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Atomic size mismatch δ and mixing enthalpy ∆Hmix of (TiZrNbCu)1−xNix and (TiZrNbNi)1−xCux alloys vs. x. The inset: ∆Hmix between the constituent elements.
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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...
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... their limitations and some erroneous predictions (such as the occurrence of an IM in the SS region and an SS in the a-HEA region, e.g., [10][11][12][13]16,23,[54][55][56]), as illustrated in Figures 2-4, these criteria are useful for a quick comparison of different HEA systems (Figure 4). The variation of thermophysical parameters with the composition within a given alloy system can, on the other hand, provide an insight into the evolution of the properties of this system (Figures 2 and 3, [24,25,52]). ...
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... their limitations and some erroneous predictions (such as the occurrence of an IM in the SS region and an SS in the a-HEA region, e.g., [10][11][12][13]16,23,[54][55][56]), as illustrated in Figures 2-4, these criteria are useful for a quick comparison of different HEA systems (Figure 4). The variation of thermophysical parameters with the composition within a given alloy system can, on the other hand, provide an insight into the evolution of the properties of this system (Figures 2 and 3, [24,25,52]). In Figures 2 and 3, we show the compositional variations of selected thermophysical parameters in characteristic quinary TE-TL [24,25] and Cantor-type alloys [45,47], respectively. ...
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... variation of thermophysical parameters with the composition within a given alloy system can, on the other hand, provide an insight into the evolution of the properties of this system (Figures 2 and 3, [24,25,52]). In Figures 2 and 3, we show the compositional variations of selected thermophysical parameters in characteristic quinary TE-TL [24,25] and Cantor-type alloys [45,47], respectively. In the calculation of these parameters, we used standard expressions (see, e.g., [12,13,24,25]), and the input parameters for ∆Hmix and δ in Figures 2 and 3 and their insets were taken from References [71] and [72], respectively. ...
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... Figures 2 and 3, we show the compositional variations of selected thermophysical parameters in characteristic quinary TE-TL [24,25] and Cantor-type alloys [45,47], respectively. In the calculation of these parameters, we used standard expressions (see, e.g., [12,13,24,25]), and the input parameters for ∆Hmix and δ in Figures 2 and 3 and their insets were taken from References [71] and [72], respectively. For simplicity, a rather wellknown variation of ∆Sconf [25], which depends only on the number of alloying components and not on their type [10][11][12][13], is not shown in these figures. ...
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... simplicity, a rather wellknown variation of ∆Sconf [25], which depends only on the number of alloying components and not on their type [10][11][12][13], is not shown in these figures. In Figure 2, showing the variations of parameters of (TiZrNbCu)1−xNix and (TiZrNbNi)1−xCux alloys with x, the concentration range of HEAs, x ≤ 0.35, is distinguished from that of Ni-or Cu-rich alloys by a different color. The range of values of ∆Hmix (from −32 to −6.6 kJmol −1 ) and of δ (from about 8% to 10%) places our alloys in a standard ∆Hmix−δ plot [12] within the region occupied with an IM (x = 0 Ni) and a-HEAs (other alloys), which is consistent with our experimental findings. ...
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... comparison of ∆Hmix and δ in Figure 2 shows that both the magnitudes and variations of δs are quite similar in the two alloy systems, whereas the corresponding variations of ∆Hmix are quite different. In (TiZrNbCu)1−xNix alloys, ∆Hmix decreases rapidly from −6.6 for x = 0 to −32 kJmol −1 at x = 0.5, whereas in (TiZrNbNi)1−xCux alloys, ∆Hmix increases nearly linearly from −28.2 to −15 kJmol −1 within the same concentration range. ...
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... (TiZrNbCu)1−xNix alloys, ∆Hmix decreases rapidly from −6.6 for x = 0 to −32 kJmol −1 at x = 0.5, whereas in (TiZrNbNi)1−xCux alloys, ∆Hmix increases nearly linearly from −28.2 to −15 kJmol −1 within the same concentration range. The inset in Figure 2 ...
