On the Activation Energy of the Diffusion Process at Migrating Grain Boundaries

Abstract

Analytical electron microscopy and in situ observations were used for local description of the diffusion process along the migrating front of the discontinuous precipitation reaction in the Al-22 at.% Zn alloy. The resulting values of the solute diffusivities determined for a wide range of ageing temperature (350–475 K) confirmed that there is no significant difference in the rate of the diffusion process along migrating and stationary grain boundaries. Moreover, the data on the activation energy were very similar to the relevant parameters for stationary grain boundaries. The discrepancies in activation energy determined for the discontinuous precipitation reaction using global characterization of the diffusion process via the Petermann-Hornbogen equation are explained in terms of the specificity of the local treatment which does not take into account the contribution to the energetic barriers coming from the stop- and -go nature of grain boundary migration during discontinuous precipitation reaction.