Journal articles: 'High entropy alloys or Complex concentrated alloys'

1

Gorsse, Stéphane, Jean-Philippe Couzinié, and Daniel B. Miracle. "From high-entropy alloys to complex concentrated alloys." Comptes Rendus Physique 19, no. 8 (December 2018): 721–36. http://dx.doi.org/10.1016/j.crhy.2018.09.004.

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Stepanov, Nikita, and Sergey Zherebtsov. "Design of High-Entropy Alloys." Metals 12, no. 6 (June 11, 2022): 1003. http://dx.doi.org/10.3390/met12061003.

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Gorsse, S., M. H. Nguyen, O. N. Senkov, and D. B. Miracle. "Database on the mechanical properties of high entropy alloys and complex concentrated alloys." Data in Brief 21 (December 2018): 2664–78. http://dx.doi.org/10.1016/j.dib.2018.11.111.

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Mishra, R. S., N. Kumar, and M. Komarasamy. "Lattice strain framework for plastic deformation in complex concentrated alloys including high entropy alloys." Materials Science and Technology 31, no. 10 (April 16, 2015): 1259–63. http://dx.doi.org/10.1179/1743284715y.0000000050.

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Gwalani, Bharat, Stephane Gorsse, Deep Choudhuri, Mark Styles, Yufeng Zheng, Rajiv S. Mishra, and Rajarshi Banerjee. "Modifying transformation pathways in high entropy alloys or complex concentrated alloys via thermo-mechanical processing." Acta Materialia 153 (July 2018): 169–85. http://dx.doi.org/10.1016/j.actamat.2018.05.009.

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Ayyagari, Aditya, Vahid Hasannaeimi, Harpreet Grewal, Harpreet Arora, and Sundeep Mukherjee. "Corrosion, Erosion and Wear Behavior of Complex Concentrated Alloys: A Review." Metals 8, no. 8 (August 3, 2018): 603. http://dx.doi.org/10.3390/met8080603.

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There has been tremendous interest in recent years in a new class of multi-component metallic alloys that are referred to as high entropy alloys, or more generally, as complex concentrated alloys. These multi-principal element alloys represent a new paradigm in structural material design, where numerous desirable attributes are achieved simultaneously from multiple elements in equimolar (or near equimolar) proportions. While there are several review articles on alloy development, microstructure, mechanical behavior, and other bulk properties of these alloys, then there is a pressing need for an overview that is focused on their surface properties and surface degradation mechanisms. In this paper, we present a comprehensive view on corrosion, erosion and wear behavior of complex concentrated alloys. The effect of alloying elements, microstructure, and processing methods on the surface degradation behavior are analyzed and discussed in detail. We identify critical knowledge gaps in individual reports and highlight the underlying mechanisms and synergy between the different degradation routes.

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Derimow, Nicholas, and Reza Abbaschian. "Liquid Phase Separation in High-Entropy Alloys—A Review." Entropy 20, no. 11 (November 20, 2018): 890. http://dx.doi.org/10.3390/e20110890.

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It has been 14 years since the discovery of the high-entropy alloys (HEAs), an idea of alloying which has reinvigorated materials scientists to explore unconventional alloy compositions and multicomponent alloy systems. Many authors have referred to these alloys as multi-principal element alloys (MPEAs) or complex concentrated alloys (CCAs) in order to place less restrictions on what constitutes an HEA. Regardless of classification, the research is rooted in the exploration of structure-properties and processing relations in these multicomponent alloys with the aim to surpass the physical properties of conventional materials. More recent studies show that some of these alloys undergo liquid phase separation, a phenomenon largely dictated by low entropy of mixing and positive mixing enthalpy. Studies posit that positive mixing enthalpy of the binary and ternary components contribute substantially to the formation of liquid miscibility gaps. The objective of this review is to bring forth and summarize the findings of the experiments which detail liquid phase separation (LPS) in HEAs, MPEAs, and CCAs and to draw parallels between HEAs and the conventional alloy systems which undergo liquid-liquid separation. Positive mixing enthalpy if not compensated by the entropy of mixing will lead to liquid phase separation. It appears that Co, Ni, and Ti promote miscibility in HEAs/CCAs/MPEAs while Cr, V, and Nb will raise the miscibility gap temperature and increase LPS. Moreover, addition of appropriate amounts of Ni to CoCrCu eliminates immiscibility, such as in cases of dendritically solidifying CoCrCuNi, CoCrCuFeNi, and CoCrCuMnNi.

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Mitrica, Dumitru, Ioana Cristina Badea, Mihai Tudor Olaru, Beatrice Adriana Serban, Denisa Vonica, Marian Burada, Victor Geanta, et al. "Modeling and Experimental Results of Selected Lightweight Complex Concentrated Alloys, before and after Heat Treatment." Materials 13, no. 19 (September 29, 2020): 4330. http://dx.doi.org/10.3390/ma13194330.

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Lightweight complex concentrated alloys (LWCCA), composed of elements with low density, have become a great area of interest due to the high demand in a large number of applications. Previous research on LWCCAs was focused on high entropy multicomponent alloy systems that provide low density and high capability of solid solution formation. Present research introduces two alloy systems (Al-Cu-Si-Zn-Mg and Al-Mn-Zn-Mg-Si) that contain readily available and inexpensive starting materials and have potential for solid solution formation structures. For the selection of appropriate compositions, authors applied semi-empirical criteria and optimization software. Specialized modeling software (MatCalc) was used to determine probable alloy structures by CALPHAD, non-equilibrium solidification and kinetic simulations. The selected alloys were prepared in an induction furnace. Specimens were heat treated to provide stable structures. Physicochemical, microstructural, and mechanical characterization was performed for the selected alloy compositions. Modeling and experimental results indicated solid solution-based structures in the as-cast and heat-treated samples. Several intermetallic phases were present at higher concentrations than in the conventional alloys. Alloys presented a brittle structure with compression strength of 486–618 MPa and hardness of 268–283 HV. The potential for uniform intermetallic phase distribution in the selected alloys makes them good candidates for applications were low weight and high resistance is required.

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Tsakiropoulos, Panos. "Refractory Metal Intermetallic Composites, High-Entropy Alloys, and Complex Concentrated Alloys: A Route to Selecting Substrate Alloys and Bond Coat Alloys for Environmental Coatings." Materials 15, no. 8 (April 12, 2022): 2832. http://dx.doi.org/10.3390/ma15082832.

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This paper considers metallic ultrahigh-temperature materials (UHTMs) and the alloying behaviour and properties of alloys and their phases by using maps of the parameters δ (based on atomic size), Δχ (based on electronegativity), and valence electron concentration (VEC), and discusses what connects and what differentiates material groups in the maps. The formation of high-entropy or complex concentrated intermetallics, namely 5-3 silicides, C14 Laves and A15 compounds, and bcc solid solutions and eutectics in metallic UHTMs and their co-existence with “conventional” phases is discussed. The practicality of maps for the design/selection of substrate alloys is deliberated upon. The need for environmental coatings for metallic UHTMs was considered and the design of bond coat alloys is discussed by using relevant maps.

