Application of Onsager’s reciprocity relations to interface motion during phase transformations

Abstract

A number of theories have been developed for the kinetics of steady-state interface motion during a phase transformation. One requirement of such theories is that they satisfy Onsager’s reciprocity relations for coupled irreversible processes. We show how to apply Onsager’s relations to a phase transformation at a moving planar interface in a two-component system. The appropriate pairs of thermodynamic forces and conjugate fluxes are determined and used to test two proposed theories for interface motion during solidification of binary alloys. It is shown that the continuous growth model ‘‘with solute drag’’ of Aziz and Kaplan is inconsistent with Onsager’s relations, but the continuous growth model ‘‘without solute drag’’ is consistent with Onsager’s relations.