Effect of Zr content on properties of Ti-Zr-Cu-Ni filler metal and its brazed joint

Four kinds of titanium-based filler metals, Ti-5Zr-15Cu-15Ni, Ti-10Zr-15Cu-15Ni, Ti-15Zr-15Cu-15Ni and Ti-25Zr-15Cu-15Ni, were fabricated by electric arc melting method, and the four kinds of filler metals were used for vacuum brazing of Ti-6Al-4V plate lap joints. The melting characteristic and wettability of the filler metals on Ti-6Al-4V were tested, and the microstructures, microhardnesses and shear strengths of the brazed joints with different filler metals were tested and analyzed. The results show that the addition of Zr has an obvious effect on the melting temperature of Ti-Zr-Cu-Ni filler metal. The gap between solidus and liquidus temperatures is wide with much higher liqiudus temperature when the content of Zr is 5wt% or 25wt%. In contrast, the gap between solidus and liquidus temperatures is narrow with lower liquidus temperature when the content of Zr is 10wt% or 15wt%. Different from other compositions of filler metals, when the content of Zr is 25wt%, there are two obvious low temperature eutectic reactions during melting process, and the filler metal appears two spreading layers phenomenon during the wetting process. And much lower microhardness was attained in the brazed joint when the content of Zr is 15wt% or 25wt%. Considering the melting characteristic of the filler metals and the microhardness and shear strength of the brazed joints, the optimized composition of the filler metal is Ti-15Zr-15Cu-15Ni, and the shear strength of the brazed joint with this filler metal is 298 MPa.