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Xing, Qiuwei, Xu Zhu, Guoju Li, Xinzhe Zhang, Xinfang Zhang, and Zhanxing Chen. "Microstructure and Mechanical Properties of Ni-Based Complex Concentrated Alloys under Radiation Environment." Crystals 12, no. 9 (September 19, 2022): 1322. http://dx.doi.org/10.3390/cryst12091322.

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The rapid development of fusion-reactor technology calls for excellent anti-irradiation materials. Complex concentrated alloy (CCA) is a newly proposed alloy concept which is a promising candidate of nuclear fusion materials by virtue of its great phase stability under irradiation. This article summarizes anti-radiation mechanism and the microstructure evolution in HEAs. The effective factors on irradiation behavior of HEAs, including entropy, sample size and temperature, are discussed. Finally, the article introduces the potential ways to solve the economic and environmental problems which the HEAs faced for their applications in the future. In summary, the HEAs usually show better irradiation resistance than traditional alloys, such as less swelling, smaller size of defects, and more stable mechanical properties. One possible reason for the irradiation resistance of HEA is the self-healing effect induced by the high-entropy and atomic-level stress among the metal atoms. The activation of the principal element should be considered when selecting components of HEA, and the high throughput technique is a potential way to reduce the design and fabrication cost of HEAs. It is reasonable to expect that coming years will see the application of novel HEAs in fusion reactors.

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Gorsse, Stéphane, and Franck Tancret. "Current and emerging practices of CALPHAD toward the development of high entropy alloys and complex concentrated alloys." Journal of Materials Research 33, no. 19 (June 4, 2018): 2899–923. http://dx.doi.org/10.1557/jmr.2018.152.

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Leong, Zhaoyuan, Nicola Morley, and Russell Goodall. "Dilatational strain biplots against enthalpy of mixing for predicting high-entropy alloys and complex concentrated alloys phase stability." Materials Chemistry and Physics 262 (April 2021): 124241. http://dx.doi.org/10.1016/j.matchemphys.2021.124241.

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13

Simić, Lidija, Rebeka Rudolf, Peter Majerič, and Ivan Anžel. "Cast Microstructure of a Complex Concentrated Noble Alloy Ag20Pd20Pt20Cu20Ni20." Materials 15, no. 14 (July 8, 2022): 4788. http://dx.doi.org/10.3390/ma15144788.

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A complex concentrated noble alloy (CCNA) of equiatomic composition (Ag20Pd20Pt20Cu20Ni20–20 at. %) was studied as a potential high—performance material. The equiatomic composition was used so that this alloy could be classified in the subgroup of high—entropy alloys (HEA). The alloy was prepared by induction melting at atmospheric pressure, using high purity elements. The degree of metastability of the cast state was estimated on the basis of changes in the microstructure during annealing at high temperatures in a protective atmosphere of argon. Characterisation of the metallographically prepared samples was performed using a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), differential scanning calorimetry (DSC), and X–ray diffraction (XRD). Observation shows that the microstructure of the CCNA is in a very metastable state and multiphase, consisting of a continuous base of dendritic solidification—a matrix with an interdendritic region without other microstructural components and complex spheres. A model of the probable flow of metastable solidification of the studied alloy was proposed, based on the separation of L—melts into L1 (rich in Ni) and L2 (rich in Ag). The phenomenon of liquid phase separation in the considered CCNA is based on the monotectic reaction in the Ag−Ni system.

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14

Roy, Indranil, Pratik K. Ray, and Ganesh Balasubramanian. "Modeling Oxidation of AlCoCrFeNi High-Entropy Alloy Using Stochastic Cellular Automata." Entropy 24, no. 9 (September 8, 2022): 1263. http://dx.doi.org/10.3390/e24091263.

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Together with the thermodynamics and kinetics, the complex microstructure of high-entropy alloys (HEAs) exerts a significant influence on the associated oxidation mechanisms in these concentrated solid solutions. To describe the surface oxidation in AlCoCrFeNi HEA, we employed a stochastic cellular automata model that replicates the mesoscale structures that form. The model benefits from diffusion coefficients of the principal elements through the native oxides predicted by using molecular simulations. Through our examination of the oxidation behavior as a function of the alloy composition, we corroborated that the oxide scale growth is a function of the complex chemistry and resultant microstructures. The effect of heat treatment on these alloys is also simulated by using reconstructed experimental micrographs. When they are in a single-crystal structure, no segregation is noted for α-Al2O3 and Cr2O3, which are the primary scale-forming oxides. However, a coexistent separation between Al2O3 and Cr2O3 oxide scales with the Al-Ni- and Cr-Fe-rich regions is predicted when phase-separated microstructures are incorporated into the model.

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Tsakiropoulos, Panos. "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)." Materials 15, no. 23 (November 28, 2022): 8479. http://dx.doi.org/10.3390/ma15238479.

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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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Tsakiropoulos, Panos. "Refractory Metal (Nb) Intermetallic Composites, High Entropy Alloys, Complex Concentrated Alloys and the Alloy Design Methodology NICE—Mise-en-scène † Patterns of Thought and Progress." Materials 14, no. 4 (February 19, 2021): 989. http://dx.doi.org/10.3390/ma14040989.

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The paper reflects on the usefulness of the alloy design methodology NICE (Niobium Intermetallic Composite Elaboration) for the development of new Nb-containing metallic ultra-high-temperature materials (UHTMs), namely refractory metal (Nb) intermetallic composites (RM(Nb)ICs), refractory high entropy alloys (RHEAs) and refractory complex concentrated alloys (RCCAs), in which the same phases can be present, specifically bcc solid solution(s), M5Si3 silicide(s) and Laves phases. The reasons why a new alloy design methodology was sought and the foundations on which NICE was built are discussed. It is shown that the alloying behavior of RM(Nb)ICs, RHEAs and RCCAs can be described by the same parameters. The practicality of parameter maps inspired by NICE for describing/understanding the alloying behavior and properties of alloys and their phases is demonstrated. It is described how NICE helps the alloy developer to understand better the alloys s/he develops and what s/he can do and predict (calculate) with NICE. The paper expands on RM(Nb)ICs, RHEAs and RCCAs with B, Ge or Sn, the addition of which and the presence of A15 compounds is recommended in RHEAs and RCCAs to achieve a balance of properties.

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Zacharis, Eleftherios, Claire Utton, and Panos Tsakiropoulos. "A Study of the Effects of Hf and Sn on the Microstructure, Hardness and Oxidation of Nb-18Si Silicide-Based Alloys-RM(Nb)ICs with Ti Addition and Comparison with Refractory Complex Concentrated Alloys (RCCAs)." Materials 15, no. 13 (June 30, 2022): 4596. http://dx.doi.org/10.3390/ma15134596.

