Brazing and interfacial reaction of commercially pure titanium with Ti-Zr-based filler metals

In the last 50 years, brazing of titanium and/or titanium alloys has been studied and a number of filler metals have been developed. Commercially pure titanium was brazed with commercially produced atomized brazing filler metal powder in an industrial vacuum furnace. Ti-Zr-based alloy filler metals were utilized in this study. We investigated the joint strength by shear strength tests and by observing the microstructure at the brazed joint. The shear strength tests revealed that the joint strength of Ti-Zr-based alloy filler metals for a brazing time of 60 min was approximately 300 MPa, which is almost the same as the base metal strength. Zirconium diffused into the base metal, thereby transforming from alpha-Ti to beta-Ti for a temperature below the alpha-beta transformation temperature of the base metal, and the diffusion of nickel and copper into the base metal was accelerated. The brazing filler metal remained at the brazed joint for a brazing time of 10 min; however, for an increased brazing time, it disappeared because of isothermal solidification. It is understood that isothermal solidification was mainly controlled by the diffusion of zirconium.