Vacuum brazing TiAl to Ti₃Al using two Ti-based filler metals

Vacuum brazing of TiAl and Ti₃Al was conducted with Ti–Zr–Cu–Ni and Ti–Zr–Fe filler metals. Microstructure and shear strength of TiAl/Ti₃Al joints were investigated. The results indicated that the joint mainly consisted of Ti-rich, Ti₂Al, and Ti₃Al phases and residual filler metal. A columnar structure in all of the brazed seams adjacent to TiAl substrate was found, and it was resulted from the interdiffusion between filler metals and solid-state TiAl substrates. The fracture surface analysis demonstrated that the existence of excessive residual filler metal and the columnar structure was detrimental to joint strength. The joint brazed at 1050 °C for 5 min using Ti–Zr–Fe filler metal presented the maximum shear strength of 196.3 MPa, and the fracture mechanism was characterized by a mixture of cleavage and quasi-cleavage fracture.