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In this paper, we present a systematic study of the as-cast and heat-treated microstructures of three refractory metal intermetallic composites based on Nb (i.e., RM(Nb)ICs), namely the alloys EZ2, EZ5, and EZ6, and one RM(Nb)IC/RCCA (refractory complex concentrated alloy), namely the alloy EZ8. We also examine the hardness and phases of these alloys. The nominal compositions (at.%) of the alloys were Nb-24Ti-18Si-5Hf-5Sn (EZ2), Nb-24Ti-18Si-5Al-5Hf-5Sn (EZ5), Nb-24Ti-18Si-5Cr-5Hf-5Sn (EZ6), and Nb-24Ti-18Si-5Al-5Cr-5Hf-5Sn (EZ8). All four alloys had density less than 7.3 g/cm3. The Nbss was stable in EZ2 and EZ6 and the C14-NbCr2 Laves phase in EZ6 and EZ8. In all four alloys, the A15-Nb3X (X = Al,Si,Sn) and the tetragonal and hexagonal Nb5Si3 were stable. Eutectics of Nbss + Nb5Si3 and Nbss + C14-NbCr2 formed in the cast alloys without and with Cr addition, respectively. In all four alloys, Nb3Si was not formed. In the heat-treated alloys EZ5 and EZ8, A15-Nb3X precipitated in the Nb5Si3 grains. The chemical compositions of Nbss + C14-NbCr2 eutectics and some Nb5Si3 silicides and lamellar microstructures corresponded to high-entropy or complex concentrated phases (compositionally complex phases). Microstructures and properties were considered from the perspective of the alloy design methodology NICE. The vol.% Nbss increased with increasing ΔχNbss. The hardness of the alloys respectively increased and decreased with increasing vol.% of A15-Nb3X and Nbss. The hardness of the A15-Nb3X increased with its parameter Δχ, and the hardness of the Nbss increased with its parameters δ and Δχ. The room-temperature-specific strength of the alloys was in the range 271.7 to 416.5 MPa cm3g−1. The effect of the synergy of Hf and Sn, or Hf and B, or Hf and Ge on the macrosegregation of solutes, microstructures, and properties of RM(Nb)ICs/RCCAs from this study and others is compared. Phase transformations involving compositionally complex phases are discussed.

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Thandorn, Tophan, and Panos Tsakiropoulos. "On the Microstructure and Properties of Nb-Ti-Cr-Al-B-Si-X (X = Hf, Sn, Ta) Refractory Complex Concentrated Alloys." Materials 14, no. 24 (December 10, 2021): 7615. http://dx.doi.org/10.3390/ma14247615.

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We studied the effect of the addition of Hf, Sn, or Ta on the density, macrosegregation, microstructure, hardness and oxidation of three refractory metal intermetallic composites based on Nb (RM(Nb)ICs) that were also complex concentrated alloys (i.e., RM(Nb)ICs/RCCAs), namely, the alloys TT5, TT6, and TT7, which had the nominal compositions (at.%) Nb-24Ti-18Si-5Al-5B-5Cr-6Ta, Nb-24Ti-18Si-4Al-6B-5Cr-4Sn and Nb-24Ti-17Si-5Al-6B-5Cr-5Hf, respectively. The alloys were compared with B containing and B free RM(Nb)ICs. The macrosegregation of B, Ti, and Si was reduced with the addition, respectively of Hf, Sn or Ta, Sn or Ta, and Hf or Sn. All three alloys had densities less than 7 g/cm3. The alloy TT6 had the highest specific strength in the as cast and heat-treated conditions, which was also higher than that of RCCAs and refractory metal high entropy alloys (RHEAs). The bcc solid solution Nbss and the tetragonal T2 and hexagonal D88 silicides were stable in the alloys TT5 and TT7, whereas in TT6 the stable phases were the A15-Nb3Sn and the T2 and D88 silicides. All three alloys did not pest at 800 °C, where only the scale that was formed on TT5 spalled off. At 1200 °C, the scale of TT5 spalled off, but not the scales of TT6 and TT7. Compared with the B free alloys, the synergy of B with Ta was the least effective regarding oxidation at 800 and 1200 °C. Macrosegregation of solutes, the chemical composition of phases, the hardness of the Nbss and the alloys, and the oxidation of the alloys at 800 and 1200 °C were considered from the perspective of the Niobium Intermetallic Composite Elaboration (NICE) alloy design methodology. Relationships between properties and the parameters VEC, δ, and Δχ of alloy or phase and between parameters were discussed. The trends of parameters and the location of alloys and phases in parameter maps were in agreement with NICE.

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Mishra, Saswat, Karthik Guda Vishnu, and Alejandro Strachan. "Comparing the accuracy of melting temperature prediction methods for high entropy alloys." Journal of Applied Physics 132, no. 20 (November 28, 2022): 205901. http://dx.doi.org/10.1063/5.0101548.

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Refractory complex concentrated alloys (RCCAs) are a relatively new class of materials that can exhibit excellent mechanical properties at high temperatures, and determining their melting temperature ( Tm) is critical to assess their range of operation. Unfortunately, the experimental determination of this property is challenging and computational tools to predict the Tm of RCCAs from first-principles calculations are highly desirable. We quantify the uncertainties associated with such predictions for two methods that can be used with density functional theory-based molecular dynamics and apply them to predict the melting temperature of equiatomic NbMoTaW. We find that a combination of free energy calculations of individual phases with a dynamical coexistence method can provide accurate results with the minimum possible computational cost. We predict the melting temperature for the RCCA NbMoTaW to be between 3000 and 3100 K.

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Gorsse, S., M. H. Nguyen, O. N. Senkov, and D. B. Miracle. "Corrigendum to database on the mechanical properties of high entropy alloys and complex concentrated alloys, data in brief 21 (2018) 2664–2678." Data in Brief 32 (October 2020): 106216. http://dx.doi.org/10.1016/j.dib.2020.106216.

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Arora, Gaurav, and Dilpuneet S. Aidhy. "Machine Learning Enabled Prediction of Stacking Fault Energies in Concentrated Alloys." Metals 10, no. 8 (August 9, 2020): 1072. http://dx.doi.org/10.3390/met10081072.

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Recent works have revealed a unique combination of high strength and high ductility in certain compositions of high-entropy alloys (HEAs), which is attributed to the low stacking fault energy (SFE). While atomistic calculations have been successful in predicting the SFE of pure metals, large variations up to 200 mJ/m2 have been observed in HEAs. One of the leading causes of such variations is the limited number of atoms that can be modeled in atomistic calculations; as a result, due to random distribution of elements in HEAs, various nearest neighbor environments may not be adequately captured in small supercells resulting in different SFE values. Such variation further increases with the increase in the number of elements in a given composition. In this work, we use machine learning to overcome the limitation of smaller system sizes and provide a methodology to significantly reduce the variation and uncertainty in predicting SFEs. We show that the SFE can be accurately predicted across the composition ranges in binary alloys. This capability then enables us to predict the SFE of multi-elemental alloys by training the model using only binary alloys. Consequently, SFEs of complex alloys can be predicted using a binary alloys database, and the need to perform calculations for every new composition can be circumvented.

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Muangtong, Piyanut, Righdan Mohsen Namus, and Russell Goodall. "Improved Tribocorrosion Resistance by Addition of Sn to CrFeCoNi High Entropy Alloy." Metals 11, no. 1 (December 24, 2020): 13. http://dx.doi.org/10.3390/met11010013.

