Preparation of oxygen vacancy through a pre-energized method to assist flash joining of Y2O3

Oxygen vacancy plays a crucial role in flash joining. In this study, we use a pre-energized method as a defect engineering technology to treat the yttrium oxide before joining, thereby increasing its oxygen vacancy concentration. After the pre-energized treatment, the joint strength is significantly improved by 68.7 % under the same conditions of 1300 ℃ with a current density of 2 mA/mm² for 300 s. This demonstrates that oxygen vacancies promote the flash joining process and reduce its onset conditions. The mechanisms of oxygen vacancy are explored experimentally and theoretically, which are identified in two areas: (1) The migration of vacancies forms fast ionic conduction paths, which allows uniform current flow and competition with established routes to enhance Joule heating. Subsequent grain homogenization further promotes overall superplastic deformation; (2) Driven by an electric field, vacancies will move to the grain boundaries to provide a channel for rapid bonding and accelerate elemental diffusion, and these diffused doping elements maybe further lead to an increase in the superplastic deformation rate.