Research on Strong Plasticity and Multiphase Fibrous Microstructures in Low‐Carbon Strip Steel via Structure Heredity and Compositional Design

To address the challenges of limited strength–ductility synergy and lead contamination in heat treatment of conventional high‐carbon pearlitic bridge cable strands, this study proposes an innovative material design strategy: by using Mn, Al, Cu, and other trace multialloying elements, the structure heredity was strengthened. Coupled with reversed austenite transformation and low‐temperature tempering, a novel strip steel with a multiphase fibrous microstructure (martensite, ferrite, and retained austenite) with superior strength–ductility synergy and work hardening was fabricated. Findings show that compositional optimization reinforces structural inheritance, resulting in a refined fibrous microstructure. Specifically, this refinement reduces martensite/ferrite grain size by 15% and narrows the average martensite lamellae width by 31.32%, and overall average Kernel average misorientation (KAM) value decreases from 1.26° to 0.84°, indicating improved initial strain distribution in microstructural deformation. Through aluminum's carbon‐depletion and enhanced stacking fault energy from manganese and aluminum, retained austenite stability increases, promoting the transformation‐induced plasticity (TRIP) effect. The synergistic interaction between fibrous microstructure and needle‐like retained austenite collectively enhances strength–ductility. Compared to base material, the material achieved tensile strength of 1413.9 ± 2.1 MPa and uniform elongation of 12.52 ± 0.08%, with a strength–ductility product improved by about 32.1%, and surpasses traditional high‐carbon pearlitic steels.