| About this Abstract |
| Meeting |
2025 TMS Annual Meeting & Exhibition
|
| Symposium
|
Steels in Extreme Environments
|
| Presentation Title |
Doubling fatigue limit by eliminating crack embryo in 1.6 GPa-grade as-quenched martensitic steel |
| Author(s) |
Kazuho Okada, Eri Nakagawa, Kaneaki Tsuzaki, Akinobu Shibata |
| On-Site Speaker (Planned) |
Kazuho Okada |
| Abstract Scope |
The fatigue limit of steel generally increases with tensile strength; however, when tensile strength exceeds ~1.4 GPa, further increases in tensile strength do not improve the fatigue limit or may even decrease it (fatigue limit ceiling). This phenomenon restricts the social implementation of ultra-high-strength steels. In this study, we successfully doubled the fatigue limit of 1.6 GPa-grade as-quenched martensitic steel (Fe-3Mn-0.2C (wt.%)) through pre-fatigue training, thereby overcoming the fatigue limit ceiling; the maximum stress corresponding to the fatigue limit increased from 675 MPa to 1300 MPa (stress ratio: 0.1). We revealed that the potential fatigue crack initiation sites, i.e., fatigue crack embryos, are high-angle grain boundaries with large elastic misfit and plastic incompatibility. Pre-fatigue deformations effectively homogenized macro/mesoscale hardness distribution and selectively work-hardened the crack embryos in the nanoscale. This process led to the crack embryo elimination and significantly improved the crack initiation limit, corresponding to the fatigue limit. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
Iron and Steel, Mechanical Properties, Other |