Mechanism of grain refinement of Mg–Al alloys by SiC inoculation

The mechanism of grain refinement was investigated for Mg–Al alloys inoculated with SiC particles. Contrary to the previously reported Al4C3 hypothesis, the ternary carbide Al2MgC2 was observed, which has a crystal structure closer to that of Mg than to that of Al4C3. In the centre of the grains, one or more “hillocks” enriched in Al and C were observed. Based on the observed phenomena, a novel mechanism is suggested to explain the grain refinement of Mg–Al alloys with the addition of SiC particles.