numerical techniques, among which the boundary element method (BEM) is considered to be most efficient. In this study the program for the calculation of 3-dimensional current distribution by use of the BEM with a linear element of trigonal type was developed and applied to the rectangular cathodes in copper electroplating. For simplicity the anode potential was assumed to be constant and the nonlinear polarization curves obtained from the potentiodynamic experiments were fitted to a linear equation over the range of current densities, 20~80mA/cm2. The effect of the cell dimension and the anode shape on current distribution was simulated. The calculated values agreed fairly well with the measured values and the thickness uniformity could be improved by the proper combination of the cell geometry and the anode shape.
11: 20 am
THE SOUTHERN PERU ILO REFINERY, DESIGN FEATURES, OPERATION AND IMPROVEMENT: F. Begazo, W.A. Enrico, Southern Peru Limited, 180 Maiden Lane, New York, NY 10038
Southern Peru Limited's Ilo Refinery, the largest in Peru, began operations in 1975 with a production capacity of 165,000 stpy. Southern Peru bought the Refinery from the state owned Minero Peru S.A. on June 1, 1994. The refinery processes blister from Southern Peru's Ilo smelter. Blister copper is processed in an anode plant equipped with two 365 st. tilting reverberatory furnaces, a 26 mold casting wheel and an anode press machine. Copper is electrorefined in a tank house equipped with 768 commercial cells, 44 stripper cells and 40 liberator cells, utilizing two electrolyte circuits and a 21,000 ampere rectifier. During 1989 through 1994, a program for improving productivity was carried out by increasing the number of cells and increasing current density to the total rectifier capacity. As a result, a capacity of 215,000 stpy of refined copper, 2 million troy ounces of silver and 6,000 troy ounces of gold per year was achieved. In 1994, Southern Peru announced plans to increase the capacity to 250,000 stpy of cathode with a US$ 18 million investment and a US$2 million investment in environmental improvement projects, as part of the purchase agreement with the Peruvian government. This paper outlines the scope of the Southern Peru Limited refinery modernization and environmental program. It describes the implementation of the electrolytic plant expansion based on installation of polymer concrete cells, a new rectifier, a new selenium roaster and a precious metal plant upgrades.
Room: 230B
Session Chairperson: Einar K. Jensen, Elkem a/s Research, N-4602 Kristiansand S., Norway
8:30 am
MATHEMATICAL MODELLING OF THE METAL FLOW IN SIDEWELL FURNACES: Y.S. Kocaefe, R.T. Bui, D. Kocaefe, Department of Applied Sciences, University of Quebec at Chicoutimi 555, Boul. de l´Université, Chicoutimi, Quebec, Canada G7H 2B1
Many different types of furnaces are used in aluminum industry for melting and treating the metal. Sidewell furnaces are commonly used for scrap melting. Metal flow in the furnace is provided by different types of equipment such as pumps and impellers, and plays an important role in furnace performance. A three-dimensional model has been developed to simulate the metal flow in such furnaces. In this paper, the model will be described, and the results will be presented showing how various operating and design parameters such as impeller position and rotational speed, sidewell geometry and arch design affect the metal flow.
8:50 am
Na AND Ca PICK-UP FROM HALL BATH IN INGOT FURNACES: David H.DeYoung, Aluminum Company of America, Molten Metal Processing Center, Alcoa Technical Center, Alcoa Center, PA 15069
A series of laboratory tests were conducted to explore the reaction of bath with Al-Mg alloys, as may occur when Hall bath enters ingot furnaces in a smelter-supplied ingot plant. Results showed that Mg clearly reacts with bath and adds Na and Ca to the metal by the reactions: 2(Na3AlF6) + 3 Mg 
6 Na + 2 AlF3 + 3 MgF2 (1) and CaF2 + Mg Ca + MgF2 (2) Temperature, Mg concentration in the alloy, the quantity of bath added to the metal, and the particle size of the bath added all influenced the reaction. At 700°C the Na and Ca pick-ups that occurred from these reactions were approximately 15 ppm while at 900°C the pick-ups were greater than 300 ppm. The pick-ups increased with increasing quantity of bath up to a limiting amount, beyond which no further pick-up occurred. The variation of the reaction with particle size indicated that the reaction is limited by the available bath-metal surface area.
9:10 am
EFFECTS OF SOLUTE INTERACTIONS ON GRAIN REFINEMENT OF COMMERCIAL ALUMINIUM ALLOYS: M.A. Kearns, P.S. Cooper, London & Scandinavian Metallurgical Co. Limited, Fullerton Road, Rotherham, South Yorkshire, S60 1DL, England
An analysis of the effects of alloy additions on the grain refinement in a series of model and commercial aluminium alloy compositions is reported. The data of Birch and Fisher published earlier describing grain refinement in 32 systems, including AA3004, AA5083, AA6063 and AA7050, are considered in terms of the supercooling effect of each alloy addition. A simple model describing grain size in terms of additive supercooling effects of individual alloy additions is proposed which fits the data reasonably well. Deviations from simple additive behaviour are evident in systems where strong intermetallic interactions occur. Interaction coefficients amongst solutes are invoked to explain these deviations. Individual alloying effects on grain refinement are treated in terms of constitutional supercooling parameters and behaviour is shown to be similar to that described in earlier studies. Zirconium is shown to have a general poisoning effect in a range of alloy compositions.
9:30 am
THE BUBBLE SIZE AND MASS TRANSFER MECHANISMS IN ROTOR STIRRED REACTORS: Stein Tore Johansen, Svend Grådahl, Per Ola Grøntvedt, Pål Tetlie, Rune Gammelsæter, SINTEF Materials Technology, N-7034 Trondheim, Norway; Karl Venås, Pal Skaret, Karl Venås a.s., Trondheim, Norway; Erling Myrbostad, Bjørn Rasch, Hydro Aluminium a.s R&D Centre, N-6600 Sunndalsøra, Norway
The performance characteristics of the HYCAST Rotor has been investigated in a water model. The removal rate of oxygen from water is measured for a large number of operational conditions. By combining different techniques the energy dissipation in the reactor, the mass transfer at the top surface and the bubble sizes may be determined experimentally. Investigations of the bubble dynamics by high speed video show that the bubbles in this type of reactors are very different from what is hitherto believed. Based on such a picture the paper demonstrates that the mass transfer and bubble sizes in the HYCAST Unit may be explained by a relatively simple theory which seems to explain all available experimental data. It is also demonstrated how we from this theory can scale from the oxygen removal in water model to hydrogen removal in liquid aluminum.
9:50 am
MODELLING OF SURFACE SEGREGATION DEVELOPMENT DURING D.C. CASTING OF ROLLING SLAB INGOTS: A. Mo, H.J. Thevik, SINTEF Materials Technology, Box 124 Blindern, N-0314 Oslo, Norway; B.R. Henriksen, E.K .Jensen, Elkem Research, Box 40, N-4602 Kristiansand, Norway
A two dimensional mathematical model for the development of macrosegregation at and close to the ingot surface during DC casting of rolling slabs is presented. The model accounts for macrosegregation caused by exudation of interdendritic melt and macrosegregation associated with solidification shrinkage. Equations for the conservation of energy, solute, momentum, and mass during the stationary phase of the process are solved numerically by a finite element method in a solution domain defined by a vertical cross section of the ingot. The main simplifications in the modelling concept are to assume the solidified part of the mushy zone to move with the casting speed, and to consider a binary alloy solidifying according to the lever rule. The thickness and solute concentration of the surface layer and the macrosegregation close to the surface are calculated, and modelling results are compared with measurements on real castings.
10:10 am BREAK
10:20 am
A MODEL TO PREDICT THE STEADY STATE PULL-IN DURING D.C.-CASTING OF ALUMINIUM SHEET INGOTS: Arild Håkonsen, Hydro Aluminium R&D Materials Technology, P.O.Box 219, N-6601 Sunndalsøra, Norway
By combining empirical results with a dimensional analysis, a model for the prediction of pull-in during DC-casting of aluminium sheet ingots is constructed. The model predicts the steady state pull-in along the rolling faces of an ingot. By using an alloy dependent constant, the nominal geometry and the casting speed, the model can easily calculate a near optimal mould shape. It is also possible to calculate the resulting shape of the rolling faces of an ingot for a given mould geometry, alloy constant and casting speed. The model requires only a spread sheet for these calculations. Comparisons with experiments show a very good agreement. The best fit values of the alloy constant for several commercial aluminium alloys are presented. The value of this constant varies within 12%.
10:40 am
THE MECHANISM OF PULL-IN DURING D.C.-CASTING OF ALUMINIUM SHEET INGOTS: Hallvard G.Fjær, Institute for Energy Technology, P.O. Box 40, N-2007 Kjeller, Norway; Arild Håkonsen, Hydro Aluminium R&D Materials Technology, P.O. Box 219, N-6601 Sunndalsøra, Norway
The pull-in phenomenon apparent in the DC-casting process of aluminium sheet ingots is investigated both analytically and by use of numerical models calculating temperatures, strains and stresses. The major part of the pull-in takes place above the bottom of the sump, but is mainly caused by thermal contractions and deformations in regions below. The strong and almost exactly linear dependency of the pull-in on the casting speed is explained. The effects on the pull-in of different cooling conditions and of various thermophysical and thermomechanical properties are investigated. 2D plain strain approximations have been successfully applied in calculating the pull-in for the centre part of the rolling face, but 3D effects are significant close to the narrow ingot surface. This is illustrated by comparison of results from 3D and 2D calculations. Modelling results are also compared with measurements of ingot thickness variations. A very good agreement is obtained.
11:00 am
WATER COOLING IN DIRECT CHILL CASTING: PART I: BOILING THEORY AND CONTROL: John Grandfield, Comalco Research Centre, P.O.Box 316, Thomastown, Victoria 3074, Australia
The intensity of the water cooling in direct chill casting affects the process heat flow and the performance of the casting process. The intensity depends on the boiling behaviour on the ingot surface. The basic mechanisms of boiling, the different boiling modes (nucleate, unstable film and stable film boiling), the effect of water composition, temperature, flow and velocity on boiling behaviour and heat transfer are reviewed. A Ä Ä Ä Ä H h h F;jÑ/æ F MPSR BBST Ì Ä L;e¯ xxx yyy {{{ ||| {{{ xxx ttt qqq sss ooo lll nnn rrr ttt qqq mmm nnn nnn nnn nnn nC casting requires a good knowledge of the heat transfer between ingot and cooling water. This is especially true for the starting phase, where most defects are initiated. An experimental set-up has been developed to characterize this heat exchange close to process operating conditions. The method is based on the measurement of the cooling of a preheated instrumented aluminium block quenched by a water curtain. A 2D transient inverse model allows to determine the distribution of heat transfer coefficient and temperature on the whole surface of the block. In this way, heat flux can be assessed both at the water impingement point and below. The results obtained with the experimental apparatus are in good agreement with heat transfer rates calculated from in-situ temperature measurements using cast-in thermocouples. This device is thus an efficient and economical method to determine the influence of cooling water characteristics on the law describing heat transfer coefficient as a function of surface temperature. These laws have been measured and introduced in a numerical simulation of DC casting in order to study the effect of water cooling and casting parameters on the thermal evolution of the ingot during the different phases of casting.
11:40 am
FUNDAMENTALS OF UBC DECOATING/DELAQUERING FOR EFFICIENT MELTING: Wesley Stevens, Francois Tremblay, Arvida Research and Development Centre, Alcan International Limited, 1955 Mellon Blvd., Jonquière, Québec, Canada G7S 4K8
Aluminum used beverage cans (UBC) should be cleaned to completely remove all organic and residues to maximize metal recovery on remelting. This process must also minimize oxide formation. The aluminum industry uses three principal decoating technologies. The most used is the rotary kiln. The other processes are the belt decoater and the fluidized bed decoater. The presentation will cover the fundamental science for decoating shredded UBC to minimize metal loss on remelting. Laboratory work and plant trials have shown the requirements for complete decoating. These are: correct temperature range for the coatings to be pyrolized, good process gas to shred contact for all the scrap, sufficient oxygen being present to complete the oxidation of the carbon compounds present. The basic principles of the three decoating technologies used for the decoating of UBC will be discussed in relation to how they correspond to the fundamental process requirements.
Room: 330C
Session Chairperson: Brent Fultz, 138-78, California Institute of Technology, Pasadena, CA 91125
8:30 am INVITED
KINETICS OF ATOMIC TRANSPORT IN THE FORMATION OF NONEQUILIBRIUM MATERIALS: Michael J. Aziz, Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge MA 02138
Rapid solidification can result in the production of nonequilibrium materials either primarily due to nucleation or primarily due to growth. Rapid growth can trap in solute or point defect supersaturations or chemical disorder, or can cause the formation of nonequilibrium microstructures. Additionally, large driving forces can permit the nucleation and growth of other metastable phases. The phenomenology and mechanisms for these processes will be discussed. Models and experiments will be reviewed.
9:00 am INVITED
DEVIATIONS FROM LINEAR DIFFUSION DURING SOLID-STATE AMORPHIZATION IN Ni-Hf DIFFUSION COUPLES: M. Atzmon, W.S.L. Boyer, The University of Michigan, Department of Nuclear Engineering and Radiological Sciences, Materials Science and Engineering, Ann Arbor, MI 48109-2104
When analyzing diffusion measurements, the diffusion coefficient is often assumed to be independent of composition and time. In this paper, studies of possible deviations from this simple picture will be reported. During amorphous alloy growth in an elemental diffusion couple, the amorphous phase has a wide homogeneity range, and the interdiffusion coefficient is unlikely to be uniform. Experimental results in Ni-Hf thin-film couples will be described, which indicate that the interdiffusion coefficient varies significantly with composition. This variation leads to significant systematic errors in determining the interfacial compositions from measured composition profiles. A more reliable measurement method will be presented. A number of authors have suggested that evolution of macrostress during amorphization by interdiffusion affects the rate of the latter. Using a combination of substrate curvature and lattice parameter measurements, we have determined the evolution of stress during interdiffusion in Ni-Hf thin-film couples. The amorphous phase is observed to form under large tensile stress, which relaxes by creep during subsequent growth. Neither this stress, nor that induced by ion irradiation, affects the interdiffusion coefficient.
9:30 am INVITED
SINTERING OF SMALL ASSEMBLIES: R.S. Averback, Huilong Zhu, M. Yeadon, J.M. Gibson, Materials Science and Engineering, University of Illinois, 1304 W. Green St., Urbana, IL 61801
The sintering of small assemblies of nanoparticles has been investigated by a combination of molecular dynamics computer simulations and in situ observations in a UHV transmission electron microscope. Because the radius of curvature of nanoparticles is so small, enormously large interfacial stresses are developed when nanoparticles come in contact with other nanoparticles or substrates, and this leads to sintering by plastic deformation of the particles on the time scale of some picoseconds. Surprisingly, these particles rotate and form twins and other low energy configurations. Several examples of such sintering will be illustrated, including nanoparticle assemblies of Cu, amorphous alloys and intermetallic compounds. Interactions between nanoparticles and substrates will also be discussed.
10:00 am INVITED
EFFECT OF FREE SURFACES ON THE KINETICS AND MORPHOLOGY OF SPINODAL DECOMPOSITION: Long-Qing Chen, Materials Science and Engineering, Penn State University, University Park, PA 16802
The kinetics of spinodal decomposition and morphological evolution near a crystalline surface were investigated by microscopic master equations in the point and pair approximations and a second-neighbor interaction model. Both two-dimensional (2-D) and 3-D model systems were considered. It is shown that, in the presence of a surface, spinodal decomposition initially involves surface segregation, followed by anisotropic decomposition in the near-surface region, and then followed by isotropic decomposition in the bulk. It is demonstrated that, due to segregation, a surface spinodal decomposition may take place for alloys whose overall average compositions are outside the bulk spinodal. It is found that the presence of a surface results in a dominant concentration wave which produces interesting transient morphological patterns such as distorted hexagonal precipitate lattices for relatively low-volume fractions and straight stripes at high volume fractions in the near-surface region. The relevance of these results to the mechanisms of diffusional phase transformations, such as spinodal ordering and decomposition, in nanoscale crystalline materials will be discussed.
10:30 am BREAK
10:45 am INVITED
SELF-PROPAGATING REACTIONS IN NANOSCALE MULTILAYER MATERIALS: Tim Weihs, Materials Science & Engineering, The Johns Hopkins University, Baltimore, MD 21218
This presentation describes self-propagating, exothermic reactions in nanoscale, multilayer materials. The talk begins with a review of self-propagating reactions in powder-based materials and then focuses on similar exothermic reactions in multilayer foils. The multilayer foils consist of alternate layers of materials that have high heats of mixing, such as Al and Ni. The individual layers (of Al or Ni) are only nanometers thick, but hundreds of these layers are sputter deposited to form one foil with a total thickness between 10 and 100 microns. The layered foils arc easily removed from their substrates, and their exothermic mixing can be started at room temperature with a small spark. Te exothermic reactions propagate al speeds greater than 10m/s and they reach final temperatures as high us 1600°C The reactions can propagate in air, vacuum, or liquids. The velocities, the heats, and the temperatures of the reactions will be presented for at least two different multilayer systems, and the chemical and structural parameters that control these properties will be addressed using an analytical model. The final segment of the talk will describe how reactive multilayer foils can be used as local heat sources to joint structural components.
11:15 am INVITED
NANOSTRUCTURED PALLADIUM ALLOY MEMBRANE MATERIALS: Kenneth J. Bryden, Jackie Y. Ying, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307
Membranes are often fabricated from palladium since it has a very high hydrogen permselectivity. Diffusion through the metal is often the rate-limiting step in hydrogen transport through palladium-based membranes. The flux through these membranes can be increased by tailoring a microstructure that allows for higher hydrogen diffusivity. Nanostructured palladium has a much higher hydrogen diffusivity than conventional palladium due to its large volume fraction of grain boundaries. Thus, nanostructured metal membranes would provide higher hydrogen fluxes and better performance. By doping palladium with another element, enhanced stability against grain growth, stability against the alpha to beta phase transition which causes cracking, and enhanced poisoning resistance can be achieved. In this study nanostructured pure palladium and palladium alloy membranes were synthesized by pulsed electrodeposition. The hydrogen permselectivity through these materials was determined in a membrane reactor and the effect of common poisons (e.g. carbon monoxide and hydrogen sulfide) on hydrogen diffusivity was also measured to relate the hydrogen permeation properties of these materials to their microstructure and elemental composition.
Room: 332
Session Chairperson: Ephraim Suhir, Lucent Technologies, Bell Laboratories, Room 7G-326, 700 Mountain Avenue, NJ 07974; Theodore Ejim, Lucent Technologies, Bell Laboratories, Engineering Research Center, P.O. Box 900, Princeton, NJ 08542
8:30 am
OPENING STATEMENTS: Dr. Darrel R. Frear, EMPMD Chair and, Senior Member of Technical Staff, Department 1811, Mail Stop 1411, P.O. Box 5800, Sandia National Laboratories, Albuquerque, NM 87185
8:40 am KEYNOTE
MICROELECTRONIC PACKAGE TRENDS--THE ROLE OF RELIABILITY IN PARTICULARLY, RELATED TO SOLDER JOINT RELIABILITY: C.P. Wong* and Rao Tummala**, Georgia Institute of Technology, Packaging Research Center (PRC), School of Materials Science & Engineering, and School of Electrical & Computer Engineering, 778 Atlantic Drive, Atlanta, GA 30332;*Professor and Assistant Director, PRC; **Pettit Chair Professor, Georgia Eminent Scholar and Director, PRC
The trends of microelectronic devices have advanced to the state that they operate in excess of 200 MHz with submicron feature size. Furthermore, these high performance IC requires Inputs/Outputs (I/O) signals that are in excess of a few 1000's. Low-cost, high performance flip-chip, area array solder joint interconnects are key to the success of this technology. In order to enhance the thermal cycle fatigue-life of these solder joints, underfill encapsulants are needed. In this talk, we will review the microelectronic packaging technology trends, the role of reliability, in particularly, the use of underfill encapsulants to enhance the thermal cycle fatigue life of solder joints will be discussed.
9:15 am KEYNOTE
SOLDER JOINTS IN ELECTRONICS--DESIGN FOR RELIABILITY: Werner Engelmaier, President, Engelmaier Associates, Inc., 23 Gunther Street, Mendham, NJ 07945
The emerging new technologies provide ever more challenges to assure the reliability of electronic products. The ever increasing demands in electronic products for higher performance, lower cost, less space (weight) is leading to ever denser interconnection needs. Solder joint reliability is becoming an even more important issue with the advent of new surface mount packages and the use of surface mounted electronics in such hostile environments as the automobile and space. The new packages are characterized by larger sizes, finer pitches, and/or problematic materials which require an up-front 'Design for Reliability (DfR)' to meet reliability requirements. The hostile environments can include thermal excursions over temperature ranges in which multiple interactive damage mechanisms are operative. The reliability of electronic assemblies requires a definitive design effort that has to be carried out concurrently with the other design functions during the developmental phase of the product. There exists a misconception in the industry, that quality manufacturing is all that is required to assure the reliability of an electronic assembly. While of course, consistent high quality manufacturing - and all that this implies is a necessary prerequisite to assure the reliability of the product, only a DfR-procedure can assure that the design - manufactured to good quality - will be reliable in its intended application. Explicit DfR-procedures need to be employed to account and compensate, at least in part, for the prevalent damage mechanisms. This needs to be complemented with 'Design for Manufacturability (DfM)' which widens the process windows and takes into account the manufacturing capabilities. These demands put an increasing burden on the designers who will require a heightened technical understanding of the underlying issues and more sophisticated design tools. Thus, adherence to quality standards, such as IPC-A-620, Acceptability of Electronic Assemblies with Surface Mount Technologies, and ANSI/J-STD-001, Requirements for Soldered Electrical and Electronic Assemblies does not assure reliable solder connections, only quality solder connections. It is for this reason that IPC-D-279, Design Guidelines for Reliable Surface Mount Technology Printed Board Assemblies, is being developed. The 'Design for Reliability (DfR)' for solder attachments in electronic interconnections will be the emphasis of the paper.
9:50 am KEYNOTE
MEETING MARKET DEMANDS--NEW AND CRITICAL TECHNOLOGIES FOR ELECTRONIC PACKAGING AND ASSEMBLIES: Jennie S. Hwang, President, H-Technologies Group Inc., 5325 Naiman Parkway, Cleveland, OH 44139
Advanced technologies are transforming manufacturing, and the information highway is speedily progressing. In this exciting and changing time, the electronic industry has responded and will continue to respond to competitive products in the global market place. The speaker will provide a capsule view of key segments of electronics hierarchy in market needs and the demands in new technologies. The presentation will separately address the market and technology in chip level, package level, and board level, as well as, the critical supporting materials and technologies. Dr. Hwang will conclude her talk by highlighting the important aspects of the reliability of solder joints in relation to the new market trends.
10:25 am BREAK
10:35 am INVITED
SOLDER MATERIALS AND SOLDER JOINTS IN FIBER OPTICS ENGINEERING--RELIABILITY REQUIREMENTS AND PREDICTED STRESSES: Ephraim Suhir, Lucent Technologies, Bell Laboratories, Physical Sciences and Engineering Division, Room 7G-326, 700 Mountain Avenue, NJ 07974
Typical solder materials and solder joints, employed in fiber-optics engineering, are examined from the stand-point of the requirements for optical performance of the devices, as well as for the short- and long term mechanical reliability of the soldered optical fibers and the solder materials themselves. We address the geometry's of, and the loading condition in, fiber-optics solder joints, and suggest several analytical stress models that enable one to evaluate thermally and mechanically induced stresses in solder joint assemblies in fiber-optics structures. These models include: thermal stresses in metallized fibers soldered into ferrules or capillaries; stresses at the menisci areas in soldered joints; comparison of the thermal stresses due to the application of "hard" (high modulus) and "soft" (low modulus) solders; interaction of the "global" and "local" thermal stresses in optical fibers whose end portions are soldered into capillaries; evaluation and interaction of mechanical and thermal stresses in solder joints during proof-testing of optical fibers soldered into ferrules; and others. The merits and shortcomings of soldered assemblies in comparison with adhesively bonded structures are also briefly discussed.