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... show an ideal solution behavior [25] which results in linear variations of their properties with x such as that depicted in Figure 1. In contrast, stronger interactions of Co and Ni atoms with TE ones (inset in Figure 2) lead to more complex variations of their properties with the concentration [24,26,37,52]. ...
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... variations of ∆Hmix and δ in (CrMnFeCo)1−xNix and (CrMnCoNi)1−xFex alloys are shown in Figure 3. We selected these two alloy systems because they, as with those shown in Figure 2, exhibit very different variations of their properties with the composition [45,47]. In these alloy systems, an FCC crystalline structure forms over a broad concentration range [45][46][47]. ...
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... note that the concentration scale in Figure 3 extends up to x = 1 due to the very broad concentration range of a single-phase solid solution with an FCC structure in (CrMnFeCo)1−xNix [45]. Taking into account that the studied concentration range in Figure 3 is considerably broader than that in Figure 2, the variations of thermophysical parameters in Figures 2 and 3 are qualitatively similar. The variation of ∆Hmix of (CrMnFeCo)1−xNix alloys with x is qualitatively similar to that in (TiZrNbCu)1−xNix alloys, whereas that in (CrMnCoNi)1−xFex alloys is similar to the variation observed in (TiZrNbNi)1−xCux alloys. ...
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... note that the concentration scale in Figure 3 extends up to x = 1 due to the very broad concentration range of a single-phase solid solution with an FCC structure in (CrMnFeCo)1−xNix [45]. Taking into account that the studied concentration range in Figure 3 is considerably broader than that in Figure 2, the variations of thermophysical parameters in Figures 2 and 3 are qualitatively similar. The variation of ∆Hmix of (CrMnFeCo)1−xNix alloys with x is qualitatively similar to that in (TiZrNbCu)1−xNix alloys, whereas that in (CrMnCoNi)1−xFex alloys is similar to the variation observed in (TiZrNbNi)1−xCux alloys. ...
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... the qualitatively similar variations of thermophysical parameters in Figures 2 and 3, the magnitudes of these parameters are quite different. As it could be expected for alloys composed of similar, adjacent elements, the values of δ in Figure 3 are small, around 1%, thus about ten times smaller than those in Figure 2. The corresponding ∆Hmix values are larger than −7.5 kJmol −1 , thus, on average, several times larger than those in Figure 2. ...
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... the qualitatively similar variations of thermophysical parameters in Figures 2 and 3, the magnitudes of these parameters are quite different. As it could be expected for alloys composed of similar, adjacent elements, the values of δ in Figure 3 are small, around 1%, thus about ten times smaller than those in Figure 2. The corresponding ∆Hmix values are larger than −7.5 kJmol −1 , thus, on average, several times larger than those in Figure 2. ...
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... the qualitatively similar variations of thermophysical parameters in Figures 2 and 3, the magnitudes of these parameters are quite different. As it could be expected for alloys composed of similar, adjacent elements, the values of δ in Figure 3 are small, around 1%, thus about ten times smaller than those in Figure 2. The corresponding ∆Hmix values are larger than −7.5 kJmol −1 , thus, on average, several times larger than those in Figure 2. Such relatively large values of ∆Hmix in Figure 3 result from moderate interatomic interactions between the alloying components [71], as seen in the inset in Figure 3. Indeed, the smallest value of ∆Hmix among these elements is that between Mn and Ni (−11.1 kJmol −1 ). ...
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... strong interactions of Ni, Co and Cu atoms with TE atoms (inset in Figure 2) and a high melting point of Nb can all affect the distribution of constituents in our TE-TL alloys [53]. Similarly, very different strengths of interatomic interactions between different components of Cantor-type alloys (inset in Figure 3) can produce a somewhat inhomogeneous distribution of elements within these alloys [9]. ...
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... quinary TE-TL MGs studied by us [23][24][25]37,52] showed complex crystallization patterns reflected in three or more exothermic maxima spread over a broad temperature range. These consecutive crystallizations are consistent with a strong but quantitatively different bonding tendency between different TE and TL atoms inferred from their thermophysical parameters shown in the inset in Figure 2. Due to this, in Figure 6, Tx denotes the onset of the first crystallization event, and Txl denotes the temperature of the exothermic maximum corresponding to the last crystallization event appearing in the corresponding DSC trace. ...
