Microstructural refinement and improvement of mechanical properties of hot-rolled Mg-3Al-Zn alloy sheets subjected to pre-extrusion and Al-Si alloying

In this study, an appropriate alloying and rolling method was sought to improve the mechanical properties of Mg-3Al-Zn alloy sheets. The effects of a pre-extrusion process, combined with Al-Si eutectic addition, on the microstructure, texture, and mechanical properties of Mg-3Al-Zn alloys were investigated in this study. The results demonstrated that the hot-rolled Mg-3Al-Zn alloys subjected to pre-extrusion and Al-Si alloying addition exhibited a distinct bimodal-distribution characteristic and optimal grain refinement. The microstructural refinement could be attributed to the particle-stimulated nucleation (PSN) effect generated by the refined Mg2Si particles, as well as the dynamic recrystallization (DRX) that occurred in the twins, resulting in ultrafine grains. The as-rolled Mg-3(Al-Si)-Zn alloy sheets subjected to pre-extrusion and Al-Si alloying (ASZ-ER) exhibited superior mechanical properties. Their yield strength (YS), ultimate tensile strength (UTS), and total elongation values were 274 MPa, 355 MPa, and 12.9%, respectively. The enhanced mechanical properties of the ASZ-ER alloy could be ascribed to grain refinement and second-phase strengthening effects.