Interfacial microstructure and mechanical properties of diffusion bonded TC4/0Cr18Ni9/Oxygen Free Copper joints

In the present study, diffusion bonding of Ti–6Al–4V alloy (TC4) and Oxygen Free Copper (OFC) by using a 0Cr18Ni9 stainless steel interlayer was investigated. The addition of 0Cr18Ni9 stainless steel interlayer improved the bonding quality. The element distribution, microstructure, compositions, mechanical properties and microhardness change of the bonded samples were studied by means of electron probe micro-analyzer (EPMA), scanning electron microscope (SEM), X-ray diffraction system (XRD) and microhardness. The results show that Ni3Ti, Fe2Ti, TiCr2 and FeTi formed at the TC4/0Cr18Ni9 interface show better mechanical properties than that of Cu–Ti compounds. Solid solutions are formed at the 0Cr18Ni9/OFC interface. The fracture of the joints had taken place through the TC4 and Ti–Fe compounds. The reaction process at the interface of TC4/0Cr18Ni9/OFC joints consisted of the physical contact stage, the generation of intermetallic compounds and the growth of intermetallic compounds. The tensile strength of joints increased firstly and then decreased with the rising bonding temperature. The sample bonded at 880 °C for 30 min under 5 MPa shows the maximum tensile strength of 140.3 MPa. There is a substantial improvement in the bonding quality, when its tensile strength is compared with 48.32 MPa for directly-bonded TC4/OFC joint.