Effect of homogenization heat treatment on microstructure evolution and mechanical properties of Mg-8Li-3Al-1Y-0.5Gd alloy

Homogenization heat treatment can effectively eliminate casting segregation and improve the overall properties of alloys, making it widely applicable in the field of alloy material processing. This study systematically investigates the effects of homogenization heat treatment on the microstructure evolution and mechanical properties of cast Mg-8Li-3Al-1Y-0.5Gd alloy. The results indicate that the heat treatment alloy mainly consists of α-Mg phase, β-Li phase, AlLi phase, and Al₂(Y,Gd) phase. As the heat treatment temperature increases, the hardness of the alloy shows a decreasing trend, while prolonging the homogenization time promotes the gradual dissolution of the AlLi phase and the precipitation of needle-like α-Mg phase from the matrix. After 4 h of homogenization treatment, the alloy achieves optimal mechanical properties, with ultimate tensile strength and yield strength reaching 296 ± 11 MPa and 256 ± 8 MPa, respectively. The strengthening is primarily attributed to the synergistic effect of solid solution strengthening from the AlLi phase and grain boundary strengthening from the α-Mg phase. Furthermore, this study explores the optimized homogenization heat treatment parameters for this alloy system, providing a theoretical basis and process guidance for homogenization treatment in subsequent plastic deformation processes.