11:00 am INVITED
MICROSTRUCTURAL ANALYSIS OF ELECTRONIC MATERIALS: Aleksander Zubelewicz, IBM Microelectronics, W-64, Bldg. 4-2, 1701 North Street, Endicott, NY 13760
The electronic industry is changing at a rapid pace. Faster and more powerful processors and ASICs continuously replace the slower devices, while price competitiveness and time-to-market becomes the true challenge for many manufacturers. The dynamic nature of the electronic industry drives for the need of using smaller packages with higher I/O count. Recently, fine pitch, a family of BGA components, and Chip Scale Packages represent the "hottest" technologies allowing for high I/O density. However, the future electronics applications will require processors operating with speed of several hundred MHz, then the present packaging technology may need further modifications. Consequently, the traditional PTH interconnection technology is being replaced by Surface Mount Technology and Ball Grid Arrays. Furthermore, new interconnection materials such as lead free solders and conductive adhesives are being seriously considered as a replacement of the commonly used lead based alloys. The objective of the paper is to discuss the behavior and failure mechanisms for the interconnection materials. Obviously, solders are at the top of the list, followed by encapsulations and conductive adhesives. During manufacturing operations, solders are used in the form of a paste, and when reflowed becomes ductile polycrystalline materials. These pastes must maintain appropriate rheological characteristics. It will be shown that a typical paste (solder or conductive adhesive) exhibits three stages of behavior: paste as a viscous solid, paste as a viscous fluid, and the transition stage between solid and fluid. Solder joints (after reflow) are thought to carry input/output electrical functions of the assembly as well as are designed to provide a mechanical support for the package or chip. Solders exhibit very complex microstructural behavior. There is a need for material model of solders, a model that can be used in the form of constitutive equations with built-in damage criteria, equipped with functions that represent microstructural evolution of solders, and allowing to predict the effect of strain/damage localization in solder joints. Moreover, this theory should lead to simple fatigue equations when needed. One such theory exists and will be discussed in the paper. In many cases, solder joints become the weakest link. Enhancement of the joint reliability can be accomplished by encapsulating them with polymer based materials. A microstructural numerical study for encapsulant will be briefly presented in the paper. It will be shown that fracture originates at the microscopic level of the materials, coalesce, and forms a localized fracture zone.
11:25 am INVITED
INCONSISTENCIES IN THE UNDERSTANDING OF SOLDER JOINT RELIABILITY PHYSICS: Liang-chi Wen, G. Mon, R. Ross, Jr., Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109
An inherent reliability problem associated with surface mount applications is that solder joints, which serve both as an electrical and a mechanical connection between part and board, are subject to thermal fatigue failure. Solder joint failure involves a complex interplay of creep and fatigue processes. Over the years, many analytical and experimental research studies have aimed to improve state-of-the-art assessment of solder joint integrity from a physics of failure perspective. Although considerable progress has been made, there still exist many inconsistent and even contradictory correlations and conclusions. This paper reviews the unique properties of near-eutectic tin-lead solder, properties such as age-softening and 'superplastic' behavior under low strain rate loading. Fundamental mechanical and thermomechanical processes are modeled to demonstrate many inconsistencies observed in the literature. These inconsistencies are to be found in both analysis and testing issues. Analytical inconsistencies arise in correlations involving Coffin-Manson and strain energy density algorithms for cycle-life prediction, the effects of mean temperature and cycle frequency, and the determination of test acceleration factors. Testing inconsistencies are to be found in the areas of mechanical versus thermal cycling, failure definations, detection methodology and treatment of failure statistics. The objective of this paper is to identify important unsettled analysis and testing issues whose resolution by the solder joint research community will assure a greater degree of solder joint reliability.
11:50 am INVITED
AUTOMATED SOLDER LIFE ANALYSIS OF ELECTRONIC MODULES: Stephen A. McKeown, Lockheed Martin Control Systems, 600 Main Street, Johnson City, NY 13790
The solder life analysis methods developed by Engelmaier and Steinberg have been incorporated into an automated method which combines the results of finite-element models, a component location file obtained from a computer-aided design tool, component data, and environment data to calculate the expected solder joint life for each surface mount technology component on an electronic module. The method uses the finite-element method to calculate the coefficient of thermal expansion at different locations on the surface of the module which is used in determining the thermal cycling life of the solder joints. Finite-element analysis is also used to determine the surface strains due to vibration of the module which also influences solder joint life. The component location is taken from a Mentor® neutral file which also provides component description and orientation. Component data includes the dimensions of the part and information on the solder joint fillet geometry. Environment data includes temperature ranges, dwell times, vibration levels, and durations of thermal/vibration missions. This information is combined in a ANSI C-language program to determine the calculated failure rate of each component for the combined environments, and the overall computed reliability of all of the analyzed solder joints.
12:10 am
WHEN IS A MODIFIED COFFIN-MANSON APPROACH VALID FOR SOLDER JOINT RELIABILITY PREDICTION?: Robert Darveaux, Amkor Electronics, 1900 S. Price Road, Chandler, AZ 85248
The Coffin-Manson approach is based on relating fatigue life to plastic strain range. The basic equation has been modified by Norris-Landzberg, Engelmaier, and others to include temperature, frequency or dwell time effects. These modifications were determined empirically on specific types of soldered assemblies. Today, they are commonly applied to a wide range of assemblies and test conditions, as well as field use conditions. The main advantage of these empirical relations is that they are easy to use. They are basically back of the envelope calculations that require almost no expertise on the part of the engineer. This paper explores the validity of modified Coffin-Manson approaches as applied to solder joint reliability analysis. Several case studies are examined, and the limits of the approach are defined.
Monday - Thursday Room: 332
February 10-13, 1997
Session Chairperson: R.K. Mahidhara, Tessera Inc., 3099 Orchard Drive, San Jose, CA 95134
ALLOY DESIGN OF Sn-Ag-In-Bi-Sb SOLDER SYSTEM USING THERMODYNAMIC CALCULATIONS: Byeong-Joo Lee and Hyuck Mo Lee, Materials Evaluation Center, Korea Research Institute of Standards and Science, Yusong P.O. Box 102, Taejon 305-600, Korea; Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Kusong-Dong 373-1, Yusong-gu, Taejon 307-701, Korea
TiN-BASED, ACTIVE METAL CONTAINING SOLDERS FOR JOINING OF ALUMINA: Tim Schwilm, O.T. Inal and Frederick G. Yost, Materials and Metallurgical Engineering Department, New Mexico Tech, Soccoro, NM 87801; Sandia National Laboratories, Albuquerque, NM 87815
THERMAL AGING CHARACTERISTICS AND WETTING FORCE MEASUREMENTS OF EUTECTIC Ag-Sn SOLDER ALLOY: Guna Selvaduray, Hason Fong and Kristine Griley, Department of Materials Engineering, San Jose State University, San Jose, CA 95192
EVALUATION OF INTERMETALLIC PHASE FORMATION AND CONCURRENT DISSOLUTION OF INTERMETALLIC DURING REFLOW SOLDERING: M. Schaefer, W. Laub, R.A. Fournelle and J. Liang, Materials Science Program, Marquette University, 1515 W. Wisconsin Ave., Milwaukee, WI 53201-1881; Allen-Bradley Company, 1201 S. Second St., Milwaukee, WI, 53204
NANOSTRUCTURAL ANALYSIS OF PADS-TREATED SOLDER SURFACE: James L. Marshall and Brett Piekarski, Department of Chemistry, University of North Texas, Denton, TX 76203-5068; Army Research Laboratory, AMSRL-EP-RC, 2800 Powder Mill Road, Adelphi, MD 20783
INTERFACIAL REACTION BETWEEN PALLADIUM AND LEAD-TIN SOLDERS: G. Ghosh, Dept. of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108
Room: 340C
Session Chairs: D.J. Srolovitz, Dept. of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136; D.P. Adams, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185
8:30 am INVITED
CORRECTION FACTORS TO THE CLASSICAL NUCLEATION RATE: David T. Wu, Dept. of Mechanical Engineering, Yale University, New Haven, CT 06520
The rate of nucleation can have a strong influence on the microstructure of thin films. This talk discusses corrections to the classical expression for nucleation rate. For heterogeneous nucleation's spherical cap model a new contact-angle dependence for the prefactor is presented, while in homogeneous nucleation the self-consistency correction is reconsidered using the idea of "kinetic potential." Both corrections can increase the nucleation rate significantly.
9:10 am INVITED
EVOLUTION OF THIN FILM MICROSTRUCTURE AND MORPHOLOGY DURING CHEMICAL VAPOR DEPOSITION: D.P.Adams, T.M. Mayer, E. Chason, B.S. Swartzentruber, Sandia National Laboratories, P.O. Box 5800, Albuquerque, N.M. 87185
We present a study of thin film growth by thermal chemical vapor deposition (CVD). In this investigation of metal growth onto Si substrates, the effects of chemical kinetic processes on both film structure and morphology are determined. Scanning tunneling microscopy is used to identify the nucleation sites and to monitor island growth during the submonolayer regime. Analysis of measured island size distributions reveals the importance of site-specific chemical reactions and precursor molecule diffusion. Also, we monitor the development of surface roughness of thicker films by x-ray reflectivity. These experiments demonstrate the influence of nucleation rate on surface morphology. Finally, we show how CVD kinetics can be manipulated by use of adsorbates which passivate chemically - reactive substrate sites. Adsorbate layers have been used to modify the nucleation rate and fabricate nanometer - size structures via selective - area growth. This work was supported by the U.S. Department of Energy under contract DE-AC04-94AL85000.
9:50 am
TEM INVESTIGATION OF CVD ALUMINA MULTILAYER COATINGS: M. Halvarsson, Department of Physics, Chalmers University of Technology, S-412 96 Göteborg, Sweden; S. Vuorinen, Research and Development, Seco Tools AB, S-737 82 Fagersta, Sweden
10:10 am BREAK
10:30 am INVITED
MOLECULAR VIEW OF CVD DIAMOND FILM GROWTH: David J. Srolovitz, Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136; Corbett Battaile*, James E. Butler, DDGas/Surface Dynamics Section, Code 6174, Naval Research Laboratory, Washington DC 20375-0001
Kinetic Monte Carlo computer simulations of the growth of diamond thin films are presented as a function of hot filament chemical vapor deposition reactor conditions. The model includes chemical reactions between surface atoms, gaseous hydrogen and hydrocarbons, and between species on adjacent surface sites. Gas phase hydrocarbon composition is varied over six orders of magnitude. The effects of surface atomic structure and morphology on growth behavior are included explicitly. The evolution of surface structure (including reconstruction) during growth and evidence for step-flow growth and surface roughening will be presented. Model predictions for the growth rates of high symmetry facets will be presented and the influence of these growth rates on surface roughness, microstructure, point defect incorporation and texture will be discussed.
10:50 am
MICROSTRUCTURAL INVESTIGATION OF THE GROWTH OF YBa2Cu3O7-x /Nd2CuO4/YbA2Cu3O7-x TRILAYERED FILMS ON LaSrGaO4 SUBSTRATES: Y.H.Li, A.E. Staton-Bevan, Department of Materials, Imperial College, London SW7 2BP, UK; Z. Trajanovic, I. Takeuchi, T. Venkatesan, Department of Physics, University of Maryland, MD 20742
A HRTEM study of an YBCO/Nd2CuO4/YBCO trilayered films on LaSrGaO4 substrate with PBCO as a template layer has shown that in-plane aligned a-axis oriented YBCO films may be grown on (100) LaSrGaO4 substrates by pulsed laser deposition, which contain some domains with the c-axis misaligned by 90° in plane of the films. A Nd2CuO4 insulating layer, with a thickness of approximately 10nm, may be grown epitaxially between a-axis oriented YBCO layers with its c-axis parallel to the c-axis of the YBCO layers. A 90°-misoriented a-axis YBCO grain in the lower YBCO layer can nucleate a 90°-misoriented Nd2CuO4 grain in the a-axis oriented Nd2CuO4 layer and this grain can further nucleate a 90°-misoriented YBCO grain in the top YBCO layer. Narrow vertical Nd2O3 plates were observed in 90°-misoriented Nd2CuO4 grains formed epitaxially with the Nd2CuO4 grains. The interface between the PBCO template layer and the LaSrGaO4 substrate is quite rough with some amorphous islands in the template layer.
11:10 am
ADVANCES IN THE PROCESSING AND APPLICATIONS OF HIGH TEMPERATURE SUPERCONDUCTING FILMS: M. Sisodia, R.K. Yadava, Dept. of Metallurgical Engineering, Malaviya Regional Engineering College, Jaipur 302 017, India
High critical temperature (high-Tc) superconductors have captured the interest of engineers and scientists world wide. For its commercial utilization in the field of microelectronics and electronic systems, they must be fabricated into desirable configurations, thin and thick films. During studies it has been observed that these superconducting thin films operating at liquid N2 temperature offer great possibilities for faster, more sensitive and precise electronics devices. Present paper reviews the fabrication techniques of high-Tc superconducting thin films which primarily includes Pulsed-Laser Deposition, Molecular ion beam epitaxy, Chemical Vapour Deposition (CVD) by using epitaxial growth on single crystal substrates (YSZ, MgO, Si, etc.) with excellent microstructural control and properties relationship. In addition to it, thick film fabrication is also discussed with major techniques like Screen Printing and Plasma Spraying along with associated processing parameters. Furthermore, advanced applications of each are enumerated at length.
Room: 330E
Session Chairpersons: Michael J. Kaufman, Dept. of Materials Science and Engineering, Univ. of Florida, 201 Rhines Hall, Gainesville, FL 32611; Bruce A. MacDonald, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22203-9966
8:25 am
OPENING REMARKS: Kwai S. Chan, Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510
8:30 am INVITED
KINETIC AND MECHANISTIC ASPECTS OF THE 
m MASSIVE TRANSFORMATION IN TIAL ALLOYS: Ping Wang, D. Veeraraghavan, Vijay K. Vasudevan, Dept. of Materials Science and Engineering, University of Cincinnati, Cincinnati, OH 45221-0012
The kinetics and temperature dependence of the 
transformation in Ti-(46-48) at.% Al alloys was studied using a novel computer-controlled temperature and electric resistivity acquisition system. Samples of the alloys were heated by controlled direct resistance heating and cooled at various rates by a helium jet quench. In situ, real time, high speed, simultaneous measurements of electrical resistivity and temperature were made during both heating and cooling. Using the resistivity and thermal arrest data, the start and finish temperatures of the various transformation modes, viz., lamellar, Widmanstatten/feathery and massive were determined as a function of cooling rate. The data obtained was correlated with light and electron microscope observations to establish transformation diagrams, and to determine the growth rate of the massive phase as a function of undercooling. The experimental data was fitted into physical models and thermodynamic quantities such as the enthalpies/driving forces of formation of the massive were determined. The activation enthalpy for boundary diffusion estimated from this data indicates that the massive transformation is controlled by interfacial (rather than volume) diffusion. Defect structures in the massive phase and the massive -parent interface were characterized in detail by TEM. The implications of these studies on the mechanism of the massive transformation will be discussed. This research is supported by grants from the National Science Foundation (Dr. Bruce MacDonald, Program Monitor) and UES/Wright Laboratory (Dr. Madan Mendiratta, Program Monitor).
9:00 am
CALCULATION OF THE TI-AL PHASE DIAGRAM: F. Zhang, S.L. Chen, Y.A. Chang, Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706; U.R. Kattner, National Institute of Standards and Technology, Gaithersburg, MD 20899
A thermodynamic description of the Ti Al system is developed in this study. Nine phases were considered in this system. They are disordered solution phases: liquid, (Ti, Al), 
(Ti, Al), (Al); ordered intermetallic phases: 2Ti3Al, TiAl, TiAl3 and stoichiometric compounds: TiAl2, Ti2Al5. The Redlich Kister equation was used to describe the excess Gibbs energy for the disordered solution phases; the generalized quasi-chemical model recently developed in our research group was used to describe the ordered intermetallic phases. The parameters describing these models were obtained by optimization using the experimental phase equilibrium and thermodynamic data available in the literature. The quasi-chemical model is an extension of the Bragg Williams model similar to the extension of the regular solution model for disordered solution phases. Thermodynamic values obtained from the model parameters as well as the calculated phase diagram are in good agreement with the experimental data. The intrinsic defect concentrations calculated from the model parameters for TiAl are compared with the predictions of the first principle calculation, the semi empirical relationship and the available experimental data, reasonable agreement is obtained. The model parameters for the ordered intermetallic phases can be converted to the format of sublattice model and Wagner Schottky model.
9:20 am
PHASE DIAGRAM MODELLING OF TiAl ALLOYS: Nigel Saunders, Thermotech Ltd, The Surrey Research Park, Guildford GU2 5YG, UK; IRC in Materials for High Performance Applications, University of Birmingham, Birmingham B15 2TT, UK
The phase relations in Ti-Al based systems are by no means well established except for the case of a few specific ternary systems. This lack of information is now being exacerbated as new generation alloys are commonly multi-component in nature. Thermodynamic phase diagram modeling for Ti-Al-X systems has been presented previously which can now form the basis for the extension of the modeling technique to multi-component alloys. Examples of calculations for a variety of multi-component alloys will be shown and the effect of light elements such as O will also be modeled. An important factor in the success of the calculation method is that the ordering of the phase to 2 can now be incorporated. 1. N. Saunders, to be published in "Titanium '95: Science and Technology," eds. P. Bleckinsop et al (London: Inst. Materials, 1996).
9:40 am
EFFECTS OF SUBLATTICE ORDERING AND COMPOSITIONAL UNCERTAINITIES ON THE DETERMINATION OF ACCURATE AND PRECISE DEBYE-WALLER AND STRUCTURE FACTORS IN TIAL: S. Jayanthi, S. Swaminathan, H.L. Fraser, Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43210; I.P. Jones, School of Metallurgy and Materials, University of Birmingham, Edgbaston B15 2TT, UK; D.M. Maher, Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC
There has been significant interest aimed at determining the anisotropy of charge densities in the intermetallic compound TiAl. Such determinations require the accurate measurement of low order structure factors, which in turn requires an accurate knowledge of the Debye-Waller factors of the given alloy/compound. Hence, the quest for assessments of charge densities in TiAl has involved determinations of the Debye-Waller factors and structure factors. The first of these are conveniently extracted from single crystal x-ray diffraction experiments, and it has been found that in samples whose compositions are Al rich sub-lattice ordering occurs, such that there are unequal values of the Debye-Waller factors for the two Ti sites. The effect of this sub-lattice ordering on the determination of the Debye-Waller factors has been assessed and will be discussed. Furthermore, the effect of compositional uncertainties on the determination of both Debye-Waller factors and structure factors has been investigated. It has been shown that sample compositions must be known to within ±0.15at.% for accurate determination of charge densities. These limitations will be discussed, and an experimental approach to overcome these will be detailed. This work has been supported by the National Science Foundation, Dr. Bruce MacDonald as Program Manager.
10:00 am BREAK
10:20 am
PHASE RELATIONS AND ALPHA DECOMPOSITION IN Ti-(25-50) Al ALLOYS: Y-W. Kim, UES, Inc., Dayton, OH 45432
The phase relations in Ti-(25-55) at.%Al involved in the decomposition and transformations of the high temperature alpha phase were investigated by conducting annealing/cooling experiments in a cooling/heating rate range of 0.2-100°C/min. X-ray and differential thermal analyses were conducted to determine phase relations, transformation temperatures and enthalpies involving various alpha-decompositions. Three types of decomposition reactions were found to exist, depending on composition and cooling rate, that is; I: 2; II: L(2 + ); and III: L(' + )L('2 + ). In Types II and III, the undercooling and the lamellar spacing (
L) for the lamellar structure (L) were related to cooling rate and Al content. The ordering reaction in Type III, 2 took place at increasingly higher temperatures (with Al content) than the Type I extrapolation due to the compositional changes. Both Type I and II reactions are favored in low Al-content alloys; however, they (Type II in particular) could take place even in Ti-48Al. This and the other reactions will be analyzed in detail.
10:40 am
GRAIN REFINEMENT AND LAMELLAR FORMATION IN HOT-WORKED Ti-(42-47)Al-(0-0.5)B ALLOYS: Y-W. Kim, UES, Inc., 4401 Dayton-Xenia Rd., Dayton, OH 45432
Small amounts of boron additions are known to effectively refine the alpha grains in hot worked TiAl alloys when heat treated in the alpha field, resulting in the formation of fine lamellar colony microstructures. The boron additions raise significantly the critical cooling rate above which the formation of fully lamellar structures begins to be suppressed. Since this cooling rate allows the lamellar spacing to be controllable to a greater range, it is critical to understand the formation mechanism and kinetics of gamma laths in the presence of boron (in the form of borides). For this, annealing and cooling experiments and microstructural observations have been conducted on forged alloys of Ti-(42-47)Al-(0-0.5)B. DTA measurements are underway to detect the undercoolings before gamma precipitation in the alpha matrix as a function of cooling rate. The results will be presented and analyzed to explain the role of borides on the grain refinement, the formulation of gamma precipitates, and the retardation of nonlamellar microstructure formation.
11:00 am
THE 2 SHEAR TRANSFORMATION: P.M. Hazzledine, UES, Inc., 4401 Dayton-Xenia Rd. Dayton, OH 45432; B.K. Kad, Dept. of Applied Mechanics & Engineering Science, University of California-San Diego, La Jolla, CA 92093; V.K. Vasudevan, Dept. of Materials Science and Engineering, Univ. of Cincinnati, Cincinnati, OH 45221
When a hexagonal close packed crystal, with ideal c/ ratio, is sheared by Shockley dislocations on alternate basal planes the resulting crystal is face centered cubic. The six Shockley vectors generate cubic structures in two orientations which are twins of each other. When the DO19 structure is sheared by the same six Shockley vectors the result is three different 12H structures and their three twins. These 12H structures are composed of tetragonal unit cell building blocks, having axial ratios 1:1:/2. In this description, all of the {100} planes have alternate compositions Ti, TiAl and the unique c axes are in six different directions, one resulting from each of the six Shockley shears. The 'tetragonal' description of the structures is the same as the tetragonal structure L10 except that in L10 the {100} planes have alternate compositions Ti, Al. Thus, shearing the DO19 structure in one of the Shockley directions by 1/2:/2 creates a crystal structure which is as close to L10 as the composition allows. The six variants of gamma may therefore be formed from a single crystal of 2 by the operation of dislocations with the six available Shockley Burgers vectors so long as the composition may be corrected by diffusion.
11:20 am
A SYSTEMATIC STUDY OF THE ELECTRONIC STRUCTURE OF STABLE AND METASTABLE FORMS OF -TIAL: J.M.K. Wiezorek, X.D. Zhang, R. Banerjee, H.L. Fraser, Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43210
Numerous theoretical, first principle calculations studies have shown that the interatomic bonding in TiAl is a mixture of covalent and metallic. There is a need to complement these studies with experimental observations. Electron energy loss spectroscopy (EELS) is capable of providing electronic structure information through the near edge fine structure in core loss peaks, since these reflect the combined effects of bonding parameters such as charge transfer, hybridization, and variation of the crystal and ligand field. In this paper, EELS has been used to study the electronic structure of stable and metastable forms of -TiAl. The near-edge EELS signatures of the equilibrium phases at Ti-25at.%Al, Ti-75at.%Al and Ti-52at.%Al have been used to assess the suitability of this experimental method for the study of the electronic structure in -TiAl compounds. Metastable phases of -Ti-50at.%Al and 2-Ti-48at.%Al have been generated by very rapid quenching from the -phase field, and thin amorphous films of -Ti-48at.%Al have been deposited by magnetron sputtering. The near edge structure of these phases have been studied using a field emission TEM equipped with an imaging parallel EELS. Furthermore, results for 2-Ti-36at.%Al and -Ti-52at.%Al in binary lamellar TiAl are presented. The results of this study are discussed with a view to the mechanical behavior and the phase stability of -TiAl based compounds. This work has been supported by a grant from the National Science Foundation with Dr. Bruce MacDonald as program manager.
