Enhanced bonding between yttrium oxide ceramic to titanium via two‐step flash joining

Abstract Flash joining (FJ) typically requires applying a threshold electric field at high temperatures to generate oxygen vacancies, a process that often imparts damage to the base material. Existing improvement approaches, such as pretreatment, can introduce oxygen vacancies in advance but involve complex processes. To address this, we propose a novel two‐step FJ technique. Unlike ordinary FJ, this method implements dual electric field: initial application at a lower temperature followed by reheating to target temperature with field reapplication. The key strategy of applying electric fields in stages is to generate vacancies prior to the joining process, which effectively lowers the onset FJ conditions. Additionally, this approach significantly enhances bonding of yttrium oxide/titanium, achieving a 65.8% increase in shear strength compared with ordinary FJ. The two‐step FJ plays a role in two ways: (i) Promoting oxygen vacancy generation to reduce current excitation time, thereby reducing damage to the base material; (ii) Vacancy aggregation at the interface to accelerate filling reactions and atomic diffusion. By applying an electric field in stages to control defects, these findings provide a new approach to improving FJ strength.