Microstructure evolution and mechanical properties of Ti2AlNb/TiAl brazed joint using newly-developed Ti–Ni–Nb–Zr filler alloy

Joining of TiAlNb alloy to TiAl intermetallics was conducted by the newly-developed Ti–Ni–Nb–Zr brazing filler alloy.The microstructure evolution of the joints was investigated by scanning electron microscope (SEM),energy dispersive spectrometer (EDS) and electron backscatter diffraction (EBSD).The macro-micro mechanical properties were studied by shear test and nano-indentation test.Typical interfacial microstructures across the brazing seam were TiAlNb substrate,α-TiAl+β-Ti,γ-TiAl+TiNi+TiNi+α-TiAl,α-TiAl+β-Ti,TiAl substrate.The TiNi phase were firstly dissolved in the joints brazed at 1000°C for 10 min and then precipitated after a prolonged holding time of 15 min.The nano-indentation test revealed that TiNi phase exhibited the highest hardness of 12.60 GPa.The joints brazed at 1000°C/15 min presented the maximum shear strength of271 MPa.The dissolution and precipitation behavior of TiNi phase was also discussed.