Effect of final rolling deformation on microstructure, work hardening and softening behavior of Mg-8Li-3Al-0.3Si alloys

The Al-27Si alloy was prepared using spray deposition and subsequently incorporated into Mg-Li alloy by vacuum melting furnace to produce a novel Mg-8Li-3Al-0.3Si (LA83-0.3Si) duplex alloy. The effect of final rolling deformation (30%, 40%, 50% and 60%) on the microstructure, mechanical properties, work hardening, and softening behavior was researched. Results indicated that the LA83-0.3Si alloy mainly comprised of α-Mg, β-Li, AlLi, and Mg2Si phases. The rolling deformation process induced elongation of the α-Mg and β-Li phase along rolling direction, facilitating the formation of α/β laminar structure, notably enhancing the strength and ductility. Increased final rolling deformation further prompted the formation of the α/β laminar structure and refined the precipitates. Consequently, the LA83-0.3Si alloy's strength progressively increased while elongation slightly diminished. At 60% deformation, the ultimate tensile strength of the LA83-0.3Si alloy reached 331MPa, with the elongation sustained to 10.9%. The rolling process led to a reduction in the work hardening rate and an increase in the softening rate. With the increase of the final rolling deformation, the work hardening rate decreases and the softening rate further increases. However, the work hardening rate increases, and the softening rate decreases due to the decreasing of the hardness ratio of α-Mg and β-Li phases at 60% deformation.