The effect of La or Ce on ageing response and mechanical properties of cast Mg–Gd–Zr alloys

Mg–8Gd–0.6Zr–1RE (RE = La or Ce, wt.%) alloys were prepared by casting. The microstructures, age hardening behavior and mechanical properties were investigated. The results show that the addition of 1 wt.% La or Ce to a Mg–8Gd–0.6Zr alloy reduces the dendrite arm spacing and slightly improves the mechanical properties and age hardening response. The Mg–8Gd–0.6Zr–1Ce alloy exhibits maximum yield and ultimate tensile strength at the peak age hardness, with values of 146 MPa and 170 MPa at room temperature, and 90 MPa and 135 MPa at 250 °C, respectively. These are about 10% higher than those of the base Mg–8Gd–0.6Zr alloy. The improvement of the mechanical properties of the aged Mg–8Gd–0.6Zr–1Ce alloy is related to the presence of metastable β′-Mg15RE3 (RE = Ce/Gd), β-Mg5RE and Mg12RE precipitates.