On the basis of a new model for the structure of crystallite conjugation regions (grain boundaries), the results of an investigation of intercrystalline diffusion in the 57Co(W) system were analyzed. A new effect was described: this was an expansion of the region of enhanced concentration of point defects. This expansion was accompanied by the decomposition of vacancy-interstitial impurity complexes. The activation enthalpy for the diffusion of substitutional atomic probes in the expanded region of enhanced concentration of point defects was found to be equal to about one-third of the activation enthalpy for bulk diffusion in this system. On the basis of a model for the new effect, diffusion parameters such as the bulk concentrations of vacancies, diffusion coefficients, activation enthalpies for the diffusion of substitutional atomic probes, and the binding energies of vacancy-interstitial impurity complexes were estimated.

Intercrystalline Diffusion of Cobalt in Polycrystalline Tungsten IV. Mechanism of Pumping-Out of Substitutional Atomic Probes during High-Temperature Intercrystalline Diffusion. S.M.Klotsman, V.N.Kaigorodov: Physics of Metals and Metallography, 1999, 87[1], 39-44