Cutting Edge of High-Entropy Alloy Superconductors from the Perspective of Materials Research

High-entropy alloys (HEAs) are a new class of materials which are being energetically studied around the world. HEAs are characterized by a multicomponent alloy in which five or more elements randomly occupy a crystallographic site. The conventional HEA concept has developed into simple crystal structures such as face-centered-cubic (fcc), body-centered-cubic (bcc) and hexagonal-closed packing (hcp) structures. The highly atomic-disordered state produces many superior mechanical or thermal properties. Superconductivity has been one of the topics of focus in the field of HEAs since the discovery of the bcc HEA superconductor in 2014. A characteristic of superconductivity is robustness against atomic disorder or extremely high pressure. The materials research on HEA superconductors has just begun, and there are open possibilities for unexpectedly finding new phenomena. The present review updates the research status of HEA superconductors. We survey bcc and hcp HEA superconductors and discuss the simple material design. The concept of HEA is extended to materials possessing multiple crystallographic sites; thus, we also introduce multisite HEA superconductors with the CsCl-type, α-Mn-type, A15, NaCl-type, σ-phase and layered structures and discuss the materials research on multisite HEA superconductors. Finally, we present the new perspectives of eutectic HEA superconductors and gum metal HEA superconductors.

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Materials Research on High-Entropy Alloy Superconductors

10.5772/intechopen.99693 ◽

2021 ◽

Author(s):

Jiro Kitagawa ◽

Naoki Ishizu ◽

Shusuke Hamamoto

Keyword(s):

Valence Electron ◽

Superconducting Property ◽

Hexagonal Structure ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Materials Research ◽

Face Centered ◽

Multi Phase ◽

High Degree

The first purpose of this chapter is materials research on face-centered-cubic (fcc) high-entropy alloy (HEA) superconductors, which have not yet been reported. We have investigated several Nb-containing multicomponent alloys. Although we succeeded in obtaining Nb-containing samples with the dominant fcc phases, no superconducting signals appeared in these samples down to 3 K. The microstructure analyses revealed that all samples were multi-phase, but the existence of several new Nb-containing HEA phases was confirmed in them. The second purpose is the report of materials research on the Mn5Si3-type HEA superconductors. This hexagonal structure offers various intermetallic compounds, which often undergo a superconducting state. The Mn5Si3-type HEA is classified into the multisite HEA, which possesses the high degree of freedom in the materials design and is good platform for studying exotic HEA superconductors. We have successfully found a single-phase Mn5Si3-type HEA, which, however, does not show a superconducting property down to 3 K. The attempt of controlling the valence electron count was not successful.

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Vacuum brazing of Al2O3 and 3D printed Ti6Al4V lap-joints using high entropy driven AlZnCuFeSi filler

Scientific Reports ◽

10.1038/s41598-021-87705-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ashutosh Sharma ◽

Byungmin Ahn

Keyword(s):

Strength Properties ◽

Lap Joints ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Plasma Sintering ◽

Spark Plasma ◽

3D Printed ◽

Face Centered ◽

Alloy Filler

AbstractIn this work, we studied the brazing characteristics of Al2O3 and 3D printed Ti–6Al–4V alloys using a novel equiatomic AlZnCuFeSi high entropy alloy filler (HEAF). The HEAF was prepared by mechanical alloying of the constituent powder and spark plasma sintering (SPS) approach. The filler microstructure, wettability and melting point were investigated. The mechanical and joint strength properties were also evaluated. The results showed that the developed AlZnCuFeSi HEAF consists of a dual phase (Cu–Zn, face-centered cubic (FCC)) and Al–Fe–Si rich (base centered cubic, BCC) phases. The phase structure of the (Cu–Al + Ti–Fe–Si)/solid solution promises a robust joint between Al2O3 and Ti–6Al–4V. In addition, the joint interfacial reaction was found to be modulated by the brazing temperature and time because of the altered activity of Ti and Zn. The optimum shear strength reached 84 MPa when the joint was brazed at 1050 °C for 60 s. The results can be promising for the integration of completely different materials using the entropy driven fillers developed in this study.

