Oxidation induced localized creep deformation in Zircaloy-2

Extensive plastic deformation in the metal underneath the oxide scale in autoclave tested Zircaloy-2 was studied using transmission electron microscopy (TEM). It was concluded that the plastic deformation is created by creep during oxidation, and is not caused by surface treatment, sample preparation or cooling from autoclave temperatures. Evidence of large strains was found in the form of dislocation tangles, dislocation patches and sub-grain formation, and also indications of twinning were found. The heavily deformed layer is around a few μm thick and no obvious difference could be seen between alloys with different strength or different oxide thickness.