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Mechanism of magnetic transition in FeCrCoNi-based high entropy alloys
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. (ENHETEN EGENSKAPER)ORCID iD: 0000-0001-9317-6205
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2016 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 103, p. 71-74Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

First-principles alloy theory and Monte-Carlo simulations are performed to investigate the magnetic properties of FeCrCoNiAlx high entropy alloys. Results show that face-centered-cubic (fcc) and body-centered-cubic (bcc) structures possess significantly different magnetic behaviors uncovering that the alloy's Curie temperature is controlled by the stability of the Al-induced single phase or fcc-bcc dual-phase. We show that the appearance of the bcc phase with increasing Al content brings about the observed transition from the paramagnetic state for FeCrCoNi to the ferromagnetic state for FeCrCoNiAl at room-temperature. Similar mechanism is predicted to give rise to room-temperature ferromagnetism in FeCrCoNiGa high entropy alloy.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 103, p. 71-74
Keywords [en]
First-principles calculation, High-entropy alloy, Magnetic transition, Monte-Carlo simulation, Aluminum, Calculations, Crystal structure, Entropy, Ferromagnetism, Intelligent systems, Magnetism, Stainless steel, Body-centered cubic (bcc) structure, Face-centered cubic, Ferromagnetic state, High entropy alloys, Magnetic transitions, Paramagnetic state, Room temperature ferromagnetism, Monte Carlo methods
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-186897DOI: 10.1016/j.matdes.2016.04.053ISI: 000376892300008Scopus ID: 2-s2.0-84964558121OAI: oai:DiVA.org:kth-186897DiVA, id: diva2:929391
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-16 Last updated: 2018-06-01Bibliographically approved
In thesis
1. Theoretical Investigations of High-Entropy Alloys
Open this publication in new window or tab >>Theoretical Investigations of High-Entropy Alloys
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

High-entropy alloys (HEAs) are composed of multi-principal elements with equal or near-equal concentrations, which open up a vast compositional space for alloy design. Based on first-principle theory, we focus on the fundamental characteristics of the reported HEAs, as well as on the optimization and prediction of alternative HEAs with promising technological applications.

The ab initio calculations presented in the thesis confirm and predict the relatively structural stability of different HEAs, and discuss the composition and temperature-induced phase transformations. The elastic behavior of several HEAs are evaluated through the single-crystal and polycrystalline elastic moduli by making use of a series of phenomenological models. The competition between dislocation full slip, twinning, and martensitic transformation during plastic deformation of HEAs with face-centered cubic phase are analyzed by studying the generalized stacking fault energy. The magnetic moments and magnetic exchange interactions for selected HEAs are calculated, and then applied in the Heisenberg Hamiltonian model in connection with Monte-Carlo simulations to get further insight into the magnetic characteristics including Curie point. The Debye-Grüneisen model is used to estimate the temperature variation of the thermal expansion coefficient.

This work provides specific theoretical points of view to try to understand the intrinsic physical mechanisms behind the observed complex behavior in multi-component systems, and reveals some opportunities for designing and optimizing the properties of materials

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 35
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-218162 (URN)978-91-7729-544-0 (ISBN)
Presentation
2017-11-15, konferensrummet, Brinellvägen 23, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20171127

Available from: 2017-11-27 Created: 2017-11-23 Last updated: 2017-11-27Bibliographically approved
2. Quantum-Mechanical Modeling of High-Entropy Alloys
Open this publication in new window or tab >>Quantum-Mechanical Modeling of High-Entropy Alloys
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

High-entropy alloys (HEAs) consisting of multi-principal elements open up a near-infinite compositional space for materials design. Extensive attention has been put on HEAs, and interesting structural, physical and chemical properties are being continuously revealed. Based on first-principle theory, here we focus on the fundamental characteristics of HEAs, as well as on the optimization and prediction of alternative alloy with promising technological applications.

The relative phase stability of different-types of HEAs is investigated from the minimum of structural energy, and the composition-, temperature-, and ordering-induced phase transformations are presented. The elastic properties are discussed through the single-crystal and polycrystalline elastic moduli by making use of a series of phenomenological models. The competition between full slip, twinning, and stacking fault in face-centered cubic HEAs is analyzed by studying the generalized stacking fault energy. The magnetic characteristics are provided through the Heisenberg Hamiltonian model in connection with Monte-Carlo simulation, and the Curie temperature of a large number of cubic HEAs is mapped out with the help of mean-filed approximation. The thermal expansion behavior is estimated by using the Debye-Grüneisen model.

This work provides some fundamental and pioneering theoretical points of view to understand the intrinsic physical mechanisms in HEAs, and reveals alternative opportunities for optimizing and designing properties of materials. The challenge of comprehending the observed complex behavior behind the multi-component nature of HEAs is great, on the other hand, the potential to enhance the underlying theoretical understanding is remarkable.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2018. p. 43
Series
TRITA-ITM-AVL ; 2018:35
National Category
Condensed Matter Physics
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-229063 (URN)978-91-7729-765-9 (ISBN)
Public defence
2018-06-12, B2, Brinellvägen 23, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2018-06-01 Created: 2018-05-31 Last updated: 2018-06-01Bibliographically approved

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Schönecker, StephanBergqvist, LarsVitos, Levente

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