Tailoring Cold Rolling Effect on Induced Strain Partitioning and Its Role in Achieving Exceptional Mechanical Properties in a Novel 20Cr Lean Duplex Stainless Steel

The effects of cold rolling reduction (10%–70%) on the microstructure, microtexture, and mechanical properties of a novel Mn–N 20Cr lean duplex stainless steel (LDSS) were systematically investigated. Scanning electron microscopy, electron backscattered diffraction, X‐ray diffraction, and transmission electron microscopy revealed a microstructure evolution, namely initially equiaxed ferrite/austenite grain bands elongated and refined along the rolling direction and ultimately formed a distinctive “pancake structure” at high deformations. A key finding was the clear strain partitioning behavior, initial deformation strain preferentially accommodated in ferrite, but as the reduction increased, strain gradually transferred to austenite through a complex interplay of shear banding, twinning, and strain‐induced martensite transformation ( γ  →  ε ‐martensite/ twin  →  α′ ‐martensite and γ  →  α′ ‐martensite). Meanwhile, ferrite is deformed by dislocation slip, with dislocation multiplication and entanglement refining grains to nanometer size (by dislocation substructure). This two‐phase deformation response enhanced strength and hardness, with yield strength from 509 MPa to over 1871 MPa after 70% reduction. Furthermore, the cold rolling process dramatically altered the mechanical stability of the austenite, as evidenced by distinct strain hardening behaviors and the development of a sharp Brass/alloy‐type texture in austenite, alongside a strong α ‐fiber and weak γ ‐fiber in ferrite. These findings provided a framework for tailoring the processing–structure–property relationships in cost‐effective, high‐strength LDSSs, underscoring their promise for advanced structural applications.