Room: 230C
Session Chairpersons: James C. Daley, Daley & Associates, 1020 W. Cactus Wren Drive, Phoenix, AZ 85021; John M. Rapkoch, Davy International, 2440 Camino Ramon, San Ramon, CA 94583
8:30 am
USE OF PVC AS A CHLORINATING AGENT IN THE RECYCLING OF METALS: F. Tailoka, D.J. Fray, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, United Kingdom
The standard free energy of formation of the oxides of the ferrous metals is generally more negative than that for the chlorides whilst the reverse is true for the equivalent compounds of the non-ferrous metals. As a source of chlorinating agent PVC has been used. PVC has the nominal formula C2H2HCI. On combustion in air, considerable heat is generated and hydrogen chloride, water vapor and carbon dioxide are evolved. It can be regarded as a free source of heat and a chlorinating agent if scrap PVC is used. In this work, this gas has successfully been used to separate zinc, lead and copper from residues such as Jarosite, EAF dust and waste materials containing copper. Dioxins were not detected either in the residues or the condensed chlorides.
8:55 am
RECOVERING MAGNESIUM FROM SOAPSTONE AND ASBESTOS TAILINGS: V.A. Leão, C.A. Silva, M.G. Menenzes, J.C. Pires, L.G. Macedo, School of Mines, Federal University of Ouro Preto, Praca Tiradentes, 20; Ouro Preto, MG, 35400-000, Brazil
Asbestos industry produces large amounts of serpentine (magnesium silicate) tailings. The effect of this on human health is well-known. Besides this, the processing of a Brazilian rock known as "Pedra sabão" (soap stone) generates powders that are discharged in the environment. This material is also a potential resource of magnesium. Magnesium oxide is used in many industries like refractory, waste water treatment, among others. The applicability of hydrochloric leaching for the recuperation of magnesium oxide from those materials has been investigated. The effect of time, temperature, particle size and solid/liquid ratio, on the leaching of magnesium and impurities, is discussed.
9:20 am
THE RECOVERY OF TELLURIUM FROM COPPER ANODE SLIME BY HYDRO-METALLURGICAL PROCESSES: K.-I. Rhee, C.-K. Lee, Korea Institute of Geology, Mining and Minerals, P.O. Box 14, Taejon, Korea 305-350; H.S. Kim, T.H. Kim, C.S. Yoo, H.J. Sohn, Y.-J. Kim, Dept of Mining & Petroleum Engrg., Seoul National University, 151-742 Seoul, Korea
The recovery of tellurium from pretreated copper anode slime was carried out by a series of hydrometallurgical processes. These include leaching of cemented Te at high temperature with oxygen purging in NaOH solution, precipitation of TeO2 from leach liquor, leaching of TeO2 in alkaline solution, precipitation of impurities by Na2S, and electrowinning of tellurium. The optimum conditions of each process were determined and discussed in terms of various parameters associated with each step to maximize the recovery and purity of tellurium.
9:45 am BREAK
10:00 am
PRODUCTION OF NON-FERROUS METALLIC CONCENTRATES FROM ELECTRONIC SCRAP: Jorge Alberto Soares Tenorio, Ricardo Perez Menett, Arthur Pinto Chaves, Department of Metallurgical and Materials Engineering, University of Sao Paulo, 05508-900, Sao Paulo, Brazil
Electronic components have metals with important valor like Au, Ag and Cu. These metals have a high performance in electric conductance. The recycling of scrap, however is too difficult because we have the presence of other metals like Fe, Al, Zn, Sn, more ceramics and plastics, all together in electronic components. This work had for subject define one way for physical separation. We have researched methods that obtained metallic concentrates non-ferrous. By the way we have used three types of scrap. We have used equipment of mineral processing. The metallic concentration make more easy the recuperation of metals because short the volume of material used. We have obtained, since of types studied an middle compassion of plastic, ceramic and metals.
10:25 am
DESIGN AND CONSTRUCTION OF A SMALL-SCALE USED BEVERAGE CAN RECYCLING UNIT: Jim S-J. Chen, Frederick Higgins, Joseph Vinch, James Kelly, Steven Smigiel, Center for Environmental Studies, College of Engineering, Temple University, Philadelphia, PA 19122
A small-scale recycling unit for used beverage cans is designed, constructed and tested. The unit consists of a rotary kiln for delacquering, a gas-fired furnace crucible for melting, a baghouse for pollution control and an air recirculating system for heat recovery and oxygen control. The delacquering kiln utilizes a counter flow thermal decoating process and the optimized operating condition was found to be at 1000°F, 6-7% O2 and a residence time of 15 minutes. In melting, a special salt mixture is made by combining cryolite and sodium chloride. The salt mixture has a low melting temperature (<1250°F) and is effective for demagging and degassing. The yield of the small-scale unit is about 90% and the energy efficiency matches those reported for large-scale facilities.
10:50 am
OPTIMIZATION OF SALT COMPOSITION IN THE RECYCLING OF ALUMINUM CANS: Jorge Alberto Soares Tenorio, Fabio Delgado, Department of Metallurgical and Materials Engineering, University of Sao Paulo, 05508-900, Sao Paulo, Brazil
During the melting processing of aluminum can scrap there is a considerable loss of metal due of metal trapping in the dross. Among all techniques available to recover this kind of scrap, the one using saline fluxes, based on NaCl / KCl equimolar composition and fluorides addition is outstanding. The investigation into the melting of AA3004 and AA5182 alloys (materials which the body and the lid of beverage cans are made of), the effect of delacquering, and the influence of different fluxes and the temperatures on the process yield are the main objectives of this work. Melting tests were carried out in order to access the effect of fluorides and the melting temperature on the recycling process yield. The fluoride efficiency for the temperature of 750°C was: CaF2 < NaF < Na3AlF6 < KF.
Room: 231C
Session Chairpersons: Donald M. Hausen, Consultant, Salt Lake City, UT; Leonard Harris, Consultant and Former General Manager, Minera Yanacocha, Peru
8:30 am
OPENING REMARKS: Donald M. Hausen, Program Organizer and 1997 Chairman of the TMS Process Mineralogy Committee
8:40 am
MINE GEOLOGY AND PROCESS ORE CONTROL AT NEWMONT MINES, CARLIN, NV: Joseph C. Rota, Newmont Exploration Ltd., 1700 Lincoln Street, Denver, CO 80203
The Carlin Trend, located in NE Nevada, has produced over 17 million ounces of gold from Newmont's open pit and underground operations since 1965. Oxidized portions of sediment-hosted disseminated submicron-sized native gold is mostly amenable to dump or heap leaching, yielding 50 to 70% recovery of contained gold. Metallurgical control and grade of heap leach ores are maintained by geological techniques and standard assays. Mine geologists provide field observation and mineralogic data by daily visual blasthole logging. Refractory components are separated from oxide to ensure high recovery. Geologic and assay data are combined to create mine polygons in an engineering computer database. Mining selectivity is thus enhanced by ore control geologists who make production decisions based on direct mineralogic observations at active mine faces.
9:05 am
BASIC CONCEPTS OF OXIDE GOLD DEPOSITS AND EXPLORATION STRATEGY: E. Daniel Baker, Senior Mineralogist, Newmont Metallurgical Services, 417 Wakara Way, Salt Lake City, UT 841O8
The term oxide gold deposits, refers to gold-bearing veins, faults, and shear zones that typically contain appreciable amounts of oxidized ore or gossanous material, resulting from oxidation of sulfides. The concept of oxide gold deposits underwent a dramatic change after the discovery of the Carlin gold mine in north central Nevada in early 196O's, and now implies large tonnage, low-grade bulk minable deposits that are processed by milling and/or heap leach methods. Oxide gold deposits may be classified into two types: (1) primary oxide ores derived directly from the effects of hydrothermal alteration on oxidized host rocks, and (2) secondary oxide ores derived from the epigenetic effects of circulating post mineral fluids oxidizing gold-bearing sulfides. Each type of oxide gold deposit has unique diagnostic mineralogic and metallurgical characteristics, that must be addressed in order to achieve a successful exploration strategy.
9:30 am
BLUE STAR SUBDISTRICT ZONED ALTERATION AND GOLD MINERALIZATION AND ITS INFLUENCE ON MINE OPERATIONS, CARLIN TREND, EUREKA COUNTY, NV: Cindy L. Williams, Newmont Exploration Ltd., Carlin NV 89822
Blue Star subdistrict open-pit gold deposits include multiple mines with 1.194 million ounces reserve and past production totalling 3.144 million ounces. The deposits are characterized by zoned alteration, including: 1) silicified core with erratic gold grade; 2) adjacent mill-grade (>0.04 oz/st) intense quartz-sericite-pyrite alteration; 3) enveloping heap-leach grades (0.006-0.04 oz/st) weaker sericite-kaolinite-quartz-pyrite alteration; 4) surrounding decarbonatized and intensely argillized waste and leach grade ore; 5) pervasively decarbonated waste; and 6) peripheral waste with local propylitic and weaker decarbonated alteration. Each alteration assemblage is characterized by distinct rock strength parameters that influences geotechnical pit slope design, as well as metallurgy and optimizing of drill/blast cycles. Alteration of barren assemblages extend hundreds of feet beyond orebodies.
9:55 am BREAK
10:05 am
GEOLOGY AND MINERALOGY RELATED TO HEAP LEACHING AT THE RAIN MINE, ELKO COUNTY, NV: Dean G. Heite, Newmont Exploration Ltd., Carlin NV 89822
Gold Mineralization at Rain is largely hosted by Mississippian Webb Formation consisting of interbedded siltstones and mudstones. The NW-striking SE-dipping Rain fault is a main feeder structure for the deposit. Five ore types based on XRD and visual rock chip logging were identified: argillaceous (>30% clays); siliceous (<20% barite; siliceous-baritic (20-40% barite); baritic (>40% barite); and calcareous (major carbonate minerals). The Rain heap-leach pad was commissioned in 1988, and to date 10.3 million tons of ore averaging 0.023 oz/st have been treated. Recovery to date through December 95 is approximately 56% for a total 132,453 ounces of gold produced. Two major factors have contributed to low leach recoveries at Rain: 1) excess argillaceous ore than expected on the pad, mostly late in the mine life, and 2) about half of the heaps were run-of-mine ore with no agglomeration. Testwork on leach grade composites indicated recoveries near 69% for material crushed to minus 1 1/5".
10:30 am
GEOLOGY OF THE TUSC GOLD DEPOSIT, EUREKA COUNTY, NV: Paul O. Malan and Leroy Schutz, Newmont Exploration Ltd., Carlin NV 89822
The Tusc gold deposit, located 8 miles NW of Carlin, Nevada, along the Carlin trend, is one of several structurally controlled gold deposits associated with the Good Hope fault within the Maggie Creek Subdistrict. Mining commenced in 1994 with an oxide reserve of 780,000 ounces of gold averaging 0.039 opt Au. The Good Hope Fault forms the SW edge of the Schroeder Mountain uplift (Carlin Window) and juxtaposes carbonate rocks of the Roberts Mountains Formation against siliceous mudstone, chert and siltstone of the Rodeo Creek Unit. Submicroscopic gold is disseminated in the shear zones of the Good Hope fault system and in crosscutting northeast-striking, high-angle faults in the lower plate carbonates in the immediate hanging wall. Wallrock alteration includes argillization, decalcification, silicification, and alunite veining, supergene leaching and oxidation. Arsenic forms a strong halo around the ore and an antimony anomaly occurs in the upper part of the deposit.
10:55 am
MULTI-METAL RECOVERABLE RESERVE ESTIMATES AND WHITTLE PIT OPTIMIZATION OF MILL AND HEAP LEACHABLE GRADE ORES AT THE MCCOY BLACK COVE MINE, NV: Songlin Zhang, Mining Engineer, Echo Bay Minerals Company, McCoy/Cove Mine, #1 McCoy Mine Rd., Battle Mountain, NV 89820
The McCoy/Cove mine, located in Eureka-Battle Mountain trend of Nevada, is a gold and silver deposit. Case studies of recoverable reserve estimation for gold and silver were made using multiple indicator kriging and volume variance correction. The grade tonnage distributions of recoverable reserves were constructed and compared with the distributions defined by blast hole assays. Optimal pits were generated by Whittle 4D pit optimization package to analyze the impact of different processing recoveries at different economic cutoffs. The results were compared with ordinary kriging. The study indicates that the proposed method for multi-mineral recoverable reserve estimation is more accurate than kriging in terms of grade and tonnage. The method of using recoverable reserves for pit optimization will maximize global reserve recovery and revenue, and is more efficient than condition simulation regarding computing power.
Room: 315A
Session Chairpersons: Gye-Won Hong, Superconductivity Research Laboratory, KAERI, Taejeon, Korea; P. Haldar, Intermagnetics General Corp., Latham, NY
8:30 am INVITED
POWER APPLICATIONS OF HIGH TEMPERATURE SUPERCONDUCTORS: P. Haldar, M.S. Walker, D.W. Hazelton, J.G. Hoehn, Jr., Intermagnetics General Corporation, Latham, NY 12208
Intermagnetics has concentrated on manufacturing long lengths of silver sheathed Bi-2223 and surface coated Bi-2212 HTS conductor. Development work has led to the successful manufacture of Bi-2223 multifilament conductor in lengths exceeding 1 km, with properties useful for most electric power applications. Surface coated, low cost, Bi-2212 conductor in lengths over 400 meters are now also being produced. Several lengths of high performance tapes have already been delivered to GE to wind the first HTS generator coil. The coils were successfully tested in a steady state, conduction cooled environment generating 40,000 amp-turns at 23.5 K. Novel and unique hybrid magnet designs are being designed and built with the availability of both Bi-2212 and Bi-2223 HTS conductors. The demonstration and test of a pre-prototype 1 MVA transformer utilizing HTS windings is planned in collaboration with ORNL, Waukesha Electric, and RG&E. The development of the largest HTS coils is continuing, for the construction of a 15 KV fault current limiter as part of the DOE-SPI program with Lockheed Martin, Southern California Edison, and LANL. Several high amp-turn coils have also been fabricated and delivered to the U.S. Navy to demonstrate a high horse power HTS homopolar motor. These demonstrations indicate the rapid progress being made to develop commercial applications of high-temperature superconductors.
8:50 am INVITED
CONTROLLED PRECIPITATION OF SECOND PHASES IN (Bi,Pb)2223 CERAMICS AND ITS INFLUENCE ON THE PINNING: P. Majewski, S. Kaesche, A. Sotelo, F. Aldlinger, Max-Planck-Institut für Metallforschung, Pulvermetallurgisches Laboratorium, Heisenbergstr. 5, D-70569 Stuttgart
Taking the temperature dependent Pb solubility of (Bi,Pb)2+xSr2Ca2Cu2O10+d [(Bi,Pb)2223] into account, it is possible to precipitate various second phases in single phase (Bi,Pb)2223 ceramics at temperatures below 840°C, i.e., Pb4Sr5CuO10, Ca2CuO3, CuO and Bi2Sr2CaCu2O8 (Bi2212). At 800°C, the kinetic of the formation is fast resulting in mm-sized second phase precipitates after about 6 h. The Jc of the samples increases with precipitation, indicating increased pinning properties of the ceramics. After a maximum increase of Jc at about 3 h, Jc decreases again.
9:10 am INVITED
EFFECT OF LEAD CONTENT ON PHASE EVOLUTION AND MICROSTRUCTURAL DEVELOPMENT IN Ag-CLAD Bi-2223 COMPOSITE CONDUCTORS: N.N. Merchant, V.A. Maroni, A.K. Fischer, S.E. Dorris, W. Zhong, N. Ashcom, Argonne National Laboratory, Argonne, IL 60439
Silver-sheathed monofilamentary Bi1.8PbxSr1.98Ca1.97Cu3.08Oy (Bi-2223) tapes prepared by a two powder process that used powder containing varying lead contents, x, from 0.2 to 0.5 were subjected to thermomechanical processing and then characterized by XRD, SEM and EDX. Texture was studied using image analysis software on scanned SEM images. It was found that tapes with low lead content (0.20 and 0.25) showed incomplete conversion to Bi-2223, had small grain size, and poor c-axis texture. Tapes having higher lead content (0.4 and 0.5) also showed incomplete conversion and the presence of lead-rich secondary phases. Tapes with lead contents of 0.30 and 0.35 showed complete conversion to Bi-2223, had the least amount of secondary phases, showed best c-axis texture, and had the highest Jc. The carbon content of the precursor powder also had a strong influence on secondary phase chemistry. Work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, as part of a DOE program to develop electric power technology, under Contract W-31-109-Eng-38.
9:30 am INVITED
EFFECT OF PARTICLE SIZE REDUCTION ON THE MICROSTRUCTURE EVOLUTION AND CRITICAL CURRENT DENSITY OF Ag/Bi-2223 TAPES: Weon-Ju Kim, Jae-Keun You, Ho Jin Lee, Hee-Gyoun Lee, Gye-Won Hong, Superconductivity Research Laboratory, Korea Atomic Energy Research Institute, P.O. Box 105, Taejon 305-600, Korea
The effects of the particle size of precursor powder on the microstructure and Jc of Ag-sheathed Bi-2223 tapes were investigated. The calcined powder with overall composition of Bi1.89Pb0.41Sr2.01Ca2.23Oy was milled for various times using planetary ball mill. The transport property of the tapes was found to depend strongly on the particle size of the precursor powder. Enhanced reactivity of the milled powder facilitated the formation of 2223 phase and resulted in an increase of Jc. Excessive milling, however, led to the amorphisation of the powder and degraded the electrical property of the tapes.
9:50 am
EFFECTIVE FABRICATION PRACTICES FOR Ag-SHEATHED SUPERCONDUCTOR: D.-W. Yuan, M. J. Pollock, J. Kajuch, Concurrent Technologies Corporation, Johnstown, PA 15904
The powder-in-tube (PIT) process has been widely used to fabricate long lengths of superconducting wires and tapes. However, problems associated with irregularly shaped cross sections resulting from the metalworking process have been identified and need to be addressed. In this investigation, Ag-clad Bi2Sr2CaCu2O8 superconductors were formed by using different wire drawing and tape rolling practices. The effects of annealing and drawing direction on geometric characteristics of the round wires were determined. Also, the impact of reduction in thickness per pass and roll configuration on the properties of the tapes was investigated. The study shows that geometrical uniformity and core dimensional stability are strongly influenced by the rolling parameters chosen. A combination of small roll diameter and small reduction per pass reduces dimensional variations. This practice also leads to higher critical current densities at cryogenic temperatures in the resulting superconducting tapes. Recommendations for optimum fabrication schemes for wires and tapes are presented.
10:10 am BREAK
10:20 am
FABRICATION OF TUBULAR SUPERCONDUCTOR STRUCTURES: J.F. Bingert, T.G. Holesinger, B.L. Bingham, D.A. Korzekwa, MST-6, LosAlamos National Laboratory, Los Alamos, NM 87545
A tubular architecture provides many potential attributes when applied to bulk superconductor structures. These include enhanced structural stability compared to wires and tapes, and isotropic field dependence transverse to the conductorís long axis. At the same time, virtues associated with traditional OPIT processing may be preserved, such as a thin, dense HTSC layer with basal-plane texture. In this study, candidate deformation processing routes for tubular composite conductors were investigated in order to determine their potential to produce desired structures and properties. These processes included tube drawing, tube ironing, and hydrostatic extrusion. For tube drawing and ironing, an HTSC precursor form was isostatically pressed over a mandrel, while the hydrostatic extrusion billet was manually loaded with powder. The as-deformed and sintered tubes were characterized for geometric uniformity, density, texture, and transport properties. An analysis of the relative stress states encountered during tube processing compared with rolling will also be presented.
10:40 am INVITED
MECHANICAL DEFORMATION AND INHOMOGENEITY OF BiSrCaCuO/Ag COMPOSITES: Z. Han and T. Freltoft, NKT Research Center A/S, Sognevej 11, DK-2605, Brøndby, Denmark
The mechanical deformation of BiSrCaCuO/Ag composites is generally an inhomogeneous process. Inadequate control of the deformation process results in sausaging and cracking, degrading the superconducting properties of the composite and reducing its mechanical strength. In this paper, we will apply our model of "powder flow" to describe the mechanical deformation process of BiSrCaCuO/Ag composites wires and tapes. Furthermore, results from experiments using a new deformation method "semi-continuous pressing" will be presented. By this method, it is possible to produce superconducting tapes with better homogeneity than obtained by conventional rolling. The influence of mechanical deformation on the strength of the tape, especially the bending strength, will also be discussed.
11:00 am INVITED
HIGH TEMPERATURE SUPERCONDUCTOR DEVELOPMENT AT TOSHIBA: HIGH TENSILE STRENGTH AgMg(Ni) SHEATHED Bi-2223 CONDUCTOR AND COILS: Y. Yamada, K. Yamamoto, K. Tasaki, H. Onoda, O. Horigami, Toshiba R&D Center, 4-1, Ukishima-Cho, Kawasaki, 210 Japan; T. Koizumi, T. Hasegawa, Showa Electric Wire and Cable Co., Ltd., 2-1-1, Odaskae, Kawasaki 210, Japan; T. Kiyoshi, K. Inoue, National Research Institute for Metals, 1-2-1, Sengen, Tukuba, Ibaraki 305, Japan
Recent activity of high temperature superconductors and its application at Toshiba will be presented. We have been developing high tensile strength conductor using AgMg(Ni) sheath material. Short samples exhibited 200 MPa of 0.2% yield strength which was 4 times to 10 times higher than that of the conventional Ag-sheathed conductor and also higher than the Nb8Sn conductor. Recently the high tensile strength conductor 100 m long was successfully fabricated and wound for the energizing test at 21 Tesla back up filed. The coil was successfully excited without any degradation. We have been also studying the effect of sausaging on critical current density. The sausaging started to occur clearly when the Vickers hardness of the oxide core was higher than that of Ag sheath. This implies that the harder sheath materials such as AgMg sheath may suppress the sausaging and improve critical current density.
11:20 am
RECENT DEVELOPMENTS IN THE FABRICATION OF HIGH-Jc Ag-CLAD (Bi,Pb)2Sr2Ca2Cu3Oy CONDUCTORS: U. Balachandran, A.N. Iyer, Energy Technology Division, Argonne National Laboratory, Argonne, IL 60439; M. Lelovic, T. Deis, N.G. Eror, Dept. of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261; P. Haldar, Intermagnetics General Corp., Latham, NY 12110
We have resolved the issue of current distribution inside Ag-clad (Bi,Pb)2Sr2Ca2Cu3Oy (Bi-2223) superconductor tapes by showing that the region of high critical current density (Jc) is next to the Ag sheath. In this talk, we report a Jc value >105 A/cm2 at 77 K in a self-field in Bi-2223 tapes made by the Ag-wire-in-tube method, in which a silver wire was introduced into the Ag tube. The Ag wire extended along the entire length of the tape. At 77 K and in self-field, a maximum Jc of 2 x 105 A/cm2 (critical current, Ic, = 22 A) was measured after three pressing cycles. Recently, we analyzed the transport current properties of Ag-clad Bi-2223 tapes as a function of cooling rate. A comparison between furnace-cooled and slow-cooled tapes showed that the slow-cooled tapes reached Ic values two or three times higher than those of the furnace-cooled tapes. Based on our observations, a cooling schedule that includes several intermediate cooling steps is suggested and will be discussed in this talk. Work at ANL and part of the work at IGC is supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, as part of a DOE program to develop electric power technology, under Contract W-31-109-Eng-38.
