Shear Banding in Polycrystalline Aluminium and Copper Pre-Deformed by ECAP and Subsequently Plane Strain Compressed

Abstract

The microstructure and texture evolution in commercially pure aluminium (AA1050 alloy) and copper have been characterized after change in strain path to elucidate the mechanisms of shear bands (SBs) formation and propagation across grain boundaries. Samples were pre-deformed in equal channel angular pressing (ECAP) and further compressed in a channel-die to form two sets of macro-SBs. The deformation-induced sub-structures and local changes in crystallographic orientations were characterized by scanning electron microscopy equipped with a high-resolution electron backscattered diffraction facility. It was found that the mechanism of micro-/macro-SBs formation is strictly crystallographic. In all the grains of the sheared zone a strong tendency to strain-induced re-orientation could be observed. Their crystal lattice rotated in such a way that one of the {111} slip planes became nearly parallel to the shear plane and the <011> (or <112>) direction became parallel to the direction of maximum shear. This crystal lattice rotation led to the formation of specific SBs components which facilitates slip propagation across grain boundaries without any visible variation in the slip direction.