Converting Segregation‐Induced Banding Into Layered Heterostructures for Enhanced Strength‐Toughness Synergy in Low‐Alloy Steel Plates

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The strength–ductility–toughness trade‐off remains a central challenge in structural steels, particularly for large‐dimension plates where advanced heterostructure‐processing routes are often difficult to scale. Here, we propose an industrially compatible strategy that converts segregation‐induced chemical banding, conventionally considered as detrimental, into a designed ferrite/martensite layered heterostructure in a low‐carbon low‐alloy plate steel. Using conventional rolling and heat‐treatment processes, controlled slow‐cooling annealing promotes the formation of continuous ferrite layers along Mn/C‐segregated regions, while subsequent intercritical quenching and tempering regulate layer continuity, martensite fraction, and mechanical contrast between phases. Compared with homogeneous dual‐phase counterparts with comparable grain size, the optimized layered steel exhibits a superior strength–ductility–toughness combination. The improved tensile performance is attributed to deformation partitioning between ferrite and martensite layers, which promotes sustained work hardening, whereas the enhanced impact toughness arises from a layered toughening mechanism in which ductile ferrite layers accommodate plastic deformation, blunt crack tips, and repeatedly retard unstable crack propagation. This work reframes segregation‐induced banding from a processing defect into a controllable microstructural design element, offering a scalable route for designing high‐performance low‐carbon low‐alloy steel plates without complex routes or major composition redesign.