Electric field suppresses intermetallics via enhanced diffusion and non-equilibrium phase transformation solid solution in ultrafast brazed Ti₂AlNb/Ti60 joints

Conventional brazing requires prolonged heating to form joints, which often results in a continuous brittle intermetallic layer that can initiate microcracks. Moreover, heating the entire workpiece induces substantial thermal stress and deformation, leading to detrimental residual stresses that impair joint performance. To address these limitations, this study adopts electric field–assisted brazing (EFAB), which utilizes pulsed electric current to generate Joule heating and electromigration effects, enabling rapid and efficient bonding at shorter processing times. EFAB was developed to join Ti₂AlNb and Ti60 alloys at 900 °C within < 1 s using a Ti-Zr-Ni-Cu-Co-Nb amorphous filler under 150 V/135 A/mm². Compared to conventional brazing (15 min dwell), EFAB eliminates brittle (Ti, Zr)₂(Cu, Ni) intermetallics through a uniform distribution of brittle elements driven by electromigration and concentration gradients, forming defect-free brazing seams comprising α-Ti + α′-Ti martensite (Ti60 side), α′-Ti martensite (brazing center), and α + β duplex (Ti₂AlNb side). Finite element simulations confirm EFAB reduces residual stress by 83 % via rapid Joule heating and α′-twinning. Interfacial electronic analysis reveals that the α-Ti/β-Ti interface exhibits remarkable charge accumulation and symmetric decay in differential charge density profiles, along with continuous transitions and robust orbital hybridization in the projected density of states. Additionally, it demonstrates an 8.7 % enhancement in separation work, with values reaching 0.3393 eV/Ų compared to 0.3123 eV/Ų (Ti₂Cu/α-Ti). These properties enable a semi-coherent α-Ti/β-Ti interface (22.4 % mismatch) versus incoherent Ti₂Cu/α-Ti (58.6 %). Consequently, EFAB joints achieve 221.9 MPa shear strength (30 % higher than conventional joints) with ductile fracture, demonstrating high-efficiency dissimilar joining of advanced titanium alloys.