Microstructural investigation of Zirconium alloys subjected to oxygen ions irradiations

In this study, samples of zircaloy-2 were irradiated with oxygen ion beam (O5+ ions with 116 MeV energy) to fluence varying from 1013 to 1015 ion/cm2. The irradiated samples were observed under a transmission electron microscope to identify the irradiation-induced defects and phase transformations. Microstructural investigations on these samples showed the presence of interstitial defects and ZrO2 precipitates in the a (hcp) matrix. The alignment of defects appeared to facilitate the formation of the ZrO2 phase in the irradiated samples. Orientation relationship between the oxide and the matrix phase was determined and a possible mechanism for the formation of the ZrO2 phase based on the entrapment of the oxygen ions has been proposed.