In Situ Reaction of Cu/Zr Diffusion Bonded with GH4169/Ti60 Dissimilar Metal Joints

Abstract

Ti−Ni is prone to form brittle intermetallic compounds (IMCs), resulting in low strength of the bond joints between nickel-based superalloys and titanium alloys. This paper investigates the effects of diffusion bonding temperature and holding time on the microstructure and mechanical properties of the joint, using Cu/Zr to achieve an in situ reaction at the GH4169/Ti60 interface. The results show that during the heating process, Cu and Zr foils first form a liquid phase, filling the interface gap and reacting in situ with the base material at the interface, mainly generating the (Ti, Zr)(Cu, Ni) and (Ti, Zr)2(Cu, Ni) phases. The addition of Cu and Zr can inhibit the formation of brittle Ti−Ni binary phases. By forming (Ti, Zr)(Cu, Ni) and (Ti, Zr)2(Cu, Ni) phases, the phase composition and microstructure of the interfacial reaction layer can be effectively regulated, thereby improving the mechanical properties of the joint. As the bonding temperature and holding time increase, atomic diffusion intensifies, which accelerates the consumption of Cu and Zr at the interface. The (Ti, Zr)(Cu, Ni) and (Ti, Zr)2(Cu, Ni) phases in the reaction layer gradually transform into Ti−Ni IMCs. Correspondingly, the thickness of the reaction layer decreases, while the thickness of the diffusion layers on both sides increases. The grain size of the joints gradually increases, and the shear strength of the joints initially increases and then decreases. Under the condition of 950 °C/10 min/10 MPa, the interface layer (Ti, Zr)(Cu, Ni) and (Ti, Zr)2Cu phases are interlaced and distributed in an “interlocking” structure, significantly enhancing the interface bonding strength. The shear strength of the joint is the maximum, reaching 282 MPa. The fracture morphology presents the characteristics of brittle fracture.