Effect of Anisotropic Thermal Conductivity on the Morphological Stability of a Binary Alloy

摘要

A linear morphological stability analysis of a planar interface during unidirectional solidification of a binary alloy was performed for the case of a crystal having an anisotropic thermal conductivity. A dispersion relation was calculated which shows that the onset of instability depends on the orientation of the growth direction with respect to crystallographic axes and on the orientation of the wave vector of the perturbation. The onset of instability can be either oscillatory (travelling waves) or non-oscillatory in time. For growth along a principal axis of the crystal there is an exchange of stabilities, and the onset of instability is non-oscillatory. The dispersion relation for a uniaxial crystal was explored in detail. Numerical results for the case of an alloy of 0.78 at % bismuth in tin are given.