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... rule of mixtures predicts a linear decrease in Tm from 2041 for x = 0 to 1883 K for x = 0.5, whereas the experimental values increase from 1121 to 1179 K over the same concentration range. The observed strong deviation of experimental values of Tm from those calculated by using the rule of mixtures is probably associated with a strong bonding tendency between alloying elements (inset in Figure 2) and with the local atomic arrangements around Ti and Zr atoms which are different from those in the stable phases of the corresponding pure metals [23][24][25]52,66]. By using the experimental values of Tm, we can compare the contributions to the free energy from ∆Hmix ( Figure 2) and ∆Sconf Tm. ...
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... observed strong deviation of experimental values of Tm from those calculated by using the rule of mixtures is probably associated with a strong bonding tendency between alloying elements (inset in Figure 2) and with the local atomic arrangements around Ti and Zr atoms which are different from those in the stable phases of the corresponding pure metals [23][24][25]52,66]. By using the experimental values of Tm, we can compare the contributions to the free energy from ∆Hmix ( Figure 2) and ∆Sconf Tm. As is common in TE-TL alloys [23,25,[52][53][54]66], ∆Hmix outweighs ∆Sconf Tm due to the strong interatomic bonding in all our alloys containing Ni (x ≥ 0.125). ...
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... is common in TE-TL alloys [23,25,[52][53][54]66], ∆Hmix outweighs ∆Sconf Tm due to the strong interatomic bonding in all our alloys containing Ni (x ≥ 0.125). Since our as-cast alloy TiZrNbCu, in which ∆Sconf Tm (12.84 kJ/mole) considerably outweighs ∆Hmix (6.6 kJ/mole, Figure 2), ∆Sconf Tm /∆Hmix = 1.95, was multiphase (IM) [23], it seems that in our alloys, configurational entropy has limited influence on the formation of either an SS or an amorphous phase. ...
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... discussed in some detail elsewhere [52], there are several reasons which support BCC-like local atomic arrangements in the studied glassy alloys composed of Ti, Zr, Nb, Cu and Ni or Co and probably all other a-HEAs composed of TE and TL atoms (e.g., [51,54,56]). We note that the large difference between the sizes of TE and TL atoms [72] and the corresponding atomic size mismatch, δ, ( Figure 2) also make the formation of a BCC-like local atomic arrangement in TE-TL alloys more likely than the FCC one [12,53,54,56]. Indeed, in all ∆Hmix vs. δ diagrams, the single-phase BCC alloys are situated at larger values of δ than those with an FCC crystalline structure [10- 13]. ...
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... variation is probably the best evidence for the ideal solution behavior which marks all properties of this alloy system from the parameters associated with the atomic structure [25] to the magnetic and mechanical parameters, which will be addressed later in the next section. The ideal solution behavior in these chemically complex MGs is likely, as in binary TE-Cu MGs [66,95], caused by the moderate bonding tendency between the TE and Cu atoms (Figure 2) and the nonmagnetic nature of Cu. . Sommerfeld coefficient γ of (TiZrNbNi)1−xCux MGs vs. x. ...
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... between the dendritic (rich in Mn) and interdendritic (some excess of Fe and Co) regions in (a) disappears upon annealing in (b). Figure S2: SEM-BSE image of a surface of a (CrMnFeCo)0.92Ni0.08 alloy and corresponding elemental mappings for (a) as-cast and (b) sample annealed at 1373 K for 6 h. ...
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Citations
... Usually, conventional alloys are based on one and rarely two principal elements [2] such as silver in sterling silver, iron in steel, and nickel in superalloys, with only smaller amounts of other elements. But this traditional strategy has become less successful due to the limited number of base elements in the periodic table [3]. Fortunately, a novel class of alloys based on multi-principal elements was independently introduced in 2004 by Yeh and his collaborators to reinforce the development of new materials. ...
