Laser welding of Ti6Al4V to Cu using a niobium interlayer

A hybrid joint with the Nb interlayer consisting of two metallurgical joining interfaces was obtained by the laser welding induced brazing method. The fusion zone comprising the Ti-based and Nb-based solid solutions formed at the Ti6Al4V/Nb interface, while the diffusion bonding layer comprising the Cu-based and Nb-based solid solutions formed at the Nb/Cu interface. The use of niobium interlayer successfully prevented the mixing of Ti and Cu in the molten pool to avoid the formation of TixCuy brittle phases. The tensile strength of the Ti6Al4V/Cu joints with the Nb interlayer increased to 225 MPa, and the joints exhibited the ductile fracture. The fracture region formed at the Cu side near the Nb/Cu interface.