Dislocation mechanisms of deformation band formation in precipitation-strengthened alloy studied via in situ micropillar compression

This study systematically investigates the formation mechanisms of deformation bands and their effects on the mechanical behavior of a precipitation-strengthened 7075 Al alloy. Through an experimental approach utilizing in situ compression tests on single-slip oriented micropillars, direct evidence is provided for the orientation evolution and the development of deformation band boundary during the formation and growth of deformation bands in the peak-aged alloy, in which high-density nano-precipitates are present. The local bend-gliding region, characterized by an orientation change, serves as the precursor to the deformation band, which evolves perpendicular to the primary slip direction. The formation plane of deformation bands in single-slip orientated crystal should be {011} planes. Within the deformation band, lattice rotation occurs around the {112} axis due to the activation of the primary slip system and geometric constraints. This process culminates in the formation of a new grain boundary or deformation band boundary, composed of edge dislocation arrays, resulting from the annihilation of the screw component within the dislocation walls. Various factors, including grain orientation, pillar size, and the presence of precipitates, are shown to impact the formation of deformation bands. These findings underscore the crucial role of primary dislocation storage in the development of deformation bands, where a significant primary slip field is generated by the primary dislocation pile-up. © 2024 Published by Elsevier B.V.