Effects of Zn and RE additions on the solidification behavior of Mg–9Al magnesium alloy

Effects of Zn and RE additions on the solidification behavior of Mg–9Al alloy were studied. Zinc (Zn) and rare earths (RE) elements were added to a maximum quantity of 1.2 and 1.6wt.%, respectively. Cooling curves were obtained under commercial production conditions. Hot tearing susceptibility was investigated using crack-ring molds. Microstructure was analyzed by metallographic examination and electron probe micro-analysis. Zinc additions decreased the end-solidifying temperature, promoted the precipitation of Mg17Al12 in grain boundaries and increased the hot-tearing susceptibility coefficient (HSC). Al4RE phase precipitation slowed down the temperature decrease at the initial stage of solidification. RE additions had little effect on HSC of Mg–9Al with low or no Zn content, while when Zn content was exceeded 0.8 wt.%, RE additions decreased HSC of Mg–9Al alloys distinctly.