Polycrystal Constitutive Modeling of ECAP: Texture and Microstructural Evolution

Abstract

This paper describes preliminary efforts to understand the grain refinement mechanism during ECAP. We develop a modeling framework for predicting microstructural and texture evolution in nanocrystalli ne materials during the Equal Channel Angular Pressing (ECAP). A 3D polycrystalline visco plastic self consistent scheme is used to predict the constitutive response and texture of the sample when subjected to this discontinuous process of rotations and shear straining. We consider a 90° die angle and simulate ECAP up to four passes for four processing routes. The model material is a rigid plastic FCC single phase polycrystal and the empirical grain size evolution model considers only the effects of grain shape. Under these assumptions, route A was the most effective and route C the least effective for grain size refinement after four passes. Route Ba was more effective than route Bc. For producing refined equiaxed grains, route Bc was more effective than Ba and A. We find that incorporation of both shape effects and accumulative dislocation effects in the grain size evolution model are necessary before informative comparison with experimental data is possible.