LAUSR

Abstract To explore the heterogeneous nucleation mechanism of Mg-Al alloy refined by Al 4 C 3 , the valence electron structure and cohesive energy of Al 4 C 3 crystal were calculated using the empirical electron theory of solids and molecules. A novel model to account for heterogeneous nucleation process of α-Mg on Al 4 C 3 is described. The weak bonds exist in the surface of Al 4 C 3 might leads to the replacement of atoms in Al 4 C 3 surface by Mg atoms in melt, which ultimately result in easily stacking of Mg atoms on the newly formed surface of Al 4 C 3 . This model also indicates that Mg-Al atom cluster preferentially occupies the atom vacancies on Al 4 C 3 surface in comparison to Mg-Mg atom cluster, which can decrease the refining efficiency of Al 4 C 3 in high Al containing magnesium alloys.