Diffusion bonding of a titanium alloy to austenitic stainless steel using copper as an interlayer

Diffusion bonding was accomplished between Ti–6Al–4V alloy and AISI 304 austenitic stainless steel utilizing copper as an interlayer in the holding time variety of 45–105 min for 925 °C under 14 MPa load in a vacuum. After bonding, the microstructural study including metallographic examination and energy dispersive spectroscopy, microhardness survey, lap shear strength test, and ram tensile test were accomplished. From the results, holding time is a major influence to develop the microstructural characteristics and improve the joints quality. The occasion of various intermetallic compounds, for example, CuTi, Cu3Ti2, FeTi, Fe2Ti, Cr2Ti has been expected from the ternary phase diagrams of Fe–Cu–Ti and Fe–Cr–Ti. These reaction items were insisted on the X-ray diffraction method. The highest bond strength of 268 MPa was attained for the pair bonded at 90 min holding time. This is a direct result of the better combination of the mating surface. With the expansion in holding time to 105 min, the quality was reduced caused by the expanded volume fraction of discontinuities.