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Among the high entropy or complex concentrated alloys (HEAs/CCAs), one type of system is commonly based on CoCrFeNi, which as an equiatomic quaternary alloy that forms a single phase FCC structure. In this work, the effect of Sn in an equiatomic quinary system with CoCrFeNi is shown to lead to a great improvement in hardness and resistance to tribocorrosion. The addition causes a phase transition from a single FCC phase in CoCrFeNi to dual phase in CoCrFeNiSn with an Ni-Sn intermetallic phase, and a CoCrFeNi FCC phase. The presence of both the hard intermetallic and this ductile phase helps to resist crack propagation, and consequent material removal during wear. In addition, the high polarization resistance of the passive film formed at the surface and the high corrosion potential of the Ni-Sn phase contribute to preventing chloride corrosion attack during corrosion testing. This film is tenacious enough for the effect to persist under tribocorrosion conditions.

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Chikova, Olga, Vladimir Tsepelev, Vladimir V’yukhin, Kseniya Shmakovа, and Vadim Il’in. "VISCOSITY AND ELECTRICAL RESISTIVITY OF LIQUID CuNiAl, CuNiAlCo, CuNiAlCoFe ALLOYS OF EQUIATOMIC COMPOSITIONS." Acta Metallurgica Slovaca 25, no. 4 (December 18, 2019): 259. http://dx.doi.org/10.12776/ams.v25i4.1358.

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<p class="AMSmaintext1">The kinematic viscosity and electrical resistivity of equiatomic liquid alloys CuNiAl, CuNiAlCo, CuNiAlCoFe were measured during heating of the sample to 2070 K and subsequent cooling. The kinematic viscosity was measured using the damped torsional vibrations of a crucible with a melt. The measuring results are discussed within the theory of absolute reaction rates. The entropy of activation of viscous flow (characteristic of the structural state of the melt) was are determined by analyzing the temperature dependences of kinematic viscosity. The electrical resistivity was measured was using the rotating magnetic field method. The temperature coefficient of resistivity (characteristic of the structural state of the melt) was are determined. The measuring results interpreted using the Nagel-Tauc model. We considerCuNiAl, CuNiAlCo, CuNiAlCoFe alloysof equiatomic compositions as the multi-principal element alloys (MPEAs), the complex concentrated alloys (CCAs), the high-entropy alloys (HEAs). It based on the available microgeterogenity concept the measuring results of the vickosity and the resistivity are discussed. We were looking for temperatureis of the heating a melt for destroy of microheterogeneity and mixing components on an atomic scale T*. The temperature T*=1800 K could be determined only for alloy CuNiAl of equiatomic composition. We have made the assumption that the heating of uid alloy CuNiAl the more 1800K in subsequent crystallization even at relatively low speeds will provide of more homogeneous structure volumetric ingots.</p>

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Vellios, Nikos, and Panos Tsakiropoulos. "The Effect of Fe Addition in the RM(Nb)IC Alloy Nb–30Ti–10Si–2Al–5Cr–3Fe–5Sn–2Hf (at.%) on Its Microstructure, Complex Concentrated and High Entropy Phases, Pest Oxidation, Strength and Contamination with Oxygen, and a Comparison with Other RM(Nb)ICs, Refractory Complex Concentrated Alloys (RCCAs) and Refractory High Entropy Alloys (RHEAs)." Materials 15, no. 17 (August 23, 2022): 5815. http://dx.doi.org/10.3390/ma15175815.

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In this work, the RM(Nb)IC alloy Nb–30Ti–10Si–5Cr–5Sn–3Fe–2Al–2Hf (NV2) was studied in the as-cast and heat-treated conditions; its isothermal oxidation at 700, 800 and 900 °C and its room temperature hardness and specific strength were compared with other Sn-containing RM(Nb)ICs—in particular, the alloy Nb–24Ti–18Si–5Cr–5Fe–5Sn (NV5)—and with RCCAs and RHEAs. The addition of Fe (a) stabilised Nbss; A15–Nb3X (X = Al, Si and Sn) and Nb3Si; metastable Nb3Si-m’ and Nb5Si3 silicides; (b) supported the formation of eutectic Nbss + Nb5Si3; (c) suppressed pest oxidation at all three temperatures and (d) stabilised a Cr- and Fe-rich phase instead of a C14–Nb(Cr,Fe)2 Laves phase. Complex concentrated (or compositionally complex) and/or high entropy phases co-existed with “conventional” phases in all conditions and after oxidation at 800 °C. In NV2, the macrosegregation of Si decreased but liquation occurred at T >1200 °C. A solid solution free of Si and rich in Cr and Ti was stable after the heat treatments. The relationships between solutes in the various phases, between solutes and alloy parameters and between alloy hardness or specific strength and the alloy parameters were established (parameters δ, Δχ and VEC). The oxidation of NV2 at 700 °C was better than the other Sn-containing RM(Nb)ICs with/without Fe addition, even better than RM(Nb)IC alloys with lower vol.% Nbss. At 800 °C, the mass change of NV2 was slightly higher than that of NV5, and at 900 °C, both alloys showed scale spallation. At 800 °C, both alloys formed a more or less continuous layer of A15–Nb3X below the oxide scale, but in NV5, this compound was Sn-rich and severely oxidised. At 800 °C, in the diffusion zone (DZ) and the bulk of NV2, Nbss was more severely contaminated with oxygen than Nb5Si3, and the contamination of A15–Nb3X was in-between these phases. The contamination of all three phases was more severe in the DZ. The contamination of all three phases in the bulk of NV5 was more severe compared with NV2. The specific strength of NV2 was comparable with that of RCCAs and RHEAs, and its oxidation at all three temperatures was significantly better than RHEAs and RCCAs.

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Ghadyani, Mohammad, Claire Utton, and Panos Tsakiropoulos. "Microstructures and Isothermal Oxidation of the Alumina Scale Forming Nb1.45Si2.7Ti2.25Al3.25Hf0.35 and Nb1.35Si2.3Ti2.3Al3.7Hf0.35 Alloys." Materials 12, no. 5 (March 5, 2019): 759. http://dx.doi.org/10.3390/ma12050759.

