Unveiling the effects of multi-element interaction on phase compatibility and interfacial bonding in AgCuSnTi/diamond brazing system via first-principles calculations

Diamond brazing is a critical joining technique for advanced thermal management and cutting applications, where joint reliability primarily depends on the resulting interlayer. In this study, first-principles calculations were conducted to investigate the effects of multi-element interaction on phase compatibility and interfacial adhesion in the AgCuSnTi/diamond brazing system. Adsorption and charge-transfer characteristics of Ag, Cu, Sn, and Ti atoms on diamond were first examined, revealing that Ti exhibited the strongest electronic interaction and acted as the primary wetting agent that enhanced interfacial bonding. To capture the compositional complexity of the interlayer, major phases were doped with additional filler elements. The calculated formation energies and mechanical parameters demonstrated strong composition dependence, with certain doped configurations compromising thermodynamic and mechanical stability. Moreover, layer-specific segregation at the diamond interface indicated that interface-closest segregation severely weakened bonding strength and facilitated premature fracture. Electronic structure and charge density analyses clarified the bonding disruption mechanisms. These results could advance the understanding of microstructure-property relationships in carbon-based materials brazed with AgCuSnTi fillers.