High-entropy alloy
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Atomic_structure_model_of_fcc_CoCrFeMnNi.png/220px-Atomic_structure_model_of_fcc_CoCrFeMnNi.png)
High-entropy alloys (HEAs) are alloys that are formed by mixing equal or relatively large proportions of (usually) five or more elements. Prior to the synthesis of these substances, typical metal alloys comprised one or two major components with smaller amounts of other elements. For example, additional elements can be added to iron to improve its properties, thereby creating an iron-based alloy, but typically in fairly low proportions, such as the proportions of carbon, manganese, and others in various steels.[2] Hence, high-entropy alloys are a novel class of materials.[1][2] The term "high-entropy alloys" was coined by Taiwanese scientist Jien-Wei Yeh[3] because the entropy increase of mixing is substantially higher when there is a larger number of elements in the mix, and their proportions are more nearly equal.[4] Some alternative names, such as multi-component alloys, compositionally complex alloys and multi-principal-element alloys are also suggested by other researchers.[5][6]
These alloys are currently the focus of significant attention in materials science and engineering because they have potentially desirable properties.[2] Furthermore, research indicates that some HEAs have considerably better strength-to-weight ratios, with a higher degree of fracture resistance, tensile strength, and corrosion and oxidation resistance than conventional alloys.[7][8][9] Although HEAs have been studied since the 1980s, research substantially accelerated in the 2010s.[2][6][10][11][12][13][14]
Development
Although HEAs were considered from a theoretical standpoint as early as 1981[15] and 1996,[16] and throughout the 1980s, in 1995 Taiwanese scientist Jien-Wei Yeh came up with his idea for ways of actually creating high-entropy alloys, while driving through the Hsinchu, Taiwan, countryside. Soon after, he decided to begin creating these special alloys in his lab, being in the only region researching these alloys for over a decade. Most countries in Europe, the United States, and other parts of the world lagged behind in the development of HEAs. Significant research interest from other countries did not develop until after 2004 when Yeh and his team of scientists built the world's first high-entropy alloys to withstand extremely high temperatures and pressures.[17] Potential applications include use in state-of-the-art race cars, spacecraft, submarines, nuclear reactors,[18] jet aircraft, nuclear weapons, long range hypersonic missiles, and so on.[19][20]
A few months later, after the publication of Yeh's paper, another independent paper on high-entropy alloys was published by a team from the United Kingdom composed of Brian Cantor, I. T. H. Chang, P. Knight, and A. J. B. Vincent. Yeh was also the first to coin the term "high-entropy alloy" when he attributed the high configurational entropy as the mechanism stabilizing the solid solution phase.[21] Cantor did the first work in the field in the late 1970s and early 1980s, though he did not publish until 2004. Unaware of Yeh's work, he did not describe his new materials as "high-entropy" alloys, preferring the term "multicomponent alloys". The base alloy he developed, equiatomic CrMnFeCoNi, has been the subject of considerable work in the field, and is known as the "Cantor alloy", with similar derivatives known as Cantor alloys.[22] It was one of the first HEAs to be reported to form a single-phase FCC (face-centred cubic crystal structure) solid solution.[23]
Before the classification of high-entropy alloys and multi-component systems as a separate class of materials, nuclear scientists had already studied a system that can now be classified as a high-entropy alloy: within nuclear fuels Mo-Pd-Rh-Ru-Tc particles form at grain boundaries and at fission gas bubbles.[24] Understanding the behavior of these "five-metal particles" was of specific interest to the medical industry because Tc-99m is an important medical imaging isotope.
Definition
There is no universally agreed-upon definition of a HEA. The originally defined HEAs as alloys containing at least 5 elements with concentrations between 5 and 35 atomic percent.[21] Later research however, suggested that this definition could be expanded. Otto et al. suggested that only alloys that form a solid solution with no intermetallic phases should be considered true high-entropy alloys, because the formation of ordered phases decreases the entropy of the system.[25] Some authors have described four-component alloys as high-entropy alloys[26] while others have suggested that alloys meeting the other requirements of HEAs, but with only 2–4 elements[27] or a mixing entropy between R and 1.5R[28] should be considered "medium-entropy" alloys.[27]
The four core effects of HEAs
Due to their multi-component composition, HEAs exhibit different basic effect than the other traditional alloys that are based only on one or two elements. Those different effect are called "the four core effects of HEAs" and are behind a lot of the particular microstructure and properties of HEAs.[29] The four core effects are high-entropy , severe lattice distortion, sluggish diffusion, and cocktail effects.
High entropy effect
The high entropy effect is the most important effect because it can enhance the formation of solid solutions and makes the microstructure much simpler than expected. The prior knowledge expected to multi component alloys to have many different interactions among elements and thus form many different kinds of binary, ternary, and quaternary compounds and/or segregated phases. Thus, such alloys would possess complicated structure brittle by nature. This expectation in fact neglects the effect of high entropy effect. Indeed, according to the Second law of thermodynamics, the state having the lowest mixing Gibbs free energy among all possible states would be the equilibrium state. Elemental phases based on one major element have small Enthalpy of mixing () and a small Entropy of mixing (), and compound phases have large but small ; on the other hand, solid-solution phases containing multiple elements have medium and high . As a result, solid-solution phases become highly competitive for equilibrium state and more stable especially at high temperatures.[30]
Severe lattice distortion effect
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/2f/Lattice_distortion_Effect.svg/365px-Lattice_distortion_Effect.svg.png)
Because solid solution phases with multi-principal elements are usually found in HEAs, the conventional crystal structure concept is thus extended from a one or two element basis to a multi-element basis. Every atom is surrounded by different kinds of atoms and thus suffers lattice strain and stress mainly due to atomic size difference. Besides the atomic size difference, both different bonding energy and crystal structure tendency among constituent elements are also believed to cause even higher lattice distortion because non-symmetrical bindings and electronic structure exist between an atom and its first neighbours. This distortion is believed to be the source of some of the mechanical, thermal, electrical, optical, and chemical behaviour of HEAs. Thus, overall lattice distortion would be more severe than that in traditional alloys in which most matrix atoms (or solvent atoms) have the same kind of atoms as their surroundings.[30]
Sluggish diffusion effect
As explained in the last section, an HEA mainly contains random solid solution and/or ordered solid solution. Their matrices could be regarded as whole-solute matrices. In HEAs, those whole-solute matrices diffusion vacancy are surrounded by different element atoms, and thus have a specific lattice potential energy (LPE). This large fluctuation of LPE between lattice sites leads to low-LPE sites can serve as traps and hinder atomic diffusion.[31] This leads to the sluggish diffusion effect.
Cocktail effect
Cocktail effect is used to emphasise the enhancement of the properties by at least five major elements. Because HEAs might have one or more phases, the whole properties are from the overall contribution of the constituent phases. Besides, each phase is solid solution and can be viewed as a composite with properties coming not only from the basic properties of constituant by the mixture rule but also from the interactions among all the constituant and from the severe lattice distortion. The Cocktail effect take into account the effect from the atomic-scale multicomponent phases and from the multi phases composite at the micro scale.[32]
Alloy design
In conventional alloy design, one primary element such as iron, copper, or aluminum is chosen for its properties. Then, small amounts of additional elements are added to improve or add properties. Even among binary alloy systems, there are few common cases of both elements being used in nearly-equal proportions such as Pb-Sn solders. Therefore, much is known from experimental results about phases near the edges of binary phase diagrams and the corners of ternary phase diagrams and much less is known about phases near the centers. In higher-order (4+ components) systems that cannot be easily represented on a two-dimensional phase diagram, virtually nothing is known.[22]
Early research of HEA was focussed on forming single-phased solid solution, which could maximize the major features of high entropy alloy: high entropy, sluggish diffusion, severe lattice distortion, and cocktail effects. It has been pointed out that most successful materials need some secondary phase to strengthen the material,[33][34] and that any HEA used in application will have a multiphase microstructure.[35] However, it is still important to form single-phased material since a single-phased sample is essential for understanding underlying mechanism of HEA and testing specific microstructure to find structure producing special properties.[35]
Phase formation
Gibbs' phase rule, , can be used to determine an upper bound on the number of phases that will form in an equilibrium system. In his 2004 paper, Cantor created a 20-component alloy containing 5 at% of Mn, Cr, Fe, Co, Ni, Cu, Ag, W, Mo, Nb, Al, Cd, Sn, Pb, Bi, Zn, Ge, Si, Sb, and Mg. At constant pressure, the phase rule would allow for up to 21 phases at equilibrium, but far fewer actually formed. The predominant phase was a face-centered cubic solid-solution phase, containing mainly Cr, Mn, Fe, Co, and Ni. From that result, the CrMnFeCoNi alloy, which forms only a solid-solution phase, was developed.[22]
The Hume-Rothery rules have historically been applied to determine whether a mixture will form a solid solution. Research into high-entropy alloys has found that in multi-component systems, these rules tend to be relaxed slightly. In particular, the rule that solvent and solute elements must have the same crystal structure does not seem to apply, as Cr, Mn, Fe, Co, and Ni have three different crystal structures as pure elements (and when the elements are present in equal concentrations, there can be no meaningful distinction between "solvent" and "solute" elements).[25]
Thermodynamic mechanisms
Phase formation of HEA is determined by thermodynamics and geometry. When phase formation is controlled by thermodynamics and kinetics are ignored, the Gibbs free energy of mixing is defined as:
where is defined as enthalpy of mixing, is temperature, and is entropy of mixing respectively. and continuously compete to determine the phase of the HEA material. Other important factors include atomic size of each element within the HEA, where Hume-Rothery rules and Akihisa Inoue [Wikidata]'s three empirical rules for bulk metallic glass play a role.
