Sponsored by: SMD Non-Ferrous Metals Committee, Light Metals Division
Program Organizer: Professor James G. Morris, Chemical & Materials Engineering, Director, Light Metals Research Labs., University of Kentucky, Lexington, KY 40506
Tuesday, AM Room: A2-3
February 6, 1996 Location: Anaheim Convention Center
Session Chairperson: James G. Morris, 175 Anderson Hall, University of Kentucky, Lexington, KY 40506
8:30 am Invited
METALLURGICAL ASPECTS OF ALUMINIUM FOR CANMAKING: P. D. C. Rogers, CarnaudMetalbox plc Research and Development, Downsview Road, Wantage, Oxon, OX12 9BP, UK
The properties of aluminum alloys used for canmaking have been the object of much research, as the demands of the Canmakers for zero defects and trouble- free running have grown. The main requirement is consistency, but the puzzle still remains why coils will not run one day, but will run the next. Work has shown the importance of controlling earing, mechanical properties, coil shape and thickness, both from coil to coil and within the coil. This means that traditional testing is inadequate, and more emphasis has to be placed on process control. It is not difficult to write a specification which describe the main metallurgical and dimensional features of body, end and tabstock, but it will not describe why material from one mill will run better, whilst the reverse is true elsewhere. While we do not have clear answers to all problems, our understanding is growing.
9:00 am Invited
MICROSTRUCTURE AND TEXTURE EVOLUTION DURING THERMO MECHANICAL PROCESSING: Niels Hansen, Materials Department, Riso National Laboratory, DK- 4000 Roskilde, Denmark
The microstructure and texture evolution during thermomechanical processing of materials and alloys is at present studied extensively by modern automated techniques such as EBSP (Electron Back Scattering Pattern) in a SEM and by the Kikuchi pattern technique in a TEM. These experimental studies are followed by the development of physical based models of deformation and recrystallization microstructures and textures. On this basis recent studies of aluminium and aluminium alloys deformed by rolling or plain strain compression are summarized with emphasis on grain subdivision on different size scales into crystallites separated by dislocation boundaries. The scale of this subdivision refines with increasing stress and strain which also significantly effects the crystallographic orientation of the crystallites. These observations are analyzed on basis of the actual slip pattern and the tendency of dislocations to accumulate in low energy configurations. Finally the observations and the results of the subsequent analysis are related to the thermomechanical behavior of aluminium and aluminium alloys.
9:30 am
THE EVOLUTION OF CRYSTALLOGRAPHIC TEXTURE DURING THE RECRYSTALLIZATION OF HOT ROLLED 5182: Phillip A. Hollinshead, Alloy Technology Division, Alcoa Laboratories, Aluminum Company of America, Alcoa Center, PA 15069
The progression of recrystallization in initially unrecrystallized hot rolled 5182 was studied by various techniques. Recrystallization nuclei could plainly be observed in an optical microscope after heating 22 seconds at the hot mill exit temperature of 675 0F and recrystallization was complete at 70 seconds. Using the backscattered Kikuchi diffraction (BKD) technique in the scanning electron microscope (SEM) the cube texture was found to be the only preferred orientation in the early stages of recrystallization. Pole figures from nearly fully recrystallized material were very similar to those from the initial recrystallized grains, indicating that the final texture was determined at a very early stage of the recrystallization process. The copper (Cu) component. {112}<111>, showed signs of decreasing more rapidly in the early stages of recrystallization relative to other components of the rolling texture. The last portion of the microstructure to recrystallize was found to be bands of the brass (Bs) component, {110}<112>. In 8 cube oriented grains at the start of recrystallization, 6 were associated with deformed regions of the cube orientation.
9:50am
EVOLUTION OF ROLLING AND RECRYSTALLIZATION TEXTURES IN A HOT ROLLED CAN BODY STOCK ALLOY: Baolute Ren, Manufacturing Technology Laboratory, Corporate Research & Development, Reynolds Metals Company, 3326 East Second Street, Muscle Shoals, AL 35661- 1258
Hot rolling is a very important step in fabrication processes of aluminum beverage can body stock. It has been indicated that the development of microstructure and texture of AA 3104 alloy during hot rolling depends significantly on hot rolling procedures. In industrial thermomechanical processing, a hot band material can be produced with a deformation structure and a dominant deformation texture, or with a recrystallized structure and a dominant recrystallization texture, even though the hot band is not subjected to a hot line anneal. In addition, a partially recrystallized hot band material can be obtained, which has both deformation and recrystallization texture orientations. In the present work, the texture evolution of AA 3104 alloy during hot rolling was studied. It was found that the Copper orientation was predominant for the deformation texture on the surface of the hot band while the Brass orientation was predominant at the mid- thickness. In the subsequent annealing or self- annealing process, this difference in the texture orientation influenced the recrystallization behavior for the structure from the surface to the mid- thickness of the hot band material.
