Abstract: Joining of ceramic and metal meets the engineering needs for high-performance structural components. However, the significant difference in thermal expansion coefficients between metals and ceramics, as well as the poor wettability of metals to ceramic surfaces, makes the joining of ceramics and metals face many challenges. In this study, "flash joining" technology was used to achieve the rapid connection of metal Cu and 5YSZ (5% yttria stabilized zirconia, molar fraction) ceramics at a relatively low temperature under the assistance of electric field/current. The effects of electric field, current density, and joining time on the "flash joining" behavior and the degree of bonding between Cu and 5YSZ were investigated. Moreover, the mechanism of “flash joining” between Cu and 5YSZ was discussed. The results showed that the densest joint between Cu and 5YSZ was obtained at the temperature of 753 ℃, the current density of 10 A/cm² and the joining time of 3 min. However, the joint began to deteriorate and even fracture when the temperature, current and joining time were further increased. Electrochemical reactions occurred during the “flash joining” process, introducing oxygen vacancies defects. Phase and microstructural analyses indicated that atomic diffusion driven by electrochemical reactions facilitated the joining of Cu and 5YSZ, with Cu atoms diffusing into the 5YSZ lattice and reduced Zr atoms diffusing into the Cu lattice. In addition, the direction of the electric field had a significant impact on the bonding between Cu and 5YSZ. A good bond was achieved when the electric field was oriented from 5YSZ to Cu, while the bonding did not occur when the electric field direction was from Cu to 5YSZ.

Key words: joining, electric field, low temperature, electrochemical reactions, oxygen vacancies