Research Progress on Irradiation Effect of Refractory High-entropy Alloy

Fourth-generation advanced nuclear reactors offer significant improvements in safety, economics, and sustainability compared to traditional designs. However, their extreme operating conditions—characterized by high temperatures, intense irradiation, and corrosive environments—impose significant challenges on conventional structural materials. Refractory high-entropy alloys (RHEAs), particularly those with body-centered cubic (BCC) structures, have emerged as a promising new class of structural materials for these advanced systems due to their high melting points, excellent high-temperature mechanical properties, and superior irradiation tolerance. The recent progress in the development and application of RHEAs for nuclear structural materials was systematically examined, focusing on four key aspects: composition design and fabrication, phase stability, irradiation damage behavior, and strategies for enhancing irradiation resistance. In terms of composition design, the vast compositional flexibility of RHEAs allows for property optimization through synergistic “cocktail” effects. For nuclear applications, additional criteria such as low neutron absorption and activation must be considered. Current design approaches involve empirical parameter evaluations (e.g., mixing enthalpy, atomic size difference), computational methods (e.g., CALPHAD, first-principles, machine learning), and high-throughput experimental screening. Fabrication techniques include vacuum arc melting, powder metallurgy, and additive manufacturing, each influencing microstructural features and material performance. Phase stability is critical for service reliability. Most RHEAs exhibit a stable single-phase BCC structure at high temperatures (＞800 ℃), but some compositions, especially those containing Al or Ti, may undergo phase separation at intermediate temperatures (300-600 ℃), forming intermetallic phases such as B2 or Laves. Predictive modeling and thermal aging experiments are commonly employed to investigate these transformations. Irradiation studies, including ion irradiation and multi-scale simulations, reveal that RHEAs typically show reduced irradiation-induced hardening and swelling compared to traditional alloys. For example, TiVNbTa exhibits a hardening rate of only 8%, versus 37% for pure V. The irradiation response, particularly helium bubble behavior, varies across compositions and is strongly influenced by vacancy-helium interactions. Atomic-scale simulations suggest that the severe lattice distortion and chemical complexity of RHEAs enhance defect recombination and inhibit the formation of large defect clusters. Several potential strategies for regulating irradiation resistance have been proposed, including the strategic addition of alloying elements, the introduction of microstructure such as nanograins and second-phase precipitates, and the doping of interstitial atoms (e.g., O and N). These approaches can effectively modify defect evolution pathways. In conclusion, while RHEAs hold great promise for nuclear applications, several challenges remain before their widespread application. These include scaling up fabrication methods, validating long-term performance stability under realistic reactor operating conditions, and fully elucidating irradiation mechanisms in complex environments. Future research should prioritize conducting in-reactor neutron irradiation experiments, developing more accurate multi-scale damage models, and establishing clear performance correlations between laboratory simulations and real-world nuclear environments. Addressing these key areas will be crucial for accelerating the engineering application of RHEAs and advancing the safety and efficiency of future nuclear energy systems.