11:40 am INVITED
DEVELOPMENT OF HTS-POWER TRANSMISSION CABLES AND RESISTIVE FAULT CURRENT LIMITERS: H.-W. Neumüller, Siemens AG, Corporate Research and Development, P.O. Box 3220, D-91050 Erlangen, FRG
Our long-term joint project covers both the development of HTS conductors and the realization of junction models demonstrating the feasibility of future prototypes. Multifilament 2223 BPSCCO tapes are reproducibly produced having jc-s up to 30 kA/cm2 for short samples and jc 
20 kA/cm2 for lengths 110 m. In a first step two layer 10 m cable dfunction model was machine wound, which showed a current capacity of 1100 A. No degradation was found under bending tests down to bending radii of 1 m. The switching elements for resistive fault current limiters consist of ceramic plates with meander shaped YBCO coatings. Two ways are investigated: both polycrystalline YSZ substrates coated by biaxially in plane oriented IBAD YSZ buffer layers (pc) and single crystal sapphire substrates (sc). 10x10 cm2 pc switching elements have been produced up to a switching power of 1500 VA (jc=60 kA/cm2). Improvements of the large scale IBAD-deposition raised jc above 105 A/cm2, small samples (1x1 cm2) attained jc=1 MA/cm2, 10x10 cm2 pc- or alternatively ø sc switching elements are the basis of the proposed 100 kVA function model.
Room: 231B
Session Chairperson: M.F.X. Gigliotti, GE Corporate Research and Development, P.O. Box 8, Schenectady, NY 12301
8:30 am INVITED
ELEVATED TEMPERATURE MECHANICAL PROPERTIES OF THE NEAR- TITANIUM ALLOY TIMETAL 1100: J. Lindemann, A. Styczynski, L. Wagner, Technical University of Brandenburg at Cottbus, 03013 Cottbus, Germany
Fully lamellar with fine (150 m) and coarse (500 m) prior B grain sizes as well as duplex structures with p volume fractions of 20 and 60% (15 m p size) were prepared in TIMETAL 1100 by thermomechanical processing. Tensile behavior and HCF properties at R=-1 and R=0.1 were evaluated at ambient and elevated (600°C) were performed at nominal stresses of 210 and 300 MPa. The fine grained fully lamellar microstructure combines the advantages of the B annealed structures (excellent creep resistance) and duplex structures (high tensile ductility) without suffering from the disadvantages of the duplex structures, i.e., anomalous mean stress sensitivity of the fatigue strength and poor creep strength. Both properties are related to the presence of the p phase. The fatigue and creep results on the various microstructures will be interpreted in terms of phase morphologies, crystallographic textures and particular deformation mechanisms.
9:00 am
PRIMARY AND ANELATIC CREEP BEHVIOUR OF A HIGH TEMPERATURE NEAR -Ti-ALLOY: M. Es-Souni, Fachhochschule Kiel, Institute of Materials Technology, Legienstr. 25, Kiel 24103, Germany
The creep behavior of a high temperature near alloy Ti 6242 Si has been investigated in the stress range from 160 to 350 MPa and a temperature range from 500 to 600°C, using constant stress tensile creep experiments. Emphasis has been put on primary and anelastic creep behavior and their dependencies on stress, strain and processes microstructures. It is shown that both primary and anelastic creep strongly depend on creep strain and applied stress. Increasing stress and/or strain results in higher primary and anelastic creep strains. Furthermore, ß-heat treated specimens with a fully transformed ß-microstructure show reduced amounts of primary and anelastic creep strains, in comparison to +ß heat treated specimens with globular -grains and variable amounts of +ß mixture. The results obtained show also very similar kinetics of primary creep build up and strain recovery and suggest similar deformation mechanisms. Based on TEM investigations of dislocation structures of crept specimens, the results are discussed with respect to different mechanisms of dislocation motion under the effect of internal stress.
9:20 am
MINIMIZING BETA FLECKS IN THE Ti-17 ALLOY: C.E. Shamblen, GE Aircraft Engines, One Neumann Way, MD M85, Cincinnati, OH 45215-6301
Normal liquid to solid partitioning of Cr during ingot solidification for the Ti-17 alloy can result in the formation of a segregation anomaly called ß flecks. These ß flecks can exhibit a significantly lower ß transus than the alloy; they may also present mechanical property issues. While the major thrust toward minimizing ß flecks is through melt process control, this paper addresses the capability of reducing the extent of Cr segregation using a high temperature ß field homogenization heat treatment. The interdiffusion coefficients for Cr in ß phase Ti-17 were determined and used in diffusion equations to calculate the rate of dissipation of the segregated regions. Correlation is shown for the calculated, and critical experiment demonstrated, increase in the ß fleck ß transus temperature with the time and temperature of these homogenization heat treatments.
9:40 am
ANISOTROPIC BIAXIAL CREEP OF TEXTURED Cp-Ti TUBING: K. Linga Murty, Ratnaji R. Kola*, North Carolina State University, Box 7909, Raleigh, NC 27695-7909;*now with AT&T Laboratories, Murray Hill, NJ
Biaxial creep behavior of thin-walled tubing of cold-worked stress-relieved cp-titanium alloy was investigated using internal pressurization superimposed with axial load at ??? K. Creep anisotropy was characterized in terms of a creep locus at a constant energy dissipation with power-law dependencies of the component (hoop and axial) strain-rates under varied stress ratios. The experimental results were fit to the modified Hill's equation with anisotropy parameters, R and P which are also the contractile strain (rate) ratios. The crystallographic texture of the tubing was characterized through inverse and direct pole figures from which the crystallite orientation distribution functions (CODF) were derived. The CODF was combined with plasticity model based on power-law stress dependence of the strain-rate and dominance of basal prism and pyramidal slip systems were considered. In contrast to the recrystallized materials, experimental results deviated from the prism-model predictions albeit the deformed microstructures revealed only prism dislocations. These differences are attributed to the grain-shape anisotropy due to cold-work. Quantitative analyses of the superimposed effects of grain shape anisotropy due to cold-work. Quantitative analyses of the superimposed effects of grain shape anisotropy on grain orientation anisotropy (texture) are underway and the results to-date will be presented. This work supported by the National Science Foundation.
10:00 am BREAK
10:20 am
MICROSTRUCTURAL STABILITY OF A HIGH TEMPERATURE -
Ti ALLOY: X.D. Zhang, J.M.K. Wiezorek, D.J. Evans and H.L. Fraser; Department of Materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, OH 43210; Materials Directorate, Wright Laboratory,. WL/MLLM, Wright Patterson AFB, OH 45433
The microstructural development of Ti-6Al-2Mo-2Cr-2Sn-2Zr-0.2Si(Ti-6-22-22S) alloy after various heat treatments has been examined by optical microscopy, scanning electron microscopy (SEM), conventional transmission electron microscopy (CTEM) and high resolution electron microscopy (HREM), coupled with high spatial resolution microanalysis. Partitioning of alloying elements and the precipitation of intermetallics as a function of heat treatment are the main issues addressed in this paper. Titanium silicide, athermal 
and ordered 2 precipitates have been observed in the and the phase respectively. The compositional homogeneity has been studied in terms of alloying element distributions in the and the phase after different heat treatments. Similar investigations for Ti-6-4 alloy are used as a benchmark for comparison. The significance of these observations will be discussed in view of the fundamental understanding and further control of the structural stability of these type of - Ti alloys.
10:40 am
INFLUENCE OF ENVIRONMENT ON THE FATIGUE CRACK PROPAGATION BEHAVIOR AT ELEVATED TEMPERATURE OF THE Ti-ALLOY IMI 834: O. Schauerte,, A. Gysler, G. Lutjering, Technical University Hamburg-Harburg, 21071 Hamburg, Germany; S. Lesterlin, J. Petit, E.N.S.M.A., 86960 Futuroscope Cedex, France
The fatigue crack propagation behavior of the high-temperature Ti-alloy IMI 834 was investigated at a test temperature of 500°C under different environmental conditions: vacuum, laboratory air, and Ar=50% relative humidity. Two different microstructures were compared, a pure lamellar and a bi-modal structure, consisting of 20% equiaxed primary a phase in a lamellar matrix. Crack propagation tests were carried out on CT-specimens under constant amplitude sinusoidal loading conditions with a frequency of 30 Hz at R=0.1 and R=0.6. The results showed for example, that at R=0.6 fatigue crack propagation for both microstructures occurred at much lower near threshold 
K- values (4 MPa-m1/2) in the two aggressive environments (air, humid Ar) as compared to those measured in vacuum (10 MPa-m1/2). Furthermore, in an intermediate K-regime (6 to 12 MPa-m1/2) the da/dN-K curves in the aggressive environments exhibited a plateau region with a nearly constant crack propagation rate of about 5x10-8m/cycle. At high growth rates these curves approached those measured in vacuum. The results will be discussed on the basis of fracture surface studies (e.g. cleavage-like features found in the aggressive environments in comparison to a ductile fracture mode in vacuum), through thickness crack front profile analysis, and crack closure measurements.
11:00 am
OXIDATION RESISTANT COATINGS FOR THE O-PHASE: T.J. Jewett, Department of Materials Science and Engineering, SUNY-Stony Brook, Stony Brook, NY 11794-2275
Following the discovery of improved oxidation resistance of Ti-Al-based alloys containing second phase precipitates of Al-rich Ti(Cr,Al)2, a similar approach was suggested for the o-phase. A schematic representation of the Ti-Al-Cr-Nb quaternary system was constructed at 800°C. Subsequently, five alloys, based on the Ti-Al-Cr-Nb quaternary system were prepared in order to probe the phase equilibria between the corresponding Ti2AlX compositions of the Ti-Al-Nb and Ti-Al-Cr ternary systems. The samples were homogenized above the beta-transus then heat treated at 800°C. The resulting phase equilibria and microstructure were evaluated. Additionally, cyclic oxidation studies, at 800 and 900°C were conducted on the heat treated samples to assess their oxidation resistance. Similar behavior for the alloys was observed at 800°C, however, at 900°C the Cr rich alloys experienced significant spalling.
11:20 am
OXIDATION BEHAVIOR OF TERNARY Ti3Al-Nb ALLOY: R.G. Reddy, Yang Li, Department of Metallurgical and Materials Engineering, University of Alabama, P.O. Box 870202, Tuscaloosa, AL 35487-0202
The oxidation behavior of ternary Ti3Al-Nb alloy has been studied in pure oxygen over the temperature range of 750°C to 1100°C. The experiments were carried out using TGA. The oxidation products were analyzed using X-ray diffraction, SEM and EDS. Parabolic rate constants were calculated. An effective activation energy of 268 KJ/mol was deduced. The oxidation products formed are non-continuous protective scale on Ti3Al-Nb alloys. The results showed that oxidation products were mainly a mixture of TiO2 (rutile) and Al2O3 (alumina). For oxidation scale at 1100°C, it exhibited a layered scale of alternate rutile and alumina. The present results were also compared with that of binary Ti3Al.
Room: Salon 6
Location: Clarion Plaza Hotel
Session Chairs: Gordon Irons, Dept. Matls Sci. and Eng., McMaster University, 1280 Main St West, Hamilton, Ontario L8S 4L7; John Pusateri, Technical Center, Horsehead Resource Dev., 300 Frankfort Road, Monaca, PA 15061
8:30 am
AN OVERVIEW OF THE INJECTION OF POWDERS AND DUSTS INTO MOLTEN METALS: Gordon A. Irons, Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 Canada
The science and technology of powder injection has evolved from its start in the desulphurization of iron over 20 years ago. The inherent advantages of powder injection are: rapid reaction rate, good mixing, the ability to handle fine materials, flexibility and low capital cost. The fundamental engineering science related to the fluid mechanics of injection, and the associated thermodynamics and kinetics of the processes will be reviewed. Due to the above advantages, this technology is finding application in the recycling of in-plant dusts and other secondary materials, and in the non-ferrous industry. Some of these developments will be highlighted.
9:15 am
IMPROVING NON-FERROUS METAL CONTROL THROUGH AUTOMATED POWDER INJECTION: R. J. Liguori, VanDeMark Metals and Alloys, Inc., One North Transit Road, Lockport, NY 14094; D.W. Hoyle, Hickman, Williams, and Company, Technicarb Division, 40 Port Avenue, P.O. Box 872, Monroe, MI 48161
This paper describes results obtained from a new and patented control process designed to automate powdered additions via subsurface injection into a molten metal furnace. The process automatically receives spectrometer data, compares it to targeted values and accordingly calculates, weighs and pneumatically feeds the additives into the metal furnace by subsurface powder injection. Current installation and trials indicate alloy savings and improved metal control. Results of injection with many different powders injected in industrial applications are discussed.
9:45 am
FLASH CONVERTING OF MK (CHALCOCITE) CONCENTRATE--AN OVERVIEW: G.J. Morgan, A.A. Shook, J.K. Brimacombe, and G.G. Richards; The Centre for Metallurgical Process Engineering, The University of British Columbia, Vancouver, BC Canada V6T 1Z4; New Technology Development, BHP Steel, Wollongong NSW, Australia 2526; Cominco Research, Trail, BC Canada V1R 4L8
Flash converting of MK concentrate (Cu2S) was considered as an option for the process flowsheet modifications at Inco's Copper Cliff operations. The flash converting of chalcocite was known to have problems, such as the generation of large amounts of dust, so a comprehensive research program was undertaken at the Centre for Metallurgical Process Engineering, University of British Columbia to examine the process. This paper is a compilation of the results of the project, some of which have been published elsewhere. The mechanism and kinetics of the combustion of individual particles of MK were determined, and dust generation criteria were established. The flash converting flame was mathematically simulated, and dust generation regions within the flame were identified. Pilot plant trials were conducted, confirming that the dust generation rate could be affected (reduced) by altering the burner configuration, and thus the flame characteristics.
10:15 am BREAK
10:30 am
DENSE PHASE PNEUMATIC INJECTION FOR FINE MATERIALS: Robert G. Goffin, Paul Wurth Ltd., 3310 South Service Road, Burlington, Ontario L7N 3M6, Canada
Pneumatic injection of various fine materials such as metallic concentrates, fluxes and fuels into pyrometallurgical vessels has become an important practice. Injection is an evolutionary step from pneumatic conveying - the receiving vessel is now a metallurgical process unit instead of a storage unit. Proper injection system design must integrate conveying, injection, metallurgical process and physical constraints, as well as the limitations of specific material characteristics. Dilute phase pneumatic conveying requires large quantities of conveying gas in order to move material. Load ratios in the order of 10:1 (weight of solid gas:weight of conveying gas) are typical. In order to eliminate the problems associated with dilute phase (including extreme pipeline and component abrasion, excess conveying gas, etc.) steady development has been made in the application of dense phase (load ratios substantially higher than 25:1) pneumatic conveying and injection technology. Load ratio selection is dependent upon many factors including specific material characteristics and system requirements. This paper will outline the advantages of dense phase pneumatic injection technology and will present successful and reliable pyrometallurgical applications.
11:00 am
COAL PARTICLE INJECTION AND DEVOLATILISATION UNDER RAPID HEATING CONDITIONS: J. Beeson, V. Sahajwalla, G. Belton, School of Materials Science and Engineering, University of New South Wales, Sydney, Australia; BHP Research, Newcastle Laboratories, Newcastle, Australia
New developments in the metallurgical industry, such as iron bath smelting processes and pulverised coal injection into blast furnaces involve coal injection and devolatilisation under rapid heating conditions. These new technologies employ coal particle heating rates around 104°C/sec. Under these conditions the volatile matter released cannot be established from standard analysis and this can have a significant effect on the process. For example the volatile matter released, which is in excess of that from standard analysis, may lead to excess gas in the top space of a bath smelter. When the efficiency of the reactor relies on a fine balance of post combustion reactions, the increase in release of volatile matter may lead to a decrease in the efficiency of the reactor. In pulverised coal injection to blast furnaces, the amount of volatiles released, and the time taken for this release, influences the combustion behaviour of the coal and char. In this study, the injection and devolatilisation of three size fractions of various coals into a drop tube furnace was investigated. The surface mean diameters of each size fraction were 92µm, 121µm, and 172µm. Four coal types were investigated, sub-bituminous, bituminous, semi-anthracite and an anthracite. These were injected at temperatures of 1000°C, 1200°C, and 1400°C. The ash content and volatile matter remaining in each of the chars was determined in order to calculate the volatile yield using the ash tracer method and the rate of volatiles release. An apparent activation energy for the release of volatiles was calculated. The results show a strong dependence of the activation energy for volatile release on coal crystallite size, as determined by X-ray diffraction. Hence the crystallite size could be an important characteristic of coals that is significant for coal selection for the new technologies in the metallurgical industry.
11:30 am
PREDICTION AND MEASUREMENT OF THE TIME-AVERAGED VELOCITIES OF INERT PARTICLES SUSPENDED IN GAS-STIRRED LIQUID BATHS: H. Pham, D.E. Langberg, M. Nilmani, G.K. Williams Cooperative Research Centre for Extractive Metallurgy, University of Melbourne, Parkville, Victoria 3052 Australia
The Digital Particle Image Velocimetry (DPIV) technique was used to measure the instantaneous velocity distribution of polyvinyl chloride particles suspended in an upright cylindrical water bath (0.218 m diameter) agitated by injection of air through a top-submerged centric lance. The time-averaged particle velocity and kinetic energy distributions were obtained from the instantaneous velocity data. The effects of gas flowrate (3.3 10-5 - 5 10-5 Nm3/s), liquid depth (0.164-0.196 m), fractional lance submergence (60-90%), and particle diameter (50-80 µm) were investigated. The magnitudes of the particle velocities and kinetic energies increased with increasing gas injection rate, and increasing lance submergence. Variation of the liquid depth had minimal influence on the particle behaviour under the conditions studied. Steady state liquid phase flowfield simulations using a commercial Computational Fluid Dynamics package were combined with a dynamic force balance on individual suspended particles to predict the time-averaged particle velocities. Satisfactory agreement was found between the predicted and measured particle velocities, outside the bubble plume region. The particle velocities were integrated with time to predict the trajectories and residence times of particles introduced into the flowfield at different positions. Particles introduced near the plume region were predicted to have much shorter residence times than particles released near the primary recirculation vortex.
Room 232C
Session Chairperson: Dr. Boris D. Bryskin, R & D Manager, Rhenium Alloys, Inc., P.O. Box 245, Elyria, OH 44036
8:30 am
WELCOME AND OPENING REMARKS: Prof. Dr. Maria A. Tylkina, Baikov Institute of Metallurgy, Russian Academy of Sciences, Moscow, Russia
Additional speakers names to be announced later.
9:20 am
RHENIUM SEVENTY YEARS OLD: Fathi Habashi, Department of Mining and Metallurgy, Laval University, Quebec City, Canada, GIK 7P4
Rhenium was discovered in Berlin in 1925 by Ida Tacke, Walter Noddack, and Otto Berg. It was isolated in milligram amounts by Ida Noddack (born Tacke) in 1926. The first 100 kg of the metal were produced seventy years ago from carbonaceous copper shist ore (Kupferschiefer) from the Mansfeld District in Germany. The process was so complicated and the price so high that production was discontinued until early 1950 when tungstenrhenium and molybdenumrhenium alloys were prepared. These alloys found important applications in industry that resulted in a great demand for the metal produced from the molybdenite fraction of porphyry copper ores. The early story of rhenium will be told from personal interviews with Ida Noddack (18961978).
9:45 am
RHENIUM BACKGROUND AND MARKETS: Tom A. Millensifer, Powmet, Inc., 2625 Sewell St., P.O. Box 5086, Rockford, IL 61125
Rhenium existed as a curiosity with little practical application for it's first nearly 50 years. Use was limited to a few specialty and high temperature alloy applications. In the early 1960's interest in the potential for catalytic use of Rhenium developed and by the early 1970's significant catalytic use had begun. Greater production was required. Leading development of production technology in the Western World was Kennecott Copper Corporation which originated industrial scale recovery techniques. In 1963 Shattuck Chemical in Denver, Colorado installed recovery facilities based on Kennecott's technology. The facilities were followed by recovery at Starck in Germany and Molycorp in Chili. In 1980 Duval Corporation, a subsidiary of Pennzoil, installed recovery facilities and began recovery in mid 1981. Today recovery from Molybdenite exists in the Western World in only three places with one other available but not operating at this time. Recovery from Copper is reported in Japan and Kazakhstan, and also from Copper Smelting in Jianxi Province China as well as at several Molybdenum Roaters in Russian and other areas of the CIS.
10:10 am INVITED
MILL PRODUCTS AND FABRICATED COMPONENTS IN RHENIUM METAL AND RHENIUM RICH ALLOYS: Jan-C. Carlén, Rhenium Alloys, Inc., P.O. Box 245, Elyria, OH 44036
For a metal which is produced in quantities around 50 tons per year worldwide, it should be difficult to talk about bulk usage. However, about 90% of the rhenium produced is used for catalysts and as an alloying element in nickelcobaltbase superalloys. This paper deals with mill products based on powder metallurgy production of rhenium and molybdenumrhenium and tungstenrhenium alloys. Rhenium is a metal which workhardens very quickly in coldworking and which cannot be hotworked because of hotshortness and poor oxidation resistance. This makes plastic forming of rhenium a very delicate process. Rhenium cannot be machined using conventional methods but other means of making complicated shapes have been developed. Alloys between rhenium and tungsten and rhenium and molybdenum have their best properties at or close to the solubility limit for rhenium in each metal, which may create problems with formation of a brittle, intermetallic phase (sigma phase). However, these alloys are much easier to form using plastic hot and cold forming. They can also be formed into various shapes using regular machining methods. Means of avoiding or eliminating the negative effect of sigma phase are briefly discussed. Finally the industrial usage of mill products and assintered products of rhenium and its alloys with molybdenum and tungsten is discussed. These materials have found many challenging applications in space, defense, electronic, energy, scientific instruments and other hightech industries.
10:35 am
THE PERSPECTIVES FOR DEVELOPMENT OF RHENIUM PRODUCTION IN RUSSIA: Albert D. Besser, A.V. Peredereev, State Research Center of Russia, 13 Acad. Korolyov Street, 129515 Moscow, Russia
The rhenium's production base in Russia is based on the processing of the concentrates of the effective tungsten-molybdenum mines (Zhirkenskyi, Sorskyi, Tyrnyauzskyi) and opening up of the new ones (Bugdainskyi, Aksukskyi and others), as well as on the recovery of rhenium from the gases during the burning of the shales. The substantial content of rhenium and of some other rare components in the volcanic slags has been revealed. The extraction technology has been developed. The processing technology of the secondary rhenium-containing raw materials and of the intermediate products has been developed and realized in the industrial conditions. The technologies concerning the extraction of more than 90% of rhenium from the molybdenite concentrates following the pyro- and hydrometallurgical processes have been developed and are ready now for the industrial realization.
