Microstructure and mechanical properties of Mg–(6, 9)RY–4Zn alloys by extrusion and aging

The microstructure and mechanical properties of Mg–(6, 9)RY–4Zn alloys (RY: Y-rich misch metal) prepared by extrusion and aging treatment have been investigated. The results demonstrate that the alloys in the as-extruded state and peak-aged state share some similar characteristics, i.e. strip-like 14H long period stacking ordered (LPSO) phase and fine dynamic recrystallization (DRX) grains with 14H LPSO lamellae, while additional basal plane stacking faults (SFs) are formed in the DRX grains of the peak-aged alloys. The peak-aged Mg–9RY–4Zn alloy exhibits optimal comprehensive mechanical properties: the microhardness is 109 Hv at room temperature (RT); the ultimate tensile strength (σ), yield strength (σ0.2) and elongation (ε) are 285 MPa, 376 MPa, 8.6% at RT and 243 MPa, 316 MPa, 16.3% at 250 °C, respectively. The high mechanical properties are mainly attributed to the fine grains, thermal stable LPSO phase and profuse SFs.