Strength–ductility synergy in a Ni–Cr–Co-based superalloy enabled by dual heterostructures induced by heterogeneous γ′ precipitation

Achieving ultrahigh strength without severe ductility loss remains challenging for γ′-strengthened Ni–Cr–Co-based wrought superalloys. Here, we develop a thermomechanical route to construct dual heterostructures in a Ni–Cr–Co-based superalloy, characterized by γ′-free ultrafine recrystallized soft regions and hard regions enriched with dense γ′ precipitates. The introduction of equiaxed γ′-free domains creates distinct soft and hard regions, giving rise to pronounced microstructural and mechanical heterogeneity. During deformation, unlike in conventional homogeneous superalloys, the heterogeneity between domains generates local strain incompatibility, promotes inter-domain plastic strain gradients and the accumulation of geometrically necessary dislocations, and thereby enhances hetero-deformation-induced (HDI) back-stress strengthening. Consequently, the heterostructure promotes the formation of higher densities of deformation twins, stacking-fault networks, and Lomer–Cottrell locks in the hard regions, while dislocations interact with coherent γ′ precipitates through combined shearing and bypassing mechanisms, thereby sustaining work hardening and deformation stability. Strengthening analysis indicates that the ultrahigh yield strength arises from the combined contributions of precipitation strengthening and enhanced HDI strengthening enabled by the amplified strength contrast between soft and hard domains. As a result, the heterostructured alloy exhibits excellent strength–ductility synergy, achieving an ultrahigh yield strength of 1531 MPa together with an elongation of 11.5%, outperforming previously reported Ni–Cr–Co-based wrought superalloys of a similar class. These findings demonstrate that dual heterostructures induced by heterogeneous γ′ precipitation provide an effective microstructural strategy for achieving strength–ductility synergy in precipitation-strengthened Ni-based superalloys.