Effects of antagonistic interaction between Cr and Ni on hydrogen solubility in a Fe-Cr-Ni ternary austenitic system: A first-principles calculation

The present study systematically investigates hydrogen (H) solubility within multi-component alloying (Cr, Ni) interaction in Fe-Cr-Ni-based austenitic alloys, which generates a novel H-induced improvement in the strength-ductility balance that is a function of dissolved H-content. We analyzed, using first-principles calculations, H-absorption energy that is directly linked to H-solubility, in an Fe-Cr-Ni face-centered cubic (FCC) ternary system with various configurations of Cr and Ni atoms. The results we obtained clarified the effects of antagonistic interactions between Cr and Ni atoms on H-absorption energy even though both alloying elements independently reduce H-absorption energy at adjacent octahedral sites (O-sites). The reduction in H-absorption energy owing to Cr was mutually more inhibited with increasing numbers of Ni atoms consisting of the same O-sites, the propensity toward which is strongly supported by the previous experimental framework. The reduction in H-absorption energy can be inherently influenced by the local magnetic state as varied by the presence of Ni in the Fe-Ni system. Although Cr also changes the local magnetic state, albeit in limited fashion, the reduction in H-absorption energy caused by the presence of Cr and the resultant mutually antagonistic effects in the Fe-Cr-Ni system can emerge not only due to the local magnetic state but also as a result of the stabilization of the FCC structure that is attributable to Cr-H interaction. The present study makes it possible to comprehensively predict the H-solubility of various Fe-Cr-Ni austenitic alloys by taking account of the antagonistic Cr-Ni interaction.