Enhanced vacuum brazing joining between Ti–48Al–2Cr–2Nb/Ti–22Al–25Nb intermetallic alloys by Zr-free Ti-based filler

This study investigates the microstructure and tensile properties of vacuum-brazed joints of Ti-48Al-2Cr-2Nb (Ti4822) and Ti-22Al-25Nb (Ti 2 AlNb) intermetallic alloys using Ti-based filler metals, with and without the addition of Zr element. Detailed microstructural characterization of the brazed joints was conducted using Electron Backscatter Diffraction and Transmission Electron Microscopy, identifying various phases and their distributions. The tensile properties were tested at room temperature and at 650°C, revealing the influence of Zr on the mechanical performance of the joints. The results demonstrated that the microstructure of joints brazed with Zr-containing filler metals exhibited a layered structure with brittle Zr-enriched intermetallic compounds, limiting their mechanical properties. Conversely, Zr-free filler metals yielded more homogeneous and ductile microstructures, significantly improving tensile strength and elongation. The Zr-free joints obtained after holding at 980 °C for 60 minutes exhibits the highest tensile strength, reaching 368.23 MPa at room-temperature and 293.46 MPa at 650 °C, respectively. These findings provide valuable insights for optimizing brazing processes and filler metal compositions to enhance the performance of TiAl-based intermetallic alloy joints.