Oxidation of Zirconium Alloys. Crystallographic Texture of Zirconia: Interpretation and Mechanical Consequences

In order to have a better knowledge of the mechanical behaviour of the oxide layers growing on zirconium alloys in pressurized water reactors, the textures of different zirconium alloys and their oxide layers are studied. The results show that the texture of the oxide layers present a feature common to all the layers: the tilt angle of the maximum intensities of the pole figures obtained on the layers is almost quite identical for all the studied substrates. The azimuthal reinforcements depend on the metallurgical state of the substrate.The crystallographic direction of monoclinic zirconia common to all the oxide grains is identified. A computation based on mechanical issues is presented: considering the anisotropic elastic properties of the monoclinic monocrystal, it is shown that the particular crystallographic direction is linked to an isotropic state of strains in the plane of the metal–oxide interface.