| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 776781 | International Journal of Fatigue | 2015 | 5 Pages |
•As-received: small-highly misoriented areas and large-slightly misoriented areas.•After cycling: extrusions over large areas of slightly misoriented lath structures.•We observed pile-ups of dislocation stress concentration.•The observed pile-ups speak of the irreversibility of slip during cycling straining.•Dislocation arrangement is the origin of microcrack nucleation at lath boundaries.
Electron back-scattered diffraction together with scanning and transmission electron microscopy were used to study nucleation of microstructural fatigue cracks in reduced-activation ferritic–martensitic steel, EUROFER 97. Cylindrical specimens were cycled over different plastic-strain ranges in order to evaluate the evolution of the dislocation structure. Surface-damage evolution was studied in smooth notched specimens by an optical in situ system equipped with a high-resolution camera. In order to understand the crack-initiation mechanism, the dislocation microstructure that develops in the near-surface regions of the notch was compared with that of the bulk. The results demonstrate a strong influence of lath-martensite boundaries on fatigue-crack nucleation.
