Microstructure and mechanical properties of the brazing joint for Ti6Al4V alloy
Ti-6Al-4V alloy is an outstanding structural material with approximately 60% of the titanium market in the world for aerospace applications because of its superior properties, such as high strength-to-weight ratio and good fatigue life. In the joining of Titanium alloys, brazing technology has been recognized as the most perspective approach. The main emphasis of recent studies was to improve the mechanical properties of the joints. This research investigates the microstructure and tensile properties of the brazed joints for the most widely used aerospace alloys namely as Ti6Al4V. The developed brazing joint materials were two kinds of amorphous Ti-Zr fillers and the brazing process was conducted in vacuum, which is below the β phase transformation temperature. The microstructure and the elements distribution were evaluated by EBSD and SEM. The tensile strength was tested by in situ-tensile test. And the local strain evolution of the matrix and the joint was analysed by DIC. Except solid solution strengthening effect by the uniform distribution of the filler elements in the joints, the interlocking microstructure consisting of acicular Widmanstätten and β lamellar structure presented throughout the entire joint by both fillers was the main reason for the higher strength of all the brazed samples. With the proper content of the Zr in the filler metal, the brazing joint took as much as 6.3% strain, resulting in the fracture of the matrix during the tensile test.
- Dr Yongjuan Jing (Beijing Aeronautical Manufacturing Technology Research Institute, AVIC)