Velocity and radius transients during pressure mediated dendritic growth of succinonitrile

Abstract

This study was part of a larger effort called the transient dendritic solidification experiment (TDSE), which uses the well known Clapeyron effect to study transient effects in dendritic solidification. The transient behaviour was studied between well defined steady states using pressure mediated changes since it is almost impossible to study the transient behaviour during growth of a dendrite from initial state to steady state. The time constants calculated for the velocity and radius transients are of the same order of magnitude. The velocity starts changing almost immediately after the pressure changes. The radius also changes rapidly but the change starts after an initial lag. This is attributed to its ‘geometric memory’ and the fact that the change in velocity results from a change in the thermal field ahead of the tip, whereas a change in radius also entails a change in the lateral thermal field. These results affirm that pressure changes affect the growth behaviour and interfacial morphology of dendrites, which can be used for controlling solidification microstructure.