Induced segregation of O atoms as the culprit for Cr atomic segregation near grain boundaries

As a ferrite-stabilizing element, Cr is highly important for improving the performance of Fe–Cr–Al electrical heating alloys. However, the 'excessive' addition of Cr can lead to significant problems due to the tendency of Cr atoms to segregate near grain boundaries, which cannot be ignored. The unknown underlying mechanism of Cr atom segregation near grain boundaries has hindered the exploitation of the potential use of these alloying elements. According to this study, when not considering the influence of other solute atoms, Cr atoms are weakly segregated at grain boundaries in ideal Fe–Cr binary system alloys. However, in an Fe–Cr–Al–C–O–N six-membered hybrid system, the Cr atoms are segregated near the grain boundaries due to interactions between the ultralight C–O atoms and the Cr atoms. Herein, a thermodynamic model of the grain boundary segregation mixed was used to explore the effect of the concentration of C–O atoms at the grain boundary on the grain boundary excess molar segregation mixed Gibbs free energy of Cr atoms. Furthermore, it is argued that the real cause of Cr atom segregation at grain boundaries is O atom-induced segregation. O atoms are repelled by C atoms at the grain boundary to the surrounding area. This finding implies that when the limiting concentration of O atoms in the alloy is effectively controlled, the segregation of Cr atoms near grain boundaries can be maximally prevented. •A thermodynamic model of the segregation mixed grain boundary demonstrate that O induces Cr segregation at grain boundary.