To the theory of grain-boundary diffusion in nanostructured materials

Using an asymptotic method of solving diffusion equations and a Laplace transform, the theory of grain-boundary diffusion is extended to the case of a coefficient of bulk diffusion strongly changing near the structural boundaries of grains under the conditions of annealing corresponding to regime C in usual polycrystals. An analysis of the layer activity measured in the diffusion experiment was performed and, on the example of copper, its radical difference from the case of equilibrium boundaries was shown. Results of numerical calculations and qualitative estimates are presented, which make it possible to establish the field of the applicability of the approach suggested.