Low activation V–Fe–Cr–Mn high-entropy alloys with exceptional strength

Abstract

V-based alloys such as V–4Cr–4Ti are one of the most promising candidate materials for fusion energy demonstration reactors, owing to their low activation and excellent resistance to neutron irradiation. However, conventional V-based alloys have poor high-temperature strength and creep resistance, resulting in a limited operating temperature window (400–700 °C). In this study, a series of low-activation VxFe65-xCr15Mn20 high-entropy alloys (HEAs) are designed and prepared by arc melting. Increasing the content of V of HEAs increases their nucleation rate during solidification, and thus decreases their grain size and increases their microhardness and strength. The yield strength of V50Fe15Cr15Mn20 HEA reaches 1189 MPa, which is mainly caused by the reduced grain size. The yield strength of V50Fe15Cr15Mn20 HEA between room temperature and 1000 °C is significantly higher than that of conventional V-based alloys. Such high high-temperature strength is explained by the high microstructural stability of the designed HEA. As a novel nuclear material, the present V50Fe15Cr15Mn20 HEA tested at a temperature of 900 °C still has a yield strength of 275 MPa, which is higher than that of conventional low-activation steels and V-based alloys.