Influence of different extrusion temperatures on microstructure and mechanical properties of Mg-Bi-Zn-Ca alloy

The combination of Ca-doped magnesium alloy and hot extrusion process has garnered significant attention due to its exceptional mechanical properties. For this purpose, Mg-Bi-Zn-Ca alloy with a low Ca content is prepared and subjected to hot extrusion at temperatures of 225, 250, and 275 °C respectively. Subsequently, the impact of hot extrusion temperature on Mg alloy's microstructure and mechanical properties is further investigated through high-performance characterization techniques and tensile experiment. The Mg alloy demonstrates exceptional yield strength and ultimate tensile strength of 382.5 MPa and 392.4 MPa at 225 °C, surpassing other Mg alloys of the same type. The strengthening of the alloy primarily arises from the synergistic effect of grain boundary reinforcement and dislocation strengthening, as the Mg alloy exhibits a bimodal grain structure at 225 °C with the smallest average grain size . The interface between DRXed grains and unDRXed regions exhibits a high density of dislocations, accompanied by a significant presence of nanoscale precipitates within the matrix. These nanoscale precipitates act as effective pinning agents, restricting grain boundary expansion and impeding dislocation motion , thereby further augmenting the strengthening mechanism . Therefore, the low cost, high strength, and simple hot extrusion process make the Mg alloy have good industrial application potential. • Mg-Bi-Zn-Ca alloy with low Ca content is prepared by hot extrusion. • The Mg alloy demonstrates exceptional yield strength and ultimate tensile strength of 382.5 MPa and 392.4 MPa at 225 °C. • The microstructure exhibits a typical bimodal grain characteristic. • Nanoscale phases effectively immobilize grain boundaries and impede dislocations motion.