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<p>Introducing high dislocation density has proven effective for attaining ultrahigh strength while retaining ductility. However, the role of high dislocation density in affecting the crack initiation and propagation (i.e., toughness) is still unclear. The present study investigates the notch fracture behavior and deformation mechanisms of a strong and ductile FeNiAl steel with yield strength of 1797 MPa and uniform elongation of 28.5%, possessing high dislocation density resulting from severe cold-rolling process. The cold rolled steel with high dislocation density exhibits superior crack initiation resistance and fracture energy compared to the annealed counterpart with low dislocation density. Pronounced necking and strain localization are found at notch roots of the cold-rolled sample, indicating enhanced plastic deformation despite its higher yield strength and lower work hardening capacity. The dual roles of high dislocation density are identified: (1) dense dislocation networks restrict dislocation mobility to enhance flow stress while limiting large-range plastic strain under gradient stress; (2) whereas coordinated short-distance slip of abundant dislocations enables intensive and severe plastic strain that suppresses crack nucleation locally, providing critical insights for designing damage-tolerant ultrahigh-strength steels.</p>

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Severe strain localization induced crack suppression in a dislocation-rich FeNiAl high-strength steel

  • 期刊论文

  • 发表日期：

    2026年5月4日

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  • Weipeng Li,
  • Xiedong Sun,
  • Haicheng Zhang,
  • Binbin He,
  • Chao Jiang

摘要

Introducing high dislocation density has proven effective for attaining ultrahigh strength while retaining ductility. However, the role of high dislocation density in affecting the crack initiation and propagation (i.e., toughness) is still unclear. The present study investigates the notch fracture behavior and deformation mechanisms of a strong and ductile FeNiAl steel with yield strength of 1797 MPa and uniform elongation of 28.5%, possessing high dislocation density resulting from severe cold-rolling process. The cold rolled steel with high dislocation density exhibits superior crack initiation resistance and fracture energy compared to the annealed counterpart with low dislocation density. Pronounced necking and strain localization are found at notch roots of the cold-rolled sample, indicating enhanced plastic deformation despite its higher yield strength and lower work hardening capacity. The dual roles of high dislocation density are identified: (1) dense dislocation networks restrict dislocation mobility to enhance flow stress while limiting large-range plastic strain under gradient stress; (2) whereas coordinated short-distance slip of abundant dislocations enables intensive and severe plastic strain that suppresses crack nucleation locally, providing critical insights for designing damage-tolerant ultrahigh-strength steels.