Interaction of C and Mn in a ∑3 grain boundary of bcc iron

The interaction of alloying elements with migrating interfaces is a key aspect that determines microstructure evolution during thermo-mechanical processing of metals and alloys. Recent advances in atomic scale resolution characterization techniques and atomistic modelling have dramatically increased the potential to generate new knowledge on interfaces thereby enabling paradigm shifts in microstructure design approaches. Computational materials science now offers exciting opportunities to formulate multi-scale process models that bridge the gap between atomistic and continuums approaches. In particular, the development of advanced high strength steels with novel alloying concepts has motivated atomistic scale simulations to predict the interaction of selected alloying elements with grain boundaries and the austeniteferrite interface in iron. Most of these simulations have so far been carried out for binary systems with one solute species. The extension of this modelling work to multi-component systems is, however, essential in order to account for potential interactions between different alloying elements in industrial steels. Here, we present ab initio simulations for the interaction of C and Mn at a ∑3 boundary in bcc iron using density functional theory (DFT). The simulation results confirm the strong co-segregation of C and Mn that has been recently observed in atom probe tomography studies of the austenite-ferrite interface in Fe-Mn-C alloys. (paper)