Ultrahigh-strength bulk alloys with martensitic structures are essential for heavy-duty applications and infrastructure. However, they often contain small-angle grain boundaries (SAGBs), which enhance ductility but weaken resistance to dislocation motion. This limitation restricts tensile strength to below 2.5 GPa, even when nanoprecipitates or hierarchical architectures are introduced. Here we overcome this limitation by developing a near-single-phase martensitic alloy with a tensile strength exceeding 3 GPa. In the model (Fe₄₉Co₄₀Mo₁₁)_99.6B_0.3C_0.1 (at.%) alloy, cold rolling followed by low-temperature annealing introduces a high density of dislocations and drives Mo, C and B atoms to cosegregate at the SAGBs, forming interface complexes. These complexes stabilize the SAGBs, reinforce barriers to dislocation motion and still permit dislocation transmission across boundaries. As a result, the alloy achieves a tensile yield strength of 3.05 GPa and a fracture elongation of 5.13%, setting a benchmark for ultrahigh-strength, ductile alloys. This simple, scalable process integrates seamlessly with existing manufacturing methods and opens a path to next-generation structural materials.

In metals and alloys, solute segregation at grain boundaries typically undermines cohesion and ductility. Here, we overturn this paradigm by showing that solvent Fe atoms can preferentially enrich low-angle grain boundaries (LAGBs) in a ferrous alloy, dramatically enhancing ductility. Cold rolling and aging generate coherent nanoprecipitates, a high dislocation density, and abundant LAGBs in an austenitic matrix, yielding an ultrahigh tensile yield strength of ∼ 1.74 GPa. Moreover, the solvent Fe enrichment at LAGBs lowers local stacking fault energy and activates austenite-to-martensite transformation under load. This transformation-induced plasticity effect stabilizes plastic flow, enabling a uniform elongation of ∼ 26.2 % despite the alloy’s exceptional strength. Our findings challenge conventional views of segregation and offer a new design strategy for ultra-strong, highly ductile alloys.

Co-reduction of multicomponent oxides with hydrogen offers a carbon-neutral approach toward sustainable alloy design. Herein, we use in situ high-energy X-ray diffraction technique to gain insights into multicomponent oxide reduction of two precursor variants: mechanically mixed powders and pre-sintered oxide mixtures, targeting an equiatomic CoFeMnNi alloy. We find distinct reduction pathways and microstructure evolution, depending on initial precursors. Mixed powders are reduced to body-centered-cubic, face-centered-cubic, and MnO phases via halite, spinel, and Mn3O4 intermediates, whereas the pre-sintered complex oxide directly transforms into a mixture of metallic and MnO phases. The post-reduction microstructures were also strongly governed by the precursor state: mixed oxides exhibit loosely packed and coarse morphology, whereas the pre-sintered ceramic material showcases two distinct morphologies, either relatively dense metal-rich regions or regions with metallic nanoparticles supported on nanoporous MnO, highlighting the significant role of initial precursors on the final microstructure. Hence, precursor design strategies may offer a single-step route to nanoporous alloys with potential applications in catalysis and energy technologies.

Refractory medium/high-entropy alloys (M/HEAs) are emerging as promising alternative materials for hydrogen storage and hydrogen combustion engines due to their favorable thermodynamic and kinetic conditions for hydrogen accommodation (for the former) and promising high-temperature mechanical properties (for the latter). A better understanding of hydrogen-metal interactions is necessary to advance the development of this material class, thus helping leverage hydrogen-based applications. Here we reveal the microstructural evolution of a TiNbZr MEA by in-situ synchrotron high-energy X-ray diffraction (HEXRD) during hydrogenation in pure H₂ gas at atmospheric pressure. At 500 °C, dissolved hydrogen atoms gradually expand the crystal lattice isotropically, and the body-centered cubic crystal remains stable up to a hydrogen concentration of ∼46.4 at.%. The thermodynamics of hydrogen accommodation associated with experimental observations in the crystal lattice is elucidated using density functional theory (DFT). The calculations suggest that tetrahedral interstitial sites are the thermodynamically favorable positions for hydrogen accommodation in both cases (i) for a single hydrogen in the special quasirandom structure supercell and (ii) at a high hydrogen concentration (∼45.4 at.%). In the latter case, hydrogen interstitials are randomly distributed on the tetrahedral sites. Upon cooling, it is observed that the body-centered cubic lattice transforms to a body-centered tetragonal structure. The DFT calculations show that this change is related to the ordering distribution of hydrogen interstitials within the TiNbZr lattice. By combining in-situ HEXRD experiments and DFT calculations, the study provides fundamental insights into hydrogen accommodation in the interstitial positions and its impact on the lattice symmetry in TiNbZr MEA.

Coherent precipitation-hardened alloys often struggle to achieve both ultrahigh strength and exceptional ductility due to their limited resistance to dislocation motion and vulnerability to glide plane softening. Here, we tackle these challenges by introducing multicomponent precipitates with much increased antiphase boundary (APB) energy. In a model Ni₃Al-type (L1₂) precipitation-hardened face-centered cubic (FCC) NiCo-based alloy, we incorporate multiple elements at the Al sublattice sites within the precipitates, reducing antisite defects and enhancing ordering degree. This process yields multicomponent precipitates with an ultrahigh APB energy (~308 ± 14 millijoules per square meter), which notably strengthens the alloy. Moreover, the exceptionally high APB energy transforms the deformation mechanism from dislocation shearing to stacking fault shearing, thereby avoiding glide plane softening. These result in a tensile yield strength of 1616 ± 9 megapascals, an ultimate tensile strength of 2155 ± 22 megapascals, and a uniform elongation of 10.1 ± 0.3% for the alloy.

Iron powder can be a sustainable alternative to fossil fuels in power supply due to its high energy density and abundance. Iron powder releases energy through exothermic oxidation (combustion), and stores back energy through its subsequent hydrogen-based reduction, establishing a circular loop for renewable energy supply. Hydrogen-based direct reduction is also gaining global momentum as possible future backbone technology for sustainable iron and steel production, with the aim to replace blast furnaces. Here, we investigate the microstructural formation mechanisms and reduction kinetics behind hydrogen-based direct reduction of combusted iron powder at moderate temperatures (400–500 °C) using thermogravimetry, ex-situ X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and electron backscatter diffraction, as well as in-situ high-energy X-ray diffraction. The influence of pre-oxidation treatment was studied by reducing both as-combusted iron powder (50 % magnetite and 50 % hematite) and the same powder after pre-oxidation (100 % hematite). A gas diffusion-limited reaction was obtained during the in-situ high-energy X-ray diffraction experiment, with successive hematite and magnetite reduction, and a strong increase in reduction kinetics with initial hematite content. Faster reduction kinetics were obtained during the thermogravimetry experiment, with simultaneous hematite and magnetite reduction. In this case, the reduction reaction was limited by a mix of phase boundary and nucleation and growth models, as analyzed by multi-step model fitting methods as well as by microstructural investigation. When not limited by gas diffusion, the pre-oxidation treatment showed almost no influence on the reduction time but a strong effect on the final microstructure of the reduced powder.