Temperature and load-ratio dependent fatigue-crack growth in the CrMnFeCoNi high-entropy alloy
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
- Univ. of New South Wales, Sydney, NSW (Australia)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Ruhr Univ., Bochum (Germany)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
Multiple-principal element alloys known as high-entropy alloys have significantly been gaining attention for the vast variety of compositions and potential combinations of properties that remain to be explored. Of these alloys, one of the earliest, the ‘Cantor alloy’ CrMnFeCoNi, demonstrates excellent damage-tolerance with tensile strengths of ~1 GPa and fracture toughness values in excess of 200 MPa√m; moreover, these mechanical properties tend to further improve at cryogenic temperatures. Yet, few studies have explored its corresponding fatigue properties. Here we expand on our previous study to examine the mechanics and mechanisms of fatigue-crack propagation in the CrMnFeCoNi alloy (~7 μm grain size), with emphasis on long-life, near-threshold fatigue behavior, specifically as a function of load ratio at temperatures between ambient and liquid-nitrogen temperatures (293 K–77 K). We discover that ΔKth fatigue thresholds are decreased with increasing positive load ratios, $$\mathcal{R}$$ between 0.1 and 0.7, but are increased at decreasing temperature. These effects can be attributed to the role of roughness-induced crack closure, which was estimated using compliance measurements. Evidence of deformation twinning at the crack tip during fatigue-crack advance was not apparent at ambient temperatures but seen at higher stress intensities (ΔK ~ 20 MPa√m) at 77 K by post mortem microstructural analysis for tests at $$\mathcal{R}$$ = 0.1 and particularly at 0.7. Overall, the fatigue behavior of this alloy was found to be superior, or at least comparable, to conventional cryogenic and TWIP steels such as 304 L or 316 L steels and Fe-Mn steels; these results coupled with the remarkable strength and fracture toughness of the Cantor alloy at low temperatures indicate significant promise for the utility of this material for applications at cryogenic environments.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; Natural Science Foundation (NSF); German Research Foundation (DFG)
- Grant/Contract Number:
- AC05-00OR22725; AC02-05CH11231
- OSTI ID:
- 1543213
- Alternate ID(s):
- OSTI ID: 1602196
OSTI ID: 1510531
- Journal Information:
- Journal of Alloys and Compounds, Journal Name: Journal of Alloys and Compounds Journal Issue: C Vol. 794; ISSN 0925-8388
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
On the Room-Temperature Mechanical Properties of an Ion-Irradiated TiZrNbHfTa Refractory High Entropy Alloy
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journal | November 2019 |