Analytical electron microscopy and in situ observations were used for the local description of diffusion along the migrating front of a discontinuous precipitation reaction in Al-22at%Zn. The resultant values of the solute diffusivities over a wide range (350 to 475K) of aging temperatures confirmed that there was no significant difference in the rates of diffusion along migrating and stationary grain boundaries. Moreover, the data on the activation energy were very similar to the relevant parameters for stationary grain boundaries. Discrepancies in activation energy, determined for the discontinuous precipitation reaction using global characterization of the diffusion process via the Petermann-Hornbogen equation, were explained in terms of the specificity of the local treatment; which did not take account of the contribution to energetic barriers arising from the stop-and-go nature of grain boundary migration during discontinuous precipitation reactions.

On the Activation Energy of the Diffusion Process at Migrating Grain Boundaries. P.Zieba, W.Gust: Interface Science, 2002, 10[1], 27-30