The demand for weight reduction in automobiles has generated strong interest in research and development of magnesium applications, especially for powertrain components. Ca-alloyed magnesium alloys have excellent creep properties and can be potentially used for powertrain applications. In order to better understand their solidification behavior, the grain structure evolution of Ca-alloyed magnesium alloys AM60 has been investigated in this study. The results of thermal analysis and microstructure evaluation indicate the occurrence of heterogeneous nucleation of primary magnesium during solidification. The crystal structural analysis suggests that the nucleation behavior of Ca-alloyed AM60 may be attributed to a good crystallographic match of // .