Contribution of deformation-induced intragranular microstructure to the plastic anisotropy of metals

Abstract
In metals, plastic deformation causes the development of dislocation patterns. These patterns depends on the material and on the strain mode. Strain path changes usually cause dramatic modifications of these substructures. In most metals, they have an important effect on the plastic anisotropy, even if the prestrain is only of the order of 10 %. The well-known Bauschinger and cross effects are often caused by these ré-arrangement of the dislocation patterns. It has recently proved possible to simulate this for IF-steel in a multilevel model for the plastic deformation of polycrystals based on the Taylor theory. It essentially simulates the development of dislocation substructure and how it is affected by strain path changes. It calculates the stress required to maintain glide on each of the slip systems. It is found that from a very small plastic strain on, the critical resolved shear stress becomes different on each slip system. This removes the ambiguity problem of the Taylor-Bishop-Hill theory. In this paper, the model is used to discuss the effect of prestrain on the yield loci of IF-steels, as well as the effect on the r-values which describe the plastic anisotropy of sheet material. Comparisons with experimental data are given.