Atomic study of hydrogen behaviors at n-ary sumation 3(111) grain boundary in equiatomic CoCrNi and CoCrNiFe alloys

High-entropy alloys are potential advanced structural materials for applications in nuclear energy due to their proved high irradiation performance. However, exposing components made of structure materials to service conditions under certain nuclear environments may induce hydrogen embrittlement (HE) as one of the typical failure mechanisms. In this work, we performed density functional theory (DFT) calculations to examine the role of specific element species in HE mechanism in CoCrNi and CoCrNiFe alloys. The solution energy, binding energy and diffusion barrier of H atoms at n-ary sumation 3 GBs (GBs is short for grain boundaries) are presented. Based on the DFT data, we found that Cr limits the H atom to a specific potential position, thus suppresses H segregation. The dipole moment interaction between H and Fe atoms weakens the binding of H atoms. The lattice distortion effect-induced trapping for H provides higher H diffusion barriers at n-ary sumation 3 GBs than that in pure Ni.

Automated summary

In this study, the role of specific elements in hydrogen embrittlement mechanism in CoCrNi and CoCrNiFe alloys was examined using density functional theory calculations. It was found that Cr restricts the hydrogen atoms to specific potential positions, suppressing hydrogen segregation. The dipole moment interaction between hydrogen and iron atoms weakens the binding of hydrogen atoms. The lattice distortion induced trapping effect provides higher hydrogen diffusion barriers at n-ary sumation 3 grain boundaries compared to pure nickel.