Recently, due to providing favorable properties, there are attractive attention in solid state bonding of Ti alloys. Production methods of Ti-6Al-4V alloys can have significant effects on properties of the solid state bonding. Due to the nature of the plasma spraying process, microstructure of Ti-6Al-4V alloy produced by Vacuum Plasma Spray Forming(VPSF) are completely different from those of conventionally manufactured alloys. These differences could create different behaviors in the solid state bonding of these alloys. In this study, Transient Liquid Phase(TLP) and Diffusion Bonding of Ti-6Al-4V alloy produced by VPSF and rolling were investigated. Bonding processes were performed along with heat treatment cycles to achieve three main structures of Ti-6Al-4V alloy. Diffusion Bonding was carried out without any interlayer at pressures of 1 and 3 MPa. TLP bonding was performed in the optimal heat treatment cycle at four copper interlayer thicknesses (2, 5, 10 and 25 microns). Microstructures were analyzed by using an optical microscope (OM) and field emission-scanning electron microscope (FE-SEM). Distribution of alloying elements at the joint area was studied by using Energy Dispersive Spectroscopy(EDS) and X-Ray Diffraction Analyze(XRD) was used for phase analyzing. Finally, mechanical properties of the joints were evaluated by measuring the shear strength. Results showed that the bonding strength of the rolling alloy was higher than VPSF alloy due to existence of voids in the VPSF structure. Maximum shear strength of DB of VPSF alloy was achieved 468 and 508 MPa in 1 and 3 MPa pressure, respectively. because of higher diffusion path in VPSF alloy, bonding width in the TLP bonding of VSPF alloy was wider than that in the rolled alloy. Maximum shear strength of TLP bonding was achieved at 2µm thickness of interlayer it was 452 and 492 MPa for VPSF and rolling alloys, respectively. Increasing the thickness of the interlayer caused reduced the bonding strength and increased hardness at the bonding region due to the presence of Ti 2 Cu intermetallic phase. Average maximum hardness in the center of the TLP bonding area of VSPF alloys at 25 µm interlayer thickness was measured 410 HV. Thus, TLP bonding could be used for joining of VPSF Ti-6Al-4V alloy successfully to carry out heat treatment of structure and welding, simultaneity. Keywords Diffusion bonding, Transient liquid phase, Titanium, Vacuum Spray Plasma Forming, Shear strength.