Room: 330A
Session Chairperson: Eui W. Lee, Code 4342, Naval Air Warfare Center, Patuxent River, MD 20670
8:30 am
ELECTRODE POTENTIAL DEPENDENCE OF ENVIRONMENTAL CRACKING IN HIGH STRENGTH 7XXX ALUMINUM ALLOYS: L.M. Young, R.P. Gangloff, Department of Materials Science and Engineering University of Virginia, Charlottesville, VA 22903
This research aims to determine the effect of electrode potential on the kinetics of environmental crack growth in precipitation hardened 7XXX aluminum alloys. High resolution compliance and electric potential measurements of da/dt provide part of the foundation to understand the mechanisms for the agingmicrostructure dependence of shorttransverse cracking. Measured Stage II growth rates in AA7075T651, immersed in aqueous chloride, are slow and depend on electrode potential and inhibitor addition. For cracking in a molybdatechloride solution, da/dt rises from 107 mm/s at 900 mVSCE (nearopen circuit) to 105 mm/s at 750 mVSCE, but is constant or declines with more noble applied polarization. The crack path is along or near highangle boundaries, but the crystallographic and microstructure details are undefined. These results are consistent with literature findings for AA7075T6 in KI solution. The potential for the maximum in da/dt is more noble for the iodide compared to the molybdate, and is most active for cracking in bare chloride solution. This transition potential is governed by the onset of substantial localized crack tip dissolution which causes an IR difference that shields the crack from changes in anodic polarization. The importance of this potential dependence is illustrated by results for AA 7050T6 in molybdate. Crack growth is faster compared to the AA7075 case if both alloys are at their open circuit potential. Crack growth in AA7050 is slower than that in AA7075 if the comparison is made at a fixed electrode potential.
8:55 am
GRAIN SIZE AND TEMPERATURE DEPENDENCE OF INELASTIC DEFORMATION IN 5083 Al ALLOY: Yong Nam Kwon, Young Won Chang, Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790784, Korea
The inelastic deformation behavior of 5083 A1 alloy has been studied to clarify the effects of grain size and temperature by conducting a series of load relaxation tests. The experimental results were then analyzed based on the recently proposed internal variable theory of inelastic deformation. The inelastic deformation of fine grained 5083 Al alloy at high temperatures is confirmed to consist of grain boundary sliding and accommodating grain matrix deformation caused by dislocation glide processes. A HallPetch type relation is found to exist between the grain size and an internal strength variable, instead of the generally used flow stress.
9:20 am
ON THE WARPAGE OF 7050 ALUMINUM PLATES: M.L. Smith, J. Foyos, E.W. Lee, C. Ho, and O.S. Es-Said, Mechanical Engineering Department, Loyola Marymount University, Los Angeles, CA 90045; Naval Air Warfare Center, Code 434200A, NAWCAD PAX, Patauxent River, MD 20670; Mechanical Engineering Department, Howard University, Washington, DC
Investigators need a consistent and accurate method to measure and report sample warpage to assess material distortion during heat treatment. Consistent and accurate sample surface profile measurement can commence only after the sample is precisely positioned. This paper proposes using a positioning fixture which exactly constrains a sample's six degrees of freedom. Mounted in this fixture, standard dimensional inspection tools such as level gauges and dial indicator are then used to measure profiles along predetermined sample surface zones. Normalizing those measurements with respect to fixture constraint points and then plotting them on a graph allow precise warpage measurement and easy distortion visualization. In this study samples of 7050 plates were machined. The samples were of 1', 1.5", and 4" thickness and the crosssectional shapes were Uchannels and I beams. Samples were solution treated and one group was quenched in water and the second group in a polyalkylene-glycol solution. The effect of the sample's thickness and shape as well as the quenching medium on the warpage behavior will be discussed.
9:45 am
DYNAMIC DEFORMATION CHARACTERISTICS OF AlLi ALLOYS: Chang Gil Lee, Ki Jong Kim, and Sunghak Lee, Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790784, Korea
This paper presents a correlation study between microstructure and dynamic deformation behavior of AlLi alloys which have great potential for structural armor materials. The selected materials were a 2090 AlLi alloy, a Weldalite 049 alloy, and a 7039 Al alloy, to allow a comparative study of different strengths and microstructures. These alloys were deformed at a very high strain rate by ballistic impact. The amount and the distribution of adiabatic shear bands were examined after the ballistic impact testing, and the dynamic shear stressstrain curves were obtained from the dynamic torsional Kolsky bar (strain rate=i-103/sec) test in order to evaluate the possibility of forming adiabatic shear bands. In the vicinity of the perforated region, adiabatic shear bands were hardly observed in the 2090 and the Weldalite alloys, whereas they easily formed in the 7039 alloy. The overall observed phenomenology was interpreted using the dynamic shear stress strain curves, together with the strength level and microstructure. In the curves, the maximum shear stress and the shear strain at the maximum stress point were of primary importance in analyzing the adiabatic shear banding behavior, suggesting that the torsional Kolsky bar test is a good tool for evaluating the ballistic performance AlLi alloys.
10:10 am
COMPETITION BETWEEN METASTABLE AND STABLE PHASES DURING SOLIDIFICATION OF AlFeVSi ALLOYS: Hyang Jin Koh, Woo Jin Park*, Sangho Ahn* and Nack J. Kim, Center for Advanced Aerospace Materials, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790784 Korea, and *Research Institute of Industrial Science and Technology, San 32, Hyojadong, Pohang 790-390, Korea
AlFeVSi alloys have been produced by strip casting and spray casting. These processes offer relatively fast solidification rates and can produce near net shape products such as thin gauge strips or billets with the fine microstructure free from segregation. It has been shown that the microstructure of the alloys consists of various phases; bcc phase, microquasicrystalline phase, icosahedral phase, and the newly found hexagonal phase. All the phases are structurally related and have close orientation relationships among them. The volume fraction and distribution of these phases depend on the solidification rate and the degree of undercooling. The degree of recalescence occurring during solidification also affects the final microstructure, in that the less thermally stable phases transform to the stable phase.
10:35 am
THE EFFECTS OF AGING ON THE DIFFUSION AND TRAPPING OF HYDROGEN IN AN AL6.2ZN2.3MG2.3CU ALLOY: George A. Young Jr., John R. Scully, Center for Electrochemical Science & Engineering, Materials Science & Engineering, The University of Virginia, Charlottesville, VA 22903
Thermal desorption spectroscopy was used to investigate the diffusion and trapping of hydrogen in a Al6.2Zn2.3Mg2.3Cu alloy and in pure aluminum. Both the peak aged (T6) and overaged (T74) tempers were investigated for the alloy. Hydrogen was uniformly charged into rodshaped samples via exposure to water vapor saturated air. Isothermal desorption scans were utilized to determine the apparent activation energy for hydrogen diffusion. Constant heating rate thermal desorption scans were performed to identify hydrogen trap sites and quantify trap binding energies. In all desorption experiments, a quadrupole mass spectrometer was used to distinguish the desorption of hydrogen from that of other atomic or molecular species. Results from isothermal experiments show that bulk diffusion of hydrogen in the overaged alloy is appreciably slower than in the peak aged temper or in pure aluminum. Constant heating rate experiments reveal multiple trapping sites in both the alloy and in pure aluminum. The effects of the number and binding energy of trap sites on the diffusivity of hydrogen is quantified and the implications of these results on the hydrogen environment assisted cracking of precipitation hardened AlZnMg alloys are discussed.
11:00 am
EVOLUTION OF MICROSTRUCTURE, FRACTURE TOUGIINESS AND FATIGUE RESISTANCE DURING PROCESSING OF 7X50 ALUMINU1\I ALLOYS: F.D.S. Marquis, Department of Metallurgical Engineering, College of Chemical, Physical, and Materials Science & Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701
The evolution of microstructures was studied in 7X50 aluminum alloys, as a function of the manufacturing variables, during laboratory and industrial processing conditions. The fracture toughness, fatigue crack initiation and fatigue crack propagation of typical microstructures was measured. Low fracture toughness values and low resistance to fatigue crack growth were observed as a result of a high degree of recrystallization and a large volume fraction of both particles and hydrogen porosity. The resistance to fatigue crack propagation was higher in microstructures consisting of deformed grains with significant substructure. The morphology of various types of particles, volume fraction of the recrystallized microstructures, the grain and subgrain morphologies were observed to influence considerably the fatigue resistance. These microstructural parameters could be controlled effectively by the amount of total strain and the strain of the final pass, and the deformation temperatures during controlled rolling and subsequent double aging during final thermomechanical processing. Relationships between microstructure/fracture toughness/fatigue resistance will be discussed.
11:25 am
EFFECT OF PRE-AGE STRETCHING ON MECHANICAL AND HIGH CYCLE FATIGUE PROPERTIES OF THE 2024-T851 ALUMINUM ALLOY FOR AIRCRAFT: Han-Cheng Shih, New-Jin Ho*, Steel and Aluminum Research & Development Dept. *Institute of Materials Science and Engineering, National Sun Yat-Sen University
Room: Salon 3
Location: Clarion Plaza Hotel
Session Chairman: Dr. N.S. Cheruvu, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228
8:30 am INVITED
STATUS, ISSUES AND CHALLENGES OF MATERIALS FOR ADVANCED LAND BASED GAS TURBINES: B.B. Seth, Westinghouse Electric Corporation, Orlando, FL 32826-2399
Abstract not available.
9:20 am DEVELOPMENT OF DIRECTIONALLY SOLIDIFIED BLADES AND VANES FOR LAND BASE TURBINE: Hisataka Kawai, Kohji Takahashi, Ikuo Okada, Taiji Trigoe, Akira Mitsuhashi; Mitsubishi Heavy Industries, Ltd, Takasago Research & Development Center, 2-1-1 Shinhama Arai-Cho, Takasago, Hygo Pref. 676 JAPAN; Mitsubishi Materials Corporation, 1-297 Kitabukuro-Cho Omiya, Saitama 330, Japan
Directionally solidified blades and vanes, so-called DS blades and vanes, have already been used in jet engines, but seldom in land-base gas turbines, because there are large differences in the size of hot parts, fuel and so on between jet engines and land-base gas turbines. It is necessary to take these differences into account when developing DS blades and vanes for land-base gas turbines. Mitsubishi Heavy Industries, Ltd. started to develop DS blades some years ago. First, material properties, such as, tensile strength, creep rupture, fatigue, other physical properties, etc, were investigated. Then, the optimization of casting conditions for large size blades (501FG/T 1st blade) was conducted. Finally, actual DS blades were cast and it was confirmed their material properties were excellent. Also their machinability and coating were evaluated and good results were obtained. As a result, DS blades were installed in an actual gas turbine (MF111G/T) in January 1994 which have been in operation since then.
9:40 am
MICROSTRUCTURAL STABILITY OF ADVANCED SINGLE CRYSTAL SUPERALLOYS: W.S. Walston, GE Aircraft Engines, 1 Neumann Way, M85, Cincinnati, OH 45215
Microstructural stability is a key parameter in the development and application of single crystal superalloys. The formation of topologically close packed (TCP) phases occurs to some degree in most single crystal superalloys. The effect of these phases on properties will be discussed. In addition, the effects of time and temperature on the formation of TCP phases will be shown for a recent single crystal superalloy, René N6. Another form of microstructural instability has recently been observed in high refractory content single crystal superalloys. This instability, termed SRZ, is a cellular phase transformation that can occur either beneath coatings or in the alloy substrate. The occurrence and effects of this instability in various alloys will be discussed. The third form of microstructural instability observed in several single crystal superalloys is the conversion of the matrix with 1 precipitates to a microstructure with a continuous phase. Several examples of this behavior will be shown. The relationship between this form of instability, rafting and creep rupture properties will also be discussed.
10:00 am BREAK
10:20 am
THE EFFECT OF CAST SIZE ON HOT CORROSION RESISTANCE OF SINGLE CRYSTAL NICKEL BASED SUPERALLOY CMSX-4: Ming Li, V. Desai, Mechanical Materials and Aerospace Engineering Department, University of Central Florida, Orlando, FL 32816; N.S. Cheruvu, Southwest Research Institute, 6220 Culebra Road, San Antonio TX 78228
Advanced single crystal (SC) nickel based superalloys have been available in small cast size for aero engine applications for a long time. Where as the SC techniques are not yet widely used in the land based engine components because of their much larger size which makes casting and the subsequent heat treatment more difficult. The difference in defects, such as microporosity, segregation, /1 eutectic, and dendritic structure, derived from casting size differences will affect the heat treatment process and the subsequent service properties, including hot corrosion/oxidation behavior. Hot corrosion tests were carried out at 900, 950, and 1000°C on specimens coated with NasSO4 in air. Three different kinds of specimens; as-cast and heat treated CMSX-4 from small and large blades, and IN738, were used to study the effects of cast defects and heat treatment on hot corrosion behavior and to compare the hot corrosion resistance of the single crystal superalloy with a typical land based turbine material. The corrosion product morphology, microstructure and composition were investigated using metallography and SEM/EDS. It is concluded that although the hot corrosion resistance of this single crystal material is not as good as that of IN738, proper heat treatment can double its hot corrosion resistance.
10:40 am
RELIABILITY OF A SINGLE CRYSTAL NIAL ALLOY FOR GAS TURBINE APPLICATIONS: R. D. Noebe, J. Salem, J. Manderscheid, NASA Lewis Research Center, M.S. 24-1, Cleveland, OH 44135; R. Darolia, General Electric Aircraft Engine Co., Cincinnati, OH 45215
Due to numerous property advantages, NiAl single crystal alloys are being investigated as a replacement for Ni-based single crystal superalloys in high pressure turbine engine sections, however, the current drawback is their lack of ductility. Consequently, a significant effort is being made to develop testing and design methodologies that will account for this lack of ductility. The present approach is to modify existing test methods and brittle design methodologies, such as those in the Ceramic Analysis and Reliability Evaluation of Structures (CARES) code, and to experimentally verify the results. To this end, the statistical nature and source of fracture in a high-strength, single crystal NiAl alloy has been studied via flexural testing of 3- and 4-point bend specimens of various crystallographic orientations. Flexural strength results indicate a wide dispersion in strength that can be characterized via normal or Weibull statistics. While the fracture strength was function of orientation, the Weibull modulus was not. Failure origins were determined for most of the specimens tested. In all cases, failure occurred from singular carbide particles or machining damage. It was also determined that the Weibull scaling law applies to uniaxial cases for effective surface area changes of 300% or less.
11:00 am
EFFECT OF SOLUTION HEAT TREATMENT ON DS TRANSVERSE STRENGTH: H. Tamaki, A. Yoshinari, A. Okayama, N. Watanabe, M. Kobayashi, Hitachi Research Laboratory, Hitachi, Ltd., Hitachi, Ibaraki, Japan
It is well known that creep-rupture strength of nickel-base superalloys strongly depends on the conditions of solution heat treatment. Jackson et al. 1 showed that creep-rupture life of MAR M 200 Hf DS in longitudinal direction increased with increasing volume fraction of fine 1 upon solution heat treatment. On the other hand, Cetel and Duhl 2 showed that creep ductility of PWA1426 DS in transverse direction decreased with increasing volume fraction of fine 1. In this study, in order to investigate the effect of solution heat treatment on DS transverse strength, CM186LC DS which is usually used without solution heat treatment was solution heat treated at 1548K for different time periods. Results are summarized as follows. (1) Creep-rupture strength of CM186LC DS in longitudinal direction increased by solution heat treatment. (2) Creep-rupture strength of CM186LC DS in transverse direction decreased by solution heat treatment. (3) Boron at grain boundaries diffused into grains by solution heat treatment. This phenomenon possibly caused the decrease of creep-rupture strength of CM186LC DS in transverse direction.
11:20 am
ALLOY 603GT: A NEW COBALT FREE ALLOY FOR GAS TURBINE COMPONENTS: D.C. Agarwal, 11210 Steeplecrest Dr. #120, Houston, TX 77065-4939; U. Brill, Krupp-VDM GmbH, Werdohl, Germany
Modern gas turbine components must possess unique combination of various high temperature strength and corrosion resistance properties for providing increased efficiency and reliability of operation. Some of these properties, which a material must have are good isothermal and cyclic oxidation resistance, good carburization resistance, good thermal stability, good stress rupture and fatigue strength and most importantly, good fabricability and weldability. Alloy 603GT is a new cobalt free nickel base alloy especially developed for modern gas turbine components. Its basic composition of high chromium, high aluminum, high carbon (25 Cr, 2.6 Al, 0.3 C, 0.1 Y, 9 Fe, Ni balance) and micro alloying with titanium and zirconium, gives this alloy a unique combination of excellent high temperature strength and superior oxidation resistance, carburization resistance, good thermal stability, grain growth resistance and spallation resistance. It's development, properties and cost effectiveness are discussed.
11:40 am
MECHANICAL PROPERTY COMPARISON OF SELECTED NICKEL BASE SUPERALLOYS FOR LAND BASED GAS TURBINE APPLICATIONS: Colin Thomas, Howmet Corporation, Whitehall, MI 49445
Abstract not available.
Room: 314B
Session Chairperson: TBA
8:30 am INVITED
INTRODUCTION OF THE NCMS LEAD-FREE SOLDER DEVELOPMENT PROJECT: Jerald Rosser, Hughes Aircraft Company, P.O.Box 11337, Building 801/E-24, Tucson, AZ 85734-1337
Since 1990, proposed legislation and consumption taxes on the use of lead have concerned the electronics industry in this country. Although the consumption of lead for electronic interconnections (via solder) is relatively low in comparison to batteries, the possibility of restricting lead usage for solder alloys would have a dramatic effect on the electronics industry. This concern lead the National Center for Manufacturing Sciences (NCMS), a not-for-profit cooperative research consortium of more than 215 U.S. North American manufacturers, to establish a multi-year Lead Free Solder Project, involving participants from industry, (GM DELCO, AT&T/Lucent Technologies, United Technologies/Hamilton Standard, GM-Hughes, Rockwell International, Ford, Texas Instruments), academia (Rensselaer Polytechnic Institute), and national laboratories (Sandia, NIST, and Electronic Manufacturing Productivity Facility). The objective of the program was to identify lead free solder alternative replacement(s) for lead bearing solders in the electronics industries. The alloy(s) must meet the interconnect performance requirements at operating environments ranging from -40 to +125°C. Over the past three years, numerous lead free alloy solders have been thoroughly evaluated. The project participants will be presenting the results of this four year NCMS evaluation of the material properties, economic impact, toxicological properties, manufacturability, modeling and reliability predictions.
9:00 am INVITED
SOLDER ALLOY DEVELOPMENT: Yun Zhu, Delco Electronics Corporation, 2705 S. Goyer Road, M/S D-16, Kokomo, IN 46904-9005
In this presentation, the process of alloy development and down selection is summarized. An initial list of more than 70 alloys was constructed, including binary, ternary, quaternary, and quinary alloys. he first selection process was applied based on the toxicology, economic, and availability criteria. Then a downselection criteria matrix, including melting temperatures, wetting behavior, and thermo-mechanical fatigue, was generated for a quantitative comparison of alloys with respect to three baseline alloys: eutectic Sn-Pb, Sn-Bi, and Sn-Ag solders. Physical testing was performed to provide the data for downselection. Extensive phase diagrams from literature and thermodynamic calculation were used to predict the melting temperature range, and compare with experimental results. A comprehensive literature search was conducted to identify publications of the past 25 years.
9:30 am INVITED
ECONOMICS, AVAILABILITY, AND TOXICOLOGY: Charles DeSantis, Hamilton Standard Division of United Technologies Corporation, M/S 3-2-F2, One Hamilton Road, Windsor Locks, CT 06096-1010; Joe Fegley, Texas Instruments, 2501 W. University, Box 801/ M/S 8013,McKinney, TX 75070; Tsung-Yu Pan, Ford Motor Company, P. O. Box 2053, SRL Building, M/D 3135, Dearborn, MI 48121-2053
Based on data from the U.S. Department of Interior, an economics/availability study was completed which estimates the impacts on supply and cost to the electronics industry if it were to replace tin-lead solder with a lead-free solder alloy. Considerations in this study included the availability of the replacement materials, world mine production and consumption, world reserves and reserve bases, present world mine production capacity, principal reserve locations, average annual price and price history. Seven alloying elements were investigated. They were antimony, bismuth, cadmium, copper, indium, silver, tin, and zinc. Limits placed on the estimated alloy cost, ore reserve consumption rate, and required mine or refining capacity permitted rank ordering of potential alloys. An extensive literature search on the toxicity of common solder alloying elements was also conducted. Available data on the disposition, toxicity, and exposure limits of these solder alloying elements were analyzed in order to rank their use risk. The process used to evaluate the economics, availability, and toxicity of lead free solders, as well as the findings of the study will be discussed.
10:00 am BREAK
10:20 am INVITED
MANUFACTURING WITH LEAD-FREE SOLDERS: John Greaves, Electronics Manufacturing Productivity Facility, 714 N. Senate Ave., Indianapolis, IN 46202-3112
Successful introduction of lead-free solders into the manufacturing process requires subtle changes in process parameters. Changes in density, melting temperature, wetting and spreading behavior, all affect the parameters necessary for optimum manufacturing and reliability. This currently results in a need to change print speeds, squeegee pressures, and stencil thicknesses. Component placement is relatively unchanged. The largest changes in manufacturing with lead-free solders are those in the reflow process. Manufacturing lead-free solders with RMA fluxes requires modifying reflow profiles to insure that the flux is active when the solder reaches the melting temperature. Manufacturing with fluxes designed for lead-free solders simply requires setting the conveyor speeds and zone temperatures to achieve the suggested profile. No substantial difference has been noticed in the cleaning of lead-free alloys and the lead-free alloys evaluated are compatible with no-clean processes as well. Wave soldering of lead-free solders using RMA fluxes can present some difficulties if the process is not well controlled. While many lead-free solders can be used in wave-soldering with no changes to the profile or pot temperature, using fluxes and profiles designed for lead-free solders can increase yields and simplify the wave-soldering process.
10:50 am INVITED
Pb-FREE SOLDER RELIABILITY COMPARISON: Gordon Whitten, Delco Electronics Corporation, 700 East Firmin St., M/S T100-34, Kokomo, IN 46904-9005
The reliability of several Lead-free solder alloys are compared. Thermal cycle testing was performed using two different profiles: 0 to +100°C, to simulate telecommunications and office environments; and -55 to +125°C, to simulate automotive and military environments. The National Center for Manufacturing Sciences (NCMS) Surface Mount Reliability Test Vehicle(SMRTV) was used to test more than 2000 joints/board with more than 10,000 joints per alloy for each temperature cycle. Five Pb-free alloys are compared to 3 baseline alloys, SnPb Eutectic, SnAg Eutectic, and SnBi Eutectic. Three parameter Wiebull analysis is used to determine failure free time, Wiebull life, and Wiebull shape parameter.
11:20 am INVITED
RELIABILITY MODELING FOR LEAD-FREE MICROELECTRONICS: Scott A. Schroeder, Rockwell International Science Center, 1049 Camino Dos Rios, Thousand Oaks, CA 91360
The NCMS Lead-Free Project Modeling Task Group was formed to determine the capability of existing models developed by the consortium members to predict low cycle fatigue life for specified test vehicles using down-selected lead-free solder alloys. A quantitative summary and objective analysis of predictions and modeling capability for down-selected alloys are generated. Life prediction results are correlated with reliability test vehicle data using a -55 to +125°C thermal cycle. The final project goal is a design guide for predicting joint fatigue life for lead-free leadless capacitors and resisters, 44 LCCC, 32 TSOP, and 132 PQFP components. Solder down-selection guidance is provided through recommendations of mechanical tests, test priority, and evaluation of hysteresis loop, thermo-mechanical fatigue, creep, and tensile property data. Alloy phase diagram modeling information provides manufacturing down-selection criteria. Additional support is provided through stress analysis of manufacturing test vehicles.
Session Chairperson: George T. Gray, III, Los Alamos National Laboratory, Los Alamos, NM 87545
8:30 am
INFLUENCE OF TEXTURE AND STRESS STATE ON THE CONSTITUTIVE RESPONSE OF AN AUTOMOTIVE STEEL: Carl M. Cady*, Shuh-Rong Chen, George T. Gray III, Los Alamos National Laboratory (LANL), MST-5 MS-G755, Los Alamos, NM 87545; John F. Bingert, David A. Korzekwa, LANL, MST-6 MS-G770, Los Alamos NM 87545
The relationships between the stress state, texture, revalue (Lankford parameter), and yield surface for a DQSK mild sheet steel have been analyzed. The strain rate and temperature sensitivity of the flow stress and the insensitivity of the strain hardening rate indicate that thermal activation over a Peierls barrier is the rate controlling mechanism for deformation in DQSK. The stress/strain response for DQSK steel is shown to be strongly influenced by strain rate and temperature which is consistent with this controlling mechanism. A calculated yield surface, using the Quadratic Hill criterion, is shown to produce an accurate correlation with the experimental results. Comparisons of the stress/strain response with the calculated yield surface and texture measurements will be shown to correlate with the relationships between the inplane and through thickness deformation.