Disordered solids form when atomic size difference is small and is not negative enough. This is because every atom is about the same size and can easily substitute for each other and is not low enough to form a compound. More-ordered HEAs form as the size difference between the elements gets larger and gets more negative. When the size difference of each individual element become too large, bulk metallic glasses form instead of HEAs. High temperature and high also promote the formation of HEA because they significantly lower , making the HEA easier to form because it is more stable than other phases such as intermetallics.[36]
The multi-component alloys that Yeh developed also consisted mostly or entirely of solid-solution phases, contrary to what had been expected from earlier work in multi-component systems, primarily in the field of metallic glasses.[21][37] Yeh attributed this result to the high configurational, or mixing, entropy of a random solid solution containing numerous elements. The mixing entropy for a random ideal solid solution can be calculated by:
where is the ideal gas constant, is the number of components, and is the atomic fraction of component . From this it can be seen that alloys in which the components are present in equal proportions will have the highest entropy, and adding additional elements will increase the entropy. A five-component, equiatomic alloy will have a mixing entropy of 1.61R.[21][38]
Parameter | Design guideline |
---|---|
∆Smix | Maximized |
∆Hmix | > -10 and < 5 kJ/mol |
Ω | ≥ 1.1 |
δ | ≤ 6.6% |
VEC | ≥ 8 for fcc, <6.87 for bcc |
However, entropy alone is not sufficient to stabilize the solid-solution phase in every system. The enthalpy of mixing (ΔH), must also be taken into account. This can be calculated using:
where is the binary enthalpy of mixing for A and B.[39] Zhang et al. found, empirically, that in order to form a complete solid solution, ΔHmix should be between -10 and 5 kJ/mol.[38] In addition, Otto et al. found that if the alloy contains any pair of elements that tend to form ordered compounds in their binary system, a multi-component alloy containing them is also likely to form ordered compounds.[25]
Both of the thermodynamic parameters can be combined into a single, unitless parameter Ω:
where Tm is the average melting point of the elements in the alloy. Ω should be greater than or equal to 1.0, (or 1.1 in practice), which means entropy dominates over enthalpy at the point of solidification, to promote solid solution development.[40][41]
Ω can be optimized by adjusting element composition. Waite J. C. has proposed an optimisation algorithm to maximize Ω and demonstrated that slight change in composition could cause huge increase of Ω.[35]
Kinetic mechanisms
The atomic radii of the components must also be similar in order to form a solid solution. Zhang et al. proposed a parameter δ, average lattice mismatch, representing the difference in atomic radii:
where ri is the atomic radius of element i and . Formation of a solid-solution phase requires a δ ≤ 6.6%, which is an empirical number based on experiments on bulk metallic glasses (BMG).[35] Exception are found on both side of 6.6%: some alloys with 4% < δ ≤ 6.6% do form intermetallics,[38][40] and solid-solution phase do appear in alloy with δ > 9%[41]
The multi-element lattice in HEAs is highly distorted because all elements are solute atoms and their atomic radii are different. δ helps evaluating the lattice strain caused by disorder crystal structure. When the atomic size difference (δ) is sufficiently large, the distorted lattice would collapse and a new phase such as an amorphous structure would be formed. The lattice distortion effect can result in solid solution hardening.[2]
Other properties
For those alloys that do form solid solutions, an additional empirical parameter has been proposed to predict the crystal structure that will form. HEAs are usually FCC (face-centred cubic), BCC (body-centred cubic), HCP (hexagonal close-packed), or a mixture of the above structures, and each structure have their own advantages and disadvantages in terms of mechanical properties. There are many methods to predict the structure of HEA. Valence electron concentration (VEC) can be used to predict the stability of the HEA structure. The stability of physical properties of the HEA is closely associated with electron concentration (this is associated with the electron concentration rule from the Hume-Rothery rules).
When HEA is made with casting, only FCC structures are formed when VEC is larger than 8. When VEC is between 6.87 and 8, HEA is a mixture of BCC and FCC, and while VEC is below 6.87, the material is BCC. In order to produce certain crystal structure of HEA, certain phase stabilizing elements can be added. Experimentally, adding elements such as Al and Cr and help the formation of BCC HEA while Ni and Co can help forming FCC HEA.[36]
Synthesis
High-entropy alloys are difficult to manufacture using extant techniques as of 2018[update], and typically require both expensive materials and specialty processing techniques.[42]
High-entropy alloys are mostly produced using methods that depend on the metals phase – if the metals are combined while in a liquid, solid, or gas state.
- Most HEAs have been produced using liquid-phase methods include arc melting, induction melting, and Bridgman solidification.[40]
- Solid-state processing is generally done by mechanical alloying using a high-energy ball mill. This method produces powders that can then be processed using conventional powder metallurgy methods or spark plasma sintering. This method allows for alloys to be produced that would be difficult or impossible to produce using casting, such as LiMgAlScTi.[40][12][43] These powders have usually an irregular shape and can be transformed into spherical shape via powder spheroidization for the use in various additive manufacturing processes.[44]
- Conventional way of mechanical alloying mix all required elements in one step, where A, B, C, D elements get milled together to form ABCD directly. Vaidya et al. have proposed a new method of creating HEA with mechanical alloying called sequential alloying, where elements are added step by step.[45] In order to create AlCrFeCoNi High entropy alloy, Vaidya team first formed binary CoNi alloy and then add Fe to form tertiary FeCoNi, Cr to form CrFeCoNi, and Al to from AlCrFeCoNi. Same alloy composition can be produced through different sequence and different sequence leads to different portion of BCC and FCC phases, showing a path dependence of this method. For example, a sequence of AlCrFeCoNi milling for 70 hours in total produces alloy with 100% BCC phase while AlCrFeCoNi sequence milling for 70 hours produces alloy with 80% BCC phase.[45]
- Gas-phase processing includes processes such as sputtering or molecular beam epitaxy (MBE), which can be used to carefully control different elemental compositions to get high-entropy metallic[46] or ceramic films.[40]
Additive manufacturing[47][18] can produce alloys with a different microstructure, potentially increasing strength (to 1.3 gigapascals) as well as increasing ductility.[48]
Other techniques include thermal spray, laser cladding, and electrodeposition.[40][49]
Modeling and simulation
The atomic-scale complexity presents additional challenges to computational modelling of high-entropy alloys. Thermodynamic modeling using the CALPHAD method requires extrapolating from binary and ternary systems.[50] Most commercial thermodynamic databases are designed for, and may only be valid for, alloys consisting primarily of a single element. Thus, they require experimental verification or additional ab initio calculations such as density functional theory (DFT).[51] However, DFT modeling of complex, random alloys has its own challenges, as the method requires defining a fixed-size cell, which can introduce non-random periodicity. This is commonly overcome using the method of "special quasirandom structures", designed to most closely approximate the radial distribution function of a random system,[52] combined with the Vienna Ab initio Simulation Package. Using this method, it has been shown that results of a four-component equiatomic alloy begins to converge with a cell as small as 24 atoms.[53][54] The exact muffin-tin orbital method with the coherent potential approximation (CPA) has also been employed to model HEAs.[53][55]
Another approach based on the KKR-CPA formulation of DFT is the theory for multicomponent alloys,[56] which evaluates the two-point correlation function, an atomic short-range order parameter, ab initio. The theory has been used with success to study the Cantor alloy, CrMnFeCoNi and its derivatives,[57] the refractory HEAs,[58][59] as well as to examine the influence of a materials' magnetic state on atomic ordering tendencies.[60]
Other techniques include the 'multiple randomly populated supercell' approach, which better describes the random population of a true solid solution (although is far more computationally demanding).[61] This method has also been used to model glassy and amorphous systems without a crystal lattice (including bulk metallic glasses).[62][63]
Further, modeling techniques are being used to suggest new HEAs for targeted applications. The use of modeling techniques in this 'combinatorial explosion' is necessary for targeted and rapid HEA discovery and application.
