Misfit dislocation network and mechanical behaviour of Fe/TiN interface under uniaxial loading

Titanium Nitride (TiN) functions as a reinforcement phase that enhances the mechanical properties of ferritic steels, with the characteristics and deformation mechanisms of the Fe-TiN interface playing a pivotal role. In this study, molecular dynamics simulations were employed to investigate four representative Fe/TiN interfaces with crystallographic orientation relations (ORs) observed in experiments. The results reveal that strong Fe-N bonding significantly affects the interface energy and work of adhesion, particularly for N-terminated interfaces. Using interface disregistry analysis and atomistic informed Frank–Bilby approach, we characterized the misfit dislocation network (MDN) structures, detailing properties such as dislocation line orientation, spacing, and Burgers vector. The MDN structure of interface with Baker-Nutting OR shows the same pattern compared with NbC/Nb interface, while Nishiyama-Wasserman and Kurdjumov-Sachs ORs show different MDN structure compared with other fcc/bcc interfaces. These differences arise from the synergistic effects of Fe-N bonding and Fe-Ti anti-bonding. Additionally, tensile and compressive loads were applied to the Fe/TiN bicrystals at $T=300\text{K}$. The analysis indicates that intersections within the MDN structure serve as nucleation sites for lattice dislocations in the Fe layer. Strain field analysis further identifies these intersections as highly strained regions, facilitating dislocation nucleation/emission.