The dissimilar joint of Ti-6Al-4V to UNS32750 was carried out in constant time and different temperatures of 900, 950, and 1000 degrees Celsius using a Cu/CNT composite interlayer with various CNT concentrations of 0, 0/5, 2, and 3 W%. The base metals were cut into the dimensions of 3×10×5 mm3. The Cu foil with a diameter of 25um was cut into the same size as those base metals' surface of 3×10 mm2. To wipe the contamination out of the surfaces, a cleansing process was conducted in an ultrasonic machine on all components. The base metals specifically were ground and polished prior to the cleansing process. The interlayer was placed between the base metals and sufficient pressure was applied using a fixture. The Scanning Electron Microscope (SEM) and the Optical Microscope (OM) were used in order to microstructurally eva‎luate the weld interface after the joined samples were cut into appropriate dimensions. Besides, the Energy-dispersive Spectroscopy (EDS) analysis equipped on the SEM machine and the X-ray Diffraction (XRD) analysis were used for phase recognition and elements distribution across the weld zone. The strength of bare-Cu-foil joints showed an increasing behavior from 288 to 296 MPa by applying temperature from 900 to 950 degrees Celsius and it dropped to 274 Mpa after reaching the highest temperature of 1000oC. The strength increase is addressed by the formation of ISZ and its decrease was due to the brittle IMCs formation such as Cr2Ti, FeTi, and Fe2Ti towards the UNS32750/interlayer interface which is the spot for microcracks propagation. Adding CNTs up to 2 W% lowered the strength value of all specimens, this decreasing trend was more intensified in 1000oC. Adding 3 W% of CNTs improved the joint strength by about 35 MPa more than that specimens of 2 W% of CNTs in 950 and 1000 degrees Celsius while the strength of 900oC-applied-temperature specimen even decreased way lower to 189 MPa. The weld zone was significantly widened with a difference of 50um by adding CNTs in 900 and 950 degrees Celsius whereas the temperature value of 1000oC showed an opposite behavior. The CNTs seem to widen the weld zone easing the elemental diffusion from the base metals at a lower temperature. TiAl3, Al2Cu3 phases, and circular TiC formation towards the UNS32750/interlayer interface beside the formation of Carbon-contained solid solution in the weld-center line increased the hardness value up to 900 and 850 in these areas, respectively. However, CNTs existence caused the weld hardness to be more distributed. A majority of brittle blocky Ti2Cu IMCs were disappeared by adding CNT to maximum concentration in 950 and 1000 degrees Celsius while the TiCu Eutectic phases outnumbered in 900oC. By eva‎luating the fractography results, the joints were considered to experience a brittle fracture due to the existence of cleavage and river pattern effects. The 3-W%-contained specimens in 950oC and 1000oC which had experienced strength increase showed delaminated fracture surfaces. It is concluded that the high TiC formation in this CNT concentration at high temperatures causes a crack deflection mechanism and leaves a lamellar pattern.

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