10:10 am BREAK
10:30 am
ANISOTROPY IN ROLLED ALUMINUM SHEET AS IDENTIFIED BY ULTRASONIC AND METALLURGICAL ANALYSIS: Wei- yang Lu, Shermann Min, Darcy Hughes Sandia Nat. Lab., Livermore CA 94550; Baolute Ren Reynolds Metals Company, Mussel Shoals, AL 35661- 1258
The use of ultrasonic techniques to measure the material anisotropy of rolled metal sheets has been demonstrated in many studies. Recently, electromagnetic acoustic transducer (EMAT) and laser ultrasonic (LU) methods have been favored since both are noncontact in nature and therefore potential candidates for in- situ process monitoring and control in rolling mills. In general wave propagation velocities are measured and then used to calculate the texture coefficients W400, W420 and W440. In addition to W4XX values, more information can be obtained from an ultrasonic interrogation. This paper describes the identification of crystallographic textures in aluminum plates using the above noncontact ultrasonic approaches. The textures of samples which include a variety of crystallographic components are evaluated using ultrasonic, x- ray methods, and transmission electron microscopy and micro- texture analysis. The microstructure and texture analysis results are compared to the results of anisotropy measured by mechanical testing. This work supported by U.S. DOE under contract No. DE- AC04- 94AL8500.
10:50 am
THE ASYMMETRY OF EARING IN ROLLED ALUMINIUM: H. E. Ekstrom, Granges Technology, Finspang, Sweden, A. Oscarsson, Swedish Institute for Metals Research, Stockholm, P. Bate, IRC, Univ. of Birmingham, UK
In practice earing may cause two different types of problem. The lowest valley of the cup rim determines the level of cutting and the amount of wastage in trimming. The highest peak may cause failure in cupping due to pinching. Earing behavior is associated both with mechanical anisotropy in the sheet and with tooling conditions. The latter often cause a skewness of the complete 0- 360[[ring]] profile and friction between tools and sheet decreases the overall earing. The contribution from the material depends mainly on the average through thickness crystallographic texture of the sheet in non- heat treatable aluminium alloys. Depending on sheet alloy composition and its thermomechanical history the texture can vary significantly giving rise to very different earing profiles. Textures and experimental earing profiles have been examined for different alloys in different conditions. Calculated earing profiles show good qualitative agreement with experimentally measured ones. The present ISO standard for an earing test does assume a greater symmetry of earing than actually occurs. A new method is proposed to replace the current one in which the difference between the mean height of the highest pair of peaks and the lowest pair of valleys is related to the mean cup height.
11:10 am
THE EFFECT OF INITIAL MICROSTRUCTURE ON THE EVOLUTION OF CRYSTALLOGRAPHIC TEXTURE IN AA 3004 DURING SIMULATION OF HOT ROLLING: G.J. Marshall, M.W. Merodith, RK Bolingbroke, Alcan International, Banbury Laboratory, Southam Road, Banbury, OX16 7SP, UK
Controlling property anisotropy, particularly earing, in can body sheet is dependent upon the annealed microstructure after hot rolling which is used to balance the textures generated during cold rolling. Essential during the hot deformation and subsequent annealing is the formation of sufficiently strong cube texture to ensure low final gauge earing. Low earing has been the industry accepted standard for many years and current research aims are addressing the growing concern of earing consistency. Significant factors in obtaining consistent hot rolled texture are the deformation conditions and the initial starting microstructure. This study has addressed the role of Mn solid solution content and AlMnSi dispersoid size and distribution on the evolution of texture during laboratory simulation of hot rolling. It will be shown that both process conditions and the size and spacing of dispersoids are critical factors in controlling texture. In contrast, significant changes to the Mn solid solution content were considerably less influential. The results will be discussed in relation to current theories for cube texture evolution during hot rolling of aluminium alloys.
11:30 am
STATIC RECRYSTALLIZATION OF AN Al- 1Mn ALLOY DURING THERMOMECHANICAL PROCESSING: P.L. Orsetti Rossi, C.V.G. Industria Venezolana de Aluminio, C.A., Zona Industrial Matanzas, PO BOX 302, Puerto Ordaz, Venezuela; C.M. Sellars, The University of Sheffield, Department of Engineering Materials, Mappin Street, Sheffield, S1 3JD, UK
The kinetics of static recrystallisation of an Al-
lMn
alloy have been investigated by rolling tapered slabs and by plane strain
compression (PSC) tests at high temperatures. A significant through-
thickness
recrystallisation gradient (macro-
heterogeneity)
has been measured on samples from rolled and annealed tapered slabs. The
kinetics follow reasonably well an Avrami equation as long as significant
precipitation does not take place. The Avrami exponent increases systematically
with strain, probably a result of an increasing micro-
homogeneity
in deformation. Since in this alloy, precipitation occurs concurrent with
recrystallisation, irregular recrystallised structures are obtained.
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