Joining of titanium—copper TA2/T2 bimetallic sheet by double side laser—TIG welding

Abstract

Abstract In this paper, laser—tungsten inert gas (TIG) hybrid welding of TA2 titanium alloy and T2 copper alloy dissimilar joint has been performed using BCuP-2 wire as filler metal. A new welding process for TA2/T2 joining was introduced on the basis of the controlling the formation of Ti–Cu intermetallics in the joint. One process was two-pass welding involving creation of a joint with one laser weld and one TIG weld separated by remaining unmelted TA2/T2 interface. The influence of the hybrid welding process on the microstructure of the interfacial intermetallic compounds, and tensile strength of joints was investigated. The grain size of the TA2 fusion weld became larger after welding, forming acicular α martensite structure. The metallurgical combination between TIG weld and T2 base metal was good, and the TIG weld was mainly composed of α-Cu solid solution and a fine layered structure. However, a reaction layer containing α-Cu + α-Ti with an average width of about 30 μm was formed at the interface between the TIG weld and TA2 base metal, and fracture occurred along the TA2 weld and the interface of the reaction layer during tensile testing. A large number of Ti–Cu brittle compounds were avoided in joints, and the maximum tensile strength reached 610 MPa.