Diffusion bonding of Ti-6Al-4V/304L steels couple using copper interlayer

Diffusion bonding is a solid-state joining technique in which two similar and dissimilarmaterials are brought together under pressure at a temperature below the melting point ofmaterials. According to the mechanisms proposed by researches, the diffusion bonding processconsists of three stages: during the first stage, the contact area increases by localizeddeformation and creep. In second step, diffusion takes place at the contact area and eliminatesthe voids at the original grain interface. Finally, the grain boundaries on the interface migrateand growth occurs. In order to get sound joint between dissimilar materials, by inserting aninterlayer with diffusion bonding compatibility in between the workpieces to be bonded, a betterbond may be obtained.In this study, Ti-6Al-4V alloy and 304L stainless steel couple were bonded using Cuinterlayer by diffusion bonding technique under three different bonding temperature (830, 850and 870 oC) and three different holding time (50, 70 and 90 min.) and pressure 1 MPa in Aratmosphere. The microstructural properties of the reaction layer occurred at diffusion bondedTi-6Al-4V/304L interface were analyzed by means of optical and scanning electron microscope(SEM). The study exhibits the presence of different reaction layers in diffusion zone and theirchemical compositions were determined by energy dispersive spectroscopy (EDS) and X-raydiffraction. The occurrence of different intermetallic compounds such as CuTi, CuTi2, Cu3Ti2,FeTi, Fe2Ti has been predicted from the ternary phase diagrams of Fe-Cu-Ti in the reactionlayer. The microhardness across and perpendicular to the interface were measured and strengthof the joints was determined with lap-sheer test.In the first chapter of study, an introduction is given. In the second chapter, titaniumalloys and stainless steels and its welding techniques are presented. In the third chapter,diffusion and diffusion bonding is presented. In the fourth chapter, literature dealing withdiffusion bonding technique and welding of Ti-6Al-4V alloys and 304L stainless steel arepresented. In the fifth chapter, experimental studies, in the sixth chapter the results anddiscussions of experiments are given. In the seventh chapter, the general results are given.Keywords: Diffusion, Diffusion bonding, Ti-6Al-4V alloy, 304L stainless steel, Cu interlayer.