Interface microstructure and mechanical properties of copper-steel joints with nickel transition layer prepared by ultrasonic additive manufacturing

In order to suppress the problems of intergranular copper infiltration, liquid phase separation and thermal cracks in the process of fusion welding between copper and 304 stainless steel, UAM technology was used to consolidate the nickel transition layer on the surface of stainless steel to achieve surface modification, and then obtained copper-304 stainless steel overlap joints by pulse TIG process. Through the study of the joint interface configuration, microstructure, microhardness distribution and room temperature tensile strength of the control group, it was found that the introduction of the nickel interlayer can realize the metallurgical isolation between copper and steel and relieve the interfacial stress. Stainless steel and copper form the high-quality brazed joint with a nickel interlayer of 0.1 mm thickness, and the ultimate tensile strength of the joint at room temperature reaches 165 MPa. The joint fracture occurred near the fusion line near the copper side, and the fracture showed a ductile fracture mode.