Joint strength improvement in dissimilar friction welding of titanium alloy to nickel alloy with interlayer

Abstract

Ag-Cu and Ag-Cu-Pd interlayers improved the joint strength between friction-welded Ti-6Al-4V and type-718 Ni-based alloys. Frictional heat melted the Ag-Cu interlayer and partially melted the Ag-Cu-Pd interlayer, and the interlayers were conjointly ejected. This suppressed the formation of intermetallic Ti-Ni compounds at the interface. The tensile strength of the joint increased from 698 MPa (Au-Ni) to 774 MPa (Ag-Cu) and 776 MPa (Ag-Cu-Pd). The underlying mechanism of this strength improvement stemmed from a combination of interlayer brazing and solute diffusion from the base metal to the interlayer. This effect was larger with the Ag-Cu and Ag-Cu-Pd interlayers compared to the Au-Ni interlayer owing to the near absence of Ni-Ti intermetallic compound formation.