The effect of radiative heat transfer on morphological stability during directional solidification of a binary melt

Abstract

The influence of radiant heat transport and impurity distribution in a semi-transparent crystal-melt system on the morphological stability of a planar interface during the crystallization of semi-transparent binary dilute melt is studied in the framework of the linear theory. Our analysis shows that the influence of radiation on stability is complex. If radiant transport of heat is sufficiently strong, and the physical properties of liquid and solid phases differ considerably, radiation will influence the loss of stability of the crystal-melt interface. The loss iof stability can also occur when the impurity is absent. It is very evident in the case N S » N L α L >α S. In addition, radiation can enhance or reduce the stability of interface through the dependence on the relation between α S, α L and λ S, λ L for the case in which the values of N S,L are small. If λ S = λ L and λ S = λ L, the stability of interface is not influenced by radiation, though the radiation undercooling exists ( N S. L = 16 n 2 bT 3 m /(3 λ S. L α S, L. ), n is refractive index, b is Stefan-Boltzmann constant, T m is the equilibrium temperature of melting, α S.L is mean value of absorption coefficient, λ S.L is heat diffusivity and the indexes S, L correspond to the solid or liquid phases).