Microstructure and mechanical properties of moderate-speed extrudable Mg-Gd-Sm-Zr alloy

Abstract

Extrusion Mg-Gd based alloy has the excellent mechanical properties, but usually at the sacrifice of productivity. In this paper, we designed a Mg-10Gd-1Sm-0.5Zr alloy, and have successfully extruded it with a die-exit speed of 3.2 m min−1, and the extrudability is improved by indirect extrusion under differential-thermal condition. The microstructure and mechanical properties of as-extruded and peak-aged alloys were investigated in detail. The results indicate that as-extruded alloys exhibit the bimodal structure composed of dynamic recrystallized (DRXed) grains and UnDRXed grains with good ductility, and its elongation (El) is 14.3% at room temperature and 26.2% at 250 °C. Aging treatment remarkably enhance the strength of as-extruded alloy, and the peak-aged alloy exhibits ultimate tensile strength (UTS) of 345 MPa, yield strength (YS) of 287 MPa and EL of 6.3% at room temperature, and has UTS of 316 MPa, YS of 268 MPa, and EL of 7.8% at 250 °C. β′ precipitation strengthening, fine-grain strengthening, solution strengthening, texture strengthening have responsible for improving strength of peak-aged alloy.