Dissimilar transient liquid phase bonding of Ti-6Al-4V alloy to Inconel 625 superalloy: effect of bonding temperature on microstructural evolutions and mechanical properties

The present study investigated the effect of bonding temperature on the dissimilar transient liquid phase (TLP)–bonded IN-625/Ti-6Al-4V dissimilar joints using a thin foil of pure copper as the interlayer. The samples were bonded in a vacuum chamber at 900, 930, and 960 °C for 60 min. The results indicated the occurrence of different intermetallic compounds such as Ti₂Cu, TiCu₂, TiCu, NiTi, and Ni₃Ti at different bonding temperatures, and it was concluded that in all the samples, isothermal solidification was accomplished. Maximum shear strength of 278 MPa was achieved at 930 °C. At lower bonding temperatures, the presence of porosities and cracks decreases the shear strength. At higher temperatures, a high-volume percentage of intermetallic compounds embrittled the specimen and reduced its shear strength. The results of scanning electron microscopy of the fracture surfaces revealed the formation of extensive cleavage fracture and river-like patterns in all samples, indicating a brittle failure mode.