An interfacial nanostructure-specific tailoring strategy to address the strength and ductility trade-off in inertia friction welded dissimilar superalloys.

Inertia friction welding (IFW) of dissimilar Ni-based superalloys offers great promise for manufacturing critical aero-engine components, yet the persistent strength-ductility trade-off in welded joints restricts their reliable service under extreme conditions. This work proposes an interfacial nanostructure-specific tailoring strategy via a double-stage aging treatment to precisely regulate the γ' strengthening phases, dislocation structures, and microtwins/stacking faults at the FGH4108/GH4065A IFWed interface. γ' strengthening phases in the as-welded joint underwent extensive dissolution and micro-precipitation at the interface, forming a fine-precipitate zone several nanometers in width, accompanied by high dislocation density and pronounced local strain concentration. After double-stage aging, the fine-precipitate zone was significantly narrowed, nanoscale γ' strengthening phases re-precipitated and grew to ∼15 nm, while abundant microtwins and stacking faults were introduced at the interface. The post-weld heat treated (PWHT) joint achieved an ultimate tensile strength of 1529.1 MPa with an elongation of 16.9% at room temperature, demonstrating simultaneous enhancement in strength and ductility. Mechanistically, the coherent strain field at the γ/γ' interface, together with the microtwins/stacking faults, elevated the energy barrier for dislocation motion and induced hetero-deformation hardening. 3D-APT analysis further confirmed that Al and Ti elements were preferentially enriched within the γ' precipitates, whereas Cr and Co tended to partition into the γ channels. Such elemental partitioning behaviors effectively reduced interfacial diffusivity and enhanced the coarsening resistance of the γ' precipitates. These findings lay a solid groundwork for the future development of integrated IFW-PWHT methodologies, offering a scalable route toward tailored microstructures in aerospace systems.