Ductile and scalable 3 GPa steel via a hierarchical microstructural architecture.

Ultrahigh-strength steels with yield strengths exceeding 3 GPa and appreciable ductility represent a transformative frontier in materials science. Conventional strengthening approaches, such as cold-work hardening, however, inevitably trade strength for total elongation, and thus are unable to deliver ductile 3 GPa steel. Here, we present a hierarchical microstructural architecture strategy applied to a designed maraging steel (Fe-16Ni-7Mo-1.6Ti-15Co-0.1Al, wt.%) that synergizes tailored precipitations with high-temperature severe plastic deformation. The multi-misfit nano co-precipitates, a high but spatially uniform density of dislocations, and ultrafine equiaxed grains are orchestrated into a hierarchical microstructure that delocalizes stress concentrations that commonly embrittle ultrahigh-strength materials and converts brittle cleavage fracture to ductile dimpling. Remarkably, the steel demonstrates 3 GPa yield strength with 47.5% reduction in area, 7.0% tensile elongation, and fracture toughness (KIc) of 26.0 ± 0.2 MPa·m1/2, which far surpasses existing 3 GPa steels. Moreover, as it exhibits an excellent fatigue strength of 1.24 GPa at ambient temperature and a yield strength of 2 GPa at 500 °C, which is achieved in industrially viable billets, this strategy unlocks scalable damage-tolerant components for extreme environments.