Insights into the effects of Sm on microstructure evolution mechanism and mechanical properties of Mg-8Gd-2Y-1Zn-0.5Zr cast alloy at high temperature

In this study, the effects of 1% Samarium (Sm) on the microstructure and room and high temperature mechanical properties of Mg-8Gd-2Y-1Zn-0.5Zr alloy are discussed and analyzed. The addition of Sm increases the volume fraction of lamellar and blocky long-period stacking ordered (LPSO) phases and promotes the precipitation of lamellar β' and β phases. The high yield strength and ultimate tensile strength of Mg-8Gd-2Y-1Sm-1Zn-0.5Zr alloy at room and high temperatures are mainly attributed to the strengthening effects of LPSO, β, and β' phases. The LPSO, β, and β' phases effectively hinder the movement of dislocations and inhabit the migration of grain boundaries. The Mg-8Gd-2Y-1Sm-1Zn-0.5Zr alloy shows superior yield strength (203.3 MPa) and ultimate tensile strength (258.9 MPa) at 350 °C, which are respectively 67.2 MPa and 23.8 MPa higher than those of Mg-8Gd-2Y-1Zn-0.5Zr alloy (136.1 MPa and 235.1 MPa).