Microstructure and superior mechanical properties of cast Mg–12Gd–2Y–0.5Sm–0.5Sb–0.5Zr alloy

The Mg–12Gd–2Y–0.5Sm–0.5Sb–0.5Zr (wt.%) alloy was prepared by casting technology. The microstructure of alloy was then investigated after solution and aging treatment (i.e., T6 heat treatment). Tensile tests were performed at a crosshead speed of 1 mm/min at ambient and elevated temperature atmosphere. The results show that the aged alloy was mainly composed of α-Mg matrix and dispersed long-period ordered β′ precipitates. At 250 °C, the alloy has shown the superior tensile strength (i.e., 345.5 MPa). The remarkable high strength of experimental alloy was mainly associated with solution strengthen of RE and precipitation strengthening of dispersive LPO structure β′ precipitates in Mg matrix. The LPO β′ precipitates provide important strengthening sources in experimental alloy, especially at elevated temperatures.

► Mg–Gd–Y alloy exhibits higher mechanical properties at room and high temperatures.
► The experimental alloy exhibits excellent mechanical properties in 20–300 °C.
► The alloy exhibits anomalous temperature dependence of tensile strength in 20–300 °C.
► The high tensile strength was mainly associated with LPO structure β′ precipitates.