Effect of annealing temperature on microstructure and mechanical properties of Mg-Zn-Zr-Nd alloy with large final rolling deformation

In this study, the Mg-3Zn-0.5Zr-χNd (χ=0, 0.6) alloys were subjected to final rolling treatment with large deformation of 50%. The impact of annealing temperatures on the microstructure and mechanical properties was investigated. The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa, a yield strength of 361 MPa, and an elongation of 7.1%. Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys. Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200 °C, with an ultimate tensile strength of 287 MPa, a yield strength of 235 MPa, and an elongation of 26.1%. The numerous deformed microstructures, twins, and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate. After annealing, a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains, and the increased volume fraction of precipitated phases, which significantly improved the elongation of the alloy. Additionally, the addition of Nd element could enhance the annealing recrystallization rate, reduce the Schmid factor difference between basal and prismatic slip systems, facilitate multi-system slip initiation and improve the alloy plasticity.