Because of their high mixing entropies, multi-component alloys can exhibit enhanced catalytic activity compared to traditional catalysts in various chemical reactions, including hydrogenation, oxidation, and reduction processes. In this work, new AgCoCuFeNi high entropy alloy nanoparticles were synthesized by the hydrogen reduction-assisted ultrasonic spray pyrolysis method. The aim was to investigate the effects of processing parameters (reaction temperature, precursor solution concentration, and residence time) on the microstructure, composition, and crystallinity of the high entropy alloy nanoparticles. The characterization was performed with scanning electron microscope, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The syntheses performed at 600, 700, 800, and 900 °C, resulted in smaller and smoother spherical particles with a near-equiatomic elemental composition as the temperature increased to 900 °C. With 0.25, 0.1, and 0.05 M precursor solutions, narrower size distribution and uniform AgCoCuFeNi nanoparticles were produced by reducing the solution concentration to 0.05 M. A near-equiatomic elemental composition was only obtained at 0.25 and 0.05 M. Increasing the residence time from 5.3 to 23.8 s resulted in an unclear particle microstructure. None of the five metal elements were formed in the large tubular reactor. X-ray diffraction revealed that various crystal phase structures were obtained in the synthesized AgCoCuFeNi particles.
... However, as noted in our previous reports, 8,25-28 a combination of experimental photoemission spectroscopy (PES) and low temperature specific heat (LTSH) studies, with the theoretical studies is required to obtain a reliable insight into the ES of the studied alloy. Indeed, a detailed insight into the ES and superconducting and other properties of binary TE-TL glassy alloys, such as Zr-TL alloys (TL=Fe, Co, Ni, Cu, Rh and Pd) has been obtained through a comparison of the calculated VB structure with the experimental one, obtained from PES. 8,29 Unfortunately, there is a very limited number of PES studies performed on HEAs and CCAs,8,[25][26][27][28]30,31 with no comparison with the theoretical electronic density of states (DOS) in these studies. ...
... In order to get some insight into the effects of Al-doping on the properties of conventional TE-TL glassy alloys we also prepared and studied three Cu-Zr based alloys, Cu45Zr55, Cu45Zr45Al10, and Cu51Zr42Al7 amorphous ribbons. For the sake of completeness these results will be compared with literature data for a similar CCAs 8,26,28,31,35 and conventional alloys. 42,43 The experimental details were described in our previous reports. ...
... 42,43 The experimental details were described in our previous reports. 8,[25][26][27][28][29]31 The valence-band structure of the as-cast Al0.5TiZrPdCuNi sample was studied by XPS. The experiments were performed at the 21-ID beamline of the NSLS II synchrotron, with 350 eV photons. ...
The valence band (VB) structure of an Al0.5TiZrPdCuNi high-entropy alloy (HEA) obtained using x-ray photoelectron spectroscopy has been compared to that recently calculated by Odbadrakh et al. [J. Appl. Phys. 126, 095104 (2019)]. Both the experimental and theoretical VBs show a split-band structure, typical for alloys consisting of the early (TE) and late (TL) transition metals. Accordingly, several electronic structure (ES) properties of this alloy, both in the glassy and crystalline state, are compared with those of similar TE-TL alloys. The comparison shows a strong effect of alloying with Al on the density of states at the Fermi level, N(EF), and on the magnetic susceptibility of Al0.5TiZrPdCuNi HEA, similar to that in conventional glassy alloys, such as Zr-Cu-Al ones. Despite some similarity in the theoretical and experimental density of states of the VBs, there are significant differences between them, which should be taken into account in any future studies of ES in HEAs and other compositionally complex alloys.
... For a long period, the development of technological alloys has been grounded on the traditional concept of solvents and solutes. The main goal of this approach was to improve the properties of the solvent element, also known as matrix, by incorporating certain quantities of solutes [1,2]. In various situations, this addition can lead to the formation of a second phase that modifies several properties. ...
