Effect of Solute Convection on the Macrosegregation in Pb-Sn Binary Alloys during Upward Directional Solidification

摘要

Upward directional solidification experiments have been carried out on Pb-Sn binary allogys. The macrosegregation along the length of a sample in hypereutectic Pb-Sn alloy is not observed. However, it is observed in the hypoeutectic Pb-Sn binary alloy. The intensity of the longitudinal macrosegregation increases as the solidification rate decreases. It can be found tha tsolute convection resulted from the density profile of interdendritic melt and induced the macrosegregation. The intensity of the interdendritic solute convection responsible for the longitudinal macrosegregation can be represented by the effective partition coefficient of the alloy. The change in the length of a mushy zone affects the intensity of the solute convection during the upward directional solidification even when steady-state dendritic growth is maintained.