Microstructure and tensile properties of Mg–Zn–Gd casting alloys

Abstract

The effects of Gd additions to a Mg–3Zn based casting alloy on the microstructure and tensile properties at room and elevated temperature have been investigated. As cast microstructures of the Mg–Zn–Gd alloys consists principally of primary Mg and Mg–Gd–Zn phases. The maximum tensile strength at both room and 175°C was found to occur at 1–2%Gd, while the elongation was continuously reduced by increasing Gd content. The ultimate tensile strength of 1–2%Gd containing alloys was comparatively high (∼150 MPa) at 175°C. The tensile creep resistance was remarkably enhanced by the Gd additions, presumably due to the formation of Mg–Gd–Zn phases. Creep deformation of only ∼0·5% was observed after 200 h (175°C and 50 MPa) in the case of 3%Gd. It was found that hot cracking resistance was slightly reduced at 1–2%Gd but recovered at 3%Gd. No significant change of fluidity was found with respect to the Gd content.