Adiabatic shear bands formation in polycrystalline aluminium

Abstract

The microstructure and texture evolutions during dynamic (or high strain rate) deformation of commercially pure AA1050 alloy have been studied to elucidate the mechanisms of shear band (SB) formation and its propagation across the flattened grains arranged in layers with special attention to texture evolution. The hat-shaped samples were compressed using drop hammer at a strain rate of 5.3 × 102 s−1. Detailed microstructure and texture characterizations were carried out using SEM equipped with EBSD facility. The shear displacement moves the upper part of the hat-shaped sample towards the bottom one leading to a strain localization in the form of SB. It was found that the strain localization occurs via deflection of flattened grains within narrow areas leading to kink-type bands that are considered to be the precursors of SB. The strain-induced crystal lattice rotation led to the formation of new texture components, different from those identified inside the undeformed matrix. It also facilitates slip propagation across the grain boundaries. The mechanism of macro-SB formation is essentially crystallographic in nature since in all grains of the sheared zone, the crystal lattice rotated in such a way that one of the {111} slip planes became nearly parallel to the shear plane and the <011> direction became parallel to the direction of maximum shear.