Foils were oxidized at 1000C, on one side only, in laboratory air. The other side was protected from oxidation by using a reducing atmosphere. After oxidation, the non-oxidized face was examined by using atomic force microscopy. Grain-boundary grooves were characterized and their depths were compared with those found in a control sample which had been heat-treated in a reducing atmosphere for the same time. The grain-boundary grooves were found to be much deeper in the case of single-side oxidized samples. It was shown that this additional grooving was directly linked to the growth of the oxide scale on the opposite side. It could be explained by the diffusion, of vacancies produced at the oxide-scale/metal interface, across the entire sample; via grain boundaries. A comparison of single-side oxidized samples, with samples oxidized on both sides, showed that voids in grain boundaries were observed only in the latter case. This proved the occurrence of vacancy condensation in the metal when the 2 faces were oxidized.

Injection of Vacancies at Metal Grain Boundaries during the Oxidation of Nickel. S.Perusin, B.Viguier, D.Monceau, L.Ressier, E.Andrieu: Acta Materialia, 2004, 52[18], 5375-80