DFT Study of Yttrium Affinity and Interfacial Bonding for O‑, N‑, and S‑Containing Inclusions in High-Cr-High-Ti...

Rare-earth additions are widely used to mitigate harmful oxygen, nitrogen, and sulfur inclusions in high-Cr, high-Ti heat-resistant alloys, yet the interfacial mechanism governing rare-earth-inclusion interactions remains unclear. Here, density functional theory (DFT) calculations are used to systematically investigate yttrium adsorption on three representative inclusion phases: TiO₂, TiN, and MnS. For each surface, we identify the most stable adsorption configurations and quantify the corresponding adsorption energetics. Differential charge density, electron localization function (ELF), and projected density of states (PDOS) analyses show that Y binding is characterized by pronounced charge redistribution and mixed ionic-covalent interactions with surface atoms, depending on inclusion chemistry. Y adsorption also stabilizes the inclusion surfaces by lowering the electronic energy and reducing high-energy surface states near the Fermi level, consistent with strengthened interfacial bonding. Together, these results provide an atomistic picture of how Y interacts with O/N/S inclusions and offer microscopic guidelines for rare-earth alloying strategies aimed at impurity control and processing optimization.