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Microstructure Refinement by Low-Temperature Ausforming in an Fe-Based Metastable High-Entropy Alloy

Metals ◽

10.3390/met11050742 ◽

2021 ◽

Vol 11 (5) ◽

pp. 742

Author(s):

Motomichi Koyama ◽

Takeaki Gondo ◽

Kaneaki Tsuzaki

Keyword(s):

Low Temperature ◽

Plastic Anisotropy ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Microstructure Refinement ◽

Hexagonal Close Packed ◽

Solution Treated Condition ◽

Solution Treated ◽

Face Centered

The effects of ausforming in an Fe30Mn10Cr10Co high-entropy alloy on the microstructure, hardness, and plastic anisotropy were investigated. The alloy showed a dual-phase microstructure consisting of face-centered cubic (FCC) austenite and hexagonal close-packed (HCP) martensite in the as-solution-treated condition, and the finish temperature for the reverse transformation was below 200 °C. Therefore, low-temperature ausforming at 200 °C was achieved, which resulted in microstructure refinement and significantly increased the hardness. Furthermore, plasticity anisotropy, a common problem in HCP structures, was suppressed by the ausforming treatment. This, in turn, reduced the scatter of the hardness.

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Vanishing of room-temperature slip avalanches in a face-centered-cubic high-entropy alloy by ultrafine grain formation

Scripta Materialia ◽

10.1016/j.scriptamat.2018.06.034 ◽

2018 ◽

Vol 155 ◽

pp. 99-103 ◽

Cited By ~ 4

Author(s):

Jian Qiang ◽

Koichi Tsuchiya ◽

Haoyan Diao ◽

Peter K. Liaw

Keyword(s):

Room Temperature ◽

Ultrafine Grain ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Grain Formation ◽

Face Centered

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Phase Evolution and Microstructure Analysis of CoCrFeNiMo High-Entropy Alloy for Electro-Spark-Deposited Coatings for Geothermal Environment

Coatings ◽

10.3390/coatings9060406 ◽

2019 ◽

Vol 9 (6) ◽

pp. 406 ◽

Cited By ~ 4

Author(s):

Sigrun N. Karlsdottir ◽

Laura E. Geambazu ◽

Ioana Csaki ◽

Andri I. Thorhallsson ◽

Radu Stefanoiu ◽

...

Keyword(s):

Bulk Material ◽

Microstructural Analysis ◽

Electrochemical Corrosion ◽

High Hardness ◽

Phase Evolution ◽

Vacuum Arc ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

Σ Phase ◽

High Entropy

In this work, a CoCrFeNiMo high-entropy alloy (HEA) material was prepared by the vacuum arc melting (VAM) method and used for electro-spark deposition (ESD). The purpose of this study was to investigate the phase evolution and microstructure of the CoCrFeNiMo HEA as as-cast and electro-spark-deposited (ESD) coating to assess its suitability for corrosvie environments encountered in geothermal energy production. The composition, morphology, and structure of the bulk material and the coating were analyzed using scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The hardness of the bulk material was measured to access the mechanical properties when preselecting the composition to be pursued for the ESD coating technique. For the same purpose, electrochemical corrosion tests were performed in a 3.5 wt.% NaCl solution on the bulk material. The results showed the VAM CoCrFeNiMo HEA material had high hardness (593 HV) and low corrosion rates (0.0072 mm/year), which is promising for the high wear and corrosion resistance needed in the harsh geothermal environment. The results from the phase evolution, chemical composition, and microstructural analysis showed an adherent and dense coating with the ESD technique, but with some variance in the distribution of elements in the coating. The crystal structure of the as-cast electrode CoCrFeNiMo material was identified as face centered cubic with XRD, but additional BCC and potentially σ phase was formed for the CoCrFeNiMo coating.

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Dynamic deformation behavior of a face-centered cubic FeCoNiCrMn high-entropy alloy

Science Bulletin ◽

10.1016/j.scib.2018.01.022 ◽

2018 ◽

Vol 63 (6) ◽

pp. 362-368 ◽

Cited By ~ 20

Author(s):

Junyang He ◽

Qi Wang ◽

Husheng Zhang ◽

Lanhong Dai ◽

Toshiji Mukai ◽

...

