Microstructure and Mechanical Properties of Ti2AlNb/GH4099 Joints Prepared by In-situ Synthesis Brazing Using Zr-Ni-Cu-Ti-Zr Interlayer

Abstract:

Vacuum brazing of Ti₂AlNb alloy to Ni-based superalloy GH4099 based on in-situ synthesis using Zr-Ni-Cu-Ti-Zr composite interlayer was carried out. The interfacial microstructure and fracture morphology of brazed joints were observed and the phase evolution mechanism of the joint was investigated. The results show that the typical interfacial microstructure of the joint is Ti₂AlNb/B2+O+β(Ti,Nb)+α-Zr+Zr₂Ni+(Ti,Zr)₂(Ni,Cu)/(Ti,Zr)(Ni,Cu)/Ti₃Al+(Ni,Cr)_ss/GH4099. With the increase in brazing temperature, the thickness of the reaction layer on the base material sides increases, (Ti,Zr)₂(Cu,Ni) intermetallic compounds aggregate to form continuous phases on both sides of the interface, and cracks grow and expand at the interface between the brazing seam and the substrate, resulting in the decrease in joint strength. The maximum shear strength of 171.87 MPa is obtained after brazing at 920 ℃ for 15 min. The fracture mode of the joint is cleavage fracture and the fracture mainly consists of brittle (Ti,Zr)₂(Cu,Ni) and (Ti,Zr)(Cu,Ni) intermetallic compounds.