Improved Mechanical Properties of Mg-1.5Sn (at.%) Alloy Due to the Synergistic Effects of a Second Phase and Incorporation of Additional Elements Through Solid-Solution Treatment

The microstructure and compressive behavior of untreated and solid-solution-treated Mg-1.5Sn alloys combined with 0.65 at.% Ca or 0.65 at.% Ca + 0.24 at.% Ag addition were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy and compression tests. A solid-solution-treated Mg-1.5Sn-0.65Ca-0.24Ag (at.%) alloy with a compressive strength of 248.9 MPa and an elasticity of 24.9% was achieved; the values of these properties were 45.7% and 40.7% higher than those of the untreated Mg-1.5Sn (at.%) alloy, respectively. Notably, the microstructure of solid-solution-treated Mg-1.5Sn-0.65Ca-0.24Ag alloy included refined grains, refined CaMgSn phase and dissolved atoms (Sn, Ca and Ag); these qualities greatly contributed to the compressive strength enhancement. Furthermore, the compressive elasticity was obviously improved due to the decrease in nucleation sites of cracks caused by the eutectic Mg 2 Sn phase. The homogenization and solid-solution treatment relieved the stress concentration and changed the lattice parameters, which also enhanced the compressive elasticity under compression. In this work, the cleavage planes of the solid-solution-treated Mg-1.5Sn-0.65Ca-0.24Ag alloy were increased and refined, and the fracture morphologies of the different alloys under compression were discussed. In conclusion, the refined grains, refined second phase and solid-solution elements improved the comprehensive mechanical properties of the Mg-1.5Sn (at.%) alloy.