Interfacial reaction and microstructure study of DSS/Cu/Ti64 diffusion-welded couple

In the present study, the interfacial reaction and microstructure behavior of diffusion-welded joints (DWJs) between duplex stainless steel (DSS) and Ti–6Al–4V alloy (Ti64) with copper interlayer were investigated. The joints were carried out at 825, 850, 875 and 900 °C temperature for 60 min under 4 MPa uniaxial pressure in vacuum. Welded joint was characterized by light microscopy and scanning electron microscopy using backscattered electron mode. Layer-wise Cu4Ti, Cu2Ti, Cu4Ti3, CuTi and CuTi2 intermetallic phases were formed at the Cu–Ti64 interface and the width of the intermetallic layers increases with increase in welding temperature. However, the DSS–Cu interface was completely free from intermetallics. The activation energy and interfacial energy of reaction phases was calculated at the interface. The activation energy values showed that the CuTi intermetallic grew faster than the other phases of the Cu–Ti-based reaction. However, CuTi2 phase first nucleates than the other Cu–Ti-based intermetallics due to its lowest interfacial energy. The highest joint tensile strength of ~ 516 MPa (~ 79% of DSS) along with ~ 6.6% ductility was achieved at 875 °C processing temperature.