Influence of hot deformation on dynamic recovery and dynamic recrystallization mechanism in a spray formed Al–Zn–Mg–Cu alloy

This study investigates the hot deformation mechanisms of a spray-formed 7050 Al-Zn-Mg-Cu alloy, focusing on the influence of temperature and strain rate via comprehensive microstructure characterization. Microstructure analysis reveals that both the dynamic recovery (DRV) and dynamic recrystallization (DRX) are governed by the Zener-Hollomon parameter (Z). DRV-formed substructures exhibit distinct stability: grains with high grain orientation spread (GOS, 3∼4°) stabilize at low temperatures, while those with low GOS (1∼2°) stabilize at high temperatures. Elevated temperature promotes DRX, but the operative mechanism critically depends on strain rate. Continuous DRX (CDRX) dominates at low rates (0.001–0.01 s -1 ), whereas discontinuous DRX (DDRX) prevails at high rates (0.1–1 s -1 ). Optimizing strain rate is key: low rates (0.001 s -1 ) achieve near-complete DRX and grain growth (80% recrystallized area), while high rates (1 s -1 ) limit recrystallization (≤50% area) despite enhanced nucleation, yielding finer grains (5–15 μm) with residual substructures. Local strain analysis shows recrystallized grains maintain low kernel misorientation (KAM<0.8°), but high strain rates increase substructure KAM by 41.3%, indicating incomplete energy dissipation. This study provides new insights on the microstructure modification by deformation for developing high performance aluminum alloys.