A Novel Mg-CaMgSn Master Alloy for Grain Refinement in Mg-Al-Based Alloys

A novel grain refinement method using a CaMgSn intermetallic phase was investigated via adding a Mg-CaMgSn master alloy to an AZ31 magnesium alloy. The results showed a remarkable grain refinement effect in as-cast AZ31, with the average grain size reduced from approximately 260-93 mu m after adding 0.45 wt.% CaMgSn particles. The added CaMgSn phase was found in grain interiors and acted as heterogeneous nucleation sites during solidification. The edge-to-edge matching model confirmed a low mismatch value of 2.3% for the {0002}(Mg)/{211}(CaMgSn) close-packed plane, suggesting that {211}(CaMgSn) was the possible matching plane for Mg nucleation. The microhardness and compressive yield strength were also improved by adding CaMgSn particles, confirming that adding Mg-CaMgSn master alloy was an effective method for refining the microstructure and improving the mechanical properties of Mg-Al-based alloys.