Grain-size-dependent microstructure effects on cyclic deformation mechanisms in CoCrFeMnNi high-entropy-alloys

MY Luo and TN Lam and PT Wang and NT Tsou and YJ Chang and R Feng and T Kawasaki and S Harjo and PK Liaw and AC Yeh and SY Lee and J Jain and EW Huang, SCRIPTA MATERIALIA, 210, 114459 (2022).

DOI: 10.1016/j.scriptamat.2021.114459

The effect of grain size on strain-controlled low-cycle fatigue (LCF) properties in the CoCrFeMnNi high-entropy alloys (HEAs) was investigated towards the distinct microstructural developments during cyclic loading at a strain amplitude of +/- 1.0%. A much more prominent secondary cyclic hardening (SCH) behavior at the final deformation stage was observed in the fine-grained (FG, 18 mu m) than in the coarse-grained (CG, 184 mu m) CoCrFeMnNi. In-situ neutron-diffraction and microscopic examination, strongly corroborated by molecular dynamic (MD) simulations, indicated that dislocation activities from planar slip to wavy slip-driven subgrain structures within the grains acted as the primary cyclic-deformation behaviors in the FG CoCrFeMnNi. Differently observed in the cyclic behavior of the CG CoCrFeMnNi was due to a transition from the planar dislocation slip to twinning. Our findings suggested that the fatigue-resistant HEAs can be designed via tuning the microstructure with an optimal range of grain size at a specific strain amplitude. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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