On the role of interfacial coherency and carbon in niobium segregation at ferrite/austenite interface: An atomistic study

Co-segregation of carbon (C) and substitutional atoms at the interface can remarkably influence the kinetics of phase transformation in steels, while decoupling their contributions by experiments remains challenging. Here, we employ Molecular Statics and hybrid Molecular Dynamics/Monte Carlo simulation approaches to comparatively investigate the niobium (Nb) segregation behaviors at both the incoherent and semi-coherent ferrite/ austenite interfaces in Fe-C-Nb systems. The calculations reveal that the atomic Virial stress perpendicular to the interface is crucial for the binding energy of Nb to the interface, and the C presence at the interface has both physical and chemical interactions with Nb. It is conventionally believed that C addition can promote Nb segregation due to their attractive interaction, while the current study indicates that C and Nb atoms tend to form clusters in ferrite, thereby weakening the Nb segregation. The present study provides a promising computational approach for investigating the elemental co-segregation in steels.