Enhanced strength-ductility synergy in AA5052 alloy through nano/ultrafine structure induced by asymmetric reverse rolling (ARR)

This study investigates the influence of asymmetric reverse rolling (ARR) strain on the microstructure, texture evolution, and mechanical properties of AA5052 aluminum alloy. Microstructural analysis revealed that deformation bands formed in α-aluminum grains at 50% ARR strain but disappeared upon further straining to 70%. Dynamic recovery (DRV) and grain subdivision commenced only after 30% ARR, facilitated by strain path changes induced by interpass sheet rotation. Intermetallic particles acted as nucleation sites for subgrains and recrystallized grains via particle-stimulated nucleation (PSN). At 70% ARR, continuous dynamic recrystallization (CDRX) generated a high density of nanoscale (20-100 nm) and ultrafine (100-500 nm) grains, attributed to strain-induced subgrain rotation. Texture analysis demonstrated intensified α-fiber orientation, with maxima of 3.1 and 3.6 multiples of random distribution at 50% and 70% ARR, respectively, linked to CDRX-driven texture sharpening. As the ARR strain increased, the difference between the hardness in the regions near the surface and the midthickness increased, creating a gradient in hardness after 70% deformation. Strength enhancement at low strains (<50%) correlated with dislocation accumulation and subgrain formation, while grain refinement dominated at 70% ARR. Strain hardening rate transitions aligned with a strengthening mechanism shift from dislocation-based to grain boundary-mediated effects. Fractography indicated retained ductile failure modes despite increased surface flatness at higher strains, consistent with strain localization in refined microstructures.