The microstructures and mechanical properties of cast Mg–Zn–Al–RE alloys

The microstructures and mechanical properties of cast Mg–Zn–Al–RE alloys with 4 wt.% RE and variable Zn and Al contents were investigated. The results show that the alloys mainly consist of α-Mg, Al2REZn2, Al4RE and τ-Mg32(Al,Zn)49 phases, and a little amount of the β-Mg17Al12 phase will also be formed with certain Zn and Al contents. When increasing the Zn or Al content, the distribution of the Al2REZn2 and Al4RE phases will be changed from cluster to dispersed, and the content of τ-Mg32(Al,Zn)49 phase increased gradually. The distribution of the Al2REZn2 and Al4RE phases, and the content of β- or τ-phase are critical to the mechanical properties of Mg–Zn–Al–RE alloys. The Mg–6Zn–5Al–4RE alloy with cluster Al2REZn2 phase and low content of β-phase, exhibits the optimal mechanical properties, and the ultimate tensile strength, yield strength and elongation are 242 MPa, 140 MPa and 6.4% at room temperature, respectively.