Phase field modeling of sub-parabolic oxidation kinetics and in-plane stress in zircaloy under neutron/proton irradiation

Abstract A detailed study of the sub-parabolic oxidation kinetics in Zircaloy system has been carried out by using phase field modeling under conditions related to oxidation in autoclave and during neutron/proton irradiation. The exploited phase field model is factored in temperature gradient and voltage change between metal and oxide surface. It is shown that the irradiation accelerates oxidation rate and induces development of conjugated in-plane stress. It is found that both in-plane and tensile stresses result in a power-law decrease in a critical time for fragmentation versus dose rate. It is shown that a critical crystallite size for the related tetragonal to monoclinic phase transformation at the oxide/metal interface decreases with the dose rate. Obtained results correlate well with experimental observations in the reference points and can be exploited to estimate corrosion resistance linked to transformation to monoclinic structure and fragmentation in zirconium-based cladding materials. This study provides a deep insight into the details of oxidation kinetics at irradiation in zirconium alloys.