Design of single-phase high-entropy alloys composed of low thermal neutron absorption cross-section elements for nuclear power plant application

Abstract

Two quinary high-entropy alloys MoNbCrVTi and MoNbCrZrTi were designed and prepared for the two following goals. The first goal is to search for single-phase high-entropy alloys composed of low thermal neutron absorption cross-section elements, and the second goal is to verify the validity of the empirical parameters calculation and CALPHAD (acronym of CALculation of PHAse Diagrams) calculation in the initiatory selection process of desired alloys from numerous candidates. The density, hardness, microstructure, and compressive mechanical properties of the two alloys were preliminarily investigated, and the phase formation of these two alloys was also discussed. The MoNbCrVTi alloy consists of a single BCC phase with typical dendritic microstructure, while the MoNbCrZrTi alloy mainly consists of a BCC phase plus a C15 Laves phase. The densities of the as-cast MoNbCrVTi and MoNbCrZrTi alloys were determined to be 7.30 ± 0.01 and 7.33 ± 0.01 g/cm3, respectively. The MoNbCrVTi alloy exhibits a hardness of 494.4 ± 7.7 Hv, a high yield strength of 1281 MPa and a fracture strain of 9.4% at room temperature. By comparison, the MoNbCrZrTi alloy exhibits a hardness of 552.9 ± 8.6 Hv, a higher yield strength of 1454 MPa but a lower fracture strain of 2.7%. The proposed two goals are basically achieved based on the preliminary results.