Cryogenic deformation-induced dislocation behavior and substructural evolution in 6061 aluminum alloy

This study systematically investigates the cryogenic deformation behavior of 6061 aluminum alloy using a multiscale approach integrating EBSD, TEM, nanoindentation, and molecular dynamics (MD) simulations. The results reveal that deformation at –196 °C suppresses dynamic recovery and dislocation entanglement, promoting dislocation slip along {111} planes and dislocation dissociation. This leads to the formation of dense, low-entanglement dislocation networks. Concurrently, a progressive increase in low-angle grain boundaries (LAGBs) and kernel average misorientation (KAM) indicates continuous lattice rotation and substructure evolution, ultimately facilitating geometry-driven dynamic recrystallization (GDRX) and the formation of lamellar-like refined grains. In contrast, room-temperature deformation is dominated by recovery, with limited lattice rotation and no significant grain refinement. Nanoindentation tests confirm enhanced hardness and greater plastic work absorption after cryogenic deformation. Atomistic simulations further demonstrate longer, straighter dislocation lines and a reduced proportion of 1/6<110> stair-rod dislocations at –196 °C, consistent with smoother, planar slip. Together, these findings establish a dislocation-to-substructure-to-microstructure hierarchy, elucidating the fundamental mechanisms responsible for cryogenic plasticity enhancement. These findings offer theoretical guidance for the design of cryogenic forming strategies aimed at enhancing precision aluminum components.