Segregation driven by collision and coagulation of minor droplets in Al-Bi immiscible alloys under aerodynamic levitation condition

The effect of collision and coagulation of minor droplets in Al-Bi immiscible alloys under aerodynamic levitation condition on the segregation structure was investigated. It was shown that the minor droplets were dominated by Marangoni motion at the initial stage of the liquid phase separation, while the centrifugal and Stokes motions were strengthened gradually with increasing the droplets radius. Analysis reveals that three segregation morphologies with Al/Bi core-shell structures can be obtained by controlling the cooling rate under aerodynamic levitation. The dimensionless average droplet radius, which characterizes the coagulation degree of minor droplets, increases rapidly with time and dramatically with the minor droplet radius.