Classical molecular dynamics simulations were used to investigate the structure and mechanical properties in the equiatomic Hf-Nb-Ta-Ti-Zr high entropy alloy. The open-source code LAMMPS was used to generate alloys with different crystalline lattices to determine the stable structure at 300 K. Alloying elements interacted under the action of the MEAM interatomic potential. The result showed that the alloy stabilizes in body-centered cubic (BCC) structure at 300 K. However, a wide dispersion of potential energy data as a function of atomic separation suggests the coexistence of another crystalline phase. Heating tests indicated a polymorphic phase transformation from BCC to hexagonal close-packed (HCP) at temperatures around 1100 K. Uniaxial tensile tests at a rate of 1×1010 s−1 along the [001], [110], and [111] crystallographic directions in cylindrical monocrystalline bars at 300 K were conducted. The results revealed a strong anisotropy of mechanical properties. This work provides a microscopic understanding of the mechanical behavior of the multicomponent alloy and aligns with the macroscopic theory of plastic deformation of single crystals.
... These new multicomponent metallic glasses offer interesting new research prospects. They allow us to expand our understanding of the effects of composition changes and chemical complexity on material properties, and they open up the possibility of comparisons with high-entropy alloys, which posses chemical but not structural disorder [12][13][14]. ...
We present a systematic study of electrical resistivity, superconductive transitions and the Hall effect for three systems of compositionally complex amorphous alloys of early (TE) and late (TL) transition metals: (TiZrNbNi)1−xCux and (TiZrNbCu)1−xCox in a broad composition range of 0<x<0.5 as well as Ti0.30Zr0.15Nb0.15Cu0.2Ni0.2, Ti0.15Zr0.30Nb0.15Cu0.2Ni0.2 and Ti0.15Zr0.15Nb0.30Cu0.2Ni0.2. All samples showed high resistivity at room temperature, 140–240 μΩ cm, and the superconducting transition temperatures decreased with increasing late transition metal content, similar to binary amorphous and crystalline high-entropy TE-TL alloys. The Hall coefficient RH was temperature-independent and positive for all samples (except for (TiZrNbCu)0.57Co0.43), in good agreement with binary TE-TL alloys. Finally, for the temperature dependence of resistivity, as far as the authors are aware, we present a new model with two conduction channels, one of them being variable range hopping, such as the parallel conduction mode in the temperature range 20–200 K, with the exponent p=1/2. We examine this in the context of variable range hopping in granular metals.
... However, the basic understanding of CCAs is still quite limited, which is detrimental to their design and their application. We note that in addition to the intrinsic complexity of CCAs, the deficiencies in their current understanding also result from shortcomings in the previous research, as already noted in previously published papers [7][8][9]11,[15][16][17][18][19][22][23][24][25][26][27][28][29]. Some examples of these caveats include the highly uneven distribution of research on CCAs regarding their composition [7], the frequently unjustified use of the rule of mixtures (ROM) for the calculation of their properties [22][23][24][25][26][27][28][29][30], the excessive use of mixing entropy to explain their formation and properties [11,[15][16][17][18][19][22][23][24][25][26][27][28][29][30][31] and highly insufficient experimental studies of their electronic structure (ES) [11,22,23,28]. ...
... We note that in addition to the intrinsic complexity of CCAs, the deficiencies in their current understanding also result from shortcomings in the previous research, as already noted in previously published papers [7][8][9]11,[15][16][17][18][19][22][23][24][25][26][27][28][29]. Some examples of these caveats include the highly uneven distribution of research on CCAs regarding their composition [7], the frequently unjustified use of the rule of mixtures (ROM) for the calculation of their properties [22][23][24][25][26][27][28][29][30], the excessive use of mixing entropy to explain their formation and properties [11,[15][16][17][18][19][22][23][24][25][26][27][28][29][30][31] and highly insufficient experimental studies of their electronic structure (ES) [11,22,23,28]. A lack of adequate insight into the ES, which in metallic systems determines almost all properties [32][33][34], is probably the main obstacle to the conceptual understanding of both crystalline (c-) and amorphous (a-) CCAs [11,22,23,28,30,[35][36][37][38]. ...
