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Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy

G. Laplanche J. Bonneville 1 C. Varvenne 2 W. A. Curtin E. P. George
1 PDP - Physique des Défauts et de la Plasticité PDP
Département Physique et Mécanique des Matériaux - Département Physique et Mécanique des Matériaux
Abstract : To reveal the operating mechanisms of plastic deformation in an FCC high-entropy alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, sigma(y), the activation volume varies from similar to 60 b(3) at 77 K to similar to 360 b(3) at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with sigma - sigma(y) (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-solution-strengthened alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Submitted on : Friday, January 19, 2018 - 9:36:50 AM
Last modification on : Wednesday, November 3, 2021 - 6:35:17 AM

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G. Laplanche, J. Bonneville, C. Varvenne, W. A. Curtin, E. P. George. Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy. Acta Materialia, Elsevier, 2018, 143, pp.257-264. ⟨10.1016/j.actamat.2017.10.014⟩. ⟨hal-01688044⟩

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