Influence of initial solid-liquid interface morphology on further microstructure evolution during directional solidification

Preparation of the initial solid-liquid interface on which growth is started is a very critical step in directional solidification experiments. Dedicated experiments concerning preparation of the initial solid-liquid interface morphology and its influence on further directionally solidified microstructure were performed on Cu-20 wt% Sn peritectic alloy in a Bridgman-type furnace. To verify the morphology of the initial solid-liquid interface, steady-state directional dendritic growth was interrupted by thermal stabilization ranging from 0 to 1 h prior to quenching. With thermal stabilization duration increase, the solid-liquid interface morphology degenerated from dendritic to cellular and finally to planar. To verify the influence of the initial state on further solidification microstructure, directional solidification experiments were performed at a low pulling rate of 1 ìm/s with different initial solid-liquid interface morphologies. The initial state affects solute redistribution and formation of peritectic coupled growth structure in the subsequent directional solidification process.