A Review of the Latest Developments in the Field of Refractory High-Entropy Alloys

Srikanth, M.; Annamalai, A. Raja; Muthuchamy, A.; Jen, Chun-Ping

doi:10.3390/cryst11060612

Cited by 68 publications

(17 citation statements)

References 75 publications

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“…The fracture toughness property goal necessitates the new materials to show some degree of metallic behaviour to distinguish them from ceramic UHTMs [ 3 ]. Research and development work is in progress to find metallic UHTMs that can be used in structural engineering applications [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”

Section: Introductionmentioning

confidence: 99%

On the Stability of Complex Concentrated (CC)/High Entropy (HE) Solid Solutions and the Contamination with Oxygen of Solid Solutions in Refractory Metal Intermetallic Composites (RM(Nb)ICs) and Refractory Complex Concentrated Alloys (RCCAs)

Tsakiropoulos

2022

Materials

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In as-cast (AC) or heat-treated (HT) metallic ultra-high temperature materials often “conventional” and complex-concentrated (CC) or high-entropy (HE) solid solutions (sss) are observed. Refractory metal containing bcc sss also are contaminated with oxygen. This paper studied the stability of CC/HE Nbss and the contamination with oxygen of Nbss in RM(INb)ICs, RM(Nb)ICs/RCCAs and RM(Nb)ICs/RHEAs. “Conventional” and CC/HE Nbss were compared. “Conventional” Nbss can be Ti-rich only in AC alloys. Ti-rich Nbss is not observed in HT alloys. In B containing alloys the Ti-rich Nbss is usually CC/HE. The CC/HE Nbss is stable in HT alloys with simultaneous addition of Mo, W with Hf, Ge+Sn. The implications for alloy design of correlations between the parameter δ of “conventional” and CC/HE Nbss with the B or the Ge+Sn concentration in the Nbss and of relationships of other solutes with the B or Ge+Sn content are discussed. The CC/HE Nbss has low Δχ, VEC and Ω and high ΔSmix, |ΔHmix| and δ parameters, and is formed in alloys that have high entropy of mixing. These parameters are compared with those of single-phase bcc ss HEAs and differences in ΔHmix, δ, Δχ and Ω, and similarities in ΔSmix and VEC are discussed. Relationships between the parameters of alloy and “conventional” Nbss also apply for CC/HE Nbss. The parameters δss and Ωss, and VECss and VECalloy can differentiate between types of alloying additions and their concentrations and are key regarding the formation or not of CC/HE Nbss. After isothermal oxidation at a pest temperature (800 oC/100 h) the contaminated with oxygen Nbss in the diffusion zone is CC/HE Nbss, whereas the Nbss in the bulk can be “conventional” Nbss or CC/HE Nbss. The parameters of “uncontaminated” and contaminated with oxygen sss are linked with linear relationships. There are correlations between the oxygen concentration in contaminated sss in the diffusion zone and the bulk of alloys with the parameters ΔχNbss, δNbss and VECNbss, the values of which increase with increasing oxygen concentration in the ss. The effects of contamination with oxygen of the near surface areas of a HT RM(Nb)IC with Al, Cr, Hf, Si, Sn, Ti and V additions and a high vol.% Nbss on the hardness and Young’s modulus of the Nbss, and contributions to the hardness of the Nbss in B free or B containing alloys are discussed. The hardness and Young’s modulus of the bcc ss increased linearly with its oxygen concentration and the change in hardness and Young’s modulus due to contamination increased linearly with [O]2/3.

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Section: Introductionmentioning

confidence: 99%

On the Stability of Complex Concentrated (CC)/High Entropy (HE) Solid Solutions and the Contamination with Oxygen of Solid Solutions in Refractory Metal Intermetallic Composites (RM(Nb)ICs) and Refractory Complex Concentrated Alloys (RCCAs)

Tsakiropoulos

2022

Materials

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“…Powder metallurgy has been used to prepare bulk RHEAs through milling, blending, pressing and sintering of pre-alloyed or raw powders [ 51 ]. After ball milling, spark plasma sintering (SPS) is the most effective sintering method to fabricate RHEA specimens [ 52 ]. SPS is a pressurized sintering method that uses DC pulse current to directly sinter with electricity, which can quickly densify HEA powders.…”

Section: The Fabrication and Processing Techniques Of W-containing Rheasmentioning

confidence: 99%

Recent Advances in W-Containing Refractory High-Entropy Alloys—An Overview

Chen

Chen²,

Liu³

et al. 2022

Entropy

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During the past decade, refractory high-entropy alloys (RHEA) have attracted great attention of scientists, engineers and scholars due to their excellent mechanical and functional properties. The W-containing RHEAs are favored by researchers because of their great application potential in aerospace, marine and nuclear equipment and other high-temperature, corrosive and irradiated fields. In this review, more than 150 W-containing RHEAs are summarized and compared. The preparation techniques, microstructure and mechanical properties of the W-containing RHEAs are systematically outlined. In addition, the functional properties of W-containing RHEAs, such as oxidation, corrosion, irradiation and wear resistance have been elaborated and analyzed. Finally, the key issues faced by the development of W-containing RHEAs in terms of design and fabrication techniques, strengthening and deformation mechanisms, and potential functional applications are proposed and discussed. Future directions for the investigation and application of W-containing RHEAs are also suggested. The present work provides useful guidance for the development, processing and application of W-containing RHEAs and the RHEA components.

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“…This is because the manufacturing process produces less scrap compared to other processes, can use a wide range of polymer types, and some works have analyzed the reprocessing of these materials [6] , [7] , [8] , [9] . Moreover, this is a promising process to be widely used in the automotive, medical, and aerospace industries, and for the same reason, new materials have been emerging to suppress these requirements [10] , [11] . However, producing the filament requires an extruder, which is expensive and the industrial one has a considerable size.…”

Section: Hardware In Contextmentioning

confidence: 99%