Age hardening and mechanical properties of Mg–Gd–Er alloy

The Mg–8Gd–0.6Zr–xEr (x = 1, 3 and 5 mass%) alloys were prepared by casting technology, and the microstructures, age hardening behaviors and mechanical properties of alloys have been investigated. Microstructures of the alloys are characterized by the presence of rosette-shaped equiaxed grains. The age hardening behaviors and the tensile properties are enhanced by adding Er element. The maximum aged hardness of Mg–8Gd–0.6Zr–5Er alloy is 97, it is nearly 1.24 times higher than that of Er-free alloy. The Mg–8Gd–0.6Zr–3Er alloy exhibits maximum ultimate tensile strength and yield strength at peak aged hardness, and the values are 261 and 173 MPa at room temperature, 203 and 122 MPa at 250 °C, respectively. This improved peak hardness and mechanical strength are mainly attributed to the fine dispersed β′-Mg15RE3 (Gd/Er) metastable phase and β-Mg5RE (Gd/Er) precipitate.