Microstructural Evolution and Hardening Behavior of a Low-Activation Ti-Nb-Zr-O Film Under He+ Irradiation

The development of accident-tolerant fuels has significantly enhanced the safety of fission reactors. The TiNbZrO alloy system has garnered considerable attention due to its excellent mechanical properties and outstanding irradiation resistance. Its unique compositional design enables effective suppression of irradiation-induced defect formation. In this study, TiNbZrO thin films are fabricated via radio-frequency magnetron sputtering and irradiated with 50 keV He ions to fluences of 5 × 1016, 1 × 1017, and 2 × 1017 ions/cm2. The microstructural evolution before and after irradiation is characterized by Transmission Electron Microscopy (TEM) and Grazing Incidence X-ray Diffraction (GIXRD), and the changes in mechanical properties are evaluated by nanoindentation. With increasing irradiation fluence, the average size of He bubbles increases from 1.10 nm to 2.06 nm, the number density decreases from 5.27 × 1024 m−3 to 1.39 × 1024 m−3, and the swelling rate rises from 0.37% to 0.64%. Although significant irradiation hardening is observed in all samples, the maximum hardening rate reaches only 31.91%, a value substantially lower than that reported for many conventional nuclear materials. This demonstrates the superior irradiation resistance of TiNbZrO thin films. The superior irradiation resistance of TiNbZrO thin films stems from two synergistic effects: high-entropy lattice distortion suppresses atomic diffusion, while oxygen complexes pin defects.