8:50 am
THE MICROTEXTURE OF FRACTURE IN LITHIUM-CONTAINING ALUMINUM ALLOYS: R. Crooks, Analytical Services and Materials, Inc., NASA Langley Research Center, M/S 188A, Hampton, VA 23681-0001; P.N. Kalu, Department of Mechanical Engineering, FAM/FSU, Tallahassee, FL; A.P. Reynolds, Department of Mechanical Engineering, University of South Carolina, Columbia, SC
An Electron Back-Scattered Pattern (EBSP) system was used on a scanning electron microscope (SEM) to examine the crystallographic features of intergranular fracture in several lithium-containing aluminum alloys. The alloys examined have thin, flat grains with a "pancake" morphology, which tend to be highly elongated in the rolling direction. Metallographically prepared and electropolished samples of longitudinal sections were examined in the SEM where absorbed current images and diffraction data were collected through-thickness, with patterns indexed to the images. Delamination fracture was then induced in the samples by torsional loading, which often produced several cracks, and samples were returned to the SEM chamber to determine the crack locations relative to the previously acquired data. The results indicate that delamination occurs between grains near the S and R texture component orientations, which are known to form during deformation processing and as a result of grain boundary initiated recrystallization, respectively.
9:10 am
ELEVATED TEMPERATURE COMPRESSIVE SLOW STRAIN RATE PROPERTIES OF SEVERAL DIRECTIONALLY SOLIDIFIED NIAL-(NB, MO) ALLOYS: J. Daniel Whittenberger, Ronald D. Noebe, NASA-Lewis Research Center, Cleveland, OH 44135; Steven M. Joslin, B.F. Oliver, The University of Tennessee, Knoxville, TN 37996-2200
Three NiAl-based alloys containing 3Nb-lOMo, 5Nb-lOMo or 13.6Nb-18Mo (at. %) were directionally solidified (ds'ed) to develop interpenetrating networks of B2 crystal structure NiAl Laves NiAlNb and bcc metallic Mo. It was hoped that the Mo would improve the fracture toughness, while the Laves phase would promote good creep resistance. Examination of the alloys indicated that the as-grown structure consisted of essentially unalloyed NAL NiAlNb alloyed with ~8.5 Mo, and a Mo solid solution containing 27Nb-7Ni-7A1. Compressive properties were measured between 1200 to 1400 K in air with strain rates ranging from ~10-4 to ~10-8s-1. The flow strengths of the two alloys with 10Mo were nearly identical and much weaker than those for NAI-13.6Nb-18Mo. Comparison the properties of this latter alloy with other ds'ed NAl-based eutectics revealed that it was the strongest material under lower temperature/fast deformation conditions, but this advantage was lost at higher temperatures and/or slower strain rates.
9:30 am
DEFORMATION AND FAILURE MECHANISMS IN MATERIALS THAT DEFORM BY TWINNING AND MARTENSITIC TRANSFORMATION: Surya R. Kalidindi, R.D. Doherty, E. El-Danaf, S. Asgari, I Shaji, Department of Materials Engineering, Drexel University, Philadelphia, PA 19104
MP35N (35% Co, 35% Ni, 10% Mo, 20% Cr) exhibits an remarkable combination of ultrahigh strength, high ductility, high fracture toughness, high corrosion resistance, and it retains its room temperature strength upto about 600°C. This alloy hardens from 390 MPa (in the annealed state) to 1385 MPa after being 53% cold drawn and then to 1935 MPa on subsequent aging of the cold-drawn material at 600°C for four hours. Furthermore, the alloy was found to show a 50% reduction in area before failure in tension tests of the cold drawn and aged samples. The mechanisms of the primary and secondary hardening obtained through cold working and subsequent aging have been investigated in this study by optical and transmission electron microscopy investigations on deformed and deformed and aged samples. Some of the interesting observations made in our study include: (i) Plots of strain hardening rate versus stress (or strain) in simple compression of annealed MP35N indicate four distinct regimes of strain hardening which when suitably normalized were found to be in excellent agreement with the corresponding measurements in several other low stacking fault energy fcc alloys. (ii) The amount of secondary hardening in MP35N depended critically on the amount of plastic deformation imposed prior to aging. It was observed that a strain of about 0.2 was needed before secondary hardening could be detected and that the increase in strength by secondary hardening saturated at a strain of about 0.6. (iii) Simple compression deformation on samples that exhibited significant secondary hardening produced extensive micro-scale shear banding. The extent of shear banding increased with increased levels of secondary hardening and macro-scale shear bands were noted in compression of heavily deformed and aged samples. (iv) Measurements of plane strain fracture toughness revealed that the 53% cold-worked samples retained high toughnesses (about 120 MPa m112) even after the secondary hardening. The formation of shear bands noted above did not seem to effect either the fracture toughness or the ductility of the deformed and aged samples compared to the deformed only samples upto about 53% reduction levels in cold-drawing. Beyond about 60% reduction levels in cold-drawing, the ductility of the deformed and aged samples was observed to drop precipitously. A detailed investigation using the optical microscope and TEM was undertaken to explain the above observations. We are presently attempting to correlate the microscopy observations to the results from the mechanical testing. These results and our current understanding of the physical origin of the properties described above will be presented.
9:50 am
MECHANICAL BEHAVIOR OF PM U720 FORGED ALLOY AT ELEVATED TEMPERATURES: Chih-An Yin, and K. A. Green, Allison Engine Company, P. O. Box 420, S-52, Indianapolis, IN 46204-0420
Material characterization tests for tensile, creep-rupture, low cycle fatigue and fatigue crack growth responses were conducted on P/M U720 forged disc alloy subjected to a specified heat treatment. The purpose of this investigation is to examine the effects of the thermomechanical processes on the high temperature mechanical behavior of this material with a special attention to the creep-rupture, low cycle fatigue and fatigue crack growth rate. The results of analysis are mainly based on the phenomenological approach and predicted methods so that the quantitative comparison can be presented. in addition, the fracture morphologies of the material at 538°C and 650°C were also investigated by SEM and optical metallography to determine the relationships of failure modes, relative fatigue and creep-rupture life to the grain size, local microstructure and defect inclusions resulted from different consolidation processes.
10:10 am BREAK
10:20 am
STUDY AND COMPARISON OF (111) DEFORMATION MICROBANDS ASSOCIATED WITH IMPACT CRATERS AND PENETRATION CHANNELS IN THICK COPPER PLATES: L.E. Murr, J.M. Rivas, E.P. Garcia, C-S. Niou, and E. Ferreyra T., Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968
While copper, having critical grain sizes greater than about 20 µm, will twin above a critical, plane-wave shock pressure of about 20 GPa, {111} deformation twins are essentially absent below impact craters or along dense rod penetration channels in copper plates (1.3 to 3.5 cm thick) where instantaneous (plane-wave impact) shock pressures exceed 100 GPa; for spheres and rods impacting at velocities between 1.5 and 6.7 km/s, with densities ranging from 2.2 to 17.6 g/cm3. However, deformation microbands consisting of elongated, dense dislocation wall structures (0.1 to 0.4, am wide), coincident with primary {111}planes; occur in bands or zones removed several millimeters from the crater or penetration channel walls, and predominantly in grains which exhibit little or no (plastic) distortion. These microbands possess misorientations ranging from 1 to 3° and appear to be created as a consequence of intense shear wave phenomena associated with these unique, high strain, high-strainrate deformation regimes. They also occur amongst dense, equiaxed, dislocation cells whose misorientations are <1°, and appear to be related to {111}deformation twins or twin faults which also emerge from or occur amongst, dislocation cells in plane-wave shock loaded copper, for example. Supported by NASA-JSC Grant NAG-9-481 and U.S. Army Contract DAAE30-94-C-0059.
10:40 am
EFFECTS OF HEAT TREATMENT AND MO CONTENT ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF FE-NI-CR-MO HIGH TEMPERATURE GEAR STEELS: Cha-Yong Lim, Sung-Joon Kim, Korea Institute of Machinery and Materials, #66 Sangnam-Dong, Changwon, Kyungnam, Korea 641-010
The effects of heat treatment and Mo content on microstructure and mechanical properties of high temperature gear steels have been investigated. High temperature gear steels require temper resistance, hot hardness, fracture toughness and impact strength for operation at elevated temperatures. The compositions (wt.%) of gear steels studied in this work were Fe-2.0Ni-l.0cr-(1~3.15)Mo-2.0Cu-0.4Mn-0.llC steels. The ingots manufactured by the vacuum induction melting were hot-rolled at 1473 K to 15mm thickness. The hot-rolled plates were quenched and tempered at various conditions. The degree of secondary hardening is increased with the Mo content due to the precipitation of fine alloy carbide (Mo2C) during tempering treatments. Continuous cooling transformation diagrams were obtained. High temperature mechanical tests (Hardness, Toughness, Impact energy) were conducted. Cylindrical compressive specimens of 8mm diameter and 12mm height were machined from the hot-rolled plates. High temperature compressive tests were carried out in an compression testing machine at various strain rates. The microstructure aRer deformation was investigated. The deformed structure was dynamically recrystallized at higher temperatures and lower strain rates. Activation energy and flow equation at high temperatures were discussed.
11:00 am
MICROSTRUCTURAL CHANGE DURING SUPERPLASTIC DEFORMATION IN LOW ALLOYED Zn-Al ALLOY: W.B. Lee, T.K. Ha, C.G. Park, Center for Advanced Aerospace Material, Univ. of Sci. & Tech., POSTECH, Pohang, 790-784, Korea
Microstructural change and deformation behavior have been observed in superplastic Zn-Al alloys. Row-alloyed Zn-Al alloys, which contains a small fraction of precipitates at grain boundary, showed superplastic deformation behaviors even at room temperature, while pure Zn is very brittle. In the present study, the effects of aluminum composition (up to 1 wt.%) on the change in the microstructure (the role of precipitates) as well as dislocation structure have been investigated during the superplastic deformation. TEM in situ deformation was also performed to investigate dislocation behavior at grain boundary during superplastic deformation of low alloyed Zn-Al alloys.
11:20 am
EFFECTS OF YIELD STRESS AND TEXTURE ON DELAYED HYDRIDE CRACKING IN Zr-2.5Nb PRESSURE TUBE: In Sup Kim, Je Yong Oh, Korea Advanced Institute of Science and Technology, Taejon 305-701, S. Korea
The delayed hydride cracking (DHC) in pressure tubes is caused by diffusion of hydrogen atoms into crack tip region, precipitation of hydride, and consequent fracture of the hydrided region under stress. To explain DHC quantitatively, many models have been proposed and the Puls model has been well recognized among them. In this study, the effects of yield stress and texture on DHC have been investigated in Zr-2.5Nb pressure tube material and experimental results were introduced and compared to Puls DHC model. The delayed hydride cracking velocity (DHCV) increased with yield stress, while the threshold stress intensity factor increased as yield stress decreased. The activation energy of DHCV was dependent on the texture. When the direction of crack propagation was longitudinal, the activation energy was 34kJ/mol. However, in the case of circumferential propagation, the energy was measured as 17kJ/mol.
11:40 am
DEVELOPMENT OF TEXTURE AND MICROSTRUCTURE DURING COLD ROLLING OF Ni3Al(B,Zr): B. Bhattacharya, R.K. Ray, Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur-208016, India
The present report deals with textural as well as microstructural developments during cold rolling of a two-phase Ni3Al(B,Zr) alloy. Basically a pure metal type texture was obtained at lower levels of deformation, while a mixed type (both pure metal and alloy type) was observed at high strain. The transition was detected after about 35% reduction which was correlated with a possible structural transformation in the /phase. The change of deformation mode from slip to twinning in was confirmed by electron microscopy. However, the second phase (Ni-base, disordered phase) in the alloy is not known to suffer any change in the deformation mode with straining. Therefore, it is suggested, that the textural development in the two phases will be of different nature; the combined effect will be reflected in the form of the textural change for the whole sample, as mentioned above.
Session Chairperson: Warren M. Garrison, Dept. of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213
8:30 am
EFFECT OF COLD WORKING ON THE OMEGA PHASE IN BETA TITANIUM ALLOYS: M.Saqib, N. Stefansson, R. Srinivasan, I. Weiss, Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45435
High specific strength, excellent corrosion resistance, good cold formability and age hardening response are some of the attractive properties of the metastable titanium alloys. The effect of cold deformation on the stability of phase present in metastable alloys is not clearly understood. In this study, two titanium alloys: TIMETAL 21S and TIMETAL LCB were fast cooled from above the -transus temperatures and subsequently cold rolled to total reductions ranging from 5 to 35%. The fast cooled microstructure consisted of phase with dispersion of athermal precipitates. Selected area electron diffraction patterns from the as-cooled and the cold rolled specimens revealed the presence of diffuse intensity maxima at 1/3<112> and 2/3<111> locations, characteristic of the presence of phase. The average integrated intensities of the diffuse maxima from the phase and the sharp diffraction spots from the phase were measured using microdensitometer. The intensity ratio; (diffuse intensity) /(diffraction spots intensity) was used as a measure of the relative volume fraction of the phase in the phase matrix. The volume fraction of the phase was found to decrease linearly with an increase in the amount of cold deformation both alloys.
8:50 am
GRAIN BOUNDARY NIOBIUM-RICH CARBIDES IN INCONEL 718*: Ming Gao, Robert P. Wei, Dept. of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA 18015
In a previous study, niobium was identified as the principal embrittling element for oxygen-enhanced crack growth in nickel based alloys, such as Inconel 718. Niobium was believed to come principally from the oxidation and decomposition of niobium-rich carbides at the grain boundaries. To better establish their type density and distribution, g.b. carbides in Inconel 718 that were exposed by crack growth at 700°C or by hydrogen embrittlement were characterized by SEM and EDS. The carbides were also analyzed by high-resolution AEM. Two types of carbides were identified; those associated with the primary NbC, and those (secondary carbides) that formed during heat treatment. The results will be presented and discussed in relation to environmentally assisted crack growth. Research supported by the National Science Foundation, Division of Materials Research, under Grant DMR-9102093.
9:10 am
THE INFLUENCE OF CARBON LEVEL ON SULFIDE PARTICLE DISTRIBUTIONS IN TITANIUM MODIFIED STEELS OF THE AF1410 TYPE: Luana E. Iorio, Warren M. Garrison, Jr., Dept. of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213
Earlier studies showed that small titanium additions to the 0.10 wt. % carbon steel HY180 lead to the gettering of sulfur as particles of Ti2CS. The Charpy impact energy of HY180 when sulfur is gettered as MnS is about 160J but increases to about 270J when sulfur is gettered as Ti2CS. The improvement in toughness is attributed to the particles of Ti2CS being more resistant to void nucleation than particles of MnS. The effects of small titanium additions on sulfide and other second phasae particle distributions and the toughness of AF1410 steel at carbon levels of 0.16 wt% and 020 wt% are being investigated. The results indicate that titanium additions lead to a substantial improvement in toughness at a carbon level of 0.16 but the improvement in toughness is less at a carbon level of 0.16 but the improvement in toughness is much less at a carbon level of 0.2. The objective of the work reported here is identification of sulfide type and measurement of sulfide size in these two higher carbon steels. Because of the large number of possible sulfides of titanium the major emphasis has been on identifying sulfide type from transmission electron microscopy diffraction results.
9:30 pm
HIGH TEMPERATURE PHASE STABILITY OF THE YTTRIA STABILIZED t' PHASE ZIRCONIAS: James S. Smith, Fu-Jen Pan, Jan-Fong Jue, Materials and Systems Research Inc., 1473 S. Pioneer Rd., Salt Lake City, UT 84104; Kevin T. Zysk, AEDC/DOT, 1099 Avenue C, Arnold Air Force Base, TN 37389-9011
Yttria doped zirconias containing 3 to 8 mole% stabilizer were fabricated by (i) sintering at 1450°C and (ii) heat treating at 2100°C for 15 minutes with a gas fired furnace to obtain (i) regular tetragonal (t) and cubic (c) phase, and (ii) largegrained tetragonal (t') and c phase materials, respectively. The materials were annealed at temperatures between 1100°C and 2000°C in air for various times. The effect of annealing time and temperature as well as cooling rate on the phase stability of the t' phase zirconia will be discussed. A working T-T-T diagram will be proposed. High temperature bending strength and compressive strength data will be presented. The possibility of precipitation strengthening in the annealed samples will also be addressed.
9:50 am BREAK
10:00 am
PHASE STABILITY IN NbCr2-BASED LAVES PHASE ALLOYS: J.H. Zhu, P.K. Liaw, Department of Materials Science and Engineering The University of Tennessee, Knoxville, TN 37996; C.T. Liu Metals and Ceramics Division Oak Ridge National laboratory Oak Ridge, TN 37831-6115
Phase stability in NbCr2-based transition-metal Laves phases is studied in this paper, using data from binary X-Cr, Nb-X, and ternary Nb-CrX phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor (e/a = the average number of electrons per atom outside the closed shells of the component atoms) is the determinate factor in controlling the phase stability of NbCr2-based transition-metal Laves phases. The e/a ratios for different Laves phase structures were determined as follows: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88-7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure was stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of transition-metal A3B intermetallic compounds and Mg-based Laves phases is also reviewed and compared wit'n the present observations in transition-metal Laves phases. Finally, experimental results on Cr-Nb-Cu ternary system were also presented and explained in light of the e/a ratio correlation with phase stability.
10:20 am
THE MARTENSITIC TRANSFORMATION CURVES FOR SHAPE MEMORY ALLOYS: H.Y. Yu, Naval Research Laboratory, Mechanics of Materials Branch, Code 6380, Washington, D.C. 20375-5343
The mechanical behavior of shape memory alloys is closely related to the martensitic phase transformation. A martensitic transformation is considered to be a first order solid state structural transformation that is diffusionless and whose initial phase maintains metastability. Conventional models, such as the "exponential model" and the "cosine model" do not describe the martensitic transformation satisfactorily. In this study, the martensitic transformation curves for thermoelasaticity and pseudoelasticitiy are obtained by using the principle of energy balance. The results are in good agreement with experimental results for steels and nitinol alloys.
10:40 am
RULE OF ADDITIVITY IN PHASE TRANSFORMATIONS: David T. Wu, Dept. of Mechanical Engineering, Yale University, P.O. Box 208284, New Haven, CT 06520
The rule of additivity is used to predict CCT diagrams from TTT diagrams. Avrami showed that a nucleation and growth reaction is additive if it is isokinetic. Later Cahn proposed site-saturation as another condition for additivity to hold. This talk presents more general conditions under which the rule of additivity is valid.
11:00 am
REVISITING THE EFFECT OF CURVATURE ON CHEMICAL POTENTIAL FOR BINARY SYSTEMS: N. Kulkarni, R T. DeHoff, 253A Rhines Hall, Depas1ment of Materials Science and Engineering, University of Florida, Gainesville, F1-32611
The effect of curvature on the chemical potential for binary systems, at constant temperature and pressure, is usually given in the literature by the Gibbs-Thomson equation. Many forms of this equation have appeared in the literature, that can be shown to be incorrect and in violation of the condition for chemical equilibrium for a two-phase system. A simple self-consistent procedure to derive the Gibbs-Thomson equation for binary systems is provided. The resultant equation for the chemical potential shift is independent of the solution model and has an inverse dependence on the width of the two-phase field.
11:20 am
METRIC AND TOPOLOGICAL CONTRIBUTIONS TO THE RATE OF CHANGE OF BOUNDARY LENGTH IN TWO DIMENSIONAL GRAIN GROWTH: R.T. DeHoff, Department of Materials Science Engineering, 253A Rhines Hall, University of Florida, Gainesville, Fl-32611
The boundary in a two dimensional grain structure decreases its length during grain growth. Four distinct processes may contribute to this length change: 1) The smooth motion of the grain edges toward their centers of curvature; 2) Migration of cell corners resulting from the edge motion; 3) The annihilation of small grains (topological process b); 4) The switching process (topological process II). Using von Neumann's assumption that the local velocity is proportional to the local boundary curvature and geometrically general kinematic equations, the contribution of each of these four processes is assessed The result is a kinetic equation in which the metric and topological contributions to the rate of grain growth in two dimensions are made explicit.
Room: 330B
Session Chairpersons: G.A. Eltringham, BHP Copper, 550 California Street, San Francisco, CA 94104; O. Ishikawa, Bechtel Corporation, 50 Beale Street, San Francisco, CA 94105
8:30 am
PRODUCTIVITY INCREASE IN FLASH SMELTING FURNACE OPERATION AT SAGANOSEKI SMELTER & REFINERY: Yoshiaki Suzuki, Chikashi Suenaga, Masatoshi Ogasawara and Yutaka Yasuda, Saganoseki Smelter & Refinery, Nippon Mining & Metals Co., Ltd., Saganoseki, Oita-Ken 879-22 Japan
Since 1973, Saganoseki Smelter & Refinery had operated two flash smelting furnace units together to produce copper of 330,000 metric tons per year until quite recently. Economical situation in 1990ís, however, required the smelter to improve the productivity to be competitive in the copper smelting industry. Under the above circumstances, the program for the smelter was drawn up in order for a single flash furnace unit to produce copper at the same level as that with the two flash smelting furnace units. The program was carried out with a lot of modifications of facilities and equipment to double the throughput of a single flash smelting furnace unit, including the pneumatic concentrate drying system, the concentrate feeding system, the concentrate burner, the furnace cooling system, etc. A new large cryogenic oxygen plant was also constructed to replace the two old plants. The production with a single flash smelting furnace unit started in March 1996. This paper describes details of the modifications and results of the operation.
8:55 am
RECENT OPERATION FOR TREATMENT OF SECONDARY MATERIALS AT MITSUBISHI PROCESS: E. Oshima, T. Igarashi, N. Hasegawa, H. Kumada, Mitsubishi Materials Corporation, Naoshima Smelter and Refinery, 4049-1, Naoshima-Cho, Kagawa-Gun, Kagawa 761-31 Japan
The Mitsubishi process has many advantages pertaining to economical and environmental matters. These advantages have led to the installations of the Mitsubishi process at new smelters being under construction. The Mitsubishi process utilizes highly oxygen-enriched blast air and uses a special lime slag in the C-furnace. These characteristics change the distribution of impurities from other processes which use PS converters. Recently an increased amount of secondary materials which contain impurities is being treated at Naoshima Smelter. In order to cope with an increment of impurities load and maintain the cathode quality, many improvements have been implemented. The paper discusses the impurities behavior in the Mitsubishi process and describes the measures taken to treat an increased amount of secondary materials.
9:20 am
COMPUTER AIDED OPTIMIZATION OF FURNACE DESIGN AND OPERATING CONDITION OF MITSUBISHI CONTINUOUS COPPER CONVERTER: Susumu Okabe, Hideya Sato, Central Research Institute, Mitsubishi Materials Corporation, 1-297, Kitabukuro-Cho, Omiya, Saitama 330 Japan
Mitsubishi Continuous Copper Converter employs the top blowing lance system for the continuous supply of reaction gases into the molten bath. In order to avoid the excessive refractory wear caused by the melt splash without loss of the reaction efficiency, the furnace design and the blowing condition should be optimized. Empirical equations which correlate the splashing rate on the side wall with the dimensions of the furnace, lance position, lance size, gas velocity and bath properties were obtained by the physical model study, and compiled into a computer program. The computer program is effectively utilized for the analysis of the actual operation and for the optimum design of new furnaces.
