Zn segregation at the prismatic Mg2Ca/Mg matrix interface in a Mg–Ca–Zn alloy

The precipitates in an aged Mg-1Ca-1Zn (wt.%) alloy are characterized using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray spectroscopy (EDS) mapping. The prismatic Mg 2 Ca phase is observed for the first time, and the orientation relationship between the prismatic β-Mg 2 Ca and the Mg matrix is characterized as (0001) β //(10 0) α and [11 0] β //[11 0] α . Zn segregation is revealed at the fully-coherent interface along (0002) β //(10 0) α . The segregated Zn atoms substitute for the interfacial Mg atoms in the α-Mg matrix, and first-principles calculations suggest that such segregation is energetically favored. Zn segregation plays a key role in the formation of prismatic β-Mg 2 Ca phase.