Materials Week '97: Monday PM Session

Focusing on physical metallurgy and materials, Materials Week '97, which incorporates the TMS Fall Meeting, features a wide array of technical symposia sponsored by The Minerals, Metals & Materials Society (TMS) and ASM International. The meeting will be held September 14-18 in Indianapolis, Indiana. The following session will be held Monday afternoon, September 15.

PROCESS AND MATERIAL BEHAVIOR MODELING SYMPOSIUM: Session II

Session Chair: Glenn S. Daehn, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210

EFFECTS OF STRAIN LOCALIZATION ON SURFACE ROUGHENING DURING SHEET FORMING: R.C. Becker, Alcoa Technical Center, 100 Technical Drive, Alcoa Center, PA 15069; H.R. Piehler, Dept. of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213

Numerical simulations of evolving surface roughening in sheet have been performed to determine the influence of microstructure and mechanical properties. The model accounts for the grain structure near the sheet surface with the behavior of the grains being characterized by a constitutive model which accounts for deformation by crystallographic slip and for rotation of the crystal lattice with deformation. In addition to the known linear dependence of surface roughening on strain and grain size, it was determined that small scale strain localization at the surface plays a significant role. Consequently, factors which affect strain localization, such as strain hardening, texture, and material homogeneity, also affect surface roughening. The results also show patterning of the strain localization which is induced by the material inhomogeneity inherent in a polycrystal.

2:20 pm

THE INFLUENCE OF ENGINEERED SURFACE TEXTURE ON THE FORMABILITY OF ALUMINUM SHEET: G.W. Jarvis, Alcoa Technical Center, Alcoa Center, PA 15069; H.R. Piehler, Dept. of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213; R.C. Becker, L.G. Hector, Alcoa Technical Center, Alcoa Center, PA 15069

To date the major impact of engineered surface texture has been its influence on tribological characteristics during sheet forming. However, the presence of the engineered surface texture may also influence the formation of strain localizations during forming. These localizations may either increase formability by spreading strain or decrease formability by leading to early localized necking. The results from large strain experiments on flat sheets with four different electron-beam textures are presented. These sheets were subjected to four different strain states ranging from drawing to plane strain using the CMU sheet-metal deformation simulator. Finite element modeling of the deformation of these surface-textured aluminum sheets was used to provide additional insights into the effect of surface texture on the development of diffuse and localized necking during forming.

2:40 pm

VERIFICATION STUDY ON THE DENSITY DISTRIBUTION PREDICTIONS OF A POWDER COMPACTION MODEL: A. Casagranda, Concurrent Technologies Corporation, Johnstown, PA 15904

A combined experimental/computational study was carried out to verify the predictions of a powder compaction simulation program. The compaction experiments were performed with a 316L stainless steel metal powder on a fully instrumental production press. The operating conditions were systematically varied to produce controlled variations in local density gradients within the compacts. The tooling loads and displacements were also monitored. Several methods were employed to measure density gradients to ensure accuracy. The powder compaction simulation was then used to predict the density gradients and tooling loads from the measured press displacements. A summary of the experimental results and comparisons to the model predictions will be presented. This work was conducted by the National Center for Excellence in Metal-working Technology, operated by Concurrent Technologies Corporation under Contract No. N00140-92-C-BC49 to the U.S. Navy as part of the U.S. Navy Manufacturing Technology Program.

3:00 pm

THE PROPERTIES AND STRUCTURE OF Al-TiC COMPOSITES: Hongping Dong, Xianglin Dong, Ferrous Metal Research Institute, Section 9, China Science Academy, 72 Wenhua Road, Shenghei District, Shenyang, China

Abstract was not available.

3:20 pm

MODELING AND VERIFICATION OF LASER CUTTING AND LINKING TECHNOLOGY IN MICROELECTRONIC DEVICES: Ampere A. Tseng, Guo-Xiang Wang, Arizona State University, Tempe, AZ 85287-6106

A series of in-situ Al-TiC composites has been developed based on ingot metallurgy and rapid solidification technology. By optimizing material composition, processing parameters and systematic microstructural analyses, this series of in-situ composites has high Young's modulus and high tensile strength both at room and high temperatures. Based on the experimental analysis, a thermodynamic criterion for in situ synthesized TiC in the Al melt and a mathematical model for computing the TiC in-situ synthesized process have been established. A theoretical basis for designing the composites has been provided based on the relations between the TiC particles (size, distribution and volume fraction), material composition and processing parameters. Based on the experimental results and comparative nucleation dynamics it has been found that newly formed TiC dispersoids could act as nuclei for a-Al following rapid solidification. The mathematical relationship between the volume fraction of TiC particles and a-Al grain size has been established.

3:40 pm

A COMPUTER SIMULATION OF FLOTATION TREATMENT PROCESS FOR MOLTEN ALUMINUM: M. Maniruzzaman, M.M. Markhlouf, Aluminum Casting Research Laboratory, Department of Mechanical Engineering, WPI Worchester, MA 01609

The quality of finished aluminum products largely depends on melt treatment prior to casting. One of the widely used treatment processes in the aluminum casting industry is flotation of aluminum inclusions using gas purging. To optimize this process it is very important to understand the basic mechanisms underlying this process. During flotation, flow behavior in the melt reactor is very complex, mainly due to turbulence in the flow field. Unfortunately, with the available equipment, it is not possible to visualize the flow pattern inside the melt reactor. In this study, a computer simulation model for flotation treatment process has been developed based on turbulent flow field calculations. Predicted inclusion trajectories and streamlines along with the analysis of governing parameters will be presented.

4:00 pm

ACTIVITY COEFFICIENT OF INFINITE DILUTE SOLUTION AND INTERACTION PARAMETER IN METALLIC MELTS: Xueyong Ding, Pong Fan, Wenzhong Wang, Qiyong Han, Department of Ferrous Metallurgy, Northeastern University, Shenyang 110006, China

The models for calculating the activity coefficient at infinite dilution and interaction parameters in metallic melts were established. The values from the models are in accordance with those from the experiments on the whole, the ratio of same sign of data between calculation and experiment reaches 95.7% and over 80% for the activity coefficient at infinite dilution, and interaction parameters in liquid Fe-base alloys at 1873K respectively. The results reveal that the higher the reliability of experimental data, the more the ratio of same sign. The values between the models and experiments are in same quantity order in general.

4:20 pm

QUANTITATIVE CHARACTERIZATION AND MODELING OF SPATIAL ARRANGEMENT OF FIBERS IN COMPOSITE: Sichen Yang, Arun M. Gokhale, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332

In the unidirectional fiber reinforced composites, the spatial arrangement of fibers is often non-uniform. These non-uniformities are related to the processing conditions, and the composite properties are in turn affected by the non-uniformities. In this paper, digital image analysis is used to quantify the non-uniform spatial arrangement of Nicalon fibers in a glass ceramic matrix composite (CMC). The quantitative data are utilized to develop a computer simulated microstructure model that is statistically equivalent to the microstructure of the CMC. The simulated microstructure model can be modified according to the variation of the processing conditions to reflect the real microstructure of the composite. Further, the simulated model can be used as an input to predict the mechanical behaviors of the composites as a representative volume element in numerical method, such as finite element analysis.