Grain refinement of Mg–Al(–Mn) alloys by SiC additions

The addition of SiC particles effectively grain refined a range of Mg–Al alloys. The greatest reductions in grain size were found for the alloys with lower Al contents. The presence of Mg2Si in the microstructure after that SiC addition, and consideration of phase equilibria suggested that the SiC transforms to Al4C3, and this is the actual nucleant. The addition of Mn poisoned the grain refining effect of the SiC addition, probably due to the formation of less potent Al–Mn–carbides.