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.