Microstructure and properties of brazing joints with a Ti-based filler of TiAl/GH536 alloy

Vacuum brazing of TiAl alloy and GH536 alloy with Ti-Zr-Fe-Cu-Ni-Co-Mo filler as interlayer was investigated. The microstructure of the brazed joints was characterized by employing SEM, EDS and XRD, and shear strength of the joints was analyzed in detail. Results show that the typical microstructure of the joint is given below: TiAl/layer I /layer II /layer III /layer IV /GH536. Layer I is mainly composed of Ti₃Al, in which some TiAl phases are embedded. Layer II is constituted by Al₃NiTi₂. Layer III mainly contains AlNi₂Ti, the other phases are Cr-rich (Cr, Ni, Fe)_SS, Ni-rich (Cr, Ni, Fe)_SS and (Ni)_SS + TiNi₃. In Layer IV, there are still Cr-rich (Cr, Ni, Fe)_SS, but a small number of Ni-rich (Cr, Ni, Fe)_SS, AlNi₂Ti and (Ni)_SS + TiNi₃ can be observed. The shear strength first increases and then decreases in the brazing temperature range of 1 110 ~ 1 170 °C for 10 min. The diffusion of atoms and the formation of intermetallic compounds are closely related to the brazing temperature. Lower or higher brazing temperature will lead to lower joint strength. It obtains a maximum value of 183 MPa at temperature of 1 150 °C with a holding time of 10 min, and the joints are mainly fractured at layer II.