Effects of erbium on microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy

Mg-7Zn-3Al-xEr (x=0.1, 0.4, 0.7) magnesium alloys were prepared by permanent mould casting. The effects of rare earth element of erbium on the microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy at both room temperature and elevated temperatures were investigated with optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, differential scanning calorimetry, and tensile testing. The results show that the quasi-continuous grain boundary networked τ(Mg32(Al, Zn)49) phases are changed into discontinuous globular particles due to the addition of Er. Spherical Al-Er compounds are also identified in the matrix. The mechanical testing reveals that, with Er addition, the elevated temperature tensile properties can be remarkably improved. The microstructure evolution during tensile deformation under both temperature and stress and its effects on the mechanical properties were further discussed.