Brazing of TC4 Alloy Using Ti-Zr-Ni-Cu-Sn Amorphous Braze Fillers

In order to address the issues of excessive brittle intermetallic compounds (IMC) formation in the TC4 brazed joints, two types of novel Ti-Zr-Cu-Ni-Sn amorphous braze fillers were designed. The microstructure and shear strength of the TC4/Ti-Zr-Ni-Cu-Sn/TC4 brazed joints were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and electronic universal materials testing machine. The results show that the optimized Ti₃₅Zr₂₅Ni₁₅Cu₂₀Sn₅ braze filler whose chemical composition is closer to the eutectic point possesses a lower melting point compared with the equiatomic Ti_23.75Zr_23.75Ni_23.75Cu_23.75Sn₅. This was beneficial to the sufficient diffusion of Cu and Ni elements with the base metal during brazing and reduces the residual (Ti,Zr)₂(Ni,Cu) content in the joint, which helps to improve the joint performance. The room-temperature and high-temperature shear strength of the TC4 brazed joints using the near eutectic component Ti₃₅Zr₂₅Ni₁₅Cu₂₀Sn₅ filler reached a maximum of 472 MPa and 389 MPa at 970 °C/10 min, which was 66% and 48% higher than that of the TC4 joints brazed with the equiatomic Ti_23.75Zr_23.75Ni_23.75Cu_23.75Sn₅ braze filler. Microstructural evolution and the corresponding mechanical response were in-depth discussed.