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Coating system(s) will be required for Nb-silicide based alloys. Alumina forming alloys that are chemically compatible with the Nb-silicide based alloy substrate could be components of such systems. The intermetallic alloys Nb1.45Si2.7Ti2.25Al3.25Hf0.35 (MG5) and Nb1.35Si2.3Ti2.3Al3.7Hf0.35 (MG6) were studied in the cast, heat treated and isothermally oxidised conditions at 800 and 1200 °C to find out if they are αAl2O3 scale formers. A (Al/Si)alloy versus Nb/(Ti + Hf)alloy map, which can be considered to be a map for Multi-Principle Element or Complex Concentrated Nb-Ti-Si-Al-Hf alloys, and a [Nb/(Ti + Hf)]Nb5Si3 versus [Nb/(Ti + Hf)]alloy map were constructed making use of the alloy design methodology NICE and data from a previously studied alloy, and were used to select the alloys MG5 and MG6 that were expected (i) not to pest, (ii) to form αAl2O3 scale at 1200 °C, (iii) to have no solid solution, (iv) to form only hexagonal Nb5Si3 and (v) to have microstructures consisting of hexagonal Nb5Si3, Ti5Si3, Ti5Si4, TiSi silicides, and tri-aluminides and Al rich TiAl. Both alloys met the requirements (i) to (v). The alumina scale was able to self-heal at 1200 °C. Liquation in the alloy MG6 at 1200 °C was linked with the formation of a eutectic like structure and the TiAl aluminide in the cast alloy. Key to the oxidation of the alloys was the formation (i) of “composite” silicide grains in which the Nb5Si3 core was surrounded by the Ti5Si4 and TiSi silicides, and (ii) of tri-aluminides with high Al/Si ratio, particularly at 1200 °C and very low Nb/Ti ratio forming in-between the “composite” silicide grains. Both alloys met the “standard definition” of high entropy alloys (HEAs). Compared with HEAs with bcc solid solution and intermetallics, the VEC values of both the alloys were outside the range of reported values. The parameters VEC,  and  of Nb-Ti-Si-Al-Hf coating alloys and non-pesting Nb-silicide based alloys were compared and trends were established. Selection of coating alloys with possible “layered” structures was discussed and alloy compositions were proposed.

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Choudhuri, D., B. Gwalani, S. Gorsse, C. V. Mikler, R. V. Ramanujan, M. A. Gibson, and R. Banerjee. "Change in the primary solidification phase from fcc to bcc -based B2 in high entropy or complex concentrated alloys." Scripta Materialia 127 (January 2017): 186–90. http://dx.doi.org/10.1016/j.scriptamat.2016.09.023.

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Thandorn, Tophan, and Panos Tsakiropoulos. "The Effect of Boron on the Microstructure and Properties of Refractory Metal Intermetallic Composites (RM(Nb)ICs) Based on Nb-24Ti-xSi (x = 16, 17 or 18 at.%) with Additions of Al, Cr or Mo." Materials 14, no. 20 (October 15, 2021): 6101. http://dx.doi.org/10.3390/ma14206101.

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This paper is about metallic ultra-high temperature materials, in particular, refractory metal intermetallic composites based on Nb, i.e., RM(Nb)ICs, with the addition of boron, which are compared with refractory metal high entropy alloys (RHEAs) or refractory metal complex concentrated alloys (RCCAs). We studied the effect of B addition on the density, macrosegregation, microstructure, hardness and oxidation of four RM(Nb)IC alloys, namely the alloys TT2, TT3, TT4 and TT8 with nominal compositions (at.%) Nb-24Ti-16Si-5Cr-7B, Nb-24Ti-16Si-5Al-7B, Nb-24Ti-18Si-5Al-5Cr-8B and Nb-24Ti-17Si-3.5Al-5Cr-6B-2Mo, respectively. The alloys made it possible to compare the effect of B addition on density, hardness or oxidation with that of Ge or Sn addition. The alloys were made using arc melting and their microstructures were characterised in the as cast and heat-treated conditions. The B macrosegregation was highest in TT8. The macrosegregation of Si or Ti increased with the addition of B and was lowest in TT8. The alloy TT8 had the lowest density of 6.41 g/cm3 and the highest specific strength at room temperature, which was also higher than that of RCCAs and RHEAs. The Nbss and T2 silicide were stable in the alloys TT2 and TT3, whereas in TT4 and TT8 the stable phases were the Nbss and the T2 and D88 silicides. Compared with the Ge or Sn addition in the same reference alloy, the B and Ge addition was the least and most effective at 800 °C (i.e., in the pest regime), when no other RM was present in the alloy. Like Ge or Sn, the B addition in TT2, TT3 and TT4 did not suppress scale spallation at 1200 °C. Only the alloy TT8 did not pest and its scales did not spall off at 800 and 1200 °C. The macrosegregation of Si and Ti, the chemical composition of Nbss and T2, the microhardness of Nbss and the hardness of alloys, and the oxidation of the alloys at 800 and 1200 °C were also viewed from the perspective of the alloy design methodology NICE and relationships with the alloy or phase parameters VEC, δ and Δχ. The trends of these parameters and the location of alloys and phases in parameter maps were found to be in agreement with NICE.

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Gorsse, Stéphane, and Oleg Senkov. "About the Reliability of CALPHAD Predictions in Multicomponent Systems." Entropy 20, no. 12 (November 24, 2018): 899. http://dx.doi.org/10.3390/e20120899.

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This study examines one of the limitations of CALPHAD databases when applied to high entropy alloys and complex concentrated alloys. We estimate the level of the thermodynamic description, which is still sufficient to correctly predict thermodynamic properties of quaternary alloy systems, by comparing the results of CALPHAD calculations where quaternary phase space is extrapolated from binary descriptions to those resulting from complete binary and ternary interaction descriptions. Our analysis has shown that the thermodynamic properties of a quaternary alloy can be correctly predicted by direct extrapolation from the respective fully assessed binary systems (i.e., without ternary descriptions) only when (i) the binary miscibility gaps are not present, (ii) binary intermetallic phases are not present or present in a few quantities (i.e., when the system has low density of phase boundaries), and (iii) ternary intermetallic phases are not present. Because the locations of the phase boundaries and possibility of formation of ternary phases are not known when evaluating novel composition space, a higher credibility database is still preferable, while the calculations using lower credibility databases may be questionable and require additional experimental verification. We estimate the level of the thermodynamic description which would be still sufficient to correctly predict thermodynamic properties of quaternary alloy systems. The main factors affecting the accuracy of the thermodynamic predictions in quaternary alloys are identified by comparing the results of CALPHAD calculations where quaternary phase space is extrapolated from binary descriptions to those resulting from ternary system descriptions.

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29

Rhode, Michael, Tim Richter, Dirk Schroepfer, Anna Maria Manzoni, Mike Schneider, and Guillaume Laplanche. "Welding of high-entropy alloys and compositionally complex alloys—an overview." Welding in the World 65, no. 8 (April 14, 2021): 1645–59. http://dx.doi.org/10.1007/s40194-021-01110-6.

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AbstractHigh-entropy alloys (HEAs) and compositionally complex alloys (CCAs) represent new classes of materials containing five or more alloying elements (concentration of each element ranging from 5 to 35 at. %). In the present study, HEAs are defined as single-phase solid solutions; CCAs contain at least two phases. The alloy concept of HEAs/CCAs is fundamentally different from most conventional alloys and promises interesting properties for industrial applications (e.g., to overcome the strength-ductility trade-off). To date, little attention has been paid to the weldability of HEAs/CCAs encompassing effects on the welding metallurgy. It remains open whether welding of HEAs/CCAs may lead to the formation of brittle intermetallics and promote elemental segregation at crystalline defects. The effect on the weld joint properties (strength, corrosion resistance) must be investigated. The weld metal and heat-affected zone in conventional alloys are characterized by non-equilibrium microstructural evolutions that most probably occur in HEAs/CCAs. The corresponding weldability has not yet been studied in detail in the literature, and the existing information is not documented in a comprehensive way. Therefore, this study summarizes the most important results on the welding of HEAs/CCAs and their weld joint properties, classified by HEA/CCA type (focused on CoCrFeMnNi and AlxCoCrCuyFeNi system) and welding process.

