A relook at the preferred growth direction of the solid-liquid interface during solidification of pure metals

A simple model for the prediction of the principal growth direction of a solid-liquid interface during solidification of pure metals of different crystal structures is developed. The existing interface controlled growth model for the growth of a solid in a liquid is suitably modified with the incorporation of density change during solidification. The idea of conjugate planes is introduced to construct virtually a unit cell of a solid and, finally, the growth of the conjugate planes is presented with respect to the plane normal. A very good match is shown between the calculated directions of highest growth rate and the experimentally found directions of the primary dendrites of a number of crystal structures. It is also shown that the differential growth of a solid in a liquid along different crystallographic directions is inherently associated with the density change and spatial distribution of atoms on the facing liquid and solid planes on solidification.