Effects of Nitrogen Doping on Microstructures and Irradiation Resistance of Ti–Zr–Nb–V–Mo Refractory High-Entropy Alloy

Interstitial strengthening with nitrogen (N) is one of the effective ways to improve the mechanical properties of HEAs, but the effects of N on the microstructures and mechanical properties of the irradiated HEAs have not been studied extensively. Here, the microstructures and mechanical properties of N-free and N-doped Ti₂ZrNbV_0.5Mo_0.2 HEAs before and after He irradiation were investigated. The results showed that the solid solution strengthening caused by interstitial N improved the yield strength at room temperature and 1023 K without significantly reducing plasticity. N doping significantly promoted the growth, aggregation and wider spatial distribution of He bubbles by enhancing the mobility of He atoms/He-vacancy complexes, with the average size of He bubbles increasing from 10.4 nm in N-free HEA to 31.0 nm in N-doped HEA. In addition, N-doped HEA showed a much higher irradiation hardness increment and hardening fraction than N-free HEA. Contrary to conventional materials doped with N, the introduction of N into Ti₂ZrNbV_0.5Mo_0.2 HEA had adverse effects on its resistance to He bubble growth and irradiation hardening. The results of this study indicated that N doping may not improve the irradiation resistance of HEAs.