Effect of Ar+ Irradiation on the Microstructure and Corrosion Resistance of Zr-4 Alloy

Zirconium alloys used as nuclear fuel cladding materials are subjected to neutron irradiation inside the reactor, which affects their corrosion resistance. Ion irradiation can be used to simulate neutron irradiation to study the effect of irradiation on corrosion behavior. In this study, the Zr-4 plate was irradiated with Ar+ at 360 degrees C with an electrostatic accelerator. The unirradiated and 5 dpa irradiated samples were corroded in 360 degrees C/18.6 MPa/3.5 mu L/L Li+1000 mu L/L B aqueous solution and 400 degrees C/10.3 MPa super-heated steam for 300 d. The microstructure of the samples was characterized by SEM and TEM. Results show that the Zr(Fe,Cr)(2 )second-phase particles in the unirradiated samples have hexagonal close-packed structures, whose Fe/Cr atomic ratio is in the range of 1.8-2.0, and the second-phase particles are amorphized after irradiation. Under the two corrosion conditions, during the corrosion process of the irradiated damage zone in the alloy matrix, the oxide film thickness of the irradiated samples is smaller than that of the unirradiated samples, indicating that Ar+ irradiation can enhance the corrosion resistance of Zr-4 to a certain extent. However, once the irradiated damage zone is fully oxidized, as corrosion proceeds, the oxide film thickness of the irradiated samples becomes greater than that of the unirradiated samples, suggesting that the oxide film formed in the irradiated damage zone facilitates the diffusion of oxidative ions, accelerating the corrosion of Zr-4. The influence of irradiation on the corrosion resistance of Zr-4 at different stages is discussed from the perspectives of microstructure evolution and stress accumulation in the oxide film induced by irradiation-induced defects.