... We note that in addition to the intrinsic complexity of CCAs, the deficiencies in their current understanding also result from shortcomings in the previous research, as already noted in previously published papers [7][8][9]11,[15][16][17][18][19][22][23][24][25][26][27][28][29]. Some examples of these caveats include the highly uneven distribution of research on CCAs regarding their composition [7], the frequently unjustified use of the rule of mixtures (ROM) for the calculation of their properties [22][23][24][25][26][27][28][29][30], the excessive use of mixing entropy to explain their formation and properties [11,[15][16][17][18][19][22][23][24][25][26][27][28][29][30][31] and highly insufficient experimental studies of their electronic structure (ES) [11,22,23,28]. A lack of adequate insight into the ES, which in metallic systems determines almost all properties [32][33][34], is probably the main obstacle to the conceptual understanding of both crystalline (c-) and amorphous (a-) CCAs [11,22,23,28,30,[35][36][37][38]. ...
Citation: Pervan, P.; Mikšić Trontl, V.; Figueroa, I.A.; Valla, T.; Pletikosić, I.; Babić, E. Compositionally Complex Alloys: Some Insights from Photoemission Spectroscopy. Abstract: Photoemission spectroscopy (PES) is an underrepresented part of current and past studies of compositionally complex alloys (CCA) such as high-entropy alloys (HEA) and their derivatives. PES studies are very important for understanding the electronic structure of materials, and are therefore essential in some cases for a correct description of the intrinsic properties of CCAs. Here, we present several examples showing the importance of PES. First, we show how the difference between the split-band structure and the common-band structure of the valence band (VB), observed by PES, can explain a range of properties of CCAs and alloys in general. A simple description of the band crossing in CCAs composed from the early and late transition metals showing a split band is discussed. We also demonstrate how a high-accuracy PES study can determine the variation in the density of states at the Fermi level as a function of Cu content in Ti-Zr-Nb-Ni-Cu metallic glasses. Finally, the first results of an attempt to single out the contributions of particular constituents in Cantor-type alloys to their VBs are presented. The basic principles of PES, the techniques employed in studies presented, and some issues associated with PES measurements are also described.
... The configuration entropy of high-entropy alloys is greater than 1.5 R. According to this definition, a mediumentropy alloy is defined as an alloy whose configuration entropy is between 1.2 R and 1.5 R and consists of an equiatomic ratio of two to four principal elements [2,3]. Due to the mechanical properties, such as high strength, high plasticity, good low-temperature fracture toughness, and excellent corrosion resistance, of medium-and high-entropy alloys, they have received extensive attention in recent years [4][5][6][7][8][9][10][11][12]. Compared with other mediumentropy alloys and high-entropy alloys, CoCrNi medium-entropy alloys have excellent comprehensive properties, such as higher ductility, strength, and fracture toughness. ...
Powder metallurgy possesses the advantages of low energy consumption, less material consumption, uniform composition, and near-final forming. In order to improve the mechanical properties and high-temperature oxidation resistance of CoCrNi medium-entropy alloy (MEA), CoCrNiAlX (X = 0, 0.1, 0.3, 0.5, 0.7) MEAs were prepared using mechanical alloying (MA) and spark-plasma sintering (SPS). The effect of aluminum content on the microstructure and properties of the MEAs was investigated. The results show that the CoCrNi MEA is composed of face center cubic (fcc) phase and some carbides (Cr23C6). With the increase in Al content, there exists Al2O3 precipitation. When the Al content is increased to Al0.5 and Al0.7, the body center cubic (bcc) phase begins to precipitate. The addition of aluminum significantly enhances the properties of the alloys, especially those containing fcc+bcc dual-phase solid solutions. The yield strength, compressive strength, and hardness of CoCrNiAl0.7 alloy are as high as 2083 MPa, 2498 MPa, and 646 HV, respectively. The high-temperature resistance also reaches the oxidation resistance level. Different oxides include Cr2O3, Al2O3, and (Co, Ni) Cr2O4 and NiCrO3 spinel oxides formed on the surface of alloys. The formation of an Al2O3 oxidation film prevents the further erosion of the matrix by oxygen elements.
... [4,[7][8][9][10][11][12][13][14] This enhancement is specific to TE-TL MGs and does not depend on the number of components in a given alloy. [4,[15][16][17] Thus, it is unlikely to be caused only by changes in the entropy of mixing. ...