Simulations have highlighted the preference for local ordering in some high-entropy alloys and, when the enthalpies of formation are combined with terms for configurational entropy, transition temperatures between order and disorder can be estimated,[64] allowing one to understand when effects like age hardening and degradation of an alloy's mechanical properties may be an issue.
The transition temperature to reach the solid solution (miscibility gap) was recently addressed with the Lederer-Toher-Vecchio-Curtarolo thermodynamic model.[65]
Phase diagram generation
CALPHAD (CALculation of PHAse Diagrams) is a method to create reliable thermodynamic databases that can be an effective tool when searching for single phase HEAs. However, this method can be limited since it needs to extrapolate from known binary or ternary phase diagrams. This method also does not take into account the process of material synthesis and can only predict equilibrium phases.[66] The phase diagrams of HEAs can be explored experimentally via High throughput experimentation (HTE). This method rapidly produces hundreds of samples allowing the researcher to explore a region of composition in one step and thus can used to quickly map out the phase diagram of the HEA.[67] Another way to predict the phase of the HEA is via enthalpy concentration. This method accounts for specific combinations of single phase HEA and rejects similar combinations that have been shown not to be single phase. This model uses first principle high throughput density functional theory to calculation the enthalpies, thus requiring no experiment input, and it has shown excellent agreement with reported experimental results.[68]
Properties and potential uses
Mechanical
The crystal structure of HEAs has been found to be the dominant factor in determining the mechanical properties. bcc HEAs typically have high yield strength and low ductility and vice versa for fcc HEAs. Some alloys have been particularly noted for their exceptional mechanical properties. A refractory alloy, VNbMoTaW maintains a high yield strength (>600 MPa (87 ksi)) even at a temperature of 1,400 °C (2,550 °F), significantly outperforming conventional superalloys such as Inconel 718. However, room temperature ductility is poor, less is known about other important high temperature properties such as creep resistance, and the density of the alloy is higher than conventional nickel-based superalloys.[40]
CrMnFeCoNi has been found to have exceptional low-temperature mechanical properties and high fracture toughness, with both ductility and yield strength increasing as the test temperature was reduced from room temperature to 77 K (−321.1 °F). This was attributed to the onset of nanoscale twin boundary formation, an additional deformation mechanism that was not in effect at higher temperatures. At ultralow temperatures, inhomogenous deformation by serrations has been reported.[69] As such, it may have applications as a structural material in low-temperature applications or, because of its high toughness, as an energy-absorbing material.[70] However, later research showed that lower-entropy alloys with fewer elements or non-equiatomic compositions may have higher strength[71] or higher toughness.[72] No ductile to brittle transition was observed in the bcc AlCrFeCoNi alloy in tests as low as 77 K.[40]
Al0.5CrFeCoNiCu was found to have a high fatigue life and endurance limit, possibly exceeding some conventional steel and titanium alloys. But there was significant variability in the results, suggesting the material is very sensitive to defects introduced during manufacturing such as aluminum oxide particles and microcracks.[73]
A single-phase nanocrystalline Al20Li20Mg10Sc20Ti30 alloy was developed with a density of 2.67 g cm−3 and microhardness of 4.9 – 5.8 GPa, which would give it an estimated strength-to-weight ratio comparable to ceramic materials such as silicon carbide,[12] though the high cost of scandium limits the possible uses.[74]
Rather than bulk HEAs, small-scale HEA samples (e.g. NbMoTaW micro-pillars) exhibit extraordinarily high yield strengths of 4 – 10 GPa — one order of magnitude higher than that of its bulk form – and their ductility is considerably improved. Additionally, such HEA films show substantially enhanced stability for high-temperature, long-duration conditions (at 1,100 °C for 3 days). Small-scale HEAs combining these properties represent a new class of materials in small-dimension devices potentially for high-stress and high-temperature applications.[46][26]
In 2018, new types of HEAs based on the careful placement of ordered oxygen complexes, a type of ordered interstitial complexes, have been produced. In particular, alloys of titanium, hafnium, and zirconium have been shown to have enhanced work hardening and ductility characteristics.[75]
Bala et al. studied the effects of high-temperature exposure on the microstructure and mechanical properties of the Al5Ti5Co35Ni35Fe20 high-entropy alloy. After hot rolling and air-quenching, the alloy was exposed to a temperature range of 650-900 °C for 7 days. The air-quenching caused γ′ precipitation distributed uniformly throughout the microstructure. The high-temperature exposure resulted in growth of the γ′ particles and at temperatures higher than 700 °C, additional precipitation of γ′ was observed. The highest mechanical properties were obtained after exposure to 650 °C with a yield strength of 1050 MPa and an ultimate tensile yield strength of 1370 MPa. Increasing the temperature further decreased the mechanical properties.[76]
Liu et al. studied a series of quaternary non-equimolar high-entropy alloys AlxCr15xCo15xNi70−x with x ranging from 0 to 35%. The lattice structure transitioned from FCC to BCC as Al content increased and with Al content in the range of 12.5 to 19.3 at%, the γ′ phase formed and strengthened the alloy at both room and elevated temperatures. With Al content at 19.3 at%, a lamellar eutectic structure formed composed of γ′ and B2 phases. Due to high γ′ phase fraction of 70 vol%, the alloy had a compressive yield strength of 925 MPa and fracture strain of 29% at room temperature and high yield strength at high temperatures as well with values of 789, 546, and 129 MPa at the temperatures of 973, 1123, and 1273K.[77]
In general, refractory high-entropy alloys have exceptional strength at elevated temperatures but are brittle at room temperature. The TiZrNbHfTa alloy is an exception with plasticity of over 50% at room temperature. However, its strength at high temperature is insufficient. With the aim of increasing high temperature strength Chien-Chuang et al. modified the composition of TiZrNbHfTa, and studied the mechanical properties of the refractory high-entropy alloys: TiZrMoHfTa and TiZrNbMoHfTa. Both alloys have simple BCC structure. Their experiments showed that the yield strength of TiZrNbMoHfTa had a yield strength 6 times greater than TiZrMoHfTa at 1200 °C with a fracture strain of 12% retained in the alloy at room temperature.[78]
Electrical and magnetic
CrFeCoNiCu is an fcc alloy that was found to be paramagnetic. But upon adding titanium, it forms a complex microstructure consisting of fcc solid solution, amorphous regions and nanoparticles of Laves phase, resulting in superparamagnetic behavior.[79] High magnetic coercivity has been measured in a FeMnNiCoBi alloy.[49] There are several magnetic high-entropy alloys which exhibit promising soft magnetic behavior with strong mechanical properties.[80] Superconductivity was observed in TiZrNbHfTa alloys, with transition temperatures between 5.0 and 7.3 K.[81]
Thermal Stability
Since high-entropy alloys are likely utilized in high temperature environment, the thermal stability is very important for designing HEA. This is especially critical for nano-crystalline where extra driving force exists for grain growth. Two aspects need to be considered for nano-crystalline HEAs: the stability of phases formed, which is dominated by the thermodynamics mechanism (see alloy design), and the retention of nanocrystallinity.[82] The stability of nano-crystalline HEAs are controlled by many factors, including grain boundary diffusion, presence of oxide etc.
