Special grain boundaries in zirconia corrosion films

Abstract

Transmission electron microscopy (TEM) studies of the oxide film on the surface of a zirconium alloy have been performed and the crystallography of interfaces has been analysed. Regions of a peculiar microstructure consisting almost entirely of twins have been discovered in the zirconia film. The TEM results have been analysed in conjunction with the known texture data, and the orientation relationships between monoclinic ZrO₂ and the α-Zr substrate are discussed. Computer simulation has been performed to reveal the possible grain boundary character distributions in different regions of the film. The relevance of the results obtained to the diffusion properties of the surface zirconia layer is discussed in this paper. It is suggested that a high concentration of special grain boundaries hinders transport through the zirconia film.