Interfacial reactions and strength properties in dissimilar titanium alloy/Ni alloy/microduplex stainless steel diffusion bonded joints

The interfacial reactions and strength properties of a titanium alloy/ microduplex stainless steel diffusion bonded joint using Ni alloy as an intermediate materials was investigated in the temperature range of 800 to 950 °C for 75 min and at 950 °C for 15-90 min in vacuum. The microstructure observations at the stainless steel/Ni alloy interface indicate the presence of γ-Fe layer up to 900 °C for 75 min and at 950 °C up to 45 min. Ni3Ti, NiTi and NiTi2 intermetallic layers were observed at the Ni alloy/titanium alloy interface at the same processing parameters and irregular shaped particles were present within the TiNi3 intermetallic layer. Beyond these processing parameters, the layer wise Fe-Ti or Fe-Cr-Ti base intermetallic compounds were observed at the microduplex stainless steel/Ni alloy interface. Maximum tensile strength of ∼639.9 MPa and shear strength of ∼477.8 MPa along with ∼9.3% ductility were obtained for the diffusion couple processed at 900 °C for 75 min.