9:45 am BREAK
10:10 am
THERMODYNAMIC CONSIDERATIONS IN THE PYROMETALLURGICAL PRODUCTION OF COPPER: R. Sridhar, J.M. Toguri, S. Simeonov, Department of Metallurgy and Materials Science, University of Toronto, Toronto, ON, Canada M5S 3E4
Smelter data from 42 plants have been examined in conjunction with available thermodynamic data of systems related to the pyrometallurgical production of copper. By combining this information with the recently reported sulfied capacity data on fayalite slags, it has been possible to calculate the entrained copper losses and the equilibrium copper losses in industrial slags. A ìCopper Pyrometallurgy Diagramî showing the oxygen pressures and the sulfur pressures in copper production, a ìCopper Smelting Diagramî showing oxygen pressure, sulfur pressure and the copper, sulfur and magnetite contents of slags when producing different matte grades by smelting a Partition Coefficient Diagram for copper smelting have been developed. These diagram are useful guides for the understanding of the thermodynamics of copper pyrometallurgy, for process control and for smelter to set their copper recovery targets.
10:35 am
IMPROVEMENTS TO AIR DISTRIBUTION IN A PEIRCE-SMITH CONVERTER: G.A. Eltringham, BHP Copper, 550 California Street, San Francisco, CA 94104
Ninety-year old technology still is responsible for producing the majority of the worldís copper. The continued development of matte making processes puts the pressure on existing converter installations to provide incremental improvements as well as additional flexibility. Testwork was carried out on the air system around the bustle main highlighting pressure drops that could be easily eliminated. Plant modifications resulted increased blowing rates and hence treatment capacity.
Room: Salon 8
Location: Clarion Plaza Hotel
Session Chairpersons: Renato G. Bautista, Department of Chemical and Metallurgical Engineering, University of Nevada, Reno, Reno, NV 89557; K. Osseo-Asare, Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802
8:30 am
SEPARATION OF RARE EARTHS, THORIUM AND URANIUM DURING MONAZITE PROCESSING BY SOLVENT EXTRACTION USING 2-ETHYL HEXYL PHOSPHONIC ACID MONO 2-ETHYL HEXYL ESTER: N.S. Narayanan, V.R. Nair, V.D. Narayanan, Indian Rare Earths, Limited, Rare Earths Div., Udyogamandal, 683 501, Kerala State, India
Monazite, one of the major sources of rare earths, is normally opened by digestion with hot concentrated caustic soda solution. Caustic digestion dissolves phosphate and leaves a hydrated mixed metal oxides cake containing thorium, uranium and rare earths. By leaching this cake with hydrochloric acid at pH 3.0 to 3.2 bulk of the rare earths are preferentially removed and separated. The slurry left after removal of major portion of rare earths contains all the thorium and uranium present in the feed monazite. In addition this slurry also contains substantial quantities of rare earths. Solvent extraction tests were carried out to develop a process to separate rare earths, thorium and uranium present in the mixed chloride solution obtained by dissolving the above slurry in hydrochloric acid.
9:00 am
PREPARATION OF DYCL3 BY DEHYDRATION IN A FLUIDIZED BED: Johan Sundström, Department of Metallurgy, Division of Process Metallurgy, The Royal Institute of Technology, S-100 44, Stockholm, Sweden.
Anhydrous DyCl3 was prepared from its hexahydrated mother-compound by batch-wise and continuous dehydration using a fluidized bed. A gas mixture of variable composition between argon and HCl was used. The productivity was high, reaching values of 0.28 mol H2O/m2xs during the dehydration to DyCl3xH2O and 0.079 mol H2O/m2xs during the dehydration to DyCl3. By using an overall reaction rate equation, developed from previous findings it was possible to predict the outcome of the continuous fluidization process. The fluidization process efficiency decreases drastically when water content is below DyCl3xO.1H2O. Therefore, in a final treatment the last traces of water were removed by slowly purging gas through a fixed bed.
9:30 am
MASS SPECTROMETRIC STUDY OF VAPORIZATION PROCESSES AND THERMODYNAMIC PROPERTIES OF DyF3-Dy2O3: V.L. Stolyarova, S. Seetharaman, The Royal Institute of Technology, S-100 44, Stockholm, Sweden
In the present work the vaporization processes and thermodynamic properties of the DyF3-Dy2O3 system were studied at the temperatures 1173-1423 K in the concentration range from the individual DyF3 to the individual Dy2 by the Knudsen effusion mass spectrometric method. It was found, the DyF3, DyOF, Dy2OF4 molecules were the main species in vapour. The DyF3 activity in the DyF3-Dy2O3 system was calculated by comparing the total ion currents of dysprosium triufluoride over the system and the individual component. The influence of the cell material (Pt, Mo, Ta) on the concentration of the DyF3, DyOF, Dy2OF4 vapour species in the gaseous phase over the DyF3-Dy2O3 was illustrated. Results, obtained in the present study are in agreement with the available information on the phase diagram of the DyF3-Dy2O3 system.
10:00 am BREAK
10:30 am
PRECIPITATION PROCESSES IN THE SEPARATION OF RARE EARTHS: K. Osseo-Asare, Department of Materials Science and Engineering, Pennsylvania, State University, University Park, PA 16802
Abstract not available.
11:00 am
Nd2Fe14B/
-Fe BASED NANOCOMPOSITE PERMANENT MAGNET MATERIALS PREPARED VIAL MECHANICAL MILLING: W.F. Miao, P.G. McCormick, R. Street, Research Centre for Advanced Mineral and Materials Processing, The University of Western Australia, Nedlands, W.A. 6907, Australia
Nanocrystalline mixtures of Nd2Fe14B and -Fe have been synthesized by mechanical milling and heat treatment. The samples exhibit isotropic magnetic behaviour, with significant remenence enhancement associated with exchange coupling across the interfaces of hard and soft magnetic phases. Magnetic Phases. Magnetic properties are found to depend on the volume fraction of the -Fe phase and heat treatment. The effect of alloy additions to increase the saturation magnetization of the soft phase and the magnetocrystalline anisotropy of the hard phase has also been investigated.
11:30 am
NOVEL TECHNIQUE FOR THE PREPARATION OF SINTERED YBCO: M.I. Hussain, F A. Khwaja, Mazhar Hussain, Anwar-Ul-Haque, Department of Physics, Quaid-I-Azam University, Islamabad, Pakistan., Department of Chemistry, Quaid-I-Azam University, Islamabad, Pakistan
We report on the preparation of YBCO sintered sample by a novel technique named "Explosion Method". The stoichiometric ratio of the compounds were mixed and the powder was encapsulated in the quartz tube. The capsule exploded at 16-hours for specific mass of the product and the size of the tube. The powder was pelletized and characteristic properties were checked. The detailed investigation is carried out on the mass of the product and the size of the capsule which plays an important role in the preparation of superconducting phase, in this method. It has been observed that explosion is important for the superconductivity. The absence of annealing is an advantage in this process, however, the sample deteriorate with time.
Room: 314A
Session Chairpersons: Professor Ali S. Argon, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; Dr. K. Sadananda, Naval Research Laboratory, Code 6323, 4555 Overlook Drive SW, Washington D.C. 20375
8:30 am
OPENING STATEMENTS: Dr. K. Sadananda, Head, Deformation and Fracture Section, Naval Research Laboratory, Code 6323, Washington D.C.
8:40 am
INTRODUCTION OF PROFESSOR EMERITUS FRANK A. McCLINTOCK: Professor Ali S. Argon, Department of Mechanical Engineering, Massachusetts Institute of Technology, Room 1-306, Cambridge, MA 02139
8:50 am KEYNOTE
DUCTILE FRACTURE: HIGHLIGHTS AND PROBLEMS: Professor Emeritus Frank A. McClintock, Massachusetts Institute of Technology, Department of Mechanical Engineering, Room 1-304, Cambridge, MA 02139
The developing understanding of fracture by hole growth is reviewed, with mention of unsolved problems: Tipper in the late 1940's showed not only the idealized limiting micro-mechanisms of fracture by cleavage and by hole growth, but also the current problems of linkages of holes by irregular fine cracks and cleavage with concurrent plastic deformation. Both micromechanisms can lead to either ductile or brittle structures; the Irwin-Williams stress intensity concept K; the Paris fatigue crack correlation; elastic-plastic fracture instability in sheet, the Hutchinson, and Rice and Rosengren annular J-fields for initial and early growth of cracks in power-law materials; The K-T and J-Q extensions; fracture mechanics for predicting the behavior of large structures from tests on small, perhaps fully plastic specimens; traditional and fitness-for-service design and maintenance; the finite element method; its strength, current limitations, and needs; history effects, including the wolf's ear fracture, very low cycle fatigue, and torsion; micro-models of crack formation and growth; McClintock and Gurson; extreme value idealizations in statistics; cooperative and multi-stage problems; crack roughening and three-dimensional effects; recent work on rigid-plastic; non-hardening mechanics of initial and continuing growth of cracks, both with and without symmetry.
9:20 am INVITED
ELASTIC-PLASTIC FRACTURE MECHANICS OF STRENGTH-MISMATCHED INTERFACE CRACKS: David M. Parks, S. Ganti, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
Recent progress in rationalizing and predicting the diverse ductile and brittle cracking behaviors seen in a given structural alloy under monotomic loading (i.e., shallow versus deep cracks; tension versus bending; ductile growth versus cleavage, etc.) has rested critically upon improved characterizations of elastic-plastic crack-front stress and deformation fields. For macroscopically homogeneous elastic-plastic materials, these improved descriptions of the crack-front fields typically include a parameter such as J or CTOD which scales the intensity of crack-tip deformation, as well as a parameter such as the T-stress or the Q parameter which accounts for the triaxiality of the crack-tip fields. When a crack lies along or near a planar material interface across which there is a significant gradient in plastic deformation resistance, the local stress and deformation fields exhibits features which differ both in magnitude and in kind from the homogeneous fields noted above. Such conditions are encountered in strength-mismatched weldments, in which the flow strength of the weld metal, Ywm, differs that of the baseplate, Ybp. Major features of such strength-mismatched interface fields are that (i) for a given macroscopic characterization of crack-tip deformation (in terms of J or CTOD), deformation preferentially focuses in the softer material, and (ii) stress triaxiality in the softer material exceeds that attainable in even the most severe of the homogeneous fields noted above. We review basic features of strength-mismatched interface crack fields as determined from finite element solutions under well-constrained and fully plastic conditions, for a range of strength mismatches and strain hardening behaviors. The fields can be well-described with slip-line fields appropriate to the level of strength-mismatch. Implications of these fields for the toughness of interface cracks are noted.
9:45 am INVITED
IN-PLANE CONSTRAINT EFFECTS IN ELASTIC-PLASTIC FRACTURE MECHANICS: John W. Hancock, J. Li, A.D. Karstensen, A. Nekkal, Department of Mechanical Engineering, University of Glasgow, Scotland G12 8QQ, UK
McClintock (1971) has shown that under plane strain conditions, the fully plastic flow fields are not unique, but depend on geometry and loading. In mode I, the loss of uniqueness is shown to originate from the nature of the elastic field and in particular the sign of the non-singular T stress. The nature of these fields is elucidated by constructing a family of plane straw slip line fields (Du and Hancock 1991). As such they belong to a family of fields which can be described by J and a second parameter which determines the level of crack tip constraint (Q/T). This family of fields are deviatorically similar but differ largely hydrostatically (O'Dowd and Shih 1991, Beteg6n and Hancock 1991). Boundary layer formulations have been used to infer the force on mixed mode slip line fields in contained yielding (Hancock, Karstensen and Nekkal 1996). These differ from those discussed by Shih (1974) in that plasticity does not surround the crack tip, due to the occurrence of an-elastic wedge on the crack flanks. Both mode I and mixed mode fields for weakly stain hardening materials can be interpreted as belonging to a single family such that constraint loss by mixed mode loading. This gives a family of fields which differ largely hydrostatically on the plane of maximum hoop stress. Finally slip line fields for cracks on the interface between a rigid subsume and a perfectly plastic material, subject to mixed mode loading have been constructed, and these are also discussed in terms of constraint effects (Li and Hancock 1996). Experimental data on the effect of in plane constraint on fracture toughness is discussed within the framework of two parameter fracture mechanics. Finally the methods by which constraint enhanced toughness can be used in safety cases based on failure assessment diagrams is discussed (MacLennan and Hancock 1995).
10:10 am BREAK
10:20 am INVITED
TOUGHENING OF METAL MATRIX COMPOSITES THROUGH CONTROL OF INTERFACE TOUGHNESS BETWEEN FIBERS AND MATRIX: Ali S. Argon, M. Seleznev, and C.F. Shih, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, Division of Engineering, Brown University, Providence, RI 02912
In Al alloys reinforced with Al203 fibers control of the size of interface precipitates of Al2Cu, through coarsening, permits control of the effective separation toughness of the interface under the deformation induced local mixed modes of interface fracture during the evolution of global composite fracture, which assures optimization of both transverse strength and axial toughness. Experiments and micromechanical modeling will be presented demonstrating the effectiveness of this strategy.
10:45 am INVITED
THE ROLE OF FRICTIONAL CRACK SLIDING ON THE COMPRESSIVE FAILURE OF ICE AND ON ITS BRITTLE-TO-DUCTILE TRANSITION: Erland M. Schulson, Department of Mechanical Engineering, Thayer School of Engineering, 8000 Cummings Hall, Darthmouth College, Hanover, NH 03755
In 1962 McClintock and Walsh pointed out that frictional sliding across the surface of closed cracks inclined to the direction of loading is an important element in brittle compressive failure. The friction reduces the effective shear stress on the crack plane and so lowers the stress concentrated at the crack tip. Frictional sliding thus increases the far-field stress for out-of-plane wing crack initiation and growth, thereby raising the failure stress (e.g., Brace and Bombolakis 1963, Nemat-Nasser and Horii 1982, and Ashby and Hallam 1986). This paper will show that the brittle compressive failure of ice can be understood in terms of the frictional crack sliding/wing crack mechanism, and that its brittle-to-ductile transition can be explained by incorporating crack-tip creep.
11:10 am INVITED
FRACTURE IN THE DUCTILE AND DUCTILE/BRITTLE REGIMES: CELL MODEL STUDIES: Robert H. Dodds and C. Fong Shi, Department of Civil Engineering, 2129 Newmark Laboratory, MC-250, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, Urbana, IL 61801; Division of Engineering, Brown University, Providence, RI 02912
Mode I crack initiation and growth under plane strain conditions in tough metals have been successfully simulated using an elastic-plastic continuum model which accounts for void growth and coalescence ahead of the crack tip. A row of void-containing cell elements is placed on the symmetry plane ahead of the initial crack. These cell elements incorporate the softening characteristics of the hole growth and its strong dependence on stress triaxiality. Under increasing strain, the voids grow and coalesce to form new crack surfaces thereby advancing the crack. The material parameters are the Young's modulus, yield stress and strain hardening exponent of the metal and two additional parameters, D and fo, characterizing the dimension of the cell element and the initial volume fraction of the void centered within the cell. Once the above material parameters have been calibrated for the material under investigation, the model can be applied to compute relationships among load, load-line displacement and crack advance with no restrictions on the extent of plastic deformation and crack advance [Xia and Shih, (1995a and 1995b)]. The model has been applied to several specimen geometries which are known to give rise to significantly different crack tip constraints and crack growth resistance behaviors. Computed results are compared with sets of experimental data for two tough steels. Details of the load, displacement and crack growth histories are accurately reproduced [Xia, Shih and Hutchinson, 1995]. Suitably defined measures of crack tip loading intensity, such as those based on the J-integral can also be computed; however such crack growth resistance curves no longer play the central role in this approach. The above model has been employed in the transition regime where a crack initiates an grows by ductile tearing but final failure can occur catastrophic cleavage fracture. Crack growth causes significant alterations in the stress field, the process zone size, the competition between ductile and brittle processes and the sampling volume. The effects are accounted for by incorporating weakest link statistics into the cell element model. The cleavage fracture model also takes into account the increase of sampling volume with crack growth and the competition between void nucleation from carbide inclusions and unstable inclusion cracking which precipitates catastrophic cleavage fracture. Load-displacement behavior, ductile tearing resistance and transition to cleavage fracture are discussed for several different test geometries and a range of microstructural parameters. The model predicts trends in the ductile/brittle transition region that agree with experimental data [Xia and Shih, (1996)].
Room: 340A
Session Chairperson: Dr. Robert J. Gottschall, Division of Materials Science (ER-13), U.S. Department of Energy, Germantown Building, 19901 Germantown Road, Germantown, MD 20874-1290
8:30 am INVITED
INTRODUCTORY REMARKS: Robert J. Gottschall, Division of Materials Science (ER-13), U.S. Department of Energy, Germantown Building, 19901 Germantown Road, Germantown, MD 20874-1290
8:45 am INVITED
FERROMAGNETIC BULK AMORPHOUS ALLOYS: Akihisa Inoue, Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980-77, Japan
Since the discoveries of bulk amorphous alloys in Ln-Al-TM, Mg-Ln-TM and Zr-Al-TM (Ln=lanthanide metal, TM=transition metal) systems for the last several years, great attention has been paid to bulk amorphous alloys. It was subsequently reported that bulk amorphous alloys were formed in Ti-Zr-TM, Zr-Ti-TM-Be and Pd-Ni-Cu-P systems. The maximum thickness reaches 40 mm and the critical cooling rate is of the order of 1K/s. However, there have been no data on bulk amorphous alloys with ferromagnetism at room temperature. We have derived three empirical rules for the achievement of large glass-forming ability from previously reported bulk amorphous alloys. Based on the three rules, we have searched new ferromagnetic bulk amorphous alloys and succeeded in finding several ferromagnetic bulk amorphous alloys in Fe-, Co- and Ln-based systems. The Fe-based bulk amorphous alloys exhibit good soft magnetic properties of 1.3 T for magnetization, 2 A/m for coercive force (Hc), 7000 for permeability at 1 kHz and 21x10-6 for magnetostriction. The Ln-based bulk amorphous alloys were prepared in the diameter range up to 15 mm and exhibited rather good hard magnetic properties of high Hc of 400 kA/m and maximum energy products of 20 kJ/m3. These discoveries seem to be promising for future progress of bulk amorphous alloys.
9:25 am INVITED
THERMODYNAMIC AND KINETIC ASPECTS OF BULK METALLIC GLASS FORMING ALLOYS: William L. Johnson, W.M. Keck Laboratory of Engineering Materials 138-78, California Institute of Technology, Pasadena, CA 91125
The development of several families of multicomponent alloys which form metallic glasses at relatively low cooling rates has triggered renewed interest in thermodynamic and kinetic properties of undercooled liquid metals as well as glass formation. Results of studies of atomic diffusion, viscosity, specific heat, liquid phase separation, and crystallization kinetics will be surveyed for alloys in the Zr-Ti-Ni-Cu-Be and Zr-Ti-Ni-Cu-Al systems. Containerless processing studies of the undercooled melts using electrostatic and electromagnetic levitation will be described. Liquid phase separation, impurity effects, and heterogeneous crystal nucleation are found to play an important and often unanticipated role in the crystallization kinetics. This has led to new understanding of the factors which govern glass formation in these bulk glass forming materials.
10:05 am INVITED
PHASE SEPARATION, CRYSTALLIZATION AND FORMATION OF QUASICRYSTALS IN BULK Zr-BASED AMORPHOUS ALLOYS: Uwe Köster, Department of Chemical Engineering, University of Dortmund, D-44221 Dortmund, Germany
Crystallization occurs by nucleation and growth. Growth may be primary, eutectic or polymorphic. Crystallization statistics as performed by TEM indicate heterogeneous nucleation with large transient times below the glass transition; nucleation and growth rates obey Arrhenius equations with activation energies typical for diffusion. Above glass transition homogeneous nucleation has been found and kinetics can be described best by Vogel-Fulcher-Tammann equations. From Crystallization studies typical metal-metalloid glasses are fragile, but the new bulk amorphous alloys are strong glasses. Amorphous phase separation prior to crystallization not only increases the glass forming ability, but also leads to the formation of nanocrystalline structures. Phase separation might be responsible for the strong influence of oxygen and hydrogen on the crystallization of Zr-based metallic glasses. Some bulk amorphous alloys transform into quasicrystals. Their nucleation and growth rates are measured in detail. The relation between glass-forming ability, existence of Laves phases and formation of quasicrystals will be discussed.
10:45 am BREAK
11:00 am INVITED
BULK NANOCRYSTALLINE AND AMORPHOUS REFRACTORY ALLOYS AND THEIR PROPERTIES: S.J. Poon, G.J. Shiflet, D.J. Li, K.J. Doherty, Department of Physics, Department of Materials Science, University of Virginia, Charlottesville, VA 22901
Synthesis of bulk samples of refractory metal alloys containing nanocrystalline and amorphous phases via conventional casting and their structural and physical properties will be reported. First, we will present results on (Fe, Ni, Cu, Nb)95Zr5 systems. Key factors for forming the titled phases will be discussed. Then we will report recent results on titanium alloys, with emphasis on structure and phase transformation.
11:40 am INVITED
BULK AMORPHOUS METALLIC ALLOYS: SYNTHESIS BY FLUXING TECHNIQUES AND PROPERTIES: Yi He, Ricardo B. Schwarz, Center for Materials Science, MS-K765, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545
Fluxing techniques have been used to study the undercooling and vitrification of glass-forming binary, ternary and quaternary alloy melts. By reducing and neutralizing heterogeneous nucleation centers, molten Pd10Fe30Ni40P20 were undercooled to 303 K or 0.26 Tm below its melting temperature Tm, while bulk amorphous Pd-Ni-P and Pd-Cu-P alloy rods with diameters ranging from 7 to 25 mm were synthesized over a wide composition range. The crystallization temperatures Tx and the glass transition temperatures Tg of these bulk amorphous alloys were determined by differential scanning calorimetry (DSC). For most bulk amorphous Pd-Ni-P alloys, the difference T=Tx-Tg is larger than 90 K, and bulk amorphous Pd40Ni40P20 cylinders with 25 mm in diameter can be easily fabricated. T for bulk amorphous Pd-Cu-P alloys is smaller than for amorphous Pd-Ni-P alloys, and exhibits a dependence on the phosphorus concentration which peaks near 20 at.% P. The glass formability of Pd-Cu-P was increased substantially when part of Cu was placed by Ni. Our results demonstrate that the critical cooling rates for glass formation in Pd-Ni-P and Pd-Cu-Ni-P alloys are the lowest among all known bulk metallic glass forming systems. The density, microhardness, elastic properties, specific heat and the glass formation range of these alloys will be reported.
Room: 330G
Session Chairperson: Elizabeth A. Holm, Sandia National Lab, Physical and Joining Metallurgy, MS 1411, Albuquerque, NM 87185-0340
8:30 am INVITED
THEORETICAL CALCULATIONS FOR INTERFACES: GRAIN BOUNDARIES IN COVALENT MATERIALS AND METAL-CERAMIC INTERFACES: Masanori Kohyama, Dept. of Material Physics, Osaka National Research Institute, AIST, 1-8-31, Midorigaoka, Ikeda, Osaka, 563, Japan
For distorted configurations at interfaces in covalent materials or for interfaces between dissimilar materials, it is difficult to develop reliable interatomic potentials. For such systems, it is desirable to perform electronic structure calculations so as to clarify the stable configurations and microscopic nature. Currently, such kinds of enormous calculations are becoming possible by virtue of the development of the efficient theoretical methods and the high-performance computers. In this paper, we present our recent band-theoretical calculations for grain boundaries in Si, SiC and diamond, and for Al-SiC interfaces. First, grain boundaries in covalent materials have been dealt with by using the transferable tight-binding method [1]. For those in Si, general features of stable configurations and general relations between local structural disorder and local electronic structure are clarified. These are compared with those in diamond. For those in SiC, effects of interfacial C-C or Si-Si bonds and interfacial stoichiometry are analyzed. Second, ab initio calculations for grain boundaries in Si and in SiC have been performed by using the first-principles molecular dynamics (FPMD) method [2]. Stability of the structural models and the nature of interfacial C-C and Si-Si bonds in SiC are analyzed more quantitatively. Third, ab initio calculations for Al-SiC interfaces have been investigated [3]. The features of Al-C and Al-Si interactions at the interfaces are clarified.
