The effects of cold rolling reduction rates and recrystallization annealing temperature on the microstructure, texture, and anisotropic properties of high-strength low-alloy (HSLA) steel were investigated using scanning electron microscopy and electron backscatter diffraction. The results revealed that the constituents of recrystallized, substructured, and deformed structures were strongly affected by cold rolling reduction rates ranging from 33.3% to 66.7% and recrystallization temperatures ranging from 780 to 840 °C. At an annealing temperature of 820 °C, when the cold rolling reduction rate was 33.3%, HSLA steel exhibited a low percentage of recrystallization, with cubic, γ-linear, rolled, and Z-texture (the texture at Euler angles φ1 = 30° and Φ = 20°–30°) structures. The rolled texture and Z-texture increased the strength anisotropy and disappeared at high cold rolling reduction rates. When the annealing temperature was increased from 780 °C to 820 °C, the proportion of recrystallized grains increased, the rolling texture disappeared, and grain orientation gradually gathered in the cubic texture and γ line texture, resulting in low anisotropy of strength. At an annealing temperature of 840 °C, the deformation of the grain disappeared; however, the anisotropy increased compared to annealing at 820 °C because of the formation of a new texture of {001}<−1–20>.

A novel ultrahigh-strength steel with Co and strengthened through nanoscale precipitation was developed. We found that the Co element had a synergistic effect on the precipitation process. The simulation results indicate that adding Co to steel can suppress the tracer diffusion coefficients of all the elements in the steel, hindering the atomic self-diffusion rate and long-range diffusion effect. A decrease in the atomic diffusion rate of precipitations will affect the nucleation, distribution, and growth of precipitations. The Atom probe tomography (APT) results indicate that the Co element not only dispersed uniformly in the matrix itself but also induced the uniform distribution of the precipitation phases. During the nucleation process of the precipitation, the rejected Co atoms formed small regions of high Co concentrations around the precipitation, inhibiting the coarsening of the precipitation. Under the synergistic effect of Co, the high number density of nanoscale NiAl and M₂C enhanced the strength of the steel.