Hot deformation constitutive modeling of 6111 aluminum alloy linking Z-parameter to the associated microstructural evolution and precipitation strengthening

This work investigates the hot deformation behavior and microstructure evolution of 6111 aluminum alloy (core layer in 4343/3003/6111/3003 brazed sheets) via thermal compression (300–500 °C, 0.01–10 s -1 ). A strain-compensated Arrhenius constitutive model was developed, accurately predicting flow stress (Mean Absolute Relative Error (AARE)=4.31%, Correlation Coefficient (R)=0.996). The Z-parameter governs dynamic recovery/recrystallization (DRV/DRX): high Z (lnZ=42.2) suppresses softening, retaining high dislocation density (0.699×10 14 m -2 ) and fine subgrains (5.1 μm); low-Z (lnZ=24.9) promotes DRV/DRX, reducing dislocations (0.207×10 14 m -2 ) and coarsening subgrains (13.7 μm). Crucially, high-Z deformation preserves substructures (dislocation walls, subgrain boundaries), which act as nucleation sites for Q′-phase precipitates during aging. This yields finer precipitates (8.5 nm vs. 9.5 nm), enhancing precipitation strengthening (Δτ p =62.1 MPa vs. 47.8 MPa) and hardness (145 HV vs. 126 HV), compared to low-Z conditions (lnZ=42.2 vs 24.9). Optimizing Z during hot rolling controls substructure retention, maximizing post-aging strength in brazed sheets. The findings establish a theoretical basis for optimizing process parameters and controlling microstructure in composite-brazed sheet production.