Microstructure and properties of titanium alloy/stainless steel joint by cold metal transfer joining technology

Cold metal transfer technology was used to weld TC4 titanium alloy and 304 stainless steel with copper-based filler metal, and the interface microstructure, mechanical properties and corrosion properties of the titanium alloy/stainless steel joint were analyzed. The results showed that TC4 titanium alloy and 304 stainless steel are joined by cold metal transfer method. The titanium alloy/stainless steel joint is mainly composed of weld metal, stainless steel-copper weld metal interface and titanium alloy-copper weld metal interface. The tension-shear strength of the titanium alloy/stainless steel joint is 306 MPa. Due to the formation of Ti-Cu, Ti-Fe intermetallics at the titanium alloy-copper weld metal interface, the joint exhibits a brittle fracture along the titanium alloy-copper weld metal interface reaction layer. Galvanic corrosion is occurred in the titanium alloy/stainless steel joint immersed in the artificial seawater solution. The corrosion mechanisms are the reduction reaction of oxygen and hydrogen evolution reaction at the cathode, the oxidation of weld metal, the formation of TiO₂ oxide film on the surface of titanium alloy and pitting corrosion of the stainless steel base metal at the anode.