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30

Senkov, O. N., S. Gorsse, and D. B. Miracle. "High temperature strength of refractory complex concentrated alloys." Acta Materialia 175 (August 2019): 394–405. http://dx.doi.org/10.1016/j.actamat.2019.06.032.

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31

Cheng, Chun-Yang, Ya-Chu Yang, Yi-Zhen Zhong, Yang-Yuan Chen, Tung Hsu, and Jien-Wei Yeh. "Physical metallurgy of concentrated solid solutions from low-entropy to high-entropy alloys." Current Opinion in Solid State and Materials Science 21, no. 6 (December 2017): 299–311. http://dx.doi.org/10.1016/j.cossms.2017.09.002.

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32

Gromov, V. E., Yu A. Shlyarova, S. V. Konovalov, S. V. Vorob'ev, and O. A. Peregudov. "Application of high-entropy alloys." Izvestiya. Ferrous Metallurgy 64, no. 10 (November 24, 2021): 747–54. http://dx.doi.org/10.17073/0368-0797-2021-10-747-754.

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From accumulated information on structure, properties, stability, and methods of manufacturing the high-entropy alloys (HEA) created early in the 21 century it follows that they possess a whole complex of useful properties that suggests their perspective application in different branches of industry. The authors have made a short review of scientific articles on analysis of possibilities of HEA application in specific science-consuming branches of the last 5 years. In biomedicine the protective coatings made of (TiZrNbHfTa)N and (TiZrNbHfTa)O HEAs possess biocompatibility, high level of mechanical properties, high wear- and corrosion resistance in physiological media, and excellent adhesion. Products made of (MoTa)χNbTiZr passed clinical tests successfully when being implanted to living muscular tissue. The developed HEAs based on rare-earth elements and metals of Fe group such as YbTbDyAlMe (Me = Fe, Co, Ni) possess magnetocaloric effect, have Curie temperature close to room one and may be used in modern refrigerator mechanisms. Changing in stoichiometric composition of CoCrFeNiTi HEAs, alloying them and performing thermal treatment, the researchers succeed in obtaining soft magnetic materials. Fields of HEA application are presented as following: catalysts of ammonia oxidation - (PtPdRhRuCe), ammonia decomposition - (RuRhCoNiIr), oxidation of aromatic alcohols - (Co0,2Ni0,2Cu0,2Mg0,2Zn0,2 ), electric catalysts of hydrogen extraction - (Ni20Fe20Mo10Cr15Co35 ), redox reactions (AlCuNiPtMn and AlNiCuPtPdAu), and oxidation of methanol/ethanol. HEAs can be used as electrodes - anodes and cathodes for Li-ion and Na-ion accumulators. Synthesized nanoporous HEA AlCoCrFeNi has high bulk density up to 700 F/cm3 and cyclic stability (>3000 cycles) and is used in supercapacitors. High-entropy oxides such as (MgNiCoCuZn)0.95Li0.05O with high dielectric properties in a wide frequency range may be used in electronic converters. Examples of HEA application are given: as coatings of ship parts being operated in sea water, various welded joints, parts of nuclear reactors. Perspectives of widening the fields of HEA application are indicated.

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Jia, Yuefei, Yandong Jia, Shiwei Wu, Xindi Ma, and Gang Wang. "Novel Ultralight-Weight Complex Concentrated Alloys with High Strength." Materials 12, no. 7 (April 8, 2019): 1136. http://dx.doi.org/10.3390/ma12071136.

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To explore a novel high strength and low modulus ultralight-weight complex concentrated alloys (ULW-CCAs), a series of light alloys are designed and explored based on some low-density and low modulus elements, such as Al, Li, Mg, Ca, Si, and Y. An Al19.9Li30Mg35Si10Ca5Y0.1 (at %) CCA with a high specific strength of 327 KPa·m−3 is successfully developed. After adjusting the composition, the Al15Li35Mg48Ca1Si1 CCA with the good compressive plasticity is successfully developed. The Al15Li38Mg45Ca0.5Si1.5 and Al15Li39Mg45Ca0.5Si0.5 CCAs exhibit good plasticity of >45%, and >60%, respectively. These ULW-CCAs show the high specific strength, good ductility, and low Young’s modulus, as compared with the previously reported CCAs.

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Lo, Kai-Chi, An-Chou Yeh, and Hideyuki Murakami. "Microstructural Investigation of Oxidized Complex Refractory High Entropy Alloys." MATERIALS TRANSACTIONS 59, no. 4 (2018): 556–62. http://dx.doi.org/10.2320/matertrans.mj201611.

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35

Singh, Prashant, Shalabh Gupta, Srinivasa Thimmaiah, Bryce Thoeny, Pratik K. Ray, A. V. Smirnov, Duane D. Johnson, and Matthew J. Kramer. "Vacancy-mediated complex phase selection in high entropy alloys." Acta Materialia 194 (August 2020): 540–46. http://dx.doi.org/10.1016/j.actamat.2020.04.063.

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36

Morris, James R., M. C. Troparevsky, Louis J. Santodonato, E. Zarkadoula, and Andreas Kulovits. "Predicting phase behavior in high entropy and chemically complex alloys." Materials Characterization 170 (December 2020): 110719. http://dx.doi.org/10.1016/j.matchar.2020.110719.

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37

Luo, Dan, Yong Xiao, Liam Hardwick, Robert Snell, Matthew Way, Xavier Sanuy Morell, Frances Livera, et al. "High Entropy Alloys as Filler Metals for Joining." Entropy 23, no. 1 (January 7, 2021): 78. http://dx.doi.org/10.3390/e23010078.

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In the search for applications for alloys developed under the philosophy of the High Entropy Alloy (HEA)-type materials, the focus may be placed on applications where current alloys also use multiple components, albeit at lower levels than those found in HEAs. One such area, where alloys with complex compositions are already found, is in filler metals used for joining. In soldering (<450 °C) and brazing (>450 °C), filler metal alloys are taken above their liquidus temperature and used to form a metallic bond between two components, which remain both unmelted and largely unchanged throughout the process. These joining methods are widely used in applications from electronics to aerospace and energy, and filler metals are highly diverse, to allow compatibility with a broad range of base materials (including the capability to join ceramics to metals) and a large range of processing temperatures. Here, we review recent developments in filler metals relevant to High Entropy materials, and argue that such alloys merit further exploration to help overcome a number of current challenges that need to be solved for filler metal-based joining methods.

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38

Ren, Xiqiang, Yungang Li, Yanfei Qi, and Bo Wang. "Review on Preparation Technology and Properties of Refractory High Entropy Alloys." Materials 15, no. 8 (April 17, 2022): 2931. http://dx.doi.org/10.3390/ma15082931.

