Interfacial microstructure and mechanical properties of Y₂O₃-MgO nanocomposite ceramic and Ti6Al4V joint brazed with AgCuTi filler

To meet the demands of the advanced infrared windows with excellent optical and mechanical properties, Y₂O₃-MgO nanocomposite ceramic and TC4 alloy were brazed by using Ag-Cu-Ti filler. The microstructure and mechanical properties were studied in detail. The typical microstructure of the brazed joint is Y₂O₃-MgO/Cu₂Y₂O₅ + Cu₃Ti₃O/TiCu + Ti₂Cu + Ag(s,s)/Ti(s,s) + Ti₂Cu/TC4. Our results indicate that Ti preferentially reacts with Y₂O₃-MgO at the initial stage. Subsequently, Cu participates in the interfacial reactions, leading to the formation of a reaction layer composed of Cu₂Y₂O₅ and Cu₃Ti₃O. Maximum shear strength of 38 ± 7 MPa was achieved when the joint was brazed at 880 °C for 10 min. The Cu₂Y₂O₅ + Cu₃Ti₃O interfacial reaction layer possesses higher hardness and modulus than the main products of the brazed joint, which is the primary weakness of the brazed joint.