Effect of Ca and Zr Additions and Aging Treatments on Microstructure and Mechanical Properties of Mg-Sn Alloy

The effect of Ca and Zr Additions and Aging Treatments on Microstructure and Mechanical Properties of Mg-Sn alloy was investigated. It was found that the grain size of as-cast Mg-4Sn-xCa and Mg-4Sn-xZr alloys was refined with the increase of alloying elements addition. The alloys were solution-treated at 480 °C and aged at 160 °C, and the aging peak appeared after 4-5 h. The difference was that the maximum tensile strength and Brinell hardness of Mg-4Sn-0.3Ca were 140.7 MPa and 44.5 HB, respectively, while in Mg-4Sn-xZr alloy, Mg-4Sn-0.5Zr was optimal. The maximum tensile strength and Brinell hardness of Mg-4Sn-0.5Zr were 137.4 MPa and 41.5 HB, respectively. This difference was mainly due to the formation of the brittle phase CaMgSn in the Mg-4Sn-xCa alloy. The excessive brittle phase was not conducive to the strength of the alloy, but could increase the hardness of the alloy. However, Zr existed as a simple substance in the alloy, which can be used as a nucleation particle to inhibit grain growth and play a role of fine grain strengthening. But the addition of Zr did not form many hard phases, so the hardness did not change much.