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Entropy 2018, 20(9), 655; https://doi.org/10.3390/e20090655

Impact of Chemical Fluctuations on Stacking Fault Energies of CrCoNi and CrMnFeCoNi High Entropy Alloys from First Principles

1
Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany
2
Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan
3
Materials Science and Engineering, Delft University of Technology, 2628 CD Delft, The Netherlands
4
Center for Elements Strategy Initiative for Structure Materials (ESISM), Kyoto University, Kyoto 606-8501, Japan
5
Center for Materials Research by Information Integration, National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan
6
Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
*
Author to whom correspondence should be addressed.
Received: 13 August 2018 / Revised: 28 August 2018 / Accepted: 29 August 2018 / Published: 30 August 2018
(This article belongs to the Special Issue New Advances in High-Entropy Alloys)
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Abstract

Medium and high entropy alloys (MEAs and HEAs) based on 3d transition metals, such as face-centered cubic (fcc) CrCoNi and CrMnFeCoNi alloys, reveal remarkable mechanical properties. The stacking fault energy (SFE) is one of the key ingredients that controls the underlying deformation mechanism and hence the mechanical performance of materials. Previous experiments and simulations have therefore been devoted to determining the SFEs of various MEAs and HEAs. The impact of local chemical environment in the vicinity of the stacking faults is, however, still not fully understood. In this work, we investigate the impact of the compositional fluctuations in the vicinity of stacking faults for two prototype fcc MEAs and HEAs, namely CrCoNi and CrMnFeCoNi by employing first-principles calculations. Depending on the chemical composition close to the stacking fault, the intrinsic SFEs vary in the range of more than 150 mJ/m 2 for both the alloys, which indicates the presence of a strong driving force to promote particular types of chemical segregations towards the intrinsic stacking faults in MEAs and HEAs. Furthermore, the dependence of the intrinsic SFEs on local chemical fluctuations reveals a highly non-linear behavior, resulting in a non-trivial interplay of local chemical fluctuations and SFEs. This sheds new light on the importance of controlling chemical fluctuations via tuning, e.g., the annealing condition to obtain the desired mechanical properties for MEAs and HEAs. View Full-Text
Keywords: high-entropy alloy; stacking-fault energy; density functional theory high-entropy alloy; stacking-fault energy; density functional theory
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Ikeda, Y.; Körmann, F.; Tanaka, I.; Neugebauer, J. Impact of Chemical Fluctuations on Stacking Fault Energies of CrCoNi and CrMnFeCoNi High Entropy Alloys from First Principles. Entropy 2018, 20, 655.

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