Effects of temperature and trace elements on the mechanical properties and dissolution-diffusion characteristics of CoCrFeNi in liquid LBE: Atomic insights from molecular dynamics

Abstract

CoCrFeNi high-entropy alloys (HEAs) represent promising structural materials for Generation IV lead-bismuth cooled reactors, and it is crucial to study the effect of the liquid lead-bismuth eutectic (LBE) environment on their mechanical properties and their dissolution process. This study employs molecular dynamics simulations to systematically investigate the effects of temperature and trace elements on the mechanical properties of the HEAs under different environments and the dissolution and diffusion process of the HEAs in liquid LBE. Results demonstrate that elevated temperatures (300–873 K) induce lattice defect proliferation and dislocation activation, leading to substantial reductions in Young’s modulus (23.3 %), yield strength (47.1 %), and ultimate tensile strength (33.3 %) compared to ambient conditions. Enhanced atomic thermal motion at high temperatures accelerates the dissolution of matrix elements (Fe>Cr>Ni>Co) and LBE atom penetration (Pb/Bi), synergistically exacerbating corrosion-induced mechanical deterioration. Microalloying effects reveal that Mo addition enhances the strength and stiffness of CoCrFeNi HEAs, while the addition of Al leads to a decrease in the tensile strength of HEAs, and Mo-Ti co-doping maximizes the strain modulation capability. Diffusion analyses identify Fe atoms as exhibiting the highest degree of diffusion, while the Al atoms exhibit the lowest degree of diffusion in liquid LBE. The addition of the Mo element slows down the infiltration process of liquid LBE, and (CoCrFeNi)₉₇Mo₃ HEAs exhibit higher tensile strength in liquid LBE compared to Al and Ti elements. Our research results may provide some references for the application of structural materials in fourth-generation lead-bismuth reactors.