The role of interlayers in the flash joining of Y2O3 transparent ceramic to titanium alloy

The application of soft metal interlayers in the joining process is an efficient strategy for enhancing the joint strength. In this study, we select the Ni interlayer from among three soft metals, meticulously adjusting various parameters to achieve optimal joint performance. These parameters include the interlayer thickness, temperature, current density and joining time. When the thickness of the Ni interlayer is 600 nm, the Y2O3/Ni/Ti-6Al-4V joint strength reaches a maximum of 65 +/- 4 MPa at 900 degrees C with a current density of 1.5 mA/mm2 for 30 s, improved by 81.6% than Y2O3/Ti-6Al-4V direct flash joining. During the flash joining process, the presence of a threshold electric field induces the formation of oxygen vacancies. These vacancies tend to accumulate at the interface, thereby facilitating rapid material transfer and reaction. Notably, the role of interlayers here is not for traditional stress relieving, but to enhance the metallurgical bonding and promote the defect reaction. Wherein, the latter includes an increase in oxygen vacancies and acceleration of atomic diffusion. Hence, it is anticipated that a wider variety of interlayers will be explored for application in flash joining technologies.