Low-temperature diffusion brazing of actively metallized Al₂O₃ ceramic tube and 5A05 aluminum alloy

A low-temperature ceramic-metal joining technique was successfully developed to produce a vacuum-tight Al₂O₃ ceramic and 5A05 aluminum alloy joint, with leak rates of less than 1.0×10^-9Pam³/s. This involved two steps: active metallization of the Al₂O₃ ceramic surface using Ag-Cu-TiH₂-B composite filler, followed by diffusion brazing of metallized Al₂O₃ ceramic and 5A05 alloy at 530°C. The microstructure, interfacial reactions and mechanical properties of the actively metallized Al₂O₃ ceramic and diffusion-brazed Al₂O₃/5A05 joint were investigated. The joint properties were determined by the formation of a continuous Ti₃Cu₃O reaction layer adjacent to Al₂O₃ ceramic, in situ synthesized TiB whiskers in the brazing seam, and dissolution thickness of 5A05 alloy. The maximum shear strength of the bonded joints reached 70MPa, while fracture propagated in the Al₂O₃ substrate, with a bowed crack path. A model for quantitatively evaluating the dissolution thickness of 5A05 aluminum alloy during diffusion brazing process was established.