Brass-type shear bands and their influence on texture formation

Abstract

The issues of brass-type shear band formation and the evolution of band microtexture components are addressed. The analysis is based on bands developed by plane strain compression in twinned {112}〈111〉 oriented copper single crystals deformed at 77 K. Substantial progress in understanding the formation of the bands was possible thanks to systematic local orientation measurements using transmission electron microscopy (TEM). The TEM orientation maps allowed investigation of the way in which unstable behavior of twin-matrix layers leads to the brass-type shear bands. It has been found that several important transitions of the deformation textures are correlated with shear banding. Early stages of shear band formation are the result of the equally effective operation of two coplanar slip systems on the {111} slip planes. This process leads to the lattice rotation about the 〈110〉 axis and to the rise of Goss orientation. For well-developed shear bands, a second rotation about the 〈112〉 direction is observed. It is accompanied by activation of new slip systems. The observed disappearance of matrix components from the shear band microtexture is the result of twinning within reoriented matrix lamellae. In the twin-oriented areas, the dominance of one of two coplanar slip systems ultimately leads to the formation of the brass texture component.