Interfacial morphology and strength of Al 2 O 3 /Nb joint brazed with Cu -Ti -Zr filler metal

Abstract

In the present work ceramic Al₂O₃ was brazed to Nb using Cu -Ti- Zr as filler metal. The morphologies and chemical compositions of the phases formed were studied by SEM combined with energy dispersive spectroscopy and X-ray diffraction. It was found that the interfacial structure of joints brazed with Cu₇₀Ti₂₅Zr₅ filler metal at 1293 K for 10 min was Al₂O₃/Cu₂Ti₄O/Nb solid solution/CuTi/Cu solid solution + CuTi with the formation of the new phases Cu₂Ti₄O, Ti solid solution, and CuTi. The joint strength was investigated using a tensile/shear testing machine. According to the experimental results, an Al₂O₃/Cu₇₀Ti₂₅Zr₅/Nb joint brazed at 1293 K for 10 min can support a stress of 162 MPa. For lower contents of Ti and lower bonding times, or higher contents of Ti and higher bonding times, the strength of the joint was lower than the above value.