Interface Characteristics of Ti-Clad V–4Cr–4Ti Alloy Diffusion-Bonded Joint Produced by Hot Forging

Diffusion bonding of V–4Cr–4Ti alloy to pure titanium (Ti) was carried out by hot forging in the temperature range between 1150 °C and 950 °C. The microstructure and mechanical properties of the bonded joint were determined by using light optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), micro-hardness measurements, and shear tests. The results indicate that the sound dissimilar joint can be obtained through hot forging processes. The interface has a width of about 100 μm and can be divided into two distinctive zones: a Widmanstatten structure zone and a β-Ti phase structure zone. According to the micro-hardness distribution profile across the substrates and the interface, the largest hardness of 332 HV was measured in a narrow region between the Ti substrate and the joint, which is remarkably higher than that of the substrates (Ti of 190 HV and V–4Cr–4Ti alloy of 258 HV). The lowest hardness of only 182 HV was found in a region in the V–4Cr–4Ti substrate adjacent to the joint. The shear test showed that the joint has a bonding strength higher than 165 MPa and a fracture of the joint took place in the region with the highest hardness.