Study of Mg-Ymm-Zn alloys with high-strength at elevated temperatures processed by water-cooled mold casting

The high quality Mg-xYmm (x=6, 9, 12)-4Zn (Ymm=Y-rich misch metal, wt%) alloy ingots with diameter of 90-95 mm and length of 600 mm were successfully fabricated by water-cooled mold casting, and the microstructure and tensile properties have been investigated. The results demonstrated that the alloys contained four secondary phases: a plenty of 18R LPSO and 14H LPSO phases and a few of Mg3Zn3RE2 and Mg24Y5-type compounds. The ultimate tensile strength of Mg-12Ymm-4Zn alloy could keep above 130 MPa until 400 °C. The excellent high-temperature strength was mainly attributed to dense LPSO lamellae strengthening Mg matrix and network-like LPSO phase reinforcing grain boundaries.