Journal
ACTA MATERIALIA
Volume 149, Issue -, Pages 388-396Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2018.02.037
Keywords
Critical resolved shear stress (CRSS); Medium and high entropy alloys (MHEAs); Twinning nucleation; Density functional theory
Funding
- Swedish Research Council
- Swedish Foundation for Strategic Research
- Swedish Foundation for International Cooperation in Research and Higher Education
- Carl Tryggers Foundation
- Swedens Innovation Agency (VINNOVA) [2014-03374]
- Hungarian Scientific Research Fund [OTKA 109570]
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The CrCoNi-based medium and high entropy alloys (MHEAs) have drawn much attention due to their exceptional mechanical properties at cryogenic temperatures. The twinning critical resolved shear stress (CRSS) is a fundamental parameter for evaluating the strength-ductility properties of MHEAs. Here we construct and apply an extended twinning nucleation Peierls-Nabarro (P-N) model to predict the twinning CRSSes of face-centered cubic (FCC) CrCoNi-based MHEAs. The order of the twinning CRSSes of the selected alloys is CrCoNi > CrCoNiMn > CrCoNiFe > CrCoNiFeMn and the values are 291, 277, 274 and 236 MPa, respectively. These theoretical predictions agree very well with the experimental twinning CRSSes of CrCoNi and CrCoNiFeMn accounting for 260 +/- 30 and 235 +/- 10 MPa, respectively and are perfectly consistent with the strength-ductility properties including yield stress, ultimate tensile stress and uniform elongation for fracture of the FCC CrCoNi-based MHEAs obtained at cryogenic temperatures. The present method offers a first-principle quantum-mechanical tool for optimizing and designing new MHEAs with exceptional mechanical properties. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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