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

Abstract

• We study oxygen interaction with Cr/Ni and vacancy in dilute fcc Fe alloys. • Interstitial O prefer the O-sites in the Cr rich region to form Cr-O complexes. • A vacancy can stably trap 6 O atoms and Cr enhances vacancy trapping ability. • Cr reduces O migration barrier while Ni increases O migration barrier. 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 Cr m O n 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.