Cooperative deformation mechanisms in a fatigued CoCrNi multi-principal element alloy: A case of low stacking fault energy

Lu, K and Chauhan, A and Litvinov, D and Schneider, M and Laplanche, G and Aktaa, J (2023) Cooperative deformation mechanisms in a fatigued CoCrNi multi-principal element alloy: A case of low stacking fault energy. In: Journal of the Mechanics and Physics of Solids, 180 .

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Abstract

Multi-principal element alloys (MPEAs) of low stacking fault energies (SFEs) often exhibit outstanding damage tolerance. In contrast to the well-understood monotonic deformation behaviors, fatigue deformation mechanisms of the low-SFE MPEAs remain fundamental questions. Using TEM, this work demonstrated two main dislocation configurations cooperating in an exemplary low-SFE CoCrNi MPEA, namely slip bands and veins/walls/cells, which are usually formed in materials with low- and high-SFEs, respectively. Under low strain amplitude of 0.3, the deformation features are found to include primary and double slip bands (dominating in �71 and 29 grains, respectively). Upon increasing strain amplitude, apart from the slip bands, dislocation substructures formed (i.e., veins/walls/cells present in � 33 and 60 grains under strain amplitude of 0.5 and 0.7, respectively) due to cross slip, despite the alloy's low-SFE. Moreover, the slip bands and walls/cells are found to serve more likely as geometrically necessary dislocations and statistically stored dislocations, respectively. Besides, the constraints from neighboring grains and Copley-Kear effect (rather than grain orientation) were suggested to play more important role in determining these dislocation patterns formation. Lastly, this work evidenced unexpected partial dislocations and stacking faults (in addition to usually observed screw dislocations) shuttling between the walls/cells by planar slip. This predominant planar slip behavior explains well the exceptional damage tolerance of low-SFE MPEAs. These insights can also advance the understanding of fatigue deformation of conventional alloys with low-SFEs. © 2023 Elsevier Ltd

Item Type:	Journal Article
Publication:	Journal of the Mechanics and Physics of Solids
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to the Elsevier Ltd.
Keywords:	Chromium alloys; Cobalt alloys; Fatigue damage; High resolution transmission electron microscopy; Iron alloys; Ternary alloys, Deformation mechanism; Dislocation; Fatigue deformation; Low stacking fault energies; Monotonic deformation; Multi-principal element alloy; Planar slip; Slip band; Strain amplitude; Transmission electron microscopy, Stacking faults
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	08 Nov 2023 03:44
Last Modified:	08 Nov 2023 03:44
URI:	https://eprints.iisc.ac.in/id/eprint/83020

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