Wednesday, AM Room: Grand D
February 7, 1996 Location: Anaheim Marriott Hotel
Session Chairperson: TBA
METALLURGICAL ASPECTS OF ALUMINIUM FOR CANMAKING: P. D. C. Roqers, CarnaudMetalbox Technology plc, Downsview Road, Wantage, Oxon, OXl2 9BP, England
The properties of alluminium 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 run one day, but will not 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 testinq is inadeguate, and more emphasis has to be placed on process control. It is not difficult to write a specification which describes 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 understandinq is growing.
INFLUENCE OF TOOLING GEOMETRY ON QUALITY OF THE SHEARED SURFACE OF ALUMINUM SHEETS: S. F. Golovashchenko, R. G. Davies, W.S.Stewart, P.O. Box 2053/MD3182 SRL, Dearborn, MI 48121
In order to achieve vehicle weight reduction, stamped aluminum outer panels, such as hoods are being used in automotive production. The present research is concerned with the process of shearing blanks for stamping. Experiments were done to analyse the influence of the gap between cutting edges and the geometry of cutting blades on the quality of the sheared surface. The results are presented in form of the macrostructures of polished samples and force displacement curves. To predict the quality of the sheared surface a numerical code based on solid mechanics equations, elastoplastic flow theory and cummulative theory of damaged was created. The die was assumed as rigid and friction between sheet and tooling was simulated in accordance to the Coloumb friction law with the restriction that its value be equal to the maximum shear stress. Fracture of material was simulated at every element of the numerical grid where the amount of plastic deformation corresponding to the fracture criterion was reached. The fracture criterion included the influence of hydrostatic pressure on material plasticity.
MODELLING OF SUPERPLASTIC FORMING PROCESSES
FOR ALUMINUM ALLOYS: Yong Nam Kwon, Young-Won Chang, Center for Advanced Aerospace Materials(CAAM) POSTECH, Pohang 790-784, Korea
Superplastic forming of thin sheet into complex components is an important manufacturing process especially in aerospace industry. The main interest in modelling the superplastic forming process is to predict the forming pressure cycle to maintain optimum formability and the resulting thickness distribution. The ABAQUS finite element code was used for the prediction of process parameter for axisymmetric cup forming and rectangular pan forming for Supral 100 and 7075 aluminum alloy. To characterize mechanical parameters of these alloys, a series of load relaxation and variable angle cone tests were used. The performance of the finite element model in comparison with the experimental results was discussed.
9:30 am BREAK
ANISOTROPY OF DYNAMIC GRAIN GROWTH OF SUPERPLASTIC ALUMINUM ALLOYS: F. Li, A. K. Ghosh, Department of Materials Science & Engineering, The University of Michigan, Ann Arbor, MI 48109-2136
Grain morphology of several superplastic aluminum sheet materials during uniaxial deformation is studied. The grains are found to undergo elongation with strain along the direction of applied stress, while both static and dynamic grain growth occur leading to an increase in the lateral dimensions of the grains. The growth behavior is examined and kinetics analyzed. Simultaneous static grain growth is also measured and subtracted from the overall grain growth to determine the extent of net dynamic grain growth. The anisotropy of the dynamic grain growth in the various directions is analyzed, and corrected with the extent of dislocation creep and that due to mantle creep process such as grain boundary sliding. An attempt is made to develop a microstructural model for dynamic grain growth.
STRUCTURAL EVOLUTION AND THE HALL-PETCH RELATIONSHIP IN AN Al-3%Mg ALLOY WITH SUBMICRON GRAIN SIZE: Minoru Furukawa, Zenji Horita, Minoru Nemoto, Dept. of Materials Science & Engineering, Kyushu University, Fukuoka 812, Japan; Ruslan Z. Valiev, Institute for Metals Superplasticity Problems, Ufa 450001, Russia; Terence G. Langdon, Dept. of Materials Science & Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453
A submicron grain size was produced in an Al-3%Mg solid solution alloy by introducing intense plastic deformation using either equal-channel angular pressing or torsion straining. These procedures produced grain sizes of the order of ~0.2 and ~0.09 m, respectively. This paper describes the structural evolution during static annealing at high temperatures and the variation of the microhardness as a function of the grain size. The results demonstrate an increase in microhardness with decreasing grain size down to the smallest grain size examined experimentally (90 nm).
MECHANICAL CHARACTERISTICS OF AN Al-Mg-Li-Zr ALLOY SUBJECTED TO EQUAL-CHANNEL ANGULAR PRESSING: Patrick Berbon, Yan Ma, Dept. of Materials Science, University of Southern California, Los Angeles, CA 90089-0241; Minoru Furukawa, Zenji Horita, Minoru Nemoto, Dept. of Materials Science & Engineering, Kyushu University, Fukuoka 812, Japan; Ruslan Z. Valiev, Institute for Metals Superplasticity Problems, Ufa 450001, Russia; Terence G. Langdon, Depts of Materials Science & Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453
Zr alloy, with an initial grain size of ~400 m, was subjected to equal-channel angular (ECA) pressing to produce an average grain size in the region of ~1-2 m. This paper describes the results obtained after tensile testing of this material, both with and without ECA pressing, at temperatures from 298 to 403K, and the variation in grain size of the ECA pressed alloy after static annealing to temperatures above 800K.
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