Low activation Ti30V30Cr5Zr5Ta30-XWX refractory high entropy alloys with excellent mechanical properties and phase stability

Abstract

Although refractory high entropy alloys (RHEAs) have the potential to serve as nuclear materials, designing a high-performance alloy that can simultaneously endure extreme environments, such as elevated temperatures and radiation exposure, remains a significant challenge. In this work, elements with high melting points and low activation characteristics are selected to design Ti₃₀V₃₀Cr₅Zr₅Ta_30-xW_x (x = 5, 10, 15, 20 at.%) RHEAs that exhibit good high-temperature strength and irradiation resistance. The phase structure, mechanical properties, deformation mechanisms, and irradiation resistance of the RHEAs were investigated and discussed. All the low-activation Ti₃₀V₃₀Cr₅Zr₅Ta_30-xW_x RHEAs exhibited excellent phase stability. Typically, the Ti₃₀V₃₀Cr₅Zr₅Ta₁₅W₁₅ RHEA exhibited a yield strength, specific yield strength, and plasticity of 1607 MPa, 172.42 MPa·cm³/g and 22.7 % respectively at room temperature. At 800 °C and 1000 °C, it still had a yield strength of 851 MPa and 558 MPa respectively. The high strength of the Ti₃₀V₃₀Cr₅Zr₅Ta₁₅W₁₅ RHEA was attributed to the solid solution strengthening mechanism, in which the W element played an important role. The deformation mechanism of Ti₃₀V₃₀Cr₅Zr₅Ta₁₅W₁₅ RHEA at both room temperature and elevated temperatures was primarily governed by dislocation slip. Using low-energy and high-flux He ions, the irradiation resistance of the Ti₃₀V₃₀Cr₅Zr₅Ta₂₀W₁₀ and Ti₃₀V₃₀Cr₅Zr₅Ta₁₅W₁₅ RHEAs were also investigated. They demonstrated better radiation resistance surpassed that of pure W, showing remained flat surface and stable phase structure.