Sluggish hydrogen diffusion and hydrogen decreasing stacking fault energy in a high-entropy alloy

Abstract

Hydrogen diffusion and its interaction with dislocations play an important role in hydrogen embrittlement, however, such a process in multiple-principal high entropy alloys (HEAs) is still elusive. Here, first-principles calculations were performed to investigate the solution and diffusion of hydrogen and its effect on the stacking fault energy of FeCoNiCrMn. It is shown that the unique lattice distortion in HEAs causes a wide distribution of local hydrogen solution energy, and the trapping of hydrogen in low energy sites increases diffusion barriers. The zigzag path and asymmetry of forward and backward diffusion result in the sluggish diffusion of hydrogen. Furthermore, hydrogen reduces unstable and stable stacking fault energies, originated from the transfer of electron between hydrogen and metal atoms, which promotes formation of deformation twins. This provides a theoretical guidance for designing novel engineering materials with optimal combination of their mechanical properties and hydrogen embrittlement resistance.