Synergistic enhancement of strength-toughness of TiAl/Ti₂AlNb diffusion bonding joint via high-energy electropulsing treatment

The new-generation turbine structure, using TiAl alloy for blades and Ti₂AlNb alloy for the disk significantly enhances the thrust-to-weight ratio and efficiency of aero-engines. The turbine blades are often attached to the disk using advanced welding technologies. However, brittle intermetallic compounds (IMCs) and residual stresses tend to form after welding, impairing the performance of TiAl/Ti₂AlNb joints. In this study, the high-energy electropulsing treatment (HEEPT) was introduced to optimise the interfacial microstructures and properties, of TiAl/Ti₂AlNb joints, substantially improving the efficiency of post-bonding heat treatment. The observed average tensile strength and elongation of TiAl/Ti₂AlNb joints reached 470.93 MPa and 0.353 %, respectively, after 1 min of HEEPT, representing increases of 41.3 % in tensile strength and 99.4 % in elongation compared with those of the joints formed via diffusion bonding (DB). This enhancement is mainly attributed to the combined effects of the thermal and electron wind effects of HEEPT, which prevent the formation of continuous brittle IMCs of AlNb₂ at the bonding interface. Additionally, the interfacial β₀/B2 phase and equiaxed α₂ phase form a soft and hard combination configuration, producing anisotropic strengthening due to deformation-induced stress. Notably, HEEPT induces the precipitation of nanoscale acicular α₂ from equiaxed α phase. Additionally, HEEPT promotes the uniform arrangement of nanoscale acicular ω from β₀/B2 phase at the bonding interface, thereby achieving a synergistic enhancement of strength and toughness. This efficient HEEPT provides a novel strategy to strengthen other dissimilar weld joints and offers a sustainable alternative to traditional heat treatment.