Shell phase selection and layer numbers of core–shell structure in monotectic alloys with stable miscibility gap

► The surface energy is a key factor to the shell phase selection. ► The effect of surface/interface energy is confirmed in SCN–H2O system. ► The surface energy also contributes to the layer number of the core–shell structure. Shell phase selection in the core–shell structure formation was investigated in the systems with stable miscibility gaps, and the shell phase selection and the formation mechanism of different layers structure are examined. It is found that the shell phase is always composed of L2 phase owing to its lower surface energy compared with that of L1 phase. This surface/interfacial energy dependent shell phase selection was confirmed by the phase separation of SCN–H2O transparent system with glass/Teflon wall which has different wetting ability to SCN and H2O. On the basis of the surface energy dependent shell phase selection, the formation mechanism of the double- and triple-layer core–shell structure is elucidated.