Laser welding of 6082 aluminum alloy to TC4 titanium alloy via pure niobium as a transition layer

A Ti/Al joint with an Nb transition layer was obtained, where aluminum alloy and Nb sheet partially melted to form the weld and diffusion bonding was formed at Ti/Nb interface. The remaining transition layer Nb acted as a diffusion barrier between TC4 titanium alloy and 6082 aluminum alloy thus successfully prevented the formation of brittle TiAl, TiAl2 and TIAl3 phases. A flat Ti–Nb diffusion zone composed of (Ti, Nb) solid solution was formed at Ti/Nb interface, while a narrow Al–Nb reaction zone was formed at the Nb/Al–FZ (aluminum alloy fusion zone) interface with the main microstructures of NbAl3, Nb2Al and Al-based solid solution. The simulation of welding temperature field and thermal cycle curve by finite element software was conducted to provide theoretical data support for clarifying the formation of the joint and interface reaction mechanism. The mechanical property of the joint was determined by the Al–Nb reaction zone which could be witnessed by observing the fracture location and hardness distribution of the joint. The joint fractured at the Al–Nb reaction zone and adjacent Al–FZ with the maximum tensile strength of 288.97 MPa.