9:10 am
ATOMIC STRUCTURE OF INTERFACES IN THE LAMELLAR TiAl AND EFFECTS OF DIRECTIONAL BONDING: V. Vitek, R. Siegl, Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104; H. Inui, M. Yamaguchi, Department of Metal Science and Technology, Kyoto University, Kyoto 606, Japan
The microstructure of nearly stoichiometric TiAl alloys, which are important candidates for high-temperature applications, consists of lamellae with L10 and DO19 structures. A serious limitation is their low room temperature ductility. The failure often occurs by cracking along the lamellar interfaces and one clue to the fracture propensity is the atomic structure of these interfaces. To investigate this atomic structure we first carried out atomistic calculations employing Finnis-Sinclair type central force many-body potentials. However, calculated atomic structures exhibit some significant discrepancies when compared with high-resolution electron microscopy observations. For this reason further calculations have been made using an ab initio electronic structure full-potential method. An excellent agreement between calculated and observed structures was then attained. This result can be interpreted in terms of the covalent type bonding across the interface. This emphasizes significance of directional bonding in TiAl which may play an important role in its mechanical behavior. *Research supported by the U.S. Dept. of Energy, Office of Basic Energy Sciences, Grant No. DE-FG02-87ER45295 and NEDO.
9:30 am
ATOMISTIC STUDY OF GRAIN BOUNDARIES IN NiAl: M. Yan, V. Vitek, S.P. Chen, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545; Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104
We have studied the grain boundary properties in NiAl B2 compound by applying the empirical N-body central force potentials of the Finnis-Sinclair type. These potentials have been constructed for B2 NiAl by fitting a number of equilibrium properties of the alloy and reproducing the asymmetric behavior of constitutionals point defects in off-stoichiometric NiAl. At the same time, these potentials assure the structural and mechanical stability of the B2 lattice. It was found that in stoichiometric NiAl alloy boundaries in surplus of Al atoms have appreciably lower cohesive strength than the stoichiometric boundaries or boundaries in surplus of Ni atoms. From the structural point of view, boundaries in surplus of Al possess the largest expansion and are associated with large "holes". On the other hand, boundaries with the stoichiometric configuration or in surplus of Ni atoms have more compact structures. The segregation of the antisite defects and vacancies at grain boundaries was also investigated by performing molecular static and Monte Carlo calculations. It was found that no antisite defects are favored at grain boundaries at the stoichiometric bulk composition. In the case of Ni in surplus in the bulk Al atoms have strong tendency to segregate to the boundary region. The effects of such grain boundary features upon the mechanical properties of NiAl will be discussed.
9:50 am
GRAIN BOUNDARY STRUCTURE TRENDS IN B2 COMPOUNDS: Batsirai Mutasa, Diana Farkas, Yuri Mishin, Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
The relaxed atomistic grain boundary structures in B2 aluminides were investigated using molecular statics and embedded atom potentials in order to explore general trends for a series of B2 compounds. Free surface energies and grain boundary structures were studied in three compounds, FeAl, NiAl and CoAl. These alloys respectively have increasing anti-phase boundary energies. The misorientations chosen for detailed study correspond to the 
5(310) and 5(210) boundaries. The effects of both boundary stoichiometry and simulation block stoichiometry on grain boundary energetics were considered. Chemical potentials and point defect energies were calculated for boundaries contained in both stoichiometric and off-stoichiometric bulks. The surface energies for these B2 aluminides were also calculated so that trends concerning the cohesive energy of the boundaries could be studied. The implications of stoiciometry, the multiplicity of the boundary structures and possible transformations between them for grain boundary brittleness are also discussed.
10:10 am BREAK
10:30 am INVITED
EPITAXY AND ORIENTATION RELATIONSHIP IN BICRYSTALS: P. Pirouz, Y. Ikuhara, F. Ernst, Deparment of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204; Department of Materials, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan; Max-Planck-Institut für Metallforschung, Seestr. 92, D-70174, Stuttgart, Germany
When two crystals are in contact, the interaction between the atoms at or near their interface often orients the crystals in a unique way. Usually, one of the two crystals is a matrix or a substrate, and the other crystal is a precipitate within the matrix, or a deposit on the substrate. In this talk, a recently-proposed method for predicting the orientation relationship (OR) between two crystals is described and experimental cases of film/substrate composites are compared with the predictions of the model. The case of three-dimensional OR, where the film-substrate orientation relationship is maintained irrespective of the substrate surface on which the film is grown, is described, and this is compared with those cases where multiple ORs may be favored resulting on the dependence of the OR on the substrate surface. Finally, the physical basis of the model is described in terms of the energy minimization of adatoms deposited on a rigid substrate.
11:10 am
STRUCTURAL CHARACTERIZATION AND MODELING OF THE ALUMINUM {111}/SAPPHIRE (0001) HETEROPHASE INTERFACE: D.L. Medlin, K.F. McCarty, R.Q. Hwang, J.E. Smugeresky, T. Tsuji and M.I. Baskes, Sandia National Laboratories, Livermore CA 94551; Shizuoka University, Jyoohoku 3-5-1, Hamamatsu 432, Japan
We are investigating Al/Al2O3 interface structure using thin films fabricated by deposition of aluminum from an effusion source onto (0001) sapphire under UHV conditions. Structural considerations suggest that the metal would grow to match the close-packed metal planes and directions with the close-packed oxygen ions of the sapphire substrate, i.e., (0001)Al2O3//(111) metal and [10-10]Al2O3//[-110]metal. Although this orientation is predominant, transmission electron microscopy observations also show the existence of two additional types of orientation relationship, corresponding to rotations of 30 degrees and ~11 degrees from the primary domain orientation. A comparison of the predictions of atomistic calculations for the interface structure and dislocation configuration with the results of high resolution and conventional transmission electron microscopy observations will be presented. This work is supported by the U.S. DOE under contract DE-AC04-94AL85000.
11:30 am
INVESTIGATION OF THE BONDING CHANGES ASSOCIATED WITH GRAIN BOUNDARY EMBRITTLEMENT: V.J. Keast, J. Bruley, D.B. Williams, P. Rez*, Department of Materials Science and Engineering, Whitaker Lab #5, Lehigh University, Bethlehem PA 18015; *Center for Solid State Science and Department of Physics, Arizona State University, Tempe, AZ 85287-1704
Grain boundary embrittlement by impurity or alloying elements is a common and technologically important phenomenon, of which the embrittlement of Cu by Bi is a classic example. Investigations, using the near edge fine structure in the electron energy loss spectrum (EELS), have indicated that there is a change in bonding at the grain boundaries associated with the segregation of Bi. Namely, there is a decrease in the density of the d states for Cu atoms at the boundary when Bi is present. The effect of variations in grain boundary misorientation on the Bi segregation levels and on the near edge structure will be described. Comparisons between results from EELS and x-ray photoelectron spectroscopy (XPS) will also be made. (Supported by NSF (DMR 93-0625)
Room: 340D
Session Chairperson: Dr. Krishna Rajan, Rensselaer Polytechnic Institute, Materials Engineering Department, MRS-110, Troy, NY 12180-8554
8:25 am
INTRODUCTION: Dr. Krishna Rajan, Rensselaer Polytechnic Institute, Materials Engineering Department, MRS-110, Troy, NY 12180-8554
8:30 am
SCIENCE & TECHNOLOGY POLICIES FOR DEVELOPMENT: AN INTERNATIONAL OVERVIEW: Dr. Krishan Rajan, Rensselaer Polytechnic Institute, Materials Engineering Department, MRS-110, Troy, NY 12180-8554
In the presentation we provide an overview of the role changing political structures and its influence on science and technology policies. Specific issues of the role of the private sector in different types of economies are from the role of multinational corporations to state owned enterprises. The different roles played by industry in these counties in promoting cooperation among the different sectors in science and technology policy are examined.
9:00 am
COMPETITIVE TECHNOLOGY DEVELOPMENT: STRATEGIC PARTNERSHIPS WITH UNIVERSITY AND GOVERNMENT: Michele Migliuolo, Vice President of Technology, Kurt J. Lesker Company, 1515 Worthington Avenue, Clairton, PA 15025
Product development in a growing small business can be difficult due to lack of internal expertise or facilities. Often technology is not developed due to an apparent lack of appropriate resources. We discuss the long standing and on-gong strategic technology transfer programs at the Kurt J. Lesker Company. We leverage financial resources (internal, government, customer) with technical resources (internal, university, customer), to develop new products and processes which are more effectively manufacturable. Our research programs serve to establish us as a manufacturer of exceptional deposition systems and component, and as an engineering firm with the knowledge which a manufacturer of devices and systems requires. It is the combination of our deposition systems and process technology which will ensure that this firm is regarded as a world leader in materials science. By allowing our company to perform research and development efforts which we would not have otherwise undertaken, our funding sources thus contribute to business growth, direct company growth, academic research, education of graduate students and researchers, and local economic growth as a result of increased employment.
9:30 am
THE ATTRACTION OF UNIVERSITY CONSULTANCY SERVICES FOR INDUSTRIAL COMPANIES: Dr. Brian Mellor, Manager, Engineering Materials Consultancy Service, University of Southampton, Southampton S017 1BJ, UK
10:00 am BREAK
10:15 am
PAPER WITHDRAWN Dr. David Edmonds, Head of Materials, Leeds University, School of Materials, Leeds LS2 9JT
10:45 am
PAPER WITHDRAWN Prof. Guilemany, University of Barcelona, Department de Enginyeria Quimica, I Metal.lurgia, Calle Marti I Franques, 1, 08028 Barcelona, Spain
11:15 am METALLURGICAL INSTITUTIONS OF HIGHER EDUCATION AND STEEL INDUSTRY IN CHINA: Prof. Zengyong Zhong, Chinese Society for Metals, 46 Dongsixi Dajie, Beijing 100711, China; Prof. Xishan Xie, University of Science and Technology, Beijing, 30 Xueyuan Road, Beijing 100083 China; Prof. Zhongwu Lu, Northeastern University, Shenyang, 110006, China
The progress of the Chinese steel industry in the last four decades and appropriate development of metallurgical institutions of higher education are briefly reviewed. The favorite and unfavorite conditions for close contact between academic institutions and industry are discussed. Principal linkages between institutions of higher education and steel industry are induced; they are the following: science popularization, continuing education, qualification and degree education staffs in-service, joint accomplishment of research projects, and supervision of student practices in steel works. The important role of The Chinese Society for Metals in respect of relationship between academic institutions and industry is emphasized. In the process of economic reform in China more close university/college industry linkages are expected.
Room: 330F
Session Chairpersons: F.H. (Sam) Froes, University of Idaho, Institute for Advanced Processes, Mines Bldg 204, Moscow, ID 83844-3026; D. Chellman, Lockheed Aeronautical Systems Co., Lockheed Corporation, Marietta, GA 30063-0150
8:30 am
RECENT ADVANCES IN THE SYNTHESIS OF LIGHT WEIGHT METALLIC MATERIALS: C.M. Ward-Close, F.H. Froes, and S.S. Cho, Chief Metal Matrix Composites, Structural Materials Centre, DRA Farnborough, Hampshire GU14 6TD, UK; Director IMAP, University of Idaho, Moscow, Idaho 83844-3026; Lockheed Technical Fellow, Advanced Structures and Materials, Lockheed Aeronautical Systems Co., Marietta, Gorgia 30063; Vice Director of RASOM, Rapidly Solidified Materials Research Center, Chungnam National University, Taedok Science Town, Taijon 305-764, Korea
Recent advances in the synthesis of light-weight metallic materials will be reviewed with emphasis on developments which have occurred since the last symposium in this series. Primary consideration will be given to alloys based on aluminium, magnesium and titanium both in monolithic and composite configurations. Emphasis will be on synthesis/processing/fabrication rather than the more traditional microstructure-mechanical property relationships. Particular attention will be given to the status of commercialisation of high performance light-weight metallic materials.
9:00 am
HYDROGEN STORAGE WITH MAGNESIUM-IRON NANOCOMPOSITES: M.A. Imam, Materials Science and Technology Division, Code 6323, US Naval Research Laboratory, Washington, DC 20375; R.L. Holtz, Geo-Centers, Inc., 10903 Indian Head Highway, Fort Washington, MD 20744
Of potential practical hydrogen storage materials (HSM), pure Mg would be best from the standpoint of hydrogen capacity per unit mass. However, pure Mg has poor hydrating reactivity due to surface oxide poisoning and low catalytic activity. Mg-Ni is a well-known attentive that is more stable against oxidation. The Ni aids catalysis of the H2 dissociate chemisorption and produces additional benefits by lowering the dehydrogenation temperature, but at the expense of a decrease in storage capacity. Theoretical considerations suggest that nanostructured Mg with low concentrations of both Ni and Fe will be an optimum Mg-based HSM. We have prepared submicron Mg-(Ni,Fe) pseudoalloys by bail milling and report here on the hydrogen storage characteristics.
9:20 am
PROCESSING AND PROPERTIES OF TITANIUM AND TITANIUM METAL MATRIX COMPOSITE BASED LAMINATES: Y.Q. Zuo, D.J. Smith, P.G. Partridge, A. Wisbey; Department of Mechanical Engineering, Interface Analysis Centre, University of Bristol, UK; Structural Materials Centre, DRA Farnborough, UK
Two laminate systems based on titanium alloy IMI834 and titanium metal matrix composite (MMC) have been manufactured by diffusion bonding. The S-type laminate contain 50% MMC in the outside layers and 50% Vol. IMI834 in the middle of the laminate. The C-type laminate contains the same volume fraction of IMI834 and MMC, but here the MMC is in the middle of the laminate. Bonding parameters: temperature, pressure and time have been optimised. Effective Young's Modulus and bend strength have been investigated using four-point bend tests, and impact fracture toughness of the laminates and control samples have been assessed by using an instrumented impact testing. For un-notched specimens, 100% IMI834 has highest fracture toughness with lowest E and strength; MMC, in contrast, has higher strength and lowest fracture toughness. However, for notched specimens, both of them have lower strength and fracture toughness compared with the S-type laminate. The measured stiffness (E) for the S-type laminate was greater than that for IMI834 by about 1.7. By laminating materials, the impact fracture toughness of S-type laminate for un-notched and notched specimens, compared with 100% MMC material, increased by about 2.7 and 4.6. Young's modulus strength, and fracture toughness can be optimised by selecting different structures. Lamination by combining tough matrices and reinforced components is an effective way to improve toughness for high strength materials, like MMC, and the properties of the materials can be tailored according to a particular application.
9:40 am
PROCESSING OF Ti/SiC COMPOSITES: A COMPARATIVE STUDY OF THE FOIL-FIBRE-FOIL AND THE TAPE-CASTING TECHNIQUES: Zheng Xiao GUO, Department of Materials, Queen Mary and Westfield College, University of London, Mile End Road, London E1 4NS, UK
Ti-based SiC fibre reinforced composites are strong, stiff and light-weight materials for high temperature applications up to 700-1000°C. As with any other advanced materials, their development has to overcome both economic and technical hurdles. Here, a study into the foil-fibre-foil and the tape-casting processing techniques is reported. The fundamental procedures involved in the techniques are compared and discussed. Possibilities of reducing product costs are analysed. Due to the reactive nature of titanium, the composites must be processed under minimum thermal exposure to reduce undesirable fibre/matrix interfacial reactions: on the other hand, care should also be taken not to use too low a temperature or too large a pressure in order to avoid fibre breakage. This requires an optimum balance of the processing temperature, pressure and time. Therefore, both theoretical and experimental investigations were conducted for the consolidation of aligned fibre mats with matrix foils or with matrix powder-tapes. The effects of processing parameters, such as temperature pressure and time, on the mechanisms of identification are evaluated. Predictions of the process model are compared with experimental findings, which shows satisfactory agreement. Various types of interfacial defects and fibre breaking have been analysed in relation to the processing parameters and fibre/matrix lay-ups. Consequently, defect- and reaction- free composites have been obtained. This is particularly successful with the assistance of a temporary hydrogenation procedure using either pre-hydrogenated foils or powder particles during processing.
10:00 am BREAK
10:20 am
CHARACTERISATION OF SIGMA SIC FIBRE/TITANIUM ALLOY MMCS FABRICATION BY PLASMA SPRAYING AND FOIL/FIBRE METHODS: A.M. Baker, P.S. Grant, M.L. Jenkins , C.M. Ward-Close, Z. Fan, B Cantor ,OCAMAC, Department Of Materials University of Oxford, Parks Road, Oxford OX1 3PH, UK
A new process for vacuum plasma spray manufacturing of multi-ply Titanium/SiC fibre MMC rings has been developed. Material produced can be identified easily by subsequent vacuum hot pressing or HIP. Ti and Ti-6A1-4V matrices have been 'spray-wound' with C coated and C/TIBx coated DRA Sigma SiC fibres. Characterisation by electron microscopy has identified interfacial reaction products, showing that the fibre/matrix reaction is similar to that for plasma sprayed monotapes. SiC fibres chemically extracted from the matrix have been subjected to tensile and bend testing to quantify process damage for spray-wound and foil/fibre material. This has shown that fibre damage from spray/winding is of a similar magnitude to that from foil/fibre processing. Possible mechanisms for fibre damage during processing have been identified.
10:40 am
CONSOLIDATION OF CONTINUOUS SiC/Ti-6Al-4V MATRIX-COATED FIBRE METAL MATRIX COMPOSITES: S. Schuler, B. Derby, M.J. Wood, C.M. Ward-Close1, Oxford Centre for Advanced Materials and Composites, OCAMAC, Department of Materials, University of Oxford, Parks Road, Oxford , OX1 3P; Structural Materials Centre, Defence Research Agency, DRA, Farnborough Hampshire, GU14 6TD, UK
The consolidation of continuous matrix-coated fibre Metal Matrix Composites, MMC, has been investigated using a theoretical as well as an experimental approach. A numerical, quantitative model has been developed for the solid-state consolidation of continuous Matrix-Coated Fibre, MCF, Metal Matrix Composites. In addition, an experimental verification programme was conducted using two different samples types, one produced under normal conditions and one containing yttrium maker layers. The marker layers were used to make the matrix deformation visible, which occurs during the consolidation, and hence offered the opportunity of a direct comparison of the predicted matrix deformation and the experimentally determined matrix deformation. The materials investigated were continuous Textron SCS-6 SiC fibres in a Ti-6A1-4V metal matrix. The fabrication route chosen was the Matrix-Coated Fibre method, developed by the DRA Farnborough, UK. In this method, the fibres are pre-coated prior to consolidation with the matrix material using Electron Beam Evaporation, a Physical Vapour Deposition technique. The thickness of the matrix-coating and hence the final fibre volume fraction of the composite can easily be varied by adjusting the coating time. For the consolidation to the final composite the matrix-coated fibres are stacked, degassed placed into a titanium container and hot-isostatically pressed. The analytical model is based on a Finite Element Model, FEM.
11:00 am
RECENT ADVANCES IN FIBER COATING TECHNOLOGY FOR USE IN SiC/Ti-MMCs: D. Upadhyays, P. Tsakiropoulos, and F.H. Froes, Institute for Materials and Advanced Processes, University of Idaho, Moscow, ID 83844-30261; Department of Materials Science and Engineering, University of Surrey, Guildford, Surrey, GU2 5XH, UK: Structural Materials Centre, DRA Farnborough, Hants GU14 6TD, UK
Continuous silicon carbide fibre-reinforced titanium-based metal matrix composites offer many advantages over conventional monolithic materials including high strength-to-density ratio. However, there is a need to design an improved protective coating for the silicon carbide fibre to combat interfacial chemical reactions as well as to accommodate large mismatch in the coefficient of thermal expansion (CTE) between the SiC fibre and titanium matrix. This paper describes the strategy for designing coating for continuous silicon carbide fibre and reports on a new coating system based on a compliant layer/ reaction barrier concept developed for titanium metal matrix, composites including those based on -TiA1. The newly developed coating system, designated FUWT1. consists of Gd/GdB3 where the Gd layer (adjacent to SiC) works as a compliant layer while the GdB3 layer works as a reaction barrier. The results of this work indicate that the FUWT coating perform well both a reaction barrier (protect the SiC fibre from reactions with titanium up to 100°C) and a compliant layer (absence of thermal cracking in AiA1 based composite). The interfacial shear strength of an as-fabricated SiC/FUWT/Ti-6A1-4V was found to be higher than the presently available SCS6/Ti-6A1-4V and Sigma (SM1240)/Ti06A1-4V composites. From the surnames of the four co-inventors: Froes, Upadhyaya, Ward-Close and Tsakiropoulos.
11:20 am
THE MANUFACTURE OF Ti ALLOY/SiC FIBRE COMPOSITES BY A NEW SPRAY/WIND PROCESS: Z.Y. Fan, P.S. Grant, B. Cantor, Department of Materials, Oxford University, Parks Road, Oxford OX1 3PH, UK.
This paper describes a new method of manufacturing Ti alloy/SiC fibre reinforced composites. Three dimensional hoop reinforced rings, cylinders and tubes are being manufactured by concurrent plasma spraying of titanium alloy and mechanical winding of SiC or other reinforcing fibres or wires. The paper will outline the manufacturing process concentrating on the range of geometry's which can be manufactured, and will discuss the variety of microstructures which can be achieved.
11:40 am
SYNTHESIS AND PHASE EQUILIBRA IN TiB2 PARTICLE REINFORCED HIGH MODULUS STEEL: Kouji Tanaka, Tadashi Oshima, and Takashi Takashi Saito, Toyota Central R&D Labs, Inc., 41-1 Yokomichi, Nagakute, Aichi, 480-11, JAPAN
This paper describes the synthesis of high modulus steel for automobile parts with an emphasis on its alloy-designing concept and phase equilibrium. Titanium diboride (TiB2) particles have been verified to be the best reinforcement for improving isotropic Young's modulus of steels. The calculated phase diagram shows that TiB2 has a narrow tow-phase equilibrium window with carbon-free Fe-Cr-Ti ferric steel and has neither solubility of iron nor chromium. Those thermo-dynamical stability's of TiB2 are responsible for maintaining its own high Young's modulus of 540GPa in the ferocity steel. Both pre-mixed and in-situ TiB2 particles effectively reinforced the ferocity steel matrix. The developed steel with 30vol.%TiB2 showed a Young's modulus of 280GPa which apparently corresponded to 350GPa due to its reduced density of 6.6g/cc compared with 7.8g/cc of the conventional steel.
12:00 noon
LIGHT WEIGHT CELLULAR STRUCTURES BASED ON ALUMINIUM COMPOSITES: O. Prakash, Dept. of Mechanical Engineering, Indian Inst. of Technology, Kanpur 208016, India; J.D. Embury, C. Sinclair, Dept of Materials Science and Engineering, McMaster University, Hamilton, Ontario, L8S 4L7, Canada; H. Sang, Metallurgy Dept., Queenís University, Kingston, Canada; P. Silvetti, F.A.M.A.F. Dept. of Physics, University of Cordoba, Argentina
An interesting form of light weight material which has emerged in the past two decades is metallic foam. This paper deals with the basic concepts of making metallic foams and a detailed study of foams produced from Al-SiC. In addition some aspects of cellular solids based on honeycomb structures are outlines including the concept of producing both two phase foams and foams with composite walls.
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