Other
The high concentrations of multiple elements leads to slow diffusion. The activation energy for diffusion was found to be higher for several elements in CrMnFeCoNi than in pure metals and stainless steels, leading to lower diffusion coefficients.[83] Some equiatomic multicomponent alloys have also been reported to show good resistance to damage by energetic radiation.[84] High-entropy alloys are investigated for hydrogen storage applications.[85][86] Some high-entropy alloys such as TiZrCrMnFeNi show fast and reversible hydrogen storage at room temperature with good storage capacity for commercial applications.[87] The high-entropy materials have high potential for a wider range of energy applications, particularly in the form of high-entropy ceramics.[88][89]
High-entropy alloy films (HEAFs)
Introduction
Most HEAs are prepared by vacuum arc melting, which obtains larger grain sizes at the μm-level. As a result, studies regarding high-performance high entropy alloy films (HEAFs) have attracted more material scientists. Compared to the preparation methods of the HEA bulk materials, HEAFs are easily achieved by rapid solidification with a faster cooling rate of 10^9 K/s.[90] A rapid cooling rate can limit the diffusion of the constituent elements, inhibit phase separation, favor the formation of the single solid-solution phase or even an amorphous structure,[91] and obtain a smaller grain size (nm) than those of HEA bulk materials (μm). So far, lots of technologies have been used to fabricate the HEAFs such as spraying, laser cladding, electrodeposition, and magnetron sputtering. Magnetron Sputtering technique is the most-used method to fabricate the HEAFs. An inert gas (Ar) is introduced in a vacuum chamber and it's accelerated by a high voltage that is applied between the substrate and the target.[92] As a result, a target is bombarded by the energetic ions and some atoms are ejected from the target surface, then these atoms reach the substrate and condense on the substrate to form a thin film.[92] The composition of each constituent element in HEAFs can be controlled by a given target and the operational parameters like power, gas flow, bias, and working distance between substrate and target during film deposition. Also, the oxide, nitride, and carbide films can be readily prepared by introducing reactive gases such as O2, N2, and C2H2. Until now, Li et al. summarized three routes to prepare HEAFs via the magnetron sputtering technique.[91] First, a single HEA target can be used to fabricate the HEAFs. The related contents of the as-deposited films are approximately equal to that of the original target alloy even though each element has a different sputtering yield with the help of the pre-sputtering step.[91] However, preparing a single HEA target is very time-consuming and difficult. For example, it's hard to produce an equiatomic CoCrFeMnNi alloy target due to the high evaporation rate of Mn. Thus, the additional amount of Mn is hard to expect and calculate to ensure each element is equiatomic. Secondly, HEAFs can be synthesized by co-sputtering deposition with various metal targets.[91] A wide range of chemical compositions can be controlled by varying the processing conditions such as power, bias, gas flow, etc. Based on the published papers, lots of researchers doped different quantities of elements such as Al, Mo, V, Nb, Ti, and Nd into the CrMnFeCoNi system, which can modify the chemical composition and structure of the alloy and improve the mechanical properties. These HEAFs were prepared by co-sputtering deposition with a single CrMnFeCoNi alloy and Al/Ti/V/Mo/Nb targets.[93][94][95][96][97] However, it needs trial and error to obtain the desired composition. Take AlxCrMnFeCoNi films as an example.[93] The crystalline structure changed from the single FCC phase for x = 0.07 to duplex FCC + BCC phases for x = 0.3, and eventually, to a single BCC phase for x = 1.0. The whole process was manipulated by varying both powers of CoCrFeMnNi and Al targets to obtain desired compositions, showing a phase transition from FCC to BCC phase with increasing Al contents. The last one is via the powder targets.[91] The compositions of the target are simply adjusted by altering the weight fractions of the individual powders, but these powders must be well-mixed to ensure homogeneity. AlCrFeCoNiCu films were successfully deposited by sputtering pressed power targets.[98]
Recently, there are more researchers investigated the mechanical properties of the HEAFs with nitrogen incorporation due to superior properties like high hardness. As above-mentioned, nitride-based HEAFs can be synthesized via magnetron sputtering by incorporating N2 and Ar gases into the vacuum chamber. Adjusting the nitrogen flow ratio, RN = N2/(Ar + N2), can obtain different amounts of nitrogen. Most of them increased the nitrogen flow ratio to study the correlation between phase transformation and mechanical properties.
Hardness and related modulus values
Both values of hardness and related modulus like reduced modulus (Er) or elastic modulus (E) will significantly increase through the magnetron sputtering method. This is because the rapid cooling rate can limit the growth of grain size, i.e., HEAFs have smaller grain sizes compared to bulk counterparts, which can inhibit the motion of dislocation and then lead to an increase in mechanical properties such as hardness and elastic modulus. For instance, CoCrFeMnNiAlx films were successfully prepared by the co-sputtering method.[93] The as-deposited CoCrFeMnNi film (Al0) exhibited a single FCC structure with a lower hardness of around 5.71 GPa, and the addition of a small amount of Al atoms resulted in an increase to 5.91 GPa in the FCC structure of Al0.07. With the further addition of Al, the hardness increased drastically to 8.36 GPa in the duplex FCC + BCC phases region. When the phase transformed to a single BCC structure, the Al1.3 film reached a maximum hardness of 8.74 GPa. As a result, the structural transition from FCC to BCC led to hardness enhancements with the increasing Al content. It is worth noting that Al-doped CoCrFeMnNi HEAs have been processed and their mechanical properties have been characterized by Xian et al.[99] and the measured hardness values are included in Hsu et al. work for comparison. Compared to Al-doped CoCrFeMnNi HEAs, Al-doped CoCrFeMnNi HEAFs had a much higher hardness, which could be attributed to the much smaller size of HEAFs (nm vs. μm). Also, the reduced modulus in Al0 and Al1.3 are 172.84 and 167.19 GPa, respectively.
In addition, the RF-sputtering technique was capable of depositing CoCrFeMnNiTix HEAFs by co-sputtering of CoCrFeMnNi alloy and Ti targets.[94] The hardness increased drastically to 8.61 GPa for Ti0.2 by adding Ti atoms to the CoCrFeMnNi alloy system, suggesting good solid solution strengthening effects. With the further addition of Ti, the Ti0.8 film had a maximum hardness of 8.99 GPa. The increase in hardness was due to both the lattice distortion effect and the presence of the amorphous phase that was attributed to the addition of the larger Ti atoms to the CoCrFeMnNi alloy system. This is different from CoCrFeMnNiTix HEAs because the bulk alloy has intermetallic precipitate in the matrix. The reason is the difference in cooling rate, i.e., the preparation method of the bulk HEAs has slower cooling rate and thus intermetallic compound will appear in HEAs. Instead, HEAFs have higher cooling rate and limit the diffusion rate, so they seldom have intermetallic phases. And the reduced modulus in Ti0.2 and Ti0.8 are 157.81 and 151.42 GPa, respectively. Other HEAFs were successfully fabricated by the magnetron sputtering technique and the hardness and the related modulus values are listed in Table 1.
For nitride-HEAFs, Huang et al. prepared (AlCrNbSiTiV)N films and investigated the effect of nitrogen content on structure and mechanical properties.[100] They found that both values of hardness (41 GPa) and elastic modulus (360 GPa) reached a maximum when RN = 28%. The (AlCrMoTaTiZr)Nx film deposited at RN = 40% with the highest hardness of 40.2 GPa and elastic modulus of 420 GPa.[101] Chang et al. fabricated (TiVCrAlZr)N on silicon substrates under different RN = 0 ~ 66.7%. At RN = 50%, the hardness and elastic modulus of the films reached maximum values of 11 and 151 GPa.[102] Liu et al. studied the (FeCoNiCuVZrAl)N HEAFs and increased the RN ratio from 0 to 50%.[103] They observed both values of hardness and elastic modulus exhibited maxima of 12 and 166 GPa with an amorphous structure at RN = 30%. Other related nitride-based HEAFs are summarized in Table 2. Compared to pure metallic HEAFs (Table 1), most nitride-based films have larger hardness and elastic muduls due to the formation of binary compound consisting of nitrogen. However, there are still some films possessing relatively low hardness, which are smaller than 20 GPa, The reason is the inclusion of non-nitride-forming elements.[91]
Until now, there are lots of studies focused on the HEAFs and designed different compositions and techniques. The grain size, phase transformation, structure, densification, residual stress, and the content of nitrogen, carbon, and oxygen also can affect the values of hardness and elastic modulus. Therefore, they still delve into the correlation between the microstructures and mechanical properties and the related applications.
Table 1. The published papers regarding the pure metallic HEAFs and their phase, hardness and related modulus values via magnetron sputtering method.
Composition | Phase | Hardness (GPa) | Related Modulus (GPa) | Reference |
---|---|---|---|---|
CrMnFeCoNi | FCC | 5.71 | Er = 172.84 | [93] |
CoCrFeMnNiAl1.3 | BCC | 8.74 | Er = 167.19 | [93] |
Al0.3CoCrFeNi | FCC + BCC | 11.09 | E = 186.01 | [104] |
CrCoCuFeNi | FCC + BCC | 15 | E = 181 | [105] |
CoCrFeMnNiTi0.2 | FCC | 8.61 | Er = 157.81 | [94] |
CoCrFeMnNiTi0.8 | Amorphous | 8.99 | Er = 151.42 | [94] |
CoCrFeMnNiV0.07 | FCC | 7.99 | E = 206.4 | [95] |
CoCrFeMnNiV1.1 | Amorphous | 8.69 | E = 144.6 | [95] |
(CoCrFeMnNi)99.5Mo0.5 | FCC | 4.62 | Er = 157.76 | [96] |
(CoCrFeMnNi)85.4Mo14.6 | Amorphous | 8.77 | Er = 169.17 | [96] |
(CoCrFeMnNi)92.8Nb7.2 | Amorphous | 8.1 | Er ~105 | [97] |
TiZrNbHfTa | FCC | 5.4 | — | [106] |
FeCoNiCrCuAlMn | FCC + BCC | 4.2 | — | [107] |
FeCoNiCrCuAl0.5 | FCC | 4.4 | — | [107] |
AlCrMnMoNiZr | Amorphous | 7.2 | E = 172 | [108] |
AlCrMoTaTiZr | Amorphous | 11.2 | E = 193 | [101] |
AlCrTiTaZr | Amorphous | 9.3 | E = 140 | [109] |
AlCrMoNbZr | BCC + Amorphous | 11.8 | — | [110] |
AlCrNbSiTiV | Amorphous | 10.4 | E = 177 | [100] |
AlCrSiTiZr | Amorphous | 11.5 | E ~206 | [111] |
CrNbSiTaZr | Amorphous | 20.12 | — | [112] |
CrNbSiTiZr | Amorphous | 9.6 | E = 179.7 | [113] |
AlFeCrNiMo | BCC | 4.98 | — | [114] |
CuMoTaWV | BCC | 19 | E = 259 | [115] |
TiVCrZrHf | Amorphous | 8.3 | E = 104.7 | [116] |
ZrTaNbTiW | Amorphous | 4.7 | E = 120 | [117] |
TiVCrAlZr | Amorphous | 8.2 | E = 128.9 | [102] |
FeCoNiCuVZrAl | Amorphous | 8.6 | E = 153 | [103] |
Table 2. Current publications regarding the nitride-based HEAFs and their structures, the related hardness and elastic modulus values.
