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Achieving superior fracture resistance under cyclic loading–specifically, a high-fatigue limit–is crucial for ensuring structural safety and supporting a sustainable society. This study demonstrates a breakthrough in overcoming the conventional fatigue limit ceiling in high-strength as-quenched martensitic steel by enhancing resistance to crack initiation. In the as-heat-treated state, high-angle boundaries with large elastic misfits and plastic incompatibility served as precursory sites for intrusions/extrusions (these are defined as “crack embryos”), eventually leading to fatigue crack initiation. Remarkably, after the pre-fatigue training, surface crack initiation is entirely suppressed, doubling the fatigue limit with minimal change in tensile strength. A novel concept of “crack embryo engineering” is introduced, which targets the prevention of crack embryo formation by extracting intrinsic microstructural self-optimization against fatigue deformation: macroscopic hardness homogenization and selective nano-hardening of the precursory sites. This self-optimization strategy offers a versatile approach to improving fatigue limit in general steels, providing an effective alternative to tempering heat treatment that inevitably sacrifices tensile strength.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: マルテンサイト鋼, 疲労限度, き裂発生

Date published: 2025-06-29

Publisher: Wiley

Journal:

• Advanced Science (ISSN: 21983844) vol. 12 issue. 33 e04165

Funding:

• Japan Science and Technology Agency JPMJAX23D5
• Japan Society for the Promotion of Science JP23K13541
• Japan Society for the Promotion of Science JP23K26410

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1002/advs.202504165

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Updated at: 2025-11-11 16:30:06 +0900

Published on MDR: 2025-11-11 16:24:13 +0900