A novel low-alloy ultrahigh-strength steel featuring excellent mechanical properties and comprising a nanolath structure was fabricated in this work using a quenching–partitioning–tempering (Q-P-T) process. The Q-P-T process comprised direct quenching and an isothermal bainitic transformation for partitioning after thermo-mechanical control processing (online Q&P) and offline tempering (reheating and tempering). The ultrafine nanolath martensite/bainite mixed structure, combined with residual austenite in the form of a thin film between the nanolaths, was formed, thereby conferring excellent mechanical properties to the steel structures. After the Q-P-T process, the yield and tensile strengths of the steels reached 1450 MPa and 1726 MPa, respectively. Furthermore, the Brinell hardness and elongation rate were 543 HB and 11.5%, respectively, with an average impact energy of 20 J at room temperature.

The effects of various rolling reductions (64.7%, 72.1%, 81.4% and 88.2%) on the microstructures and mechanical behaviors of Sc-containing Al-3.2Cu-1.5Li-based alloys were experimentally investigated through XRD, SEM (equipped with EBSD), TEM and the tensile test. The results showed that the grains of hot-rolled and T6-treated alloys are mainly dominated by substructure features, and the addition of the trace Sc element can obviously impede the static and dynamic recrystallization due to the formation of fine and stable nano-Al₃(Sc, Zr) particles. Additionally, the combined effects of fine grains, dispersion, substructure and precipitation strengthening make the alloys with a rolling reduction of 81.4% possess higher tensile properties. With an increase in the rolling reduction, the tensile strength of the alloys increases first and then decreases, while the elongation gradually increases and then reaches a plateau, which was ascribed to the variation in the grain size and substructure features.