Interfacial microstructure and properties of TiAl alloy brazed joint with Ni-34Ti brazing alloy

TiAl alloy was successfully brazed using Ni34Ti eutectic brazing alloy in this paper. The interfacial microstructure of TiAl brazed joints was characterized. In particular, the effects of brazing temperature on the interfacial microstructure and joining properties were investigated in details. Ni-34Ti eutectic brazing alloy was mainly composed of TiNi phase and TiNi3 phase. The melting point of this brazing alloy was about 1 120 ℃. The TiAl brazed joints presented a symmetrical characteristic. No pores and micro-cracks existed in the brazed joints. The microstructure analyses results showed that the brazed joints mainly consisted of TiNiAl2, B2, TiNiAl and TiNi2Al phases. The rapid diffusion of element Al in the brazed seam dominated the formation of Ti-Ni-Al ternary compounds. The maximum shear strength at room temperature reached 87 MPa when the joints were brazed at 1 180 ℃ for 10 min. The fracture analyses revealed that brittle fracture preferred to initiate and propagate in the TiNi2Al-rich region during shear test, which indicated that the existence of a large number of brittle TiNi2Al phases was harmful to the performance of TiAl brazed joints.