Brazing Characteristics and Bonding Strength of Pure Titanium Joints Brazed with Low-Melting Temperature Zi–17Ti–22Ni Filler Metal

: The brazing characteristics and bonding strengths of pure titanium joints are evaluated for joints brazed with Zr-17Ti-22Ni filler. Vacuum brazing was conducted at temperatures between the melting temperatures of the filler metals and the beta-transition temperature of pure titanium at 3 MPa of pressure for 5 min. Fracturing of the pure titanium joint brazed at 1,093 K occurred before yielding during the tensile tests owing to the presence of a serious segregation region containing harder and more brittle [Ti, Zr]2Ni intermetallic compounds. In contrast, in pure titanium joints brazed at and above 1,113 K, fracturing occurred at the base metal. The yield strengths of the samples brazed at 1,113 K-1,133 K were estimated to be in the range of 320-350 MPa and the ultimate tensile strengths likewise ranged from 350 to 380 MPa. The strength of pure titanium brazed at 1,153 K decreased rapidly. The results of this study show that the optimum temperature to ensure good performance after the brazing of pure titanium with Zr-17Ti-22Ni as a filler metal ranges from 1,113 K to 1,133 K.