Microstructure and properties of titanium alloy/copper-nickel/stainless steel welded joints

Cold metal transfer welding of titanium alloy and stainless steel was carried out using copper-nickel composite filler metal. The effects of copper-nickel composite filler metal on the microstructure and mechanical properties of the joint were investigated by scanning electron microscope and X-ray diffractometer. The results show that defect-free welded joint was obtained, and Ti-Ni intermetallic compound was formed in the joint. As the hardness of the Ti-Ni intermetallic compound is lower than that of the Ti-Fe and Ti-Cu intermetallic compounds, the tensile property of the joint was improved. When the welding current was set at 182 A, the maximum tensile and shear strength of the joint was achieved at 348 MPa. The titanium alloy/stainless steel joint was composed of stainless steel-weld metal interface, stainless steel-pure nickel-titanium alloy interface, titanium alloy-weld metal interface and weld metal, and Ti-Cu, Ti-Ni, Al-Cu-Ti and Al-Ni-Ti-Fe-Cu intermetallic compounds were formed in the joint. With the increase of welding current, there was a gradual growth in the microhardness and the width of the interface reaction layer on the titanium alloy side.