Journal
SCRIPTA MATERIALIA
Volume 202, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.scriptamat.2021.113985
Keywords
Medium-and high-entropy Alloys; Deformation twinning; Fatigue; Crack initiation; Persistent slip marking
Categories
Funding
- National Science Foundation [DMR-1905748]
- U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division
- Thermo Fisher Scientific & Czechoslovak Microscopy Society fellowship
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The CrCoNi alloy exhibited cyclic hardening and softening behavior during low cycle fatigue testing, leading to failure. Deformation twins generated during the cycling process showed well-developed persistent slip markings.
Cylindrical specimens of CrCoNi alloy with electropolished surfaces were subjected to constant total strain amplitude low cycle fatigue. The alloy exhibited an initial period of cyclic hardening followed by cyclic softening until failure occurred. At the end of hardening stage at the peak of cyclic stress, well-developed persistent slip markings (PSMs) consisting of extrusions and intrusions were associated with thin deformation twins. A sophisticated experimental workflow was designed to extract information from the surface and the bulk of tested material. A combination of SEM, EBSD, ECCI, FIB and HR-STEM was used to study the internal structure and the surface profiles around the deformation twins, which were produced during the initial period of cyclic loading. Furthermore, localized cyclic plastic strain and stress concentrations near deformation twins led not only to early, well-developed PSMs, but also to the activation of TWIP and TRIP plasticity even at low macroscopic stress amplitudes. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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