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Deformation Mechanisms of CoCrFeMnNi High-Entropy Alloy Under Low-Cycle-Fatigue Loading

27 Pages Posted: 18 May 2021 Publication Status: Accepted

See all articles by Kaiju Lu

Kaiju Lu

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials

Ankur Chauhan

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials

Aditya Srinivasan Tirunilai

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials

Jens Freudenberger

Leibniz Institute for Solid State and Materials Research (IFW) - Institute for Metallic Materials

Alexander Kauffmann

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials

Martin Heilmaier

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials

Jarir Aktaa

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials

Abstract

Plastic deformation during low-cycle fatigue (LCF) in equiatomic face-centered cubic (FCC) CoCrFeMnNi high-entropy alloy (HEA) is accumulated by dislocation substructure formation, which leads to crack initiation. Whilst these substructures have been reported before, little has been done to clarify their formation mechanisms and the effects of strain amplitude, cycle number and grain orientation. In this study, cyclic deformation behavior and microstructural evolution of CoCrFeMnNi were examined for two different grain sizes at room temperature. Microstructural investigations by transmission electron microscopy showed that, while the dislocation structures at low strain amplitude (0.3%) mainly consisted of planar slip bands, at higher strain amplitudes (0.5% and 0.7%), wavy-substructures including veins, wall, labyrinth and cells prevailed. Slip mode also changes from initially planar-slip to wavy-slip with increasing cycle numbers, which defines the cyclic stress response. Dislocations in veins, walls, labyrinth and cells are found to have different Burgers vectors, suggesting that apart from wavy-slip, multiple-slip also contributes to their formation. Moreover, distinct dislocation substructure in grains is dictated more by the constraints from neighboring grains rather than by their orientation. Additionally, the formation of various dislocation structures in a single grain is also linked to the constraint effects from the neighboring grains.

Keywords: High entropy alloy; Fatigue; Dislocation; Transmission electron microscopy (TEM); Grain size

Suggested Citation

Lu, Kaiju and Chauhan, Ankur and Tirunilai, Aditya Srinivasan and Freudenberger, Jens and Kauffmann, Alexander and Heilmaier, Martin and Aktaa, Jarir, Deformation Mechanisms of CoCrFeMnNi High-Entropy Alloy Under Low-Cycle-Fatigue Loading. Available at SSRN: https://ssrn.com/abstract=3848994 or http://dx.doi.org/10.2139/ssrn.3848994

Kaiju Lu (Contact Author)

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials ( email )

Hermann-von-Helmholtz-Platz 1
Eggenstein-Leopoldshafen, 76344
Germany

Ankur Chauhan

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials ( email )

Hermann-von-Helmholtz-Platz 1
Eggenstein-Leopoldshafen, 76344
Germany

Aditya Srinivasan Tirunilai

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials ( email )

Jens Freudenberger

Leibniz Institute for Solid State and Materials Research (IFW) - Institute for Metallic Materials

Helmholtzstr. 20
01069 Dresden
Germany

Alexander Kauffmann

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials ( email )

Martin Heilmaier

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials ( email )

Jarir Aktaa

Karlsruhe Institute of Technology (KIT) - Institute for Applied Materials

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