7 - Anisotropic and Inhomogeneous Plastic Deformation of Polycrystalline Solids

Abstract

Anisotropy and inhomogeneity are two inherent characteristics of the plastic deformation of polycrystalline solids. The anisotropy results mainly from crystallographic texture due to the rotation of grains into preferred orientations as well as from morphological texture due to the nonequiaxial shape, size, and arrangement of highly deformed grains. The inhomogeneity results mainly from inhomogeneous slip within the grains, as well as from constraints imposed for deformation compatibility at grain boundaries. For a comprehensive understanding of these characteristics, it is necessary to study systematically the material properties at three different length scales: the properties of the slip system at the microscale; the properties of the single crystal at the crystallite scale; and the overall properties of the polycrystal at the macroscale. Crystal plasticity theories have been extensively used to describe crystallographic texture and corresponding polycrystal stress-strain curves. While these theories are in general capable of modeling the evolution and spatial distribution of textures, they may not lead to accurate predictions for the stress-strain curves, as they disregard the effect of microstructure at the crystallite scale. The relevant calculations are often complicated because of the large number of grains involved in the averaging procedures used to cast the microscopic flow equations into macroscopic stress-strain relations.