Low-activation Ti₂ZrTaₓV0.5Cr0.2 high entropy alloys: microstructures, mechanical properties, and He irradiation behavior

Abstract

The high entropy alloys (HEAs) with body-centered cubic (BCC) structure have been widely demonstrated to exhibit excellent irradiation resistance and hold great promise for nuclear structural applications. By integrating the concept of HEAs with the design of low-activation materials, a novel series of Ti2ZrTaxV0.5Cr0.2 (x = 0.25, 0.50, 0.75, 1.00) HEAs was prepared. The effects of Ta content on phase composition, microstructures, and tensile properties were investigated. As the Ta content decreased, brittle Laves phases precipitated in the interdendritic regions of alloys with x = 0.25, 0.50, and 0.75, leading to brittle fracture. In contrast, the single-phase BCC-structured Ti2ZrTaV0.5Cr0.2 alloy demonstrated superior comprehensive mechanical properties, with a fracture elongation of approximately 10% and a yield strength of 924 MPa. After 1 MeV He ion irradiation at 1023 K with a fluence of 3 × 1016 ions/cm², the Ti2ZrTaV0.5Cr0.2 alloy exhibited excellent phase stability with no secondary phase precipitation. Faceted He bubbles with an average size of 9.8 nm and an extremely low number density of 8.7 × 1020 m− 3 were observed in the peak damage region, which were attributed to the unique vacancy diffusion characteristics of BCC-structured HEAs. The Ti2ZrTaV0.5Cr0.2 alloy exhibited a stable phase structure, a low number density of He bubbles under irradiation, and superior mechanical properties, making it a promising candidate for structural applications in advanced nuclear energy systems.