Effect of microalloying with Ca and Al on the microstructure, mechanical and corrosion properties of the ZM60 alloy

The microstructure, mechanical and corrosion properties of the ZM60 alloy with different contents of Al and Ca were investigated by optical microscopy(OM), x-ray diffraction(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile tests. The results show that the as-cast ZM60 alloy consisted of -Mg and Mg51Zn20 phases. There is no obvious change of microstructure when adding 1 wt% of Al to the ZM60 alloy. With the increasing addition of Al, Mg32(Al,Zn)49 phase presented in the alloy replacing the Mg51Zn20 phase. The microstructure of the as-cast alloy in which Ca and Al were simultaneously added was composed of -Mg, Al8Mn5and Mg32(AlZn)49 phases. The grain size of the extruded alloys were well refined with the addition of Al or a mixture of Al and Ca. The grain refining effect of adding Al and Ca is better than adding Al alone, leading to the smallest grain size of2.2 m. The strengthening mechanism of the alloys were mainly fine-grain strengthening with the addition of Al and Ca. Compared with the ZK60A alloy, the tensile strength of the ZAMX6100 alloy increased by about 20MPa, the yield strength increased by about 30MPa, and the elongation was similar. The corrosion resistance of Mg-6Zn alloy was also improved significantly through adding Al and Ca.