Effects of surface tension anisotropy on interfacial instability in directional solidification

Effects of surface tension anisotropy on the planar interfacial stability are studied with asymptotic analysis method in both the solidification from undercooled pure melts and the unidirectional solidification of binary alloys. The asymptotic approach developed by Xu is adopted to study the interfacial stability here, which is different from that used by other investigators previously in their works. A simple linear analysis result is obtained, i.e., the surface tension anisotropy may compete to determine interfacial stability near some critical conditions in unidirectional solidification of binary alloys. The exsitstence of the surface tension anisotropy enlarges the instability region of disturbed wave number. And the threshold of instability is strongly affected by surface tension anisotropy, especially at high pulling velocity or high temperature gradient.