Facilitating low-temperature diffusion bonding between oxygen-free Al2O3 ceramic and pure Cu through inclusion of 0.8 La (wt.%) to Ti pre-metallized interlayer: Microstructural evolution, metallurgical reactions, and mechanical properties

The primary objective in this work was to characterize the microstructure, metallurgical reactions, and mechanical properties of joints between oxygen-free Al2O3 ceramic and pure Cu substrates following diffusion bonding at temperatures of 250, 300, or 350 degrees C using a metallization interlayer of Ti-0.8La (wt.%). Diffusion bonding of oxygen-free Al2O3 ceramic and pure Cu substrates was performed using vacuum hot-press diffusion. The joints to be bonded were prepared by applying a pre-metallization interlayer of Ti-0.8La (wt.%). Experiment results demonstrated the successful diffusion bonding of oxygen-free Al2O3 ceramic and pure Cu substrates at temperatures of 350 degrees C. During the process of bonding, the Ti and La diffused toward the Al2O3 substrate to produce a homogeneous diffusion zone with no defects (i.e., cracking or porosity) at the interface. Adding a small quantity of La significantly increased the hardness of the joints as a function of bonding temperature. No indentation cracking was observed at the interface. At an elevated bonding temperature, the inclusion of La reduced the activation energy required for element diffusion, thereby increasing bonding strength in the interfacial diffusion zone and improving the ductility of Al2O3.