On the mechanism of fatigue crack initiation in high-angle grain boundaries

0557623 - ÚFM 2023 RIV GB eng J - Journal Article
Mazánová, Veronika - Heczko, Milan - Polák, Jaroslav
On the mechanism of fatigue crack initiation in high-angle grain boundaries.
International Journal of Fatigue. Roč. 158, MAY (2022), č. článku 106721. ISSN 0142-1123. E-ISSN 1879-3452
R&D Projects: GA ČR(CZ) GA18-03615S; GA MŠMT(CZ) LQ1601
Institutional support: RVO:68081723
Keywords : stage-i propagation * high-strain fatigue * twin boundaries * crystallographic orientation * slip bands * intrusions * extrusions * nucleation * growth * steel * Fatigue crack initiation * High-angle grain boundary * Persistent slip bands * Extrusions and intrusions * Void-like discontinuities
OECD category: Materials engineering
Impact factor: 6, year: 2022
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S0142112322000020?via%3Dihub

Fatigue crack initiation in high-angle grain boundaries is often observed experimentally, however, its mechanism is a subject of controversy. Low cycle fatigue loading has been applied to super-austenitic stainless steel Sanicro 25 and surface features developed during cyclic loading with high strain amplitudes were studied and analyzed using SEM, EBSD and FIB cuts. Dense array of persistent slip markings developed on the surface of grains was found. Extrusions and intrusions emerged not only in the direction of the surface but also normal to the grain boundaries. Growing extrusions were bent and started to push two neighbor grains locally apart leading to production of void-like discontinuities. Deepening intrusions produced void-like defects or microcracks on the grain boundary. Both these processes led to the substantial weakening of the grain boundary. Coalescence of void-like discontinuities and microcracks on the grain boundary during cyclic loading led to the production of the grain boundary crack. Presented and discussed experimental findings lead to novel mechanism of high-angle grain boundary crack initiation and raise serious doubts about the theories of brittle-like origin of grain boundary cracks.
Permanent Link: http://hdl.handle.net/11104/0331587