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.