In this article, the modification effects on Al–Mg2Si before and after heat treatment were investigated with Ca, Sb and (Ca+Sb). In comparison with single Ca or Sb, the samples with composition modifier (Ca+Sb) own the optimum microstructure. Especially the sample with the molar ration of Ca and Sb as 1:1 obtained relatively higher properties, of which the Brinell hardnesses before and after heat treatment have been remarkably increased 31.74% and 28.93% in comparison with bare alloy. According to DSC analysis, it was found that the nucleation behaviors of primary Mg2Si phase could be significantly improved through the chemical modifier. Some white particles were found embedded in the center of Mg2Si phases, which was deduced to be Ca5Sb3 through XRD and FESEM analyses. Furthermore, Ca5Sb3 possess rather low mismatch degree with Mg2Si particles with PTCLab software, meaning that the efficient nuclear capability of Ca5Sb3 for Mg2Si particles could be supposed.
