Abstract
A model is proposed to explain diffusion-induced migration of a grain boundary or a liquid film on a unified basis. The driving energies for both phenomena are identified as the interface free energy and the free energy of mixing, the latter being predominant in most cases. The grain boundary or the liquid film migrates owing to thermally activated motion of atoms across the interface under the influence of the driving energies. An expression for the velocity of migration is derived, and it is shown that this depends parabolically on solute concentration. The model explains numerous experimental facts.