Improvement of joint strength in dissimilar friction welding of Ti-6Al-4V alloy to type-718 nickel-based alloy using the Au-Ni interlayer

An Au-Ni interlayer was used to improve the joint strength between the Ti-6Al-4V alloy friction welded to the 718 Ni-based alloy. The interlayer was melted and ejected at the interface of the joint during friction welding, showing that frictional heat played a role in brazing of the interlayer. The melted interlayer suppressed the formation of intermetallic compounds between titanium and nickel at the interface. The tensile strength of the joint significantly increased from 460 MPa for direct friction-welded joints, to 698 MPa when the interlayer was added. The mechanism underlying the strength improvement of the friction-welded joint was the unique phenomenon of a combination of brazing of the interlayer and diffusion of solutes in the base metal to the interlayer.