Microstructure and mechanical properties of T2 copper /316L stainless steel explosive welding composite with small size wavy interface

Copper/stainless steel composite is often used for preparation of superconducting busbar “double box” lap joints. However, it is a challenge for the large thickness T2 copper/316L stainless steel composite is fabricated by explosive welding, because of the bonding interface is always present many problems such as large ripple size, many microscopic defects, low bonding strength and poor sealing etc. In this paper, the big-thickness T2 copper/316L stainless steel composite with small size wavy interface was successfully fabricated by explosive welding. Microstructure of bonding interface indicated that the welding process could be divided into three stages: detonation growth stage, detonation stabilization stage, detonation descent stage. The morphology of bonding interface presented a regular wavy interface and no defects such as cracks, voids and intermetallic compound were formed in the stable stage, which was consistent with the results of ultrasonic and permeability quality inspection. The hardness of copper side and stainless steel side close to the bonding interface reached 131HV and 432HV, respectively. Dynamic recrystallization and fine grain generated in the bonding interface. The mechanical properties of tensile strength, pull-off strength and shear strength in the stable detonation stage is greater than 110 MPa, which is meeting the requirements of preparation of superconducting busbar “double box” lap joints. The deformation failure mainly occurred in the copper side near the bonding interface, which presented a higher bonding strength than copper. Some dimples and tearing edges with different sizes on the fracture surfaces, indicating that the fracture was a typical ductile fracture.