Analysis of properties and failure mechanism of Ti600/Ni-25% Si joint

Brazing of Ti600 to Ni-25%Si alloy was performed using Ti-Zr-Ni-Cu amorphous filler foil. The influence of brazing temperature on the microstructures and mechanical property of brazed joints have been studied and the strengthening mechanism of the Ti600/Ni-25%Si brazed joint was clarified. The results show that the brazing seam contains multiple reaction zones. With the increase of brazing temperature, the zone III comprised by (Ti,Zr)₂Si and Ti₂Ni disappears gradually while the zone IV with Ti₅Si₃ dispersing in Ti₂Ni gradually occupies the brazing seam. As the brazing temperature increases, the shear strength of brazed joints first augmented, reached the peak value of 177 MPa at 960 ℃ and then decreased. The dispersing Ti₅Si₃ phase distributing in the brittle Ti₂Ni phase, which hinders the crack propagation and strengthens the brittle Ti₂Ni, improves the shear strength of the brazed joint obtained at elevated temperature.