Development of an effective modifier for hypereutectic Mg–Si alloys

The Mg–30B2O3 modifier with the composition of Mg and B2O3, sintered in the temperature range between 250 and 450 °C, has been developed as a low-cost and effective modifier for hypereutectic Mg–Si alloys. With 0.2–1.0 wt.% B (introduced in the form of Mg–30B2O3), the morphology of the primary Mg2Si transforms from coarse dendrite shape into fine polyhedral shape with the size about 10 μm. The modification mechanism of B2O3 is attributed to the adsorption and poisoning manners due to the presence of B in the melts by the decomposition of B2O3.