Effects of alloying elements on the hydrogen behaviors of FCC Co-free concentrated solid solution alloys

Abstract

This study investigated hydrogen behaviors in two cobalt-free concentrated solid solution alloys (CSAs) Fe₅₀Mn₂₅Ni₁₀Cr₁₅ and Ni_57.6Cr_19.2Fe_19.2Nb₄ combining experiments and theoretical methods. We aimed to reveal and elucidate the influencing mechanisms of alloying elements on the hydrogen behaviors of CSAs. After deuterium charging, Ni_57.6Cr_19.2Fe_19.2Nb₄ exhibits higher concentration of deuterium and vacancies than Fe₅₀Mn₂₅Ni₁₀Cr₁₅. Density function theory calculations reveal that Ni_57.6Cr_19.2Fe_19.2Nb₄ has lower dissolution energies, which is attributed to the opposite effects of Fe and Ni on hydrogen solubility and severe lattice distortion primarily induced by Nb. The Ni_57.6Cr_19.2Fe_19.2Nb₄ alloys have higher hydrogen binding energy and jump barriers, which enhance hydrogen stability. Furthermore, the precipitates enriched with Nb formed during deformation can block the movements of dislocations and hydrogen, which strengthen the materials and retard the formation and propagation of cracks. Our study highlights the important role of the Nb enriched precipitates for the resistances to hydrogen embrittlement, whose formation is induced by the synergetic effects of hydrogen and deformation. The experimental observations are well explained by theoretical modeling and provide valuable insights for developing CSAs with enhanced resistance to hydrogen embrittlement.