Grain refining mechanism in Mg–Al base alloys with carbon addition

In this study, carbon addition affects the formation mechanism and morphology of Al8(Mn, Fe)5, which serves as a nucleation site for α-Mg, conclusively leading to grain refinement of Mn-containing Mg–Al alloys. However, the grain size was decreased on slightly by carbon addition in Mn-free Mg–Al alloys, where Al4C3 particles were observed in the eutectic region. Therefore, it is suggested that Mn is necessary for considerable grain refinement of Mg–Al alloys, and that Al8(Mn, Fe)5 is an effective nucleant in Mn-containing Mg–Al alloys.