Effect of Sr Additions on the Microstructure and Strength of a Mg-Al-Ca Ternary Alloy

The effect of Sr additions on the microstructure and strength of a Mg-5Al-3Ca alloy was investigated by replacing Ca with Sr. In the as-cast alloys, the major intermetallic compound observed at the α-Mg dendrite cell boundary region changes from the Al-rich (Mg, Al)2Ca phase to the Mg-rich Mg17Sr2 phase with increasing Sr content. This results in an increased Al solute content in the α-Mg phase in the high-Sr containing alloys. More than 1 wt pct of Sr enhances the solid-solution strength of the α-Mg phase, resulting in the increased compression strength of the alloys.