Interdiffusion in Au/Ag thin films at room temperature was studied indirectly by means of Rutherford back-scattering, and the presence of diffusion-induced grain boundary migration was deduced. The fact that such migration occurred in the absence of any significant lattice diffusion ruled out many mechanisms. However, it was possible that a modified version of a model in which the diffusion was entirely confined to the boundary core could produce some small driving force for migration. In a modified model, if misfitting solute atoms (confined to the core) diffused into the core with an associated Kirkendall effect, the core slab was expected to undergo at least some dilatation. However, this would be constrained by the 2 adjoining crystals. The result was expected to be the establishment of biaxial stresses parallel to the boundary in the 2 crystals which adjoined the boundary. These would differ because of the difference in crystal orientation and the effects of elastic anisotropy. A force would therefore exist which caused the boundary to migrate towards the crystal with the higher elastic energy. The magnitude of the force would obviously depend upon the rate at which the stresses tended to increase due to the inward diffusion of solute atoms and the rate at which they could be reduced by relaxation processes in the boundary core.

J.Sommer, Y.M.Chiang, R.W.Balluffi: Scripta Metallurgica et Materialia, 1995, 33[1], 7-12