The microstructure and mechanical properties of cast Mg-5Sn based alloys

The effects of 1 wt.% Ce-rich misch-metal, 3 wt.% Bi, 0.4 wt.% Sb, and 2 wt.% Ca additions on the micro structure, mechanical properties, and creep resistance of a cast Mg-5Sn alloy were studied. Impression creep tests were carried out at 150 and 225 °C under constant stresses of 300 and 175 MPa. The results showed that creep resistance, hardness, and shear strength of the base alloy were significantly enhanced with the addition of ternary alloying elements. This was attributed to the concurrent formation of Mg₂Sn particles with the more thermally stable CaMgSn, Mg₃Sb₂, Mg₃Bi₂ and MgSnRE phases which strengthen both matrix and grain boundaries during deformation in the investigated system. Among all tested materials, the Mg-5Sn-2Ca alloy indicated the highest mechanical properties and creep resistance due to the refined microstructure as well as the type and volume fraction of the intermetallic phases present in this alloy.