Design of low-activation refractory high-entropy alloys with improved plasticity

Abstract

Low-activation refractory high-entropy alloys (LARHEAs) as structural materials have a great demand in nuclear reactors. However, currently developed LARHEAs generally have poor room temperature ductility, which greatly limits their wide applications. In this study, two kinds of LARHEAs with chemical compositions of TiZrTaCr and TiZrTaV in equal atomic percentage were designed based on low neutron absorption cross section, low neutron activation, and mixing enthalpy parameters. The LARHEA samples were prepared by high vacuum arc-melting techniques, and their phase structures and mechanical properties were studied. It was found that the TiZrTaCr LARHEA exhibited two body-center-cubic (BCC) and one Cr2Zr intermetallic compound phases, and it had a yield strength of 1364 ± 54 MPa, but it was brittle, while the TiZrTaV LARHEA formed three BCC solid solution phases, and it had a high yield strength of 1312 ± 57 MPa with a room temperature compression plasticity of 13% ± 0.8%. Cr2Zr intermetallic compound formation in the solid solution matrix could have led to the brittleness of the LARHEAs, which was mainly due to the large negative mixing enthalpy of the Cr element with Zr element in this alloy system. This study proposed a basic method for LARHEA design to optimize the microstructures and improve the mechanical properties as structural materials.