Composition | RN (%) | Phase | Hardness (GPa) | Elastic Modulus (GPa) | Reference |
---|---|---|---|---|---|
(FeCoNiCuVZrAl)N | 30 | Amorphous | 12 | E = 166 | [103] |
(TiZrNbHfTa)N | 25 | FCC | 32.9 | — | [106] |
(TiVCrAlZr)N | 50 | FCC | 11 | E = 151 | [102] |
(AlCrTaTiZr)N | 14 | FCC | 32 | E = 368 | [109] |
(FeCoNiCrCuAl0.5)N | 33.3 | Amorphous | 10.4 | — | [107] |
(FeCoNiCrCuAlMn)N | 23.1 | Amorphous | 11.8 | — | [107] |
(AlCrMnMoNiZr)N | 50 | FCC | 11.9 | E = 202 | [108] |
(TiVCrZrHf)N | 3.85 | FCC | 23.8 | E = 267.3 | [116] |
(NbTiAlSiW)N | 16.67 | Amorphous | 13.6 | E = 154.4 | [118] |
(NbTiAlSi)N | 16.67 | FCC | 20.5 | E = 206.8 | |
(AlCrNbSiTiV)N | 5 | FCC | 35 | E ~ 337 | [100] |
28 | FCC | 41 | E = 360 | ||
(AlCrTaTiZr)N | 50 | FCC | 36 | E = 360 | [119] |
(Al23.1Cr30.8Nb7.7Si7.7Ti30.7)N50 | — | FCC | 36.1 | E ~ 430 | [120] |
(Al29.1Cr30.8Nb11.2Si7.7Ti21.2)N50 | FCC | 36.7 | E ~ 380 | ||
(AlCrSiTiZr)N | 5 | Amorphous | 17 | E ~ 232 | [111] |
30 | FCC | 16 | E ~ 232 | ||
(AlCrMoTaTiZr)N | 40 | FCC | 40.2 | E = 420 | [101] |
(AlCrTaTiZr)N | 50 | FCC | 35 | E = 350 | [121] |
(CrTaTiVZr)N | 20 | FCC | 34.3 | E ~ 268 | [122] |
(CrNbTiAlV)N | 67.86 | FCC | 35.3 | E = 353.7 | [123] |
(HfNbTiVZr)N | 33.33 | FCC | 7.6 | E = 270 | [124] |
High-entropy ultra-high temperature ceramics
A subset of ultra-high temperature ceramics (UHTC) includes high-entropy ultra-high temperature ceramics, also referred to as compositionally complex ceramics (CCC). This class of materials is a leading choice for applications that experience extreme conditions, such as hypersonic applications which endure very high temperature, corrosion, and high strain rates.[125][126] In general, UHTCs possess desirable properties including high melting temperature, high thermal conductivity, high stiffness and hardness, and high corrosion resistance.[127] CCCs exemplify the tunability of UHTC systems by adding in more elements to the overall composition in approximately equimolar proportions. These high-entropy materials have displayed enhanced mechanical properties and performance compared to the traditional UHTC system.[128]
As an emerging field, a fully comprehensive relationship between composition, microstructure, processing, and properties is not yet completely developed. Therefore, there is a lot of ongoing research in this field to better understand this system and its ability to scale to implementation in extreme environment applications. A multitude of factors contribute to the elevated mechanical properties in CCC. Notably, the complex microstructure and particular processing parameters enables these systems to display improved properties such as higher hardness.[129] A plausible reason as to why CCCs may exhibit even higher hardness than traditional UHTCs may be due to the integration of various transition metals of different sizes in the CCC high-entropy lattice, rather than just a single repeating element of the same size in the metallic sites. Plastic deformation in materials is due to the movement of dislocations. Generally speaking, increased movement of dislocations throughout the lattice leads to deformation, while inhibition of dislocation motion leads to less deformation and a harder material. In ceramics, dislocation motion is extremely limited due to more constraints in the ceramic bonding structure, which explains their higher hardness over metals. Since the CCC structure has a wider variety of elemental sizes, it will become even more difficult for any dislocations to move in these systems, increasing the strain energy needed to move dislocations. This phenomena may explain the further improved hardness that is observed.[130][131] In addition to the direct effects that the microstructure has on enhancing properties, optimizing processing parameters for CCCs is crucial. For instance, powders may be processed using high energy ball milling (HEBM) which relies on the principle of mechanical alloying. Mechanical alloying balances competing mechanisms of deformation and recovery, including micro-forging, cold welding, and fracturing.[132] With the proper balance achieved, this processing step yields a refined and homogeneous powder, which subsequently facilitates proper densification of the final part and desirable mechanical properties.[133] Incomplete densification or an unacceptable fraction of voids diminishes the overall mechanical properties, as it would lead to premature failure. To conclude, high-entropy UHTCs or CCCs are extremely promising candidates for applications in extreme environments as evidenced so far by their enhanced properties.
See also
References
- ^ a b Wang, Shaoqing (13 December 2013). "Atomic Structure Modeling of Multi-Principal-Element Alloys by the Principle of Maximum Entropy". Entropy. 15 (12): 5536–5548. Bibcode:2013Entrp..15.5536W. doi:10.3390/e15125536.
- ^ a b c d e Tsai, Ming-Hung; Yeh, Jien-Wei (30 April 2014). "High-Entropy Alloys: A Critical Review". Materials Research Letters. 2 (3): 107–123. doi:10.1080/21663831.2014.912690.
- ^ Yeh, J.-W.; Chen, S.-K.; Lin, S.-J.; Gan, J.-Y.; Chin, T.-S.; Shun, T.-T.; Tsau, C.-H.; Chang, S.-Y. (May 2004). "Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes". Advanced Engineering Materials. 6 (5): 299–303. doi:10.1002/adem.200300567. ISSN 1438-1656. S2CID 137380231.
- ^ Ye, Y.F.; Wang, Q.; Lu, J.; Liu, C.T.; Yang, Y. (July 2016). "High-entropy alloy: challenges and prospects". Materials Today. 19 (6): 349–362. doi:10.1016/j.mattod.2015.11.026.
- ^ Miracle, D.B.; Senkov, O.N. (January 2017). "A critical review of high entropy alloys and related concepts". Acta Materialia. 122: 448–511. Bibcode:2017AcMat.122..448M. doi:10.1016/j.actamat.2016.08.081. ISSN 1359-6454.
- ^ a b George, Easo P.; Raabe, Dierk; Ritchie, Robert O. (2019-06-18). "High-entropy alloys". Nature Reviews Materials. 4 (8): 515–534. Bibcode:2019NatRM...4..515G. doi:10.1038/s41578-019-0121-4. ISSN 2058-8437. OSTI 1550755. S2CID 196206754.
- ^ Raabe, Dierk; Tasan, Cemal Cem; Springer, Hauke; Bausch, Michael (2015-07-21). "From High-Entropy Alloys to High-Entropy Steels". Steel Research International. 86 (10): 1127–1138. doi:10.1002/srin.201500133. ISSN 1611-3683. S2CID 53702488.
- ^ Gludovatz, Bernd; Hohenwarter, Anton; Catoor, Dhiraj; Chang, Edwin H.; George, Easo P.; Ritchie, Robert O. (2014-09-05). "A fracture-resistant high-entropy alloy for cryogenic applications". Science. 345 (6201): 1153–1158. Bibcode:2014Sci...345.1153G. doi:10.1126/science.1254581. ISSN 0036-8075. PMID 25190791. S2CID 1851195.
