Microstructure and properties of Ti₃Al diffusion bonding joints with TiAlNbTaHf high-entropy alloy interlayer

This study innovatively employed a TiAlTaNbHf high-entropy alloys (HEA) as an intermediate layer material and successfully achieved high-quality bonding of Ti₃Al alloy using vacuum diffusion bonding technology. The interfacial microstructure of the bonded joint was systematically characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while its mechanical properties were evaluated through shear tests. Results demonstrated that the joint achieved optimal performance at 950 °C, with a maximum shear strength of 637 MPa. More importantly, this work provides an in-depth analysis of the micro-phase composition at the diffusion reaction interface (DRI) between the Ti₃Al alloy and the HEA interlayer, clarifying the formation mechanism of solid solutions and the precipitation behavior of the needle-like O phase. By introducing a novel HEA interlayer design, enhancing the performance and reliability of the bonded joint. The findings offer a reliable experimental basis and theoretical support for optimizing the diffusion bonding process of Ti₃Al alloy, presenting a new strategy for improving the joining quality of titanium‑aluminum intermetallic compounds.