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Refractory high entropy alloys have broad application prospects due to their excellent comprehensive properties in high temperature environments, and they have been widely implemented in many complex working conditions. According to the latest research reports, the preparation technology of bulk and coating refractory high entropy alloys are summarized, and the advantages and disadvantages of each preparation technology are analyzed. In addition, the properties of refractory high entropy alloys, such as mechanical properties, wear resistance, corrosion resistance, oxidation resistance, and radiation resistance are reviewed. The existing scientific problems of refractory high entropy alloys, at present, are put forward, which provide reference for the development and application of refractory high entropy alloys in the future, especially for plasma-facing materials in nuclear fusion reactors.

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39

Chen, Bing, Suzhi Li, Hongxiang Zong, Xiangdong Ding, Jun Sun, and Evan Ma. "Unusual activated processes controlling dislocation motion in body-centered-cubic high-entropy alloys." Proceedings of the National Academy of Sciences 117, no. 28 (June 29, 2020): 16199–206. http://dx.doi.org/10.1073/pnas.1919136117.

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Atomistic simulations of dislocation mobility reveal that body-centered cubic (BCC) high-entropy alloys (HEAs) are distinctly different from traditional BCC metals. HEAs are concentrated solutions in which composition fluctuation is almost inevitable. The resultant inhomogeneities, while locally promoting kink nucleation on screw dislocations, trap them against propagation with an appreciable energy barrier, replacing kink nucleation as the rate-limiting mechanism. Edge dislocations encounter a similar activated process of nanoscale segment detrapping, with comparable activation barrier. As a result, the mobility of edge dislocations, and hence their contribution to strength, becomes comparable to screw dislocations.

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40

Wu, Junxia, Peiyou Li, Hongfeng Dong, Yuefei Jia, Yaling Liu, Wei Zhang, and Mina Zhang. "Composition design, microstructure, and mechanical properties of novel Ti–Co–Ni–Zr complex concentrated alloys." International Journal of Materials Research 112, no. 11 (November 1, 2021): 880–89. http://dx.doi.org/10.1515/ijmr-2021-8196.

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Abstract The composition design of complex concentrated alloys originates from the composition design of amorphous alloys. To expand the composition design of alloys, herein, the compositions of novel Ti–Co–Ni–Zr complex concentrated alloys were obtained by the proportional mixing of Ti2Co intermetallics and Ni64Zr36 binary eutectic. The theory and method of this new alloy design are also discussed. The as-cast Ti28Co14Ni37.12Zr20.88, Ti30Co15Ni35.2Zr19.8, and Ti32 . Co16Ni33.3Zr18.7 alloys were composed of body-centered cubic TiNi and Ti2Ni phases. The Ti28Co14Ni37.12Zr20.88 alloy exhibited high yield strength (2 164 MPa) and compressive strength (2 539 MPa) under quasi-static compression at roomtemperature. The high strength of Ti28Co14Ni37.12Zr20.88 alloy is related to the precipitation of Ti2Ni along the grain boundary and the precipitation in the crystal. This paper validates that using the proportional mixing method of intermetallics and eutectic alloy is an effective method to design complex concentrated alloys with high strength.

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41

Daoud, Haneen M., Anna M. Manzoni, Rainer Völkl, Nelia Wanderka, and Uwe Glatzel. "Oxidation Behavior of Al8Co17Cr17Cu8Fe17Ni33, Al23Co15Cr23Cu8Fe15Ni15, and Al17Co17Cr17Cu17Fe17Ni17Compositionally Complex Alloys (High-Entropy Alloys) at Elevated Temperatures in Air." Advanced Engineering Materials 17, no. 8 (June 15, 2015): 1134–41. http://dx.doi.org/10.1002/adem.201500179.

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Manzoni, Anna M., and Uwe Glatzel. "New multiphase compositionally complex alloys driven by the high entropy alloy approach." Materials Characterization 147 (January 2019): 512–32. http://dx.doi.org/10.1016/j.matchar.2018.06.036.

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43

Farnell, Mackinzie S., Zachary D. McClure, Shivam Tripathi, and Alejandro Strachan. "Modeling environment-dependent atomic-level properties in complex-concentrated alloys." Journal of Chemical Physics 156, no. 11 (March 21, 2022): 114102. http://dx.doi.org/10.1063/5.0076584.

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Complex-concentrated-alloys (CCAs) are of interest for a range of applications due to a host of desirable properties, including high-temperature strength and tolerance to radiation damage. Their multi-principal component nature results in a vast number of possible atomic environments with the associated variability in chemistry and structure. This atomic-level variability is central to the unique properties of these alloys but makes their modeling challenging. We combine atomistic simulations using many body potentials with machine learning to develop predictive models of various atomic properties of CrFeCoNiCu-based CCAs: relaxed vacancy formation energy, atomic-level cohesive energy, pressure, and volume. A fingerprint of the local atomic environments is obtained combining invariants associated with the local atomic geometry and periodic-table information of the atoms involved. Importantly, all descriptors are based on the unrelaxed atomic structure; thus, they are computationally inexpensive to compute. This enables the incorporation of these models into macroscopic simulations. The models show good accuracy and we explore their ability to extrapolate to compositions and elements not used during training.

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44

Ikeda, Yuji, Blazej Grabowski, and Fritz Körmann. "Ab initio phase stabilities and mechanical properties of multicomponent alloys: A comprehensive review for high entropy alloys and compositionally complex alloys." Materials Characterization 147 (January 2019): 464–511. http://dx.doi.org/10.1016/j.matchar.2018.06.019.

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45

Górecki, K., P. Bała, T. Kozieł, and G. Cios. "Necessary Thermodynamics Factors to Obtain Simple Solid Solutions in High-Entropy Alloys from the Al-Ti-Co-Ni-Fe System." Archives of Metallurgy and Materials 62, no. 4 (December 1, 2017): 2141–45. http://dx.doi.org/10.1515/amm-2017-0316.

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AbstractIn this paper findings regarding the design and synthesis of High-Entropy Alloys based on mixing enthalpy, mixing entropy,δparameter, Ω parameter and valence electron concentration are presented. Four alloys were synthesised with different predicted crystalline structures. Results of the microstructure and crystal structure studies are presented. It was shown that predicted structures as well as complex intermetallic phases exist in the material. The validity of valence electron concentration as well as additional parameters such as mixing enthalpy, mixing entropy and others necessary to obtain only the solid solution in High-Entropy Alloys were examined.

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46

Babić, Emil, Đuro Drobac, Ignacio Alejandro Figueroa, Mathilde Laurent-Brocq, Željko Marohnić, Vesna Mikšić Trontl, Damir Pajić, et al. "Transition from High-Entropy to Conventional Alloys: Which Are Better?" Materials 14, no. 19 (October 5, 2021): 5824. http://dx.doi.org/10.3390/ma14195824.