... Compared with the SiC-reinforced AMCs, the metal particlesreinforced AMCs have better mechanical properties. In recent years, a new type of alloy, high-entropy alloy (HEA), has gradually entered the field of vision [14][15][16]. High-entropy alloys are also known as multi-principal or multi-component alloys [17]. HEAs have many advantages, such as a high strength and good plasticity, so they are paid more attention to in material science and engineering [18]. ...
Aluminum matrix composites (AMCs) reinforced by 1.5 and 3 wt% FeCoCrNi high-entropy alloy particles (HEAp) were obtained by a stir casting process. The AMCs strip was further prepared by room temperature rolling (RTR, 298 K) and cryorolling (CR, 77 K). The mechanical properties of the AMCs produced by RTR and CR were studied. The effect of a microstructure on mechanical properties of composites was analyzed by scanning electron microscopy (SEM). The results show that CR can greatly improve the mechanical properties of the HEAp/AMCs. Under 30% rolling reduction, the ultimate tensile strength (UTS) of the RTR 1.5 wt% HEAp/AMCs was 120.3 MPa, but it increased to 139.7 MPa in CR composites. Due to the volume shrinkage effect, the bonding ability of CR HEAp/AMCs reinforcement with Al matrix was stronger, exhibiting higher mechanical properties
... (Very recently, the validity of the approximate proportionality between E and H V has been established for Ti-Zr-Nb-Cu-Ni MGs.) 88 For this type of MGs, one can also estimate the yield stress from H V 84 and, providing that one knows Poisson's ratio, calculate the values of G and B from that of E. Since the vibrational properties, in particular, the Debye temperatures, of MGs (e.g., Refs. 17, 24, and 27) are also related to the strength of interatomic bonding, the observed increase in the Debye temperature in our alloys, going from x = 0.2 to 0.43, 51 also supports the increase in the strength of interatomic bonding with increasing Co content. ...
In this article, we describe the characterization of a newly fabricated amorphous alloy system (TiZrNbCu)1−xCox covering a broad composition range from high-entropy (HEA) to Co-rich alloys (x ≤ 0.43). We investigated thermal stability, atomic and electronic structure, and magnetic and mechanical properties as a function of chemical composition x. One of the important findings is that all studied properties change their dependence on concentration x within the HEA range. In particular, it has been found that the average atomic volume deviates from Vegard’s law for x > 0.2, the concentration for which the average atomic packing fraction suddenly changes. The valence band structure, studied with ultraviolet photoemission spectroscopy, shows a split-band shape with 3d-states of Co approaching the Fermi level on increasing x. Due to the onset of magnetic correlations, magnetic susceptibility rapidly increases for x > 0.25. Very high microhardness increases rapidly with x. The results are compared with those for similar binary and quinary metallic glasses and with those for Cantor type of crystalline alloys.
Because of their high mixing entropies, multi-component alloys can exhibit enhanced catalytic activity compared to traditional catalysts in various chemical reactions, including hydrogenation, oxidation, and reduction processes. In this work, new AgCoCuFeNi high entropy alloy nanoparticles were synthesized by the hydrogen reduction-assisted ultrasonic spray pyrolysis method. The aim was to investigate the effects of processing parameters (reaction temperature, precursor solution concentration, and residence time) on the microstructure, composition, and crystallinity of the high entropy alloy nanoparticles. The characterization was performed with scanning electron microscope, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The syntheses performed at 600, 700, 800, and 900 °C, resulted in smaller and smoother spherical particles with nearly equiatomic elemental composition as temperature increased to 900 °C. With 0.25, 0.1, and 0.05 M precursor solutions, narrower size distribution and uniform AgCoCuFeNi nanoparticles were produced by reducing the solution concentration to 0.05 M. Near equiatomic elemental composition was only obtained at 0.25 and 0.05 M. Increasing the residence time from 5.3 to 23.8 s resulted in unclear particle microstructure. None of the five metal elements were formed in the large tubular reactor. X-ray diffraction revealed that various crystal phase structures were obtained in the synthesized AgCoCuFeNi particles.
