Brazing of Ti2AlNb and TMCs using the amorphous TiZrHfNiCu high-entropy filler alloy

The reliable combination of Ti₂AlNb alloy with Ti matrix composites (TMCs) is critical for promoting their utilization in the aerospace field. In this work, the TiZrHfNiCu high-entropy amorphous filler foil was employed to braze the TMCs and Ti₂AlNb alloy. The evolution of the microstructure and mechanical characteristics of the joints under varied temperatures for 10 min was studied. The formation mechanism of the joints was illustrated and the inherent relationship between the microstructure and the bonding strength was also established. The results show that all the joints obtained at different temperatures consist of three zones. At 940 °C, the microstructure of the joint can be characterized as: (α + β)-Ti, (Ti, Zr, Hf)₂(Ni, Cu) with traces of TiB and Y₂O₃ (for the zone I)/continuous (Ti, Zr, Hf)₂(Ni, Cu) with minor (α + β)-Ti (for the zone II)/continuous B₂ layer with a little O phase (for the zone III). In such a case, the highest shear strength of the joint was obtained, reaching 206.1 MPa. When brazed at 910 °C, the Ti–rich reaction layer formed at the zone I/zone II interface led to early fracture of the joint. While increasing the brazing temperature over 970 °C, the β-Ti and minor IMCs would be formed in zone III, deteriorating the joint strength. The work realized the sound joining between TMCs and Ti₂AlNb alloys, paving the way for their more extensive application in the aviation field.