Comparative study of irradiation resistance for multicomponent concentrated HfNbTiZr and dilute V-4Cr-4Ti alloys irradiated with He ions

To clarify the efficiency of irradiation resistance, investigation of body-centered cubic concentrated HfNbTiZr and dilute V-4Cr-4Ti alloys, irradiated by 40 keV He ions up to 5 × 10¹⁶, 1 × 10¹⁷ and 5 × 10¹⁷ cm^–2 fluences at room temperature, was carried out. Similar to V-4Cr-4Ti, HfNbTiZr possesses high phase stability and surface erosion resistance to irradiation with He ions up to 5 × 10¹⁷ cm^-2. Using transmission electron microscopy, a more than 2-fold increase in overall swelling, as well as its intensification with increasing fluence was observed for HfNbTiZr compared to V-4Cr-4Ti. Combining atomistic calculations and simulations based on the Modified Embedded Atom Method interatomic potential and Density Functional Theory, the energetics of defects and helium-vacancy complexes, as well as their dynamics, were studied for alloys. It was shown that in the HfNbTiZr and dilute vanadium alloys the number of radiation-induced vacancies (v) can be comparable. According to the binding energy curves, there is a tendency for higher He accumulation in helium-vacancy complexes due to the increased He/v ratio in HfNbTiZr compared to V-4Cr-4Ti (∼1.5 versus ∼1.1). It was found that the kick-out of lattice atoms is enhanced in HfNbTiZr and is suppressed in V-4Cr-4Ti. Therefore, the more intense He bubble growth in HfNbTiZr may be due to the kick-out mechanism, which leads to a decrease in the He/v ratio and stimulates helium-vacancy complexes to trap additional He atoms. Our results can be used to improve the bubble swelling resistance in the design of new multicomponent concentrated alloys.