Microstructure and Mechanical Property of Titanium Film-Modified Sapphire/High Nb-TiAl Alloy Joints Using Ag-Cu Filler by Vacuum Brazing

The aim of this study is to evaluate the effect of Ti films prepared by plasma surface alloying technique on the sapphire for improving the bonding properties of sapphire/γ-TiAl alloy. The Ti films contained pure Ti, oxides (e.g., Ti 2 O and TiO 2 ) and intermetallic (Ti 3 Al) because of the deposition and chemical reactions between Ti element and sapphire. The wettability and brazing quality for sapphire/γ-TiAl alloy have been improved effectively by formation of new phases such as TiCuAl and AlCu(Ti,Nb) and Cu 4 Ti and Ti 3 Cu 3 O phases. The results show that with the increased brazing temperature, the width of diffusion and reaction regions enlarged because of the diffusion and reaction, leading to the raised shear strength of the joints. After brazing at 875°C for 10 min, the maximum shear strength reached as high as 158 MPa. Therefore, the current results provide a promising future for brazing the sapphire/γ-TiAl alloy.