Effect of diffusion on Phase Transformations

Abstract

In a multi-component system at the solid-liquid equilibrium the compositions of the two coexisting phases are only equal in the case of a congruently melting compound, at the melting point maximum or minimum of a solution, and in the limiting case, of the melting point of a pure component. In general, a difference in composition exists between liquid and solid. This composition difference changes during the solidification process, except at an invariant equilibrium. At a moderate solidification rate of a homogeneous liquid, a crystalline solid forms with non uniform composition.