Macrosegregation and channel segregation formation of faceted mushy zone in solidification of Sn–Ni hypereutectic alloy in a temperature gradient

Abstract

Numerous investigations on the macrosegregation and channel segregation formation have been reported during eutectic solidification. However, the current analyses are focused on the non-faceted dendritic mushy zone while the faceted mushy zone during solidification has not been reported before. In this work, the macrosegretion and channel segregation formation are studied in directional solidification of Sn-15at.%Ni hypereutectic alloy where the solidified Ni3Sn4 phase exhibits faceted lath-type growth morphology. Similar to previous works on non-faceted mushy zone, more channels can be witnessed in the (Liquid + Ni3Sn4) mushy zone at lower growth velocities. More obvious macrosegregation can be formed in samples at lower growth velocities where the thermosolutal convection is more severe. However, distinct from previous reports, the effective solute distribution coefficient is not constant in the faceted mushy zone of this alloy. Besides, the experimental results demonstrates that the convection can reduce the interspacing of Ni3Sn4 phase during directional solidification. In addition, the thermosolutal convection has more significant influence on the interspacing of Ni3Sn4 phase than the solutal buildup at the tip of Ni3Sn4 phase.