- ^ Li, Zezhou; Zhao, Shiteng; Ritchie, Robert O.; Meyers, Marc A. (2019-05-01). "Mechanical properties of high-entropy alloys with emphasis on face-centered cubic alloys". Progress in Materials Science. 102: 296–345. doi:10.1016/j.pmatsci.2018.12.003. ISSN 0079-6425. OSTI 1634203. S2CID 140083145.
- ^ Lavine, M. S. (4 September 2014). "A metal alloy that is stronger when cold". Science. 345 (6201): 1131. Bibcode:2014Sci...345Q1131L. doi:10.1126/science.345.6201.1131-b.
- ^ Shipman, Matt (December 10, 2014). "New 'high-entropy' alloy is as light as aluminum, as strong as titanium alloys". Phys.org.
- ^ a b c Youssef, Khaled M.; Zaddach, Alexander J.; Niu, Changning; Irving, Douglas L.; Koch, Carl C. (9 December 2014). "A Novel Low-Density, High-Hardness, High-entropy Alloy with Close-packed Single-phase Nanocrystalline Structures". Materials Research Letters. 3 (2): 95–99. doi:10.1080/21663831.2014.985855.
- ^ Yarris, Lynn (4 September 2014). "A Metallic Alloy That is Tough and Ductile at Cryogenic Temperatures". News Center.
- ^ Gludovatz, B.; Hohenwarter, A.; Catoor, D.; Chang, E. H.; George, E. P.; Ritchie, R. O. (4 September 2014). "A fracture-resistant high-entropy alloy for cryogenic applications". Science. 345 (6201): 1153–1158. Bibcode:2014Sci...345.1153G. doi:10.1126/science.1254581. PMID 25190791. S2CID 1851195.
- ^ Vincent AJB; Cantor B: part II thesis, University of Sussex (1981).
- ^ Huang KH, Yeh JW. A study on multicomponent alloy systems containing equal-mole elements [M.S. thesis]. Hsinchu: National Tsing Hua University; 1996.
- ^ Yeh, J.-W.; Chen, S.-K.; Lin, S.-J.; Gan, J.-Y.; Chin, T.-S.; Shun, T.-T.; Tsau, C.-H.; Chang, S.-Y. (May 2004). "Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes". Advanced Engineering Materials. 6 (5): 299–303. doi:10.1002/adem.200300567. ISSN 1438-1656.
- ^ a b Sonal, Sonal; Lee, Jonghyun (December 2021). "Recent Advances in Additive Manufacturing of High Entropy Alloys and Their Nuclear and Wear-Resistant Applications". Metals. 11 (12): 1980. doi:10.3390/met11121980.
- ^ Wei-han, Chen (10 June 2016). "Taiwanese researcher gets special 'Nature' coverage - Taipei Times". The Taipei Times.
- ^ Yeh, Jien Wei; Chen, Yu Liang; Lin, Su Jien; Chen, Swe Kai (November 2007). "High-Entropy Alloys – A New Era of Exploitation". Materials Science Forum. 560: 1–9. doi:10.4028/www.scientific.net/MSF.560.1. S2CID 137011733.
- ^ a b c d Yeh, J.-W.; Chen, S.-K.; Lin, S.-J.; Gan, J.-Y.; Chin, T.-S.; Shun, T.-T.; Tsau, C.-H.; Chang, S.-Y. (May 2004). "Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes". Advanced Engineering Materials. 6 (5): 299–303. doi:10.1002/adem.200300567. S2CID 137380231.
- ^ a b c Cantor, B.; Chang, I.T.H.; Knight, P.; Vincent, A.J.B. (July 2004). "Microstructural development in equiatomic multicomponent alloys". Materials Science and Engineering: A. 375–377: 213–218. doi:10.1016/j.msea.2003.10.257.
- ^ Cantor, B.; Chang, I. T. H.; Knight, P.; Vincent, A. J. B. (2004-07-01). "Microstructural development in equiatomic multicomponent alloys". Materials Science and Engineering: A. 375–377: 213–218. doi:10.1016/j.msea.2003.10.257. ISSN 0921-5093.
- ^ Middleburgh, S. C.; King, D. M.; Lumpkin, G. R. (April 2015). "Atomic scale modelling of hexagonal structured metallic fission product alloys". Royal Society Open Science. 2 (4): 140292. Bibcode:2015RSOS....240292M. doi:10.1098/rsos.140292. PMC 4448871. PMID 26064629.
- ^ a b c Otto, F.; Yang, Y.; Bei, H.; George, E.P. (April 2013). "Relative effects of enthalpy and entropy on the phase stability of equiatomic high-entropy alloys". Acta Materialia. 61 (7): 2628–2638. Bibcode:2013AcMat..61.2628O. doi:10.1016/j.actamat.2013.01.042.
- ^ a b Zou, Yu; Maiti, Soumyadipta; Steurer, Walter; Spolenak, Ralph (February 2014). "Size-dependent plasticity in an Nb25Mo25Ta25W25 refractory high-entropy alloy". Acta Materialia. 65: 85–97. Bibcode:2014AcMat..65...85Z. doi:10.1016/j.actamat.2013.11.049. S2CID 137229215.
- ^ a b Gali, A.; George, E.P. (August 2013). "Tensile properties of high- and medium-entropy alloys". Intermetallics. 39: 74–78. doi:10.1016/j.intermet.2013.03.018.
- ^ Miracle, Daniel; Miller, Jonathan; Senkov, Oleg; Woodward, Christopher; Uchic, Michael; Tiley, Jaimie (10 January 2014). "Exploration and Development of High Entropy Alloys for Structural Applications". Entropy. 16 (1): 494–525. Bibcode:2014Entrp..16..494M. doi:10.3390/e16010494.
- ^ Yeh, Jien-Wei (December 2013). "Alloy Design Strategies and Future Trends in High-Entropy Alloys". JOM. 65 (12): 1759–1771. Bibcode:2013JOM....65l1759Y. doi:10.1007/s11837-013-0761-6. ISSN 1047-4838. S2CID 255409483.
- ^ a b Murty, B. S.; Yeh, Jien-Wei; Ranganathan, S.; Bhattacharjee, P. P. (2019-03-16). High-Entropy Alloys. Elsevier. ISBN 978-0-12-816068-8.
- ^ Tsai, K.-Y.; Tsai, M.-H.; Yeh, J.-W. (August 2013). "Sluggish diffusion in Co–Cr–Fe–Mn–Ni high-entropy alloys". Acta Materialia. 61 (13): 4887–4897. Bibcode:2013AcMat..61.4887T. doi:10.1016/j.actamat.2013.04.058.
- ^ Yeh, Jien-Wei (2006-12-31). "Recent progress in high-entropy alloys". Annales de Chimie Science des Matériaux. 31 (6): 633–648. doi:10.3166/acsm.31.633-648.
- ^ Pickering, E. J.; Jones, N. G. (2016-04-02). "High-entropy alloys: a critical assessment of their founding principles and future prospects". International Materials Reviews. 61 (3): 183–202. Bibcode:2016IMRv...61..183P. doi:10.1080/09506608.2016.1180020. ISSN 0950-6608. S2CID 138005816.
- ^ Miracle, D. B.; Senkov, O. N. (2017-01-01). "A critical review of high entropy alloys and related concepts". Acta Materialia. 122: 448–511. Bibcode:2017AcMat.122..448M. doi:10.1016/j.actamat.2016.08.081. ISSN 1359-6454.
- ^ a b c d Waite, J. C. (2019). Refractory body-centred cubic high-entropy alloys for nuclear fusion (PhD thesis). University of Oxford.
- ^ a b Gao, Michael C (2018). High-Entropy Alloys: Fundamentals and Applications. Springer. ISBN 978-3-319-80057-8.
- ^ Greer, A. Lindsay (December 1993). "Confusion by design". Nature. 366 (6453): 303–304. Bibcode:1993Natur.366..303G. doi:10.1038/366303a0. S2CID 4284670.
- ^ a b c Zhang, Y.; Zhou, Y. J.; Lin, J. P.; Chen, G. L.; Liaw, P. K. (June 2008). "Solid-Solution Phase Formation Rules for Multi-component Alloys". Advanced Engineering Materials. 10 (6): 534–538. doi:10.1002/adem.200700240. S2CID 136048022.
- ^ Takeuchi, Akira; Inoue, Akihisa (2005). "Classification of Bulk Metallic Glasses by Atomic Size Difference, Heat of Mixing and Period of Constituent Elements and Its Application to Characterization of the Main Alloying Element". Materials Transactions. 46 (12): 2817–2829. doi:10.2320/matertrans.46.2817.
- ^ a b c d e f g h Zhang, Yong; Zuo, Ting Ting; Tang, Zhi; Gao, Michael C.; Dahmen, Karin A.; Liaw, Peter K.; Lu, Zhao Ping (April 2014). "Microstructures and properties of high-entropy alloys". Progress in Materials Science. 61: 1–93. doi:10.1016/j.pmatsci.2013.10.001.
