Measurements were made of chemical diffusivity at the reaction front of discontinuous precipitation or dissolution. The results showed that there were no substantial differences in comparison with the tracer diffusivities of stationary grain boundaries in Al-Zn solid solutions. This was attributed to a localized treatment which comprised  in situ  observation in the transmission electron microscope. A number of approximations, which usually arose from considering discontinuous precipitation and dissolution reactions to be phenomena which were averaged over the whole volume of the sample, were avoided. It was clearly shown that an increase in the number of growth kinetics parameters, as obtained by using a local treatment instead of a global treatment of discontinuous precipitation and discontinuous dissolution, led to a gradual decrease in the discrepancies between tracer diffusivities for stationary boundaries and chemical diffusivities of a moving reaction front.

Local Values of the Diffusivities at the Migration Front of Discontinuous Precipitates in Al-22at%Zn Alloy P.Zięba, W.Gust: Scripta Materialia, 1998, 39[1], 13-20