Microstructure and mechanical properties of high-performance Mg–Y–Er–Zn extruded alloy

•We obtained a Mg–Y–Er–Zn alloy with high strength, plasticity and heat-resistance.•Hot extrusion and aging treatment can improve the performance of this alloy.•Lamellar strips with 18R LPSO structure are characterized in as-extruded alloy.•Fine lamellar grains with 14H LPSO structure are examined in alloys after peak-aging.

The Mg–8Y–1Er–2Zn (wt.%) alloy with high strength, plasticity and heat-resistance was prepared by the hot extrusion technique and the following aging treatment. The microstructure and mechanical properties were investigated. The results show that long period stacking ordered (LPSO) phase is different from common inermetallics, and the former can be bent by plastic deformation and presents good combination with the Mg matrix. The good mechanical properties of as-extruded alloy are mainly attributed to the lamellar strips with 18R LPSO structure as well as the microstructure refinement. Aging treatment at 220 °C can further improve the strength but not at the expense of plasticity. The ultimate tensile strength (UTS) and elongation to failure (ε) of as-extruded alloy at peak hardness are 390 MPa and 18% at room temperature, and 322 MPa and 30% at 250 °C, respectively. The formation of fine α-Mg recrystallization grains with high number density of 14H LPSO structure is mainly responsible for the superior mechanical properties of extruded alloy after peak-aging.