- ^ a b Yang, Xiao; Zhang, Yong (15 February 2012). "Prediction of high-entropy stabilized solid-solution in multi-component alloys". Materials Chemistry and Physics. 132 (2–3): 133–138. doi:10.1016/j.matchemphys.2011.11.021.
- ^ Johnson, Duane; Millsaps, Laura (1 May 2018). "Ames Lab takes the guesswork out of discovering new high-entropy alloys". Ames Laboratory News. U.S. Dept. of Energy. Archived from the original on 30 March 2019. Retrieved 10 December 2018.
high-entropy alloys are notoriously difficult to make, requiring expensive materials and specialty processing techniques. Even then, attempts in a laboratory don't guarantee that a theoretically possible compound is physically possible, let alone potentially useful.
- ^ Ji, Wei; Wang, Weimin; Wang, Hao; Zhang, Jinyong; Wang, Yucheng; Zhang, Fan; Fu, Zhengyi (January 2015). "Alloying behavior and novel properties of CoCrFeNiMn high-entropy alloy fabricated by mechanical alloying and spark plasma sintering". Intermetallics. 56: 24–27. doi:10.1016/j.intermet.2014.08.008. S2CID 136470556.
- ^ Abdullah, Muhammad Raies; Peng, Zhen (2024). "" Review and perspective on additive manufacturing of refractory high entropy alloys"". Materials Today Advances. 22: 100497. doi:10.1016/j.mtadv.2024.100497. ISSN 2590-0498.
- ^ a b Vaidya, Mayur; Prasad, Anil; Parakh, Abhinav; Murty, B. S. (2017-07-15). "Influence of sequence of elemental addition on phase evolution in nanocrystalline AlCoCrFeNi: Novel approach to alloy synthesis using mechanical alloying". Materials & Design. 126: 37–46. doi:10.1016/j.matdes.2017.04.027. ISSN 0264-1275.
- ^ a b Zou, Yu; Ma, Huan; Spolenak, Ralph (10 July 2015). "Ultrastrong ductile and stable high-entropy alloys at small scales". Nature Communications. 6 (1): 7748. Bibcode:2015NatCo...6.7748Z. doi:10.1038/ncomms8748. PMC 4510962. PMID 26159936.
- ^ Chaudhary, V.; Mantri, S. A.; Ramanujan, R. V.; Banerjee, R. (2020-10-01). "Additive manufacturing of magnetic materials". Progress in Materials Science. 114: 100688. doi:10.1016/j.pmatsci.2020.100688. ISSN 0079-6425. S2CID 219742591.
- ^ Irving, Michael (2022-08-10). "3D-printable 5-metal alloy proves ultra-strong but ductile". New Atlas. Retrieved 2022-08-10.
- ^ a b Yao, Chen-Zhong; Zhang, Peng; Liu, Meng; Li, Gao-Ren; Ye, Jian-Qing; Liu, Peng; Tong, Ye-Xiang (November 2008). "Electrochemical preparation and magnetic study of Bi–Fe–Co–Ni–Mn high-entropy alloy". Electrochimica Acta. 53 (28): 8359–8365. doi:10.1016/j.electacta.2008.06.036.
- ^ Zhang, Chuan; Zhang, Fan; Chen, Shuanglin; Cao, Weisheng (29 June 2012). "Computational Thermodynamics Aided High-Entropy Alloy Design". JOM. 64 (7): 839–845. Bibcode:2012JOM....64g.839Z. doi:10.1007/s11837-012-0365-6. S2CID 136744259.
- ^ Gao, Michael; Alman, David (18 October 2013). "Searching for Next Single-Phase High-Entropy Alloy Compositions". Entropy. 15 (12): 4504–4519. Bibcode:2013Entrp..15.4504G. doi:10.3390/e15104504.
- ^ Zunger, Alex; Wei, S.-H.; Ferreira, L. G.; Bernard, James E. (16 July 1990). "Special quasirandom structures". Physical Review Letters. 65 (3): 353–356. Bibcode:1990PhRvL..65..353Z. doi:10.1103/PhysRevLett.65.353. PMID 10042897.
- ^ a b Niu, C.; Zaddach, A. J.; Oni, A. A.; Sang, X.; Hurt, J. W.; LeBeau, J. M.; Koch, C. C.; Irving, D. L. (20 April 2015). "Spin-driven ordering of Cr in the equiatomic high-entropy alloy NiFeCrCo". Applied Physics Letters. 106 (16): 161906. Bibcode:2015ApPhL.106p1906N. doi:10.1063/1.4918996.
- ^ Huhn, William Paul; Widom, Michael (19 October 2013). "Prediction of A2 to B2 Phase Transition in the High-Entropy Alloy Mo-Nb-Ta-W". JOM. 65 (12): 1772–1779. arXiv:1306.5043. Bibcode:2013JOM....65l1772H. doi:10.1007/s11837-013-0772-3. S2CID 96768205.
- ^ Tian, Fuyang; Delczeg, Lorand; Chen, Nanxian; Varga, Lajos Karoly; Shen, Jiang; Vitos, Levente (30 August 2013). "Structural stability of NiCoFeCrAlx high-entropy alloy from ab initio theory". Physical Review B. 88 (8): 085128. Bibcode:2013PhRvB..88h5128T. doi:10.1103/PhysRevB.88.085128.
- ^ Khan, Suffian N.; Staunton, J. B.; Stocks, G. M. (2016-02-16). "Statistical physics of multicomponent alloys using KKR-CPA". Physical Review B. 93 (5): 054206. arXiv:1512.05797. Bibcode:2016PhRvB..93e4206K. doi:10.1103/PhysRevB.93.054206. S2CID 119106573.
- ^ Woodgate, Christopher D.; Staunton, Julie B. (2022-03-17). "Compositional phase stability in medium-entropy and high-entropy Cantor-Wu alloys from an ab initio all-electron Landau-type theory and atomistic modeling". Physical Review B. 105 (11): 115124. arXiv:2212.08468. Bibcode:2022PhRvB.105k5124W. doi:10.1103/PhysRevB.105.115124. S2CID 247527599.
- ^ Woodgate, Christopher D.; Staunton, Julie B. (2023-01-30). "Short-range order and compositional phase stability in refractory high-entropy alloys via first-principles theory and atomistic modeling: NbMoTa, NbMoTaW, and VNbMoTaW". Physical Review Materials. 7 (1): 013801. arXiv:2211.09911. Bibcode:2023PhRvM...7a3801W. doi:10.1103/PhysRevMaterials.7.013801. S2CID 253707945.
- ^ Woodgate, Christopher D.; Staunton, Julie B. (2024-04-05). "Competition between phase ordering and phase segregation in the TixNbMoTaW and TixVNbMoTaW refractory high-entropy alloys". Journal of Applied Physics. 135 (13). arXiv:2401.16243. doi:10.1063/5.0200862. ISSN 0021-8979.
- ^ Woodgate, Christopher D.; Hedlund, Daniel; Lewis, L. H.; Staunton, Julie B. (2023-05-01). "Interplay between magnetism and short-range order in medium- and high-entropy alloys: CrCoNi, CrFeCoNi, and CrMnFeCoNi". Physical Review Materials. 7 (5): 053801. arXiv:2303.00641. Bibcode:2023PhRvM...7e3801W. doi:10.1103/PhysRevMaterials.7.053801. S2CID 258187648.
- ^ Middleburgh, S.C.; King, D.M.; Lumpkin, G.R.; Cortie, M.; Edwards, L. (June 2014). "Segregation and migration of species in the CrCoFeNi high-entropy alloy". Journal of Alloys and Compounds. 599: 179–182. doi:10.1016/j.jallcom.2014.01.135.
- ^ King, D.J.M.; Middleburgh, S.C.; Liu, A.C.Y.; Tahini, H.A.; Lumpkin, G.R.; Cortie, M.B. (January 2015). "Formation and structure of V–Zr amorphous alloy thin films". Acta Materialia. 83: 269–275. Bibcode:2015AcMat..83..269K. doi:10.1016/j.actamat.2014.10.016. hdl:10453/41214.
- ^ Middleburgh, S.C.; Burr, P.A.; King, D.J.M.; Edwards, L.; Lumpkin, G.R.; Grimes, R.W. (November 2015). "Structural stability and fission product behaviour in U3Si". Journal of Nuclear Materials. 466: 739–744. Bibcode:2015JNuM..466..739M. doi:10.1016/j.jnucmat.2015.04.052.
