Macrosegregation driven by movement of minor phase in (Al0.345Bi0.655)90Sn10 immiscible alloy

Abstract

Formation of macrosegregation structure in (Al0.345Bi0.655)90Sn10 (mass percent, the same below) immiscible alloy was investigated by spraying its melt into silicone oil. Two kinds of typical macrosegregation structures were obtained in the dispersed alloy spheres: core/shell structure and crescent structure. Based on the estimated temperature field inside the alloy spheres, the velocities of thermal Marangoni, solutal Marangoni, and Stokes motions of the Bi-rich minor droplets were calculated. Analysis shows that surface segregation, Soret effect, thermal Marangoni motion, solutal Marangoni motion, and Stokes motion play a key role in the formation of Al/Bi–Sn core/shell structure. If the liquid alloy spheres solidify on the condition that the radius of the Bi-rich minor droplets is smaller than a critical value, it will form Al/Bi–Sn core/shell structure, while the crescent structure will be formed when the liquid alloy spheres frozen on the condition that the radius of the Bi-rich minor droplets exceeds the critical value.