Interfacial Microstructure and Shear Strength of Ti50Al50 Joint Vacuum Brazed with Ti-Cu-Ni-Nb-Al-Zr-Hf Amorphous Filler Alloy

作者：Li Li; Zhao Wei; Feng Zhixue; Zhang Yuxin; Huang Zhichao; Li Xiaoqiang^*

来源：RARE METAL MATERIALS AND ENGINEERING, 2022, 51(2): 378-385.

• Ti50Al50 (at%) alloy
• Ti-Cu-Ni-Nb-Al-Zr-Hf amorphous filler
• vacuum brazing
• microstructure
• shear strength

Amorphous Ti-9.5Cu-8Ni-8Nb-7Al-2.5Zr-1.8Hf (wt%) filler alloy was employed to vacuum braze Ti50Al50 (at%) alloy at the brazing temperatures ranging from 1140 to 1220 degrees C for 30 min. The effect of brazing temperature on the microstructure and shear strength of the brazed joints was investigated. Results show that all the brazed joints are mainly divided into three reaction layers regardless of the brazing temperature, and both of alpha(2)-Ti3Al and Ti2Cu(Ni) phases exist in each reaction layer, but their size and distribution change significantly with brazing temperature, especially the Ti2Cu(Ni) phase in isothermal solidification layer II. The continuous alpha,-Ti3Al layer I is stable below 1200 degrees C but breaks and loses its barrier effect above 1200 degrees C. It is notable that the alpha(2)-Ti3Al precipitated in the brazed seam can act as a nucleation inhibitor and refine the crystal grain. Shear test results show that the average shear strength of Ti50Al50 brazed joints first increases and then decreases with brazing temperature and the maximum shear strength of 184 MPa is obtained at 1180 degrees C. alpha(2)-Ti3Al mainly occupies the fracture surface with cleavage characteristics.