Effects of Sr+Ti+B addition on the microstructures and mechanical properties of ZA53 sand-casting magnesium alloy

As-cast microstructures of the sand-casting magnesium alloys ZA53 (Mg-5%Zn-3%Al-0.2%Mn) contain δ-Mg and τ(Mg₃₂(Al, Zn)₄₉) phases. By adding trace elements Sr, Ti and B into the melt of the ZA53 alloys, the primary grain of 6-Mg was refined, meanwhile the morphology of T phase was changed from semi-netted shape to short rods or spheres, and the distribution of T phase tended to be more homogeneous. In the case of additions of 0.06%Ti, 0.012%B, and 0.1%Sr, δ-Mg grain was greatly refined and the best mechanical properties were got.