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.

Titanium and zirconia (ZrO₂) ceramics are widely used in biomedical fields. This study aims to achieve reliable brazed joints of titanium/ZrO₂ using biocompatible Au filler for implantable medical products. The effects of brazing temperature and holding time on the interfacial microstructures and mechanical properties of titanium/Au/ZrO₂ joints were fully investigated by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD). The results indicated that the typical interfacial microstructure of the titanium/Au/ZrO₂ joint was titanium/Ti₃Au layer/TiAu layer/TiAu₂ layer/TiAu₄ layer/TiO layer/ZrO₂ ceramic. With an increasing brazing temperature or holding time, the thickness of the Ti₃Au + TiAu + TiAu₂ layer increased gradually. The growth of the TiO layer was observed, which promoted metallurgical bonding between the filler metal and ZrO₂ ceramic. The optimal shear strength of ~35.0 MPa was obtained at 1150 °C for 10 min. SEM characterization revealed that cracks initiated and propagated along the interface of TiAu₂ and TiAu₄ reaction layers.

In this study, C-plane (0001) sapphire was successfully brazed to titanium using AuSn20 filler metal, following metallization on the surface of the sapphire with Sn-3Ti (wt.%). At 1000 °C, Sn-3Ti had good wettability on the surface of the sapphire, with the lowest equilibrium contact angle of 57°. The reaction phases in the joints were identified, and the typical interfacial microstructure of the brazed joint brazed at 550 °C for 30 min was titanium substrate/Au-Sn-Ti layer/Ti₆Sn₅ + AuSn₂ + AuSn₄ + massive Au-Sn-Ti/TiO phase/sapphire. The shear test was utilized to evaluate the bonding strength of the titanium/sapphire joints. The highest shear strength reached 18.7 MPa when brazed at 550 °C for 35 min. The crack was initiated at the sapphire/brazing seam interface and propagated into the Au-Sn-Ti reaction layer.