Investigation on the mechanical properties and microstructures of Mg-Zn-Al-Cu cast magnesium alloys

This paper selected some new elements of Mg-Zn-Al magnesium alloys as experimental alloys to study the microstructures and mechanical properties of ZAC843 permanent mold casting magnesium alloy by adding Cu and Sr, Ti, especially the effects of Sr, Ti addition on the microstructures. It was found that the microstructure was consisted of δ-Mg and Mg₃₂(Al, Zn)₄₉, without Mg₁₇Al₁₂ when Cu was added into ZAC843 permanent mold casting magnesium alloy, and the Cu element was dissolved into Mg₃₂(Al, Zn)₄₉ after hot-treatment. It can improve the melting point of Mg₃₂(Al, Zn)₄₉ and the solid temperature of ZAC843 magnesium alloy. The addition of trace Sr and Ti has better influences on the microstructure, however, only adding Sr can not change the microstructure effectively. When the experimental alloys was heat treated, the microstructure was refined and the mechanical properties were improved, especially, for the ZAC843A permanent mold casting magnesium alloy (σ_b=253 MPa T6).