Oxygen interaction with alloying elements (Cr/Ni) and vacancies in dilute austenitic iron alloys: A first-principles study

We investigate oxygen (O) interaction with alloying elements (Cr/Ni) and vacancies and O migration property in dilute austenitic iron alloys to understand the stability of oxygen-related clusters by first-principles calculations. First, O prefers to occupy the octahedral interstitial sites in the Cr-rich region, the O-Cr interaction is attractive with the binding energy of 0.24 eV, while the O-Ni (-0.16 eV) and O-O (-0.25 eV) interactions are repulsive. The stability and atomic configurations of small CrmOn clusters are determined for m,n = 1-4. The O-vacancy interaction is strong attraction with the binding energy of 1.16 eV, while the Cr-vacancy and Ni-vacancy interactions are weak attraction. Furthermore, we compare multi-O trapping in a vacancy, Cr-vacancy and Ni-vacancy and determined the stability of vacancy-O-n and Cr/Ni-vacancy-O-n complexes for n = 1-7. A Cr-vacancy/Ni-vacancy can stably trap 6 O atoms as the same as those of alone vacancy and Cr presence enhances the trapping ability of vacancy. Finally, O prefers to migrate between two octahedral sites by passing a tetrahedral site, the presence of Cr reduces O migration barrier while Ni increases it.

Automated summary

By first-principles calculations, we investigated the interaction of oxygen with alloying elements and vacancies, as well as the migration property of oxygen in dilute austenitic iron alloys. Oxygen prefers to occupy octahedral interstitial sites in the Cr-rich region, with strong attractive interaction with Cr. The interaction with Ni and O itself is repulsive. The interaction between oxygen and vacancies is strong, while the interactions with Cr-vacancy and Ni-vacancy are weak.