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

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, σ y, the activation volume varies from ~60 b3 at 77 K 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 σ - σ 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. Lastly, 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.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ; ORCiD logo [5]
  1. Ruhr-Univ., Bochum (Germany)
  2. Univ. of Poitiers, Futuroscope Cedex (France)
  3. Aix-Marseille Univ., Marseille (France)
  4. EPRL, Lausanne (Switzerland)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 143; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; High-entropy alloys; CoCrFeMnNi plastic deformation mechanisms; Stress relaxation; Dislocations; Activation volume
OSTI Identifier:
1409262

Laplanche, Guillaume, Bonneville, J., Varvenne, C., Curtin, W. A., and George, Easo P.. Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy. United States: N. p., Web. doi:10.1016/j.actamat.2017.10.014.
Laplanche, Guillaume, Bonneville, J., Varvenne, C., Curtin, W. A., & George, Easo P.. Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy. United States. doi:10.1016/j.actamat.2017.10.014.
Laplanche, Guillaume, Bonneville, J., Varvenne, C., Curtin, W. A., and George, Easo P.. 2017. "Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy". United States. doi:10.1016/j.actamat.2017.10.014. https://www.osti.gov/servlets/purl/1409262.
@article{osti_1409262,
title = {Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy},
author = {Laplanche, Guillaume and Bonneville, J. and Varvenne, C. and Curtin, W. A. and George, Easo P.},
abstractNote = {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, σy, the activation volume varies from ~60 b3 at 77 K to ~360 b3 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 σ - σy (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. Lastly, 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.},
doi = {10.1016/j.actamat.2017.10.014},
journal = {Acta Materialia},
number = C,
volume = 143,
place = {United States},
year = {2017},
month = {10}
}