The project addresses the effects of composition, microstructure and processing on the formability of Mg alloys for lightweight applications in transportation industry. A modified deformation processing known as multiple coining/corrugating and flattening (MCF) will be used to produce randomly-oriented ultra-fine grains for improved forming characteristics, in particular the increased strain-rate sensitivity at relatively low temperatures. A major objective is to perform detailed analyses of microstructure, microtexture, tensile flow response and biaxial forming behavior of Mg sheets. The evolution of distributions in grain size and grain misorientation will be analyzed as functions of processing steps and temperature. Particular attention will be paid to deformation mechanisms including twinning and slip, and the kinetics of dynamic recrystallization and grain growth. Quantitative relations between microstructural parameters and stress- strain-strain rate response will be sought on the basis of experimental results and existing theories, and optimum formability paths will be delineated. The standard AZ31B alloy will be considered along with a modified alloy by adding rare earth and transition elements for improved resistance to corrosion and creep. Along with the experimental studies, physically based constitutive relations will be used to predict forming limit curves and thinning in biaxially deformed samples, for comparison with experimental data. %%% The proposed effort, jointly shared by the University participants and collaborators, Daimler Chrysler Corporation and Thixomat, Inc., considers two Mg alloys to explore processing-microstructure-flow relations and their influence on formability limit. The results of this fundamental study will define more clearly the effects of composition, microstructure and processing on the formability of Mg alloys that find applications in transportation and other industries where lightweight materials are a prerequisite. The project involves researchers at the university and the industrial laboratories. ***
