Enhanced strength and plasticity of low-cost cast Mg-7.0Zn-5.0Al-0.3Mn alloys via Cu addition

To achieve both high strength and high plasticity in low-cost cast magnesium alloys, we designed and developed rare-earth-free Mg-7.0Zn-5.0Al-0.3Mn-xCu (x = 0.3, 0.6, 0.9 wt.%) alloys (ZAM750-xCu). The results demonstrate that the ZAM750-0.9Cu alloy exhibits outstanding comprehensive properties after aging treatment, with ultimate tensile strength, yield strength, and elongation reaching 318 MPa, 188 MPa, and 10.9 %, respectively. The improved performance is primarily attributed to the enhanced growth-limiting factor via Cu addition, leading to notable grain refinement. Additionally, copper promotes the precipitation of the second phase, causing its transformation from a spherical to a short rod-like shape, which effectively pins dislocations. Furthermore, the reduction in the c/a axis ratio and the presence of stacking faults significantly enhance the activity of the non-basal slip system. This study provides valuable insights into the effect of Cu on the comprehensive performance of magnesium alloys, offering both theoretical and practical guidance for the development of high-performance, low-cost magnesium alloys.