Behzad Binesh

Transient liquid phase (TLP) bonding was employed to process IN718/Ti–6Al–4V bimetallic joint using a pure Cu interlayer. The effect of bonding temperature in the range of 870°C to 990°C was studied on the microstructure and mechanical properties of the joints. The microstructural examinations revealed that the isothermal solidification of β-Ti phase in the joint region occurs at the bonding temperature above 910°C. The width of athermally solidified zone consisting of TiCu, Ti2Cu, TiCu2Al and Ti2Ni eutectic and intermetallic phases decreased significantly with increasing the bonding temperature to 950°C and then increased with further increasing the bonding temperature to 990°C. Two different trends of microhardness changes were observed along the joint region of the TLP samples. The maximum hardness value (444 VHN) and the minimum hardness value (260 VHN) were measured in the athermally solidified and the isothermally solidified zones, respectively. The maximum shear strength of 367 MPa was recorded for the sample with the lowest amount of intermetallic phases in the joint zone. According to the fractography of the shear-fractured surfaces, the failure mode changed from brittle to ductile with decreasing the amount of intermetallic phases in the joint area.