Keyword(s):

Deformation Behavior ◽

Dynamic Deformation ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Dynamic Deformation Behavior ◽

Face Centered

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Effect of Mn Addition on the Microstructures and Mechanical Properties of CoCrFeNiPd High Entropy Alloy

Entropy ◽

10.3390/e21030288 ◽

2019 ◽

Vol 21 (3) ◽

pp. 288

Author(s):

Yiming Tan ◽

Jinshan Li ◽

Jun Wang ◽

Hongchao Kou

Keyword(s):

Intermetallic Compound ◽

Interface Energy ◽

High Entropy Alloy ◽

Strengthening Effect ◽

Face Centered Cubic ◽

Liquid Interfaces ◽

High Entropy ◽

Single Face ◽

Face Centered ◽

Fcc Phase

CoCrFeNiPdMnx (x = 0, 0.2, 0.4, 0.6, 0.8) high entropy alloys (HEAs) were prepared and characterized. With an increase in Mn addition, the microstructures changed from dendrites (CoCrFeNiPd with a single face-centered-cubic (FCC) phase) to divorced eutectics (CoCrFeNiPdMn0.2 and CoCrFeNiPdMn0.4), to hypoeutectic microstructures (CoCrFeNiPdMn0.6), and finally to seaweed eutectic dendrites (CoCrFeNiPdMn0.8). The addition of Mn might change the interface energy anisotropy of both the FCC/liquid and MnPd-rich intermetallic compound/liquid interfaces, thus forming the seaweed eutectic dendrites. The hardness of the FCC phase was found to be highly related to the solute strengthening effect, the formation of nanotwins and the transition from CoCrFeNiPd-rich to CoCrFeNi-rich FCC phase. Hierarchical nanotwins were found in the MnPd-rich intermetallic compound and a decrease in either the spacing of primary twins or secondary twins led to an increase in hardness. The designing rules of EHEAs were discussed and the pseudo binary method was revised accordingly.

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Tension/compression asymmetry in additive manufactured face centered cubic high entropy alloy

Scripta Materialia ◽

10.1016/j.scriptamat.2016.10.023 ◽

2017 ◽

Vol 129 ◽

pp. 30-34 ◽

Cited By ~ 51

Author(s):

Jithin Joseph ◽

Nicole Stanford ◽

Peter Hodgson ◽

Daniel Mark Fabijanic

Keyword(s):

High Entropy Alloy ◽

Face Centered Cubic ◽

High Entropy ◽

Face Centered ◽

Tension Compression Asymmetry

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Effect of Molybdenum Additives on Corrosion Behavior of (CoCrFeNi)100−xMox High-Entropy Alloys

Entropy ◽

10.3390/e20120908 ◽

2018 ◽

Vol 20 (12) ◽

pp. 908 ◽

Cited By ~ 9

Author(s):

Wenrui Wang ◽

Jieqian Wang ◽

Honggang Yi ◽

Wu Qi ◽

Qing Peng

Keyword(s):

Corrosion Behavior ◽

Compressive Strain ◽

Compressive Yield Strength ◽

High Entropy Alloys ◽

Face Centered Cubic ◽

Σ Phase ◽

High Entropy ◽

Passivation Film ◽

Face Centered ◽

Mo Content

The present work investigates the influence of micro-alloyed Mo on the corrosion behavior of (CoCrFeNi)100−xMox high-entropy alloys. All of the (CoCrFeNi)100−xMox alloys exhibit a single face-centered cubic (FCC) solid solution. However, the (CoCrFeNi)97Mo3 alloy exhibits an ordered sigma (σ) phase enriched in Cr and Mo. With the increase of x (the Mo content) from 1 to 3, the hardness of the (CoCrFeNi)100−xMox alloys increases from 124.8 to 133.6 Vickers hardness (HV), and the compressive yield strength increases from 113.6 MPa to 141.1 MPa, without fracture under about a 60% compressive strain. The potentiodynamic polarization curve in a 3.5% NaCl solution indicates that the addition of Mo has a beneficial effect on the corrosion resistance to some certain extent, opposed to the σ phase. Furthermore, the alloys tend to form a passivation film in the 0.5 M H2SO4 solution in order to inhibit the progress of the corrosion reaction as the Mo content increases.

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