The continuum double-diffusivity model was shown to be capable of analyzing diffusion in the presence of dislocations and grain boundaries which acted as high-diffusivity paths. The 2 (reaction-constant) fitting-parameters of the model exhibited an exponential dependence upon temperature. There was an apparent decrease in the value of these parameters, by several orders of magnitude, as the temperature decreased from 625 to 520K. A departure from Arrhenius behavior in the case of Au self-diffusion via dislocations, instead of the Arrhenius behavior which applied in the case of Cu self-diffusion through grain boundaries, could be interpreted in terms of dislocation density changes between experiments. Changes in dislocation density resulted in changes in the local geometry and in the microscopic configuration. The volume fraction of high-diffusivity paths was not the same for all experiments. This had an effect upon the calculated dislocation densities.

Further Experimental Evidence of the Double Diffusivity Model. D.A.Konstantinidis, E.C.Aifantis: Scripta Materialia, 1999, 40[11], 1235-41