Abstract: TC4 titanium alloy was brazed with B-Ti57CuZrNi solder. The wettability of B-Ti57CuZrNi solder on the surface of TC4 titanium alloy and the effect of brazing parameters on microstructure and mechanical properties of TC4 titanium alloy brazed joint were studied. The results show that the B-Ti57CuZrNi solder is well spread on surface of the TC4 titanium alloy, and effective metallurgical bonding is formed. With the increase of brazing temperature and holding time, the overall width of the brazing weld zone becomes wider, and the needle-like α phase transition growing to the center of the weld becomes more and longer. When the welding temperature is low and the holding time is short, there are large Cu-rich and Ni-rich white as-cast microstructure in the joint. When the brazing temperature is 930 ℃ and the holding time is 15 min, the tensile strength of the joint at room temperature is low, which easily occurs brittle fracture at the weld zone, while the elongation of the joint at room temperature is low when the holding time is lower than 30 min. High brazing temperature (>960 ℃) and long holding time (>45 min) are unfavorable to the tensile strength and elongation of the joint at 400 ℃. Considering the excellent tensile properties of brazed joints at room temperature and 400 ℃, the brazing temperature should be 950 ℃ and the holding time should be 30 min.

Key words: B-Ti57CuZrNi solder, TC4 titanium alloy, butt welding brazing, mechanical properties