Effect of Nd and Y addition on microstructure and mechanical properties of as-cast Mg–Zn–Zr alloy

Direct chill cast Mg–Zn–Zr alloys with different amount of Nd and Y additions have been investigated in this study. The interdendritic phases of as-cast Mg–5Zn–0.6Zr alloy were comprised of a small amount of Zn2Zr3 and Mg4Zn7. They were changed by the addition of Nd to T phase or T phase coexisting with W phase, and the additions of Nd and Y to W phase, occurring with a refinement of dendritic size, an increase of interdendritic phase amount and an improvement in the thermal stability of interdendritic phases. There was a strong dependence of tensile properties on microstructure. The continuous networks of intergranular phases in Mg–Zn–Nd–Zr alloys significantly deteriorated the ultimate strength and elongation, whereas the less continuity of intergranular phases in the Mg–Zn–Nd–Y–Zr alloys favored the ultimate strength and elongation.