The Al2Ca intermetallic compound was prepared by melting process in a vacuum induction furnace. And the A12Ca compound was added in as-cast AZ31 alloys for grain refinement. The effect of its additional levels on grain refinement of as-cast AZ31 alloy was investigated and the mechanism of the grain refinement was discussed. The results reveal that the addition of 1.1% Al2Ca （mass fraction） decreases the average grain size of as-cast AZ31 alloy from 354 to 198 μm. And the thermal stability of the grains refined by Al2Ca is superior. The grain refining mechanism is attributed to the combined effects of solute and heterogeneous nucleation from the Al2Ca.
