This invention discloses a high-strength, high-
ductility, low-density steel and its preparation method. The composition is: C: 0.85–1.15%, Mn: 9.5–12%, Al: 8.5–11.5%, Ni: 2.5–3.5%, Cr: 2–3%, V: 0.3–0.5%, S≤0.005%, P≤0.008%, iron, and unavoidable impurities. The preparation method includes
smelting,
casting,
forging, hot rolling, cold rolling, and recrystallization annealing processes. Through a high-C, medium-Mn, and high-Al synergistic design, Cr suppresses
grain boundary carbide segregation, Ni promotes the formation of the B2 ordered phase, and V microalloying promotes the
precipitation of the VC precipitate, forming a multi-scale
layered structure composed of banded δ-ferrite, equiaxed (Fe,Ni)Al-type B2 phase,
austenite, and nano-VC precipitates. The recrystallization annealing process achieves multi-scale
layered structure control and synergistic strengthening of equiaxed (Fe,Ni)Al-type B2 phase and VC nanoprecipitates through rapid heating-short holding-rapid cooling. This invention breaks through the
bottleneck of balancing strength,
plasticity, and density in low-density steel, providing a high-performance material solution for automotive lightweighting.