First-Principles Investigation of the adsorption growth mechanism of MnS on Ti(C,N) surfaces and the interaction mechanism at composite inclusion Interfaces

Controlling the fine dispersion distribution of inclusions in steel can effectively induce the nucleation of intragranular ferrite, refine the microstructure grains, and improve the welding performance of steel. To clarify the nucleation mechanism and polymerization evolution of composite inclusions, this study combines first-principles calculations with experimental characterization. A MnS–Ti(C,N) composite adsorption model was constructed using Materials Studio. The results indicate that the inclusions are primarily composed of Ti, N, S, Mn, and O, with MnS embedded spherically within Ti(C,N). MnS is adsorbed on the Ti(C,N) surface (with a C:N ratio of 3:1) as both 5-unit clusters and single atoms. A synergistic diffusion principle—where Mn serves as the substrate for the subsequent vertical upward adsorption of S atoms—governs single-atom adsorption. During cluster adsorption, an electron-rich region forms around Mn atoms, enhancing interfacial stability through dipole formation. In single-atom adsorption, significant S-p and N-p orbital overlap occurs, indicating strong interactions, while Ti-d and Mn-d orbitals hybridize near the Fermi level, increasing material conductivity. This work provides a theoretical basis for inclusion control and new oxide metallurgy technology.