Interfacial microstructure and tensile strength of TiAl joint brazed with an improved Ti-Zr-Cu-Ni filler

Ti-16.5Zr-13.5Cu-8.5Ni (wt.%) as a filler and brazing process as 950 °C/60 min were supplied in this study for brazing cast TiAl alloys with fully lamella structure. The interface microstructure and element diffusion were analyzed and measured by SEM, EBSD, and EPAM. And the mechanical properties of joints were evaluated. The sound joints were achieved with strength as 575 MPa at room temperature and remained as 410 MPa and 385 MPa in average at 700 °C and 760 °C, respectively. It was attributed to lots of fine grains with soft orientation as BCC [120] in the joint to the tensile direction. It was found that the fracture happened in the local zones with very large grains and the extreme misorientation between grains in the joint. Even though most grains as Ti3Al phase were found in the joint, there was no sign indicating the formed IMC related to the fracture.