Macroscopic liquid phase separation of Fe-Sn immiscible alloy investigated by both experiment and simulation

The macroscopic phase separation of undercooled liquid Fe50Sn50 immiscible alloy was investigated by both drop tube experiment and the modified Model H. Core-shell structures with two, three, and five layers were formed during experiment. The concentric shells comprised of Fe-rich phase and Sn-rich phase distribute periodically in the solidified droplet, and the Sn-rich phase is always located at the sample surface owing to its smaller surface tension. The simulated results of modified Model H reproduce core-shell structures with the same layers, which justifies the prediction of this model. If the fluidity parameter C-f and solute concentration phi satisfy the physical conditions of both C-f < 1 and 0 <phi < 0.45 or C-f >= 1, the phase separation morphology exhibits the double-layer core-shell structure, whereas the multilayer core-shell structure is expected to form under the conditions of both C-f < 1 and 0.45 <phi < 0.5. The forming ability of core-shell structure for various immiscible alloys can be predicted accordingly.