Solidification distance of planar interface and interface instability in directional solidification of Cu-Cr alloy

The liquid solute distribution in an initial transient zone has been investigated at different growth rates in directional solidification. The results show that the planar interface instability can take place in the transient zone and the,critical growth rate calculated for the occurrence of the planar interface instability is presented. The solidification distances for the growth of the planar interface with various growth rates are obtained at two types of directional solidification processes. The calculation results based on the theoretical analysis are in agreement with the experiment results of Cu-0.5%Cr alloy, in which the liquid density difference between Cu and Cr elements enlarges the value of the solidification distance for the growth of the planar interface during directional solidification.