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The study of the transition from high-entropy alloys (HEAs) to conventional alloys (CAs) composed of the same alloying components is apparently important, both for understanding the formation of HEAs and for proper evaluation of their potential with respect to that of the corresponding CAs. However, this transition has thus far been studied in only two types of alloy systems: crystalline alloys of iron group metals (such as the Cantor alloy and its derivatives) and both amorphous (a-) and crystalline alloys, TE-TL, of early (TE = Ti, Zr, Nb, Hf) and late (TL = Co, Ni, Cu) transition metals. Here, we briefly overview the main results for the transition from HEAs to CAs in these alloy systems and then present new results for the electronic structure (ES), studied with photoemission spectroscopy and specific heat, atomic structure, thermal, magnetic and mechanical properties of a-TE-TL and Cantor-type alloys. A change in the properties of the alloys studied on crossing from the HEA to the CA concentration range mirrors that in the ES. The compositions of the alloys having the best properties depend on the alloy system and the property selected. This emphasizes the importance of knowing the ES for the design of new compositional complex alloys with the desired properties.

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47

Sanchez, Jon Mikel, Alejandro Pascual, Iban Vicario, Joseba Albizuri, Teresa Guraya, and Haize Galarraga. "Microstructure and Phase Formation of Novel Al80Mg5Sn5Zn5X5 Light-Weight Complex Concentrated Aluminum Alloys." Metals 11, no. 12 (December 1, 2021): 1944. http://dx.doi.org/10.3390/met11121944.

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In this work, three novel complex concentrated aluminum alloys were developed. To investigate the unexplored region of the multicomponent phase diagrams, thermo-physical parameters and the CALPHAD method were used to understand the phase formation of the Al80Mg5Sn5Zn5Ni5, Al80Mg5Sn5Zn5Mn5, and Al80Mg5Sn5Zn5Ti5 alloys. The ingots of the alloys were manufactured by a gravity permanent mold casting process, avoiding the use of expensive, dangerous, or scarce alloying elements. The microstructural evolution as a function of the variable element (Ni, Mn, or Ti) was studied by means of different microstructural characterization techniques. The hardness and compressive strength of the as-cast alloys at room temperature were studied and correlated with the previously characterized microstructures. All the alloys showed multiphase microstructures with major α-Al dendritic matrix reinforced with secondary phases. In terms of mechanical properties, the developed alloys exhibited a high compression yield strength up to 420 MPa, high compression fracture strength up to 563 MPa, and elongation greater than 12%.

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Zhang, Jing, Kook Noh Yoon, Min Seok Kim, Heh Sang Ahn, Ji Young Kim, Wook Ha Ryu, and Eun Soo Park. "Manipulation of Microstructure and Mechanical Properties in N-Doped CoCrFeMnNi High-Entropy Alloys." Metals 11, no. 9 (September 18, 2021): 1487. http://dx.doi.org/10.3390/met11091487.

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Herein, we carefully investigate the effect of nitrogen doping in the equiatomic CoCrFeMnNi high-entropy alloy (HEA) on the microstructure evolution and mechanical properties. After homogenization (1100 °C for 20 h), cold-rolling (reduction ratio of 60%) and subsequent annealing (800 °C for 1 h), a unique complex heterogeneous microstructure consisting of fine recrystallized grains, large non-recrystallized grains, and nanoscale Cr2N precipitates, were obtained in nitrogen-doped (0.3 wt.%) CoCrFeMnNi HEA. The yield strength and ultimate tensile strength can be significantly improved in nitrogen-doped (0.3 wt.%) CoCrFeMnNi HEA with a complex heterogeneous microstructure, which shows more than two times higher than those compared to CoCrFeMnNi HEA under the identical process condition. It is achieved by the simultaneous operation of various strengthening mechanisms from the complex heterogeneous microstructure. Although it still has not solved the problem of ductility reduction, as the strength increases because the microstructure optimization is not yet complete, it is expected that precise control of the unique complex heterogeneous structure in nitrogen-doped CoCrFeMnNi HEA can open a new era in overcoming the strength–ductility trade-off, one of the oldest dilemmas of structural materials.

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Simić, Lidija, Srećko Stopić, Bernd Friedrich, Matej Zadravec, Žiga Jelen, Rajko Bobovnik, Ivan Anžel, and Rebeka Rudolf. "Synthesis of Complex Concentrated Nanoparticles by Ultrasonic Spray Pyrolysis and Lyophilisation." Metals 12, no. 11 (October 24, 2022): 1802. http://dx.doi.org/10.3390/met12111802.

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The development of new multicomponent nanoparticles is gaining increasing importance due to their specific functional properties, i.e., synthesised new complex concentrated nanoparticles (CCNPs) in the form of powder using ultrasonic spray pyrolysis (USP) and lyophilisation from the initial cast Ag20Pd20Pt20Cu20Ni20 alloy, which was in the function of the material after its catalytic abilities had been exhausted. Hydrometallurgical treatment was used to dissolve the cast alloy, from which the USP precursor was prepared. As a consequence of the incomplete dissolution of the cast alloy and the formation of Pt and Ni complexes, it was found that the complete recycling of the alloy is not possible. A microstructural examination of the synthesised CCNPs showed that round and mostly spherical (not 100%) nanoparticles were formed, with an average diameter of 200 nm. Research has shown that CCNPs belong to the group with medium entropy characteristics. A mechanism for the formation of CCNPs is proposed, based on the thermochemical analysis of element reduction with the help of H2 and based on the mixing enthalpy of binary systems.

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Osintsev, K. A., V. E. Gromov, S. V. Konovalov, Yu F. Ivanov, and I. A. Panchenko. "High-entropy alloys: Structure, mechanical properties, deformation mechanisms and application." Izvestiya. Ferrous Metallurgy 64, no. 4 (June 4, 2021): 249–58. http://dx.doi.org/10.17073/0368-0797-2021-4-249-258.

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The article considers a brief review of the foreign publications on the study of the structure, phase composition and properties of five-component high-entropy alloys (HEAs) in different structural states in a wide temperature range over the past two decades. HEAs attract the attention of scientists with their unique and unusual properties. The difficulties of comparative analysis and generalization of data are noted due to different methods of obtaining HEAs, modes of mechanical tests for uniaxial compression and tension, sizes and shapes of the samples, types of thermal treatments, and phase composition (bcc and fcc crystal lattices). It is noted that the HEA with a bcc lattice has mainly high strength and low plasticity, and the HEA with a fcc lattice has low strength and increased plasticity. A significant increase in the properties of the FeMnCoCrNi HEA with a fcc lattice can be achieved by alloying with boron and optimizing the parameters of thermal mechanical treatment at alloying with carbon in the amount of 1 % (at.). The deformation curves analyzed in the temperature range –196 ÷ 800 °C indicate an increase in the yield strength with a decrease in the grain size from 150 to 5 microns. As the temperature decreases, the yield strength and elongation increase. The effect of deformation rate on the mechanical properties is an increase in the ultimate strength and yield strength, which is most noticeable at high rates of 10–2 ÷ 103 s–1. The features of HEAs deformation behavior in the mono- and poly-crystalline states are noted. The complex of high operational properties of HEAs makes it possible to use them in various industries. There are good prospects of using energy treatment to modify the surface layers and further improve HEAs properties.

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Journal articles on the topic 'High entropy alloys or Complex concentrated alloys'

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