- ^ King, D. M.; Middleburgh, S. C.; Edwards, L.; Lumpkin, G. R.; Cortie, M. (18 June 2015). "Predicting the Crystal Structure and Phase Transitions in High-Entropy Alloys". JOM. 67 (10): 2375–2380. Bibcode:2015JOM....67j2375K. doi:10.1007/s11837-015-1495-4. hdl:10453/41212. S2CID 137273768.
- ^ Lederer, Yoav; Toher, Cormac; Vecchio, Kenneth S.; Curtarolo, Stefano (October 2018). "The search for high-entropy alloys: A high-throughput ab-initio approach". Acta Materialia. 159: 364–383. arXiv:1711.03426. Bibcode:2018AcMat.159..364L. doi:10.1016/j.actamat.2018.07.042. hdl:21.11116/0000-0003-639F-B. S2CID 119473356.
- ^ Gao, M. C.; Carney, C. S.; Doğan, Ö. N.; Jablonksi, P. D.; Hawk, J. A.; Alman, D. E. (2015-11-01). "Design of Refractory High-Entropy Alloys". JOM. 67 (11): 2653–2669. Bibcode:2015JOM....67k2653G. doi:10.1007/s11837-015-1617-z. ISSN 1543-1851. OSTI 1258464. S2CID 137121640.
- ^ Ruiz-Yo, Benjamine (2016). "The Different Roles of Entropy and Solubility in High Entropy Alloy Stability". ACS Combinatorial Science. 18 (9): 596–603. doi:10.1021/acscombsci.6b00077. PMID 27494349 – via JSTOR.
- ^ Troparevsky, M. Claudia (2015). "Criteria for Predicting the Formation of Single-Phase High-Entropy Alloys". Physical Review X. 5 (1): 011041. Bibcode:2015PhRvX...5a1041T. doi:10.1103/PhysRevX.5.011041.
- ^ Naeem, Muhammad; He, Haiyan; Zhang, Fan; Huang, Hailong; Harjo, Stefanus; Kawasaki, Takuro; Wang, Bing; Lan, Si; Wu, Zhenduo; Wang, Feng; Wu, Yuan; Lu, Zhaoping; Zhang, Zhongwu; Liu, Chain; Wang, Xun-Li (27 March 2020). "Cooperative deformation in high-entropy alloys at ultralow temperatures". Science Advances. 6 (13): eaax4002. Bibcode:2020SciA....6.4002N. doi:10.1126/sciadv.aax4002. PMC 7101227. PMID 32258390.
- ^ Otto, F.; Dlouhý, A.; Somsen, Ch.; Bei, H.; Eggeler, G.; George, E.P. (September 2013). "The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy". Acta Materialia. 61 (15): 5743–5755. Bibcode:2013AcMat..61.5743O. doi:10.1016/j.actamat.2013.06.018.
- ^ Wu, Z.; Bei, H.; Otto, F.; Pharr, G.M.; George, E.P. (March 2014). "Recovery, recrystallization, grain growth and phase stability of a family of FCC-structured multi-component equiatomic solid solution alloys". Intermetallics. 46: 131–140. doi:10.1016/j.intermet.2013.10.024.
- ^ Zaddach, A.J.; Scattergood, R.O.; Koch, C.C. (June 2015). "Tensile properties of low-stacking fault energy high-entropy alloys". Materials Science and Engineering: A. 636: 373–378. doi:10.1016/j.msea.2015.03.109.
- ^ Hemphill, M.A.; Yuan, T.; Wang, G.Y.; Yeh, J.W.; Tsai, C.W.; Chuang, A.; Liaw, P.K. (September 2012). "Fatigue behavior of Al0.5CoCrCuFeNi high-entropy alloys". Acta Materialia. 60 (16): 5723–5734. Bibcode:2012AcMat..60.5723H. doi:10.1016/j.actamat.2012.06.046.
- ^ Shipman, Matt. "New 'high-entropy' alloy is as light as aluminum, as strong as titanium alloys". Phys.org. Retrieved 29 May 2015.
- ^ "Enhanced strength and ductility in a high-entropy alloy via ordered oxygen complexes". Phys.org.
- ^ Bała, Piotr; Górecki, Kamil; Bednarczyk, Wiktor; Wątroba, Maria; Lech, Sebastian; Kawałko, Jakub (January 2020). "Effect of high-temperature exposure on the microstructure and mechanical properties of the Al5Ti5Co35Ni35Fe20 high-entropy alloy". Journal of Materials Research and Technology. 9 (1): 551–559. doi:10.1016/j.jmrt.2019.10.084. hdl:10084/139162.
- ^ Liu, Dajin; Yu, Pengfei; Li, Gong; Liaw, P.K.; Liu, Riping (May 2018). "High-temperature high-entropy alloys AlxCo15Cr15Ni70−x based on the Al-Ni binary system". Materials Science and Engineering: A. 724: 283–288. doi:10.1016/j.msea.2018.03.058.
- ^ Juan, Chien-Chang; Tsai, Ming-Hung; Tsai, Che-Wei; Lin, Chun-Ming; Wang, Woei-Ren; Yang, Chih-Chao; Chen, Swe-Kai; Lin, Su-Jien; Yeh, Jien-Wei (July 2015). "Enhanced mechanical properties of HfMoTaTiZr and HfMoNbTaTiZr refractory high-entropy alloys". Intermetallics. 62: 76–83. doi:10.1016/j.intermet.2015.03.013.
- ^ Wang, X.F.; Zhang, Y.; Qiao, Y.; Chen, G.L. (March 2007). "Novel microstructure and properties of multicomponent CoCrCuFeNiTix alloys". Intermetallics. 15 (3): 357–362. doi:10.1016/j.intermet.2006.08.005.
- ^ V. Chaudhary, R. Chaudhary, R. Banerjee, R. V. Ramanujan, Accelerated and Conventional Development of Magnetic High-Entropy Alloys, Materials Today, 49, 231-252 (2021), https://doi.org/10.1016/j.mattod.2021.03.018
- ^ Vrtnik, S.; Koželj, P.; Meden, A.; Maiti, S.; Steurer, W.; Feuerbacher, M.; Dolinšek, J. (February 2017). "Superconductivity in thermally annealed Ta-Nb-Hf-Zr-Ti high-entropy alloys". Journal of Alloys and Compounds. 695: 3530–3540. doi:10.1016/j.jallcom.2016.11.417.
- ^ Vaidya, Mayur; Muralikrishna, Garlapati Mohan; Murty, Budaraju Srinivasa (2019-03-14). "High-entropy alloys by mechanical alloying: A review". Journal of Materials Research. 34 (5): 664–686. Bibcode:2019JMatR..34..664V. doi:10.1557/jmr.2019.37. ISSN 0884-2914. S2CID 139131076.
- ^ Tsai, K.-Y.; Tsai, M.-H.; Yeh, J.-W. (August 2013). "Sluggish diffusion in Co–Cr–Fe–Mn–Ni high-entropy alloys". Acta Materialia. 61 (13): 4887–4897. Bibcode:2013AcMat..61.4887T. doi:10.1016/j.actamat.2013.04.058.
- ^ Granberg, F.; Nordlund, K.; Ullah, Mohammad W.; Jin, K.; Lu, C.; Bei, H.; Wang, L. M.; Djurabekova, F.; Weber, W. J.; Zhang, Y. (1 April 2016). "Mechanism of Radiation Damage Reduction in Equiatomic Multicomponent Single Phase Alloys". Physical Review Letters. 116 (13): 135504. Bibcode:2016PhRvL.116m5504G. doi:10.1103/PhysRevLett.116.135504. PMID 27081990.
- ^ Sahlberg, Martin; Karlsson, Dennis; Zlotea, Claudia; Jansson, Ulf (10 November 2016). "Superior hydrogen storage in high-entropy alloys". Scientific Reports. 6 (1): 36770. Bibcode:2016NatSR...636770S. doi:10.1038/srep36770. PMC 5103184. PMID 27829659.
- ^ Karlsson, Dennis; Ek, Gustav; Cedervall, Johan; Zlotea, Claudia; Møller, Kasper Trans; Hansen, Thomas Christian; Bednarčík, Jozef; Paskevicius, Mark; Sørby, Magnus Helgerud; Jensen, Torben René; Jansson, Ulf; Sahlberg, Martin (February 2018). "Structure and Hydrogenation Properties of a HfNbTiVZr High-Entropy Alloy". Inorganic Chemistry. 57 (4): 2103–2110. doi:10.1021/acs.inorgchem.7b03004. hdl:11250/2557801. PMID 29389120.
- ^ Edalati, P.; Floriano, R.; Mohammadi, A.; Li, Y.; Zepon, G.; Li, H.W.; Edalati, K. (March 2020). "Reversible room temperature hydrogen storage in high-entropy alloy TiZrCrMnFeNi". Scripta Materialia. 178: 387–390. doi:