Diffusion-induced grain-boundary migration was studied in the Ni-Cu system, at temperatures ranging from 723 to 1023K, by using optical microscopy, scanning electron microscopy and electron probe microanalysis. Four different stages of grain boundary migration were found during diffusion-induced grain-boundary migration and were called: nucleation, initial, stationary and mixed. During the mixed stage, diffusion-induced grain-boundary migration occurred at the same time as diffusion-induced recrystallization, and it was impossible to separate the 2 phenomena. The electron probe microanalysis measurements revealed that the Cu concentration in the diffusion-induced grain-boundary zone did not remain constant, but increased with increasing annealing time. The highest Cu concentration which did not depend upon the annealing conditions was found in the middle of the diffusion-induced grain-boundary migration zones. On the basis of the measured Cu distributions in the diffusion-induced grain-boundary migration zones, the coherency-strain driving force for grain-boundary migration was calculated. In some cases, the calculated values were lower than the energy difference across the grain-boundary, due to its curvature. It was concluded that some other driving force was involved. The nucleation and initial stages of the diffusion-induced grain-boundary migration could be explained in terms of a model that was based upon diffusion-induced grain-boundary stresses. Arrhenius parameters were determined for diffusion along, and across, the grain boundaries in Ni-rich Ni-Cu alloys.

C.Y.Ma, E.Rabkin, W.Gust, S.E.Hsu: Acta Metallurgica et Materialia, 1995, 43[8], 3113-24