Grain refining efficiency of a new Al–1B–0.6C master alloy on AZ63 magnesium alloy

A new Al–1B–0.6C master alloy for grain refinement of Mg–Al-based alloys has been fabricated by melt reaction in the present work. Through XRD and EPMA detection, it is found that Al–1B–0.6C master alloy mainly contains Al3BC particles with the size distribution from 2 μm to 8 μm. The reaction between Al4C3 and B in Al melt forms the new Al3BC phase. Grain refinement experiments reveal that the master alloy can refine AZ63 (Mg–6Al–3Zn–0.4Mn) alloy efficiently. At 760 °C, the grain size is sharply reduced from 710 μm to 70 μm with the addition of 2 wt.% Al–1B–0.6C master alloy, and the grain morphology of α-Mg transits from a characteristic sixfold symmetrical shape to a petal-like shape. The grain refining mechanism is attributed to the presence of Al3BC particles in the master alloy which can act as effective nucleating substrates of primary α-Mg.