Deformation Mechanisms in High Entropy Alloys

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: closed (30 May 2021) | Viewed by 9737

Special Issue Editor


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Guest Editor
Materials and Metallurgical Engineering, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801, USA
Interests: computational materials science; atomistic simulations; dislocation plasticity; phase trasformations; microstrucutral characterization

Special Issue Information

Dear Colleagues,

High-Entropy alloys (HEAs), for the first time, have allowed us to “map” previously unexplored regions in multidimensional composition phase-space. This extraordinary access to the phase-space provides exciting opportunities to not only engineer novel microstructures but also manipulate deformation mechanisms that directly impact the strength–ductility trade-off. Examples of such mechanisms include twining-induced plasticity (TWIP), transformation-induced plasticity (TRIP), interfacial strengthening mechanisms, stacking faults, precipitate/dislocation interactions, dislocation/dislocation interactions, etc. Even the structure of dislocation cores in a multielement environment is being revisited, because the notion of Peierls stress for single elements needs to be adapted to multicomponent systems. Currently, there is a worldwide effort to catalogue deformation mechanisms in multitudes of HEA compositions and to develop models to computationally predict and understand such mechanisms.

The purpose of the Special Issue “Deformation mechanisms in High-Entropy Alloys” is to provide an international forum for such ground-breaking studies. We welcome scientific contributions, such as full-length articles, involving experimental, theoretical, and computational studies on deformation mechanisms in HEAs. Scientists working in a wide range of disciplines are invited to contribute to this cause.

The keywords listed below cover a broad range of topics within the realm of HEA deformation. However, innovative topics that fall outside the list but are connected to HEAs will be welcomed.

Dr. Deep Choudhuri
Guest Editor

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Keywords

  • High-entropy or complex concentrated alloys
  • Dislocation plasticity
  • TRIP/TWIP
  • Strengthening mechanism
  • Interface mediated plasticity
  • Defect interaction and generation
  • Stacking fault
  • Dislocation core structures
  • Strength–ductility tradeoff

Published Papers (3 papers)

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Research

13 pages, 5298 KiB  
Article
Influence of Temperature and Plastic Strain on Deformation Mechanisms and Kink Band Formation in Homogenized HfNbTaTiZr
by Hans Chen, Theresa Hanemann, Sascha Seils, Daniel Schliephake, Aditya Srinivasan Tirunilai, Martin Heilmaier, Klaus-Peter Weiss and Alexander Kauffmann
Crystals 2021, 11(2), 81; https://doi.org/10.3390/cryst11020081 - 21 Jan 2021
Cited by 6 | Viewed by 2460
Abstract
Due to its outstanding ductility over a large temperature range, equiatomic HfNbTaTiZr is well-suited for investigating the influence of temperature and plastic strain on deformation mechanisms in concentrated, body centered cubic solid solutions. For this purpose, compression tests in a temperature range from [...] Read more.
Due to its outstanding ductility over a large temperature range, equiatomic HfNbTaTiZr is well-suited for investigating the influence of temperature and plastic strain on deformation mechanisms in concentrated, body centered cubic solid solutions. For this purpose, compression tests in a temperature range from 77 up to 1073 K were performed and terminated at varying plastic strains for comparison of plastic deformation behavior. The microstructure and chemical homogeneity of a homogenized HfNbTaTiZr ingot were evaluated on different length scales. The compression tests reveal that test temperature significantly influences yield strength as well as work hardening behavior. Electron backscatter diffraction aids in shedding light on the acting deformation mechanisms at various temperatures and strains. It is revealed that kink band formation contributes to plastic deformation only in a certain temperature range. Additionally, the kink band misorientation angle distribution significantly differs at varying plastic strains. Full article
(This article belongs to the Special Issue Deformation Mechanisms in High Entropy Alloys)
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14 pages, 4487 KiB  
Article
Deep Learning-Based Hardness Prediction of Novel Refractory High-Entropy Alloys with Experimental Validation
by Uttam Bhandari, Congyan Zhang, Congyuan Zeng, Shengmin Guo, Aashish Adhikari and Shizhong Yang
Crystals 2021, 11(1), 46; https://doi.org/10.3390/cryst11010046 - 7 Jan 2021
Cited by 19 | Viewed by 4183
Abstract
Hardness is an essential property in the design of refractory high entropy alloys (RHEAs). This study shows how a neural network (NN) model can be used to predict the hardness of a RHEA, for the first time. We predicted the hardness of several [...] Read more.
Hardness is an essential property in the design of refractory high entropy alloys (RHEAs). This study shows how a neural network (NN) model can be used to predict the hardness of a RHEA, for the first time. We predicted the hardness of several alloys, including the novel C0.1Cr3Mo11.9Nb20Re15Ta30W20 using the NN model. The hardness predicted from the NN model was consistent with the available experimental results. The NN model prediction of C0.1Cr3Mo11.9Nb20Re15Ta30W20 was verified by experimentally synthesizing and investigating its microstructure properties and hardness. This model provides an alternative route to determine the Vickers hardness of RHEAs. Full article
(This article belongs to the Special Issue Deformation Mechanisms in High Entropy Alloys)
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11 pages, 2689 KiB  
Article
Designing (Ultra)Fine-Grained High-Entropy Alloys by Spark Plasma Sintering and Equal-Channel Angular Pressing
by Lisa-Marie Rymer, Thomas Lindner, Philipp Frint, Martin Löbel and Thomas Lampke
Crystals 2020, 10(12), 1157; https://doi.org/10.3390/cryst10121157 - 18 Dec 2020
Cited by 8 | Viewed by 2322
Abstract
Single-phase, face-centered cubic (FCC) high-entropy alloys (HEA) are promising materials for future applications. In order to improve the mechanical properties, especially the tensile strength of these materials, this study focuses on the combination of spark plasma sintering (SPS) and equal-channel angular pressing (ECAP). [...] Read more.
Single-phase, face-centered cubic (FCC) high-entropy alloys (HEA) are promising materials for future applications. In order to improve the mechanical properties, especially the tensile strength of these materials, this study focuses on the combination of spark plasma sintering (SPS) and equal-channel angular pressing (ECAP). The initial fine-grained microstructure produced by SPS is further refined by ECAP in a 90°-die. Optical microscopy and electron backscatter diffraction (EBSD) confirm this considerable grain refinement, leads to a grain size below 1 µm after 1 ECAP pass. An alternating arrangement of fine-grained areas and much coarser regions, aligned under an angle of approximately 27°, is found. Moreover, a first microstructural investigation of the twin structure is conducted. The mechanical behavior was investigated by hardness measurements and tensile testing. Both the hardness and tensile strength are remarkably increased after ECAP. In contrast, the uniform elongation and elongation at fracture are significantly reduced due to the strengthening mechanisms of strain hardening and grain refinement. It is concluded that the combination of SPS and ECAP is an attractive approach for designing (ultra)fine-grained HEAs with superior properties. The investigated techniques could be applied to understand the underlying microstructural mechanisms. Full article
(This article belongs to the Special Issue Deformation Mechanisms in High Entropy Alloys)
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