Brazing of TiAl and Ti₂AlNb alloys using high-entropy braze fillers

To address the excessive formation of brittle compounds when brazing TiAl alloys, a TiZrHfCoNiCu high-entropy brazed filler was developed to realize the brazing of TiAl/Ti₂AlNb couples. The TiAl/Ti₂AlNb brazed joints can be divided into 4 zones, i.e., 2 diffusion zones at the TiAl/braze filler, Ti₂AlNb/braze filler interfaces and 2 zones divided inside the brazed seam. α₂ + γ-TiAl were the main reaction products formed at the TiAl/braze filler interface and α₂+ Ti_0.5Al_0.12Nb_0.38 were the main reaction products at the Ti₂AlNb/braze filler interface. Effects of brazing temperatures on the interfacial microstructure and mechanical properties of the TiAl/Ti₂AlNb brazed joints were investigated. When brazing at 1100°C/15 min, the highest shear strength can reach 157 MPa (room temperature), and 123 MPa (650°C) respectively. The relationship between the microstructure and the corresponding mechanical response were discussed in detail. This research can offer new insights on developing desirable brazing filler when joining TiAl and TiAl based alloys.