Modeling texture and microstructural evolution in the equal channel angular extrusion process

In this work, we develop a modeling framework for predicting the visco-plastic deformation, microstructural evolution (distributions of grain shape and size) and texture evolution in polycrystalline materials during the equal channel angular extrusion (ECAE) process, a discontinuous process of severe shear straining. The foundation of this framework is a visco-plastic self-consistent (VPSC) scheme. We consider a 90degrees die angle and simulate ECAE up to four passes for four processing routes, (A, C, B-A and B-C, as denoted in the literature) for an FCC polycrystalline material. We assume that the FCC single crystal has a constant critical resolved shear stress (CRSS), so that hardening by dislocation activity is suppressed, and the influence of grain shape distribution and texture as well as their interaction can be isolated. Many deformation microstructural features, such as grain size and shape distribution, texture, and geometric hardening-softening, were highly dependent on processing route. Using a grain subdivision criterion based on grain shape, route A was the most effective, then route B-A and route B-C and lastly route C, the least effective for grain size refinement, in agreement with redundant strain theory. For producing refined equiaxed grains, route B-C was more effective than routes B-A and A. We show that grain-grain interactions tend to weaken texture evolution and consequently geometric hardening and softening in all routes. (C) 2002 Elsevier Science B.V. All rights reserved.