Medical titanium and alumina (Al₂O₃) bioceramic are widely utilized as biomaterials. A reliable brazed joint of titanium and alumina was successfully obtained using biocompatible Au foil for implantable devices in the present study. The interfacial microstructure and reaction products of titanium/Au/Al₂O₃ joints brazed under different conditions were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). In this study, the typical interfacial microstructure of the titanium/Au/Al₂O₃ joint was titanium/Ti₃Au layer/TiAu layer/TiAu₂ layer/TiAu₄ layer/Au + granular TiAu₄ layer/TiO_x phase/Al₂O₃ ceramic. With increasing brazing temperature or holding time, the thicknesses of Ti₃Au + TiAu + TiAu₂ layers adjacent to the titanium substrate increased gradually. Shear tests indicated that the joint brazed at 1115 °C for 3 min exhibited the highest shear strength of 39.2 MPa. Typical fracture analysis displayed that the crack started at the Al₂O₃ ceramic and propagated along the interface of TiAu₂ and TiAu₄ reaction layers.

In this study, reliable Ti₂AlNb/high-Nb-containing TiAl alloy (TAN) joints were achieved by diffusion bonding. The effects of bonding temperature and holding time on the interfacial microstructure and mechanical properties were fully investigated. The interfacial structure of joints bonded at various temperatures and holding times was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the typical microstructure of the Ti₂AlNb substrate/O phase/Al(Nb,Ti)₂ + Ti₃Al/Ti₃Al/TAN substrate was obtained at 970 °C for 60 min under a pressure of 5 MPa. The formation of the O phase was earlier than the Al(Nb,Ti)₂ phase when bonding temperature was relatively low. When bonding temperature was high enough, the Al(Nb,Ti)₂ phase appeared earlier than the O phase. With the increase of bonding temperature and holding time, the Al(Nb,Ti)₂ phase decomposed gradually. As the same time, continuous O phase layers became discontinuous and the Ti₃Al phase coarsened. The maximum bonding strength of 66.1 MPa was achieved at 970 °C for 120 min.