Influence of pre-stretching and annealing on microstructure and mechanical properties evolution of twin-roll cast Mg-2Al-1Zn-1Ca (wt.%) plates

Pre-stretching and annealing treatments were conducted on twin roll cast Mg-2Al-1Zn-1Ca (AZX211, in wt.%) plates with a rare earth-like texture. Varying amounts of deformation were applied along the rolling direction (RD) and transverse direction (TD) of AZX211 alloy in order to modify its mechanical properties at room temperature. The results demonstrate that pre-stretching treatment effectively enhances the yield strength (YS), especially along the RD. The strengthening mechanism is attributed to the production of a large number of dislocations and sub-grain boundaries, but the work-hardening ability of the plate will be greatly weakened. Additionally, annealing treatment substantially improves the plasticity and in-plane anisotropy and restores the work-hardening ability. The notable distinction in the pre-stretching process between different directions lies in the underlying deformation mechanism. In case of RD, deformation is predominantly governed by the slip mechanism of {0002} <11−20> basal slip and {10−10} <11−20> prismatic slip, while along the TD, deformation is primarily controlled by {0002} <11−20> basal slip without significant twinning deformation. When a 6% pre-stretching is conducted, the initial rare earth-like texture of the sample transforms into a symmetrically distributed double-peak basal texture, accompanied by grain refinement. This texture transformation is chiefly due to the dominance of {0002} <11−20> basal slip-driven deformation. Moreover, the annealed sample maintains a strong basal texture, owing to strain-induced recrystallization.