High-performance magnesium alloy with multi-element synergistic strengthening: Design, microstructure, and tensile properties

Given the limitations of the phase diagram method and the blindness of the trial-and-error method in the composition design of multi-element Mg alloys, the design of multi-element synergistic strengthening Mg alloys was conducted in this work inspired by the design concept of high entropy alloys. Out of the requirement of low-cost and high-performance wrought Mg alloys, inexpensive Al, Ca, Mn, Zn and Sn were added in different ratios. The experimental alloys were prepared by casting and one-step hot extrusion. The optimal composition was Mg-1.4Sn-0.93Zn-0.83Ca-0.67Mn-0.39Al (named as AXMZT-5) showing the best combination of strength and elongation. The microstructure of extruded pure Mg and the AXMZT-5 alloy was studied in detail to reveal the reason for the excellent yield strength (YS) of AXMZT-5 up to 280 MPa, 197% higher than that of pure Mg. Fine-grained structure, residual dislocations, and relatively uniformly distributed nanoparticles of CaMgSn, Ca2(Mg, Al)6Zn3, and Al-Mn phases are attributed to the high YS. In addition, the sharp (0001) basal fiber texture from the un-recrystallized grains in the bimodal microstructure also contribute to the increase of strength. A large number of fine recrystallized grains make the AXMZT-5 alloy exhibit a ductile-dominated fracture mode, which results in its excellent elongation. •The composition design of the multi-element synergistic strengthening magnesium alloys.•The yield strength of the alloy with the optimal composition was up to 280 MPa, 197% higher than pure magnesium.•The strengthening mechanisms of the alloy with optimal mechanical properties were discussed in detail.