Microstructure and mechanical properties of as-cast Mg-Sn-Ca alloys and effect of alloying elements

The effect of Sn, Ca, Al, Si and Zn addition on the compressive strength of cast Mg-Sn-Ca (TX) alloys was studied in the temperature range of 25-250 degrees C and correlated with the microstructure. The Sn to Ca mass ratio up to 2.5 contributes to the formation of Mg2Ca phase at the grain boundaries and CaMgSn in the matrix, while a ratio of 3 gives only CaMgSn phase mostly in the matrix. While the compressive strength decreases with the increase in temperature, for Sn/Ca up to 2.5, a plateau occurs in 100-175 degrees C, which is attributed to the strengthening by Mg2Ca. However, for ratio of 3, the strength is lower and decreases more gradually. Mg-3Sn-2Ca (TX32) has the highest strength and the addition of 0.4% Al increases its strength but simultaneous addition of Si lowers the strength. Likewise, the addition of Zn improves its strength but simultaneous addition of Al slightly decreases the strength. The results are correlated with the types of intermetallic phases that form in various alloys.