MORPHOLOGICAL STABILITY OF A PLANAR INTERFACE SUBJECT TO RAPID QUENCHING

Rapid quenching of a solid-liquid interface is a common method of inve stigating solidification morphologies and the distribution of solute d uring crystallisation. As the destabilisation of the interface needs a certain but up to now unknown time interval, the quantities finally o bserved might change during the quenching process. In this paper the d estabilisation of a planar interface with respect to a suddenly acting cooling rate is investigated. A linear stability analysis is performe d considering the time-dependent concentration profile in front of an infinitesimal perturbed planar front, as superposition of the base sta te and a perturbation. Both profiles are estimated numerically. The ti me interval necessary for destabilisation is calculated as a function of wavelength. A comparison with the predictions of the analysis of Se kerka and Coriell (and Mullins and Sekerka) using the instantaneous va lue of the concentration gradient and solidification velocity is perfo rmed. (C) 1998 Elsevier Science B.V. All rights reserved.