Peculiarities of deformation of CoCrFeMnNi at cryogenic temperatures

Tirunilai, Aditya Srinivasan; Sas, Ján; Weiss, Klaus-Peter; Chen, Hans; Szabó, Dorothée Vinga; Schlabach, Sabine; Haas, Sebastian; Geißler, David; Freudenberger, J.; Heilmaier, Martin; Kauffmann, Alexander

doi:10.1557/jmr.2018.252

Cited by 67 publications

(49 citation statements)

References 54 publications

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“…Tirunilai et al compared the deformation behavior of the CoCrFeMnNi HEA and pure Cu at cryogenic temperatures [299]. Here, tensile tests were performed at RT (295 K), 77, 8, and 4.2 K. For the experiments performed at 4.2 K, the samples were placed in a liquid He bath, whereas samples were placed in a vacuum cryostat when tested at 8 K. To examine the serration behavior in the HEA, tensile tests were performed at mean plastic strain rates of 6 × 10 −5 , 3 × 10 −4 , and 1 × 10 −3 s −1 .…”

Section: Strain Rate (S −1 )mentioning

confidence: 99%

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confidence: 99%

“…The engineering stress vs. strain curves for the CoCrFeMnNi HEA compressed at strain rates ranging from 6 × 10 −5 to 1 × 10 −3 s −1 at 8 K (reproduced from Reference[299] with permission).Metals 2020, 10, x FOR PEER REVIEW 47 of 72 serrations were absent. A magnified view of the serrated-flow behavior in the doped sample is displayed in…”

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A Review of the Serrated-Flow Phenomenon and Its Role in the Deformation Behavior of High-Entropy Alloys

Brechtl

Chen

Lee

et al. 2020

Metals

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High-entropy alloys (HEAs) are a novel class of alloys that have many desirable properties. The serrated flow that occurs in high-entropy alloys during mechanical deformation is an important phenomenon since it can lead to significant changes in the microstructure of the alloy. In this article, we review the recent findings on the serration behavior in a variety of high-entropy alloys. Relationships among the serrated flow behavior, composition, microstructure, and testing condition are explored. Importantly, the mechanical-testing type (compression/tension), testing temperature, applied strain rate, and serration type for certain high-entropy alloys are summarized. The literature reveals that the serrated flow can be affected by experimental conditions such as the strain rate and test temperature. Furthermore, this type of phenomenon has been successfully modeled and analyzed, using several different types of analytical methods, including the mean-field theory formalism and the complexity-analysis technique. Importantly, the results of the analyses show that the serrated flow in HEAs consists of complex dynamical behavior. It is anticipated that this review will provide some useful and clarifying information regarding the serrated-flow mechanisms in this material system. Finally, suggestions for future research directions in this field are proposed, such as the effects of irradiation, additives (such as C and Al), the presence of nanoparticles, and twinning on the serrated flow behavior in HEAs.

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Section: Strain Rate (S −1 )mentioning

confidence: 99%

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confidence: 99%

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A Review of the Serrated-Flow Phenomenon and Its Role in the Deformation Behavior of High-Entropy Alloys

Brechtl

Chen

Lee

et al. 2020

Metals

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“…The occurrence of twins under tribological load was mentioned in the literature for an austenitic steel [7]. For CoCrFeMnNi, deformation twinning was widely reported under different loading conditions [30,[49][50][51][52]. Twinning already occurred at lower strains compared to the maximum strain determined by grain boundary bending in Fig.…”

Section: The Formation Of Twinsmentioning

confidence: 92%

Microstructural changes in CoCrFeMnNi under mild tribological load

et al. 2020

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The lack of a principle element in high-entropy alloys (HEA) leads to unique and unexpected material properties. Tribological loading of metallic materials often results in deformed subsurface layers. As the microstructure feedbacks with friction forces, the microstructural evolution is highly dynamic and complex. The concept of HEAs promises high solid solution strengthening, which might decrease these microstructural changes. Here, we experimentally investigated the deformation behavior of CoCrFeMnNi in a dry, reciprocating tribological contact under a mild normal load. After only a single stroke, a surprisingly thick subsurface deformation layer was observed. This layer is characterized by nanocrystalline grains, twins and bands of localized dislocation motion. Twinning was found to be decisive for the overall thickness of this layer, and twin formation within the stress field of the moving sphere is analyzed. The localization of dislocation activity, caused by planar slip, results in a grain rotation. Fragmentation of twins and dislocation rearrangement lead to a nanocrystalline layer underneath the worn surface. In addition, oxide-rich layers were found after several sliding cycles. These oxides intermix with the nanocrystalline layer due to material transfer to the counter body and re-deposition to the wear track. Having revealed these fundamental mechanisms, the evolution of such deformation layers in CoCrFeMnNi under a tribological load might lead to other HEAs with compositions and properties specifically tailored to tribological applications in the future.

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“…In contrast, twinning is activated at lower strains, when testing at cryogenic temperatures was performed. Even though, ε-martensite formation was not found (< 77 K) [10,22,24]. While the contribution of mechanical twinning to the total plastic strain is low, twinning causes significant strain hardening [24].…”

Section: Introductionmentioning

confidence: 99%

Origins of strength and plasticity in the precious metal based high-entropy alloy AuCuNiPdPt

et al. 2020

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The precious metal based High-Entropy Alloy (HEA) AuCuNiPdPt is of single phase fcc structure in the homogenised state. • Decomposition occurs during annealing AuCuNiPdPt at intermediate temperatures. • AuCuNiPdPt deforms by deformation twinning and dislocation slip at room temperature. • AuCuNiPdPt shows a high yield strength of 820 MPa and a high yield ratio of 0.66 at room temperature as well as significant strain hardening during deformation. • The strengthening mechanisms of AuCuNiPdPt are assessed.

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Peculiarities of deformation of CoCrFeMnNi at cryogenic temperatures

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Cited by 67 publications

References 54 publications

A Review of the Serrated-Flow Phenomenon and Its Role in the Deformation Behavior of High-Entropy Alloys

A Review of the Serrated-Flow Phenomenon and Its Role in the Deformation Behavior of High-Entropy Alloys

Microstructural changes in CoCrFeMnNi under mild tribological load

Origins of strength and plasticity in the precious metal based high-entropy alloy AuCuNiPdPt

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