Compositional gradient induced by heterogeneous domain synergy strategy toward high-performance diffusion bonding

To pursue lightweight structures with the merit of high strength that could fulfil the critical demands of aerospace field, primarily governed by interfacial domain relationships, has become paramount. Herein, compositional gradient established by controllable Al content led to the generation of heterogeneous domains with coherent relationships to promote synergistic deformation and regulate anisotropy. High-performance diffusion bonding of Ti₂AlNb/GH4169 dissimilar metals was achieved with a shear strength of 349 MPa, which was attributed to the formation of primary Cr–Ti bond and the decrement of the Ni-Cr covalent bond content. The interfacial region was transformed from the soft domains of Cr_ss and (Cr, Ni, Fe)_ss phases to the heterogeneous domains of Ni₃(Al, Ti), Ni₁₀Zr₇, Cr_ss and (Cr, Ni, Fe)_ss phases. Mobile dislocations, originating from the soft domains, were imported into the hard domains through the coherent interface, which enabled the dynamic equilibrium of impeding dislocations without terminating them. First-principle calculations indicated that the bonding strength at the Al-doped Cr/(Cr, Fe, Ni) interface was elevated to 0.32 J/m² due to evident interfacial charge transfer promoting strong interatomic attraction. The bonding strength of the Ni₃(Al, Ti)/Cr interface reached 4.64 J/m², which was associated with the high adhesion Cr–Ti bond with metallic and covalent characteristics.