A SELF-CONSISTENT VISCOPLASTIC MODEL - PREDICTION OF ROLLING TEXTURESOF ANISOTROPIC POLYCRYSTALS

The plastic properties of anisotropic polycrystalline aggregates and p olyphase materials are in general non-homogeneous and, as a consequenc e, so is the local plastic deformation. We present in this work a mode l that describes the plastic behaviour of non-homogeneous materials co mposed of anisotropic regions (grains or phases). Our model is based o n describing each region as a viscoplastic inclusion embedded in the e ffective medium represented by the other grains, and incorporates expl icitly the grain interaction with its surroundings and the plastic ani sotropy of grain and matrix. Within the model the grain response is co upled to the overall response of the polycrystal and the grain deforma tion may differ from the polycrystal's. A characteristic of our approa ch is that those deformation systems with lower critical resolved shea r stress tend to be more active, and less than five systems per grain are sufficient to accommodate the imposed overall deformation. In this work we explore the consequences and the limits of the model, and its dependence on the assumed rate sensitivity as well. We combine the se lf-consistent formulation with a volume fraction transfer scheme for t reating the reorientation due to twinning, and simulate rolling textur es of brass (f.c.c.), Zircaloy (h.c.p.), calcite (trigonal) and uraniu m (orthorhombic). We compare the results with experimental measurement s and Taylor-type predictions, infer information concerning the micros copic deformation mechanisms and discuss the limits of applicability o f the approach.