Mg adsorption on MgAl2O4 surfaces and the effect of additive Ca: A combined experimental and theoretical study

Abstract

Ca is often added to many magnesium alloys as it has a flame retardant effect and could improve the alloy properties. Our previous research proved that Ca had a great influence on the grain refining effect of Mg-3%Al alloy treated by carbon inoculation, the grain difference was 88 µm for cases with or without Ca. In this work, we have studied the effect of Ca on the Mg-3%Al alloy refined from MgAl2O4 through a combination of experimental and theoretical study. Ca has a clear effect on the grain refining effect of MgAl2O4 for the grain difference is 34 µm. It is found that Ca promoted Mg adsorption on MgAl2O4(110) surface. In contrast, Ca has little effect on the adsorption of Mg on (100) and (111) surfaces of MgAl2O4. After comparing the effects of Ca on grain refining of Mg-3%Al alloy by different heterogenous nucleation, i.e., Al4C3, Al2MgC2 and MgAl2O4, we show that the effect of Ca on heterogeneous nucleation refinement effect of magnesium alloy is closely related to the impact of Ca on the adsorption of Mg on nucleation particles surfaces.