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− 9 Pa∙m3/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 70 MPa, 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.