**Microstructure Evolution and Mechanical Properties of Titanium**/**Alumina Brazed Joints for Medical Implants**

**Hong Bian 1,2,3, Xiaoguo Song 1,2,3,\*, Shengpeng Hu 3, Yuzhen Lei 3, Yide Jiao 3, Shutong Duan 3, Jicai Feng 1,2 and Weimin Long <sup>4</sup>**


Received: 7 May 2019; Accepted: 31 May 2019; Published: 3 June 2019

**Abstract:** 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/TiOx 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.

**Keywords:** brazing; titanium; alumina; interfacial microstructure; mechanical properties
