Microstructure and Properties of TA2 Titanium Joints Brazed with Ti–Zr–Cu–Ni Filler Metal

TA2 titanium was brazed with a Ti–37.5Zr–15Cu–10Ni filler metal at 860–890 °C for 20 min to investigate the influence of temperature on joint properties. Raising the brazing temperature reduced residual filler in the seam center and transformed the microstructure from heterogeneous phases to a uniform α-(Ti,Zr) solid-solution matrix, accompanied by significant widening of the diffusion layer. At brazing temperatures of 890 °C, the hardness decreased to below 300 HV0.5 and became more uniform as brittle phases were suppressed. The shear strength reached a maximum of 302 MPa, and the fracture morphology exhibited characteristics of ductile fracture. Micro-electrochemical testing indicated that the joint brazed exhibited an almost uniform current distribution and significantly reduced localized corrosion. Although a small fraction of the Widmanstätten structure was observed at this temperature, it did not impair the overall mechanical performance. These findings demonstrate that a moderate increase in brazing temperature promotes elemental diffusion, alleviates brittle phase enrichment, and markedly enhances the mechanical properties and corrosion resistance of TA2 joints.