Fatigue stress concentration and notch sensitivity in nanocrystalline metals
Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zones underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.
- Authors:
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- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Publication Date:
- Report Number(s):
- SAND-2015-6744J
Journal ID: ISSN 0884-2914; applab; PII: S0884291416000662
- Grant/Contract Number:
- AC04-94AL85000
- Type:
- Accepted Manuscript
- Journal Name:
- Journal of Materials Research
- Additional Journal Information:
- Journal Volume: 31; Journal Issue: 06; Journal ID: ISSN 0884-2914
- Publisher:
- Materials Research Society
- Research Org:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Org:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 36 MATERIALS SCIENCE; fatigue; nanocrystalline; defects; notches; fracture
- OSTI Identifier:
- 1254322
- Free Publicly Accessible Full Text
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Accepted Manuscript (DOE)
- Publisher's Version of Record
- https://doi.org/10.1557/jmr.2016.66