A novel 2.2‐GPa grade ultrastrong Fe‐based alloy via synergistic strengthening of dislocations and precipitates

Abstract Ultrastrong steels are widely used to manufacture load‐bearing components in the automotive and aerospace industries, for light‐weighting, enhanced fuel efficiency, and reduced costs. A martensitic steel with fine grains, containing 0.34 wt% carbon and 2.85 wt% alloying elements, was produced through the combined technique of thermomechanical controlled processing, austenitizing, water quenching, and tempering (TMCP‐Q&T). A lath martensitic matrix with high‐density dislocations, accompanied by the twinned martensite and retained austenite, was obtained using this technique. The dispersed nanoscale ε‐carbide and (Ti,Mo)C phases were distributed at both boundaries and interiors of martensite laths. The mean size of prior‐austenite grains was refined to 7.7 μm, and the average width of martensite laths was 190 nm. Notably, the novel steel exhibited an excellent combination of ultimate tensile strength (2.2 GPa) and ductility (9.4%), which were superior to those of 300 M steel (2 GPa, 8%). Moreover, a significant 40% reduction in the alloying element content was achieved relative to 300 M steel, and the raw material cost was decreased by 17% correspondingly. The enhanced tensile strength of this martensitic steel is mainly attributed to dislocation strengthening and precipitation strengthening, which contribute 53% and 21% to the yield strength, respectively. This discovery provides a new strategy for fabricating a 2.2‐GPa grade ultrastrong steel with good ductility at a low cost, making it highly desirable for industrial applications.