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

Abstract

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, Al 2REZn 2, Al 4RE and τ-Mg 32(Al,Zn) 49 phases, and a little amount of the β-Mg 17Al 12 phase will also be formed with certain Zn and Al contents. When increasing the Zn or Al content, the distribution of the Al 2REZn 2 and Al 4RE phases will be changed from cluster to dispersed, and the content of τ-Mg 32(Al,Zn) 49 phase increased gradually. The distribution of the Al 2REZn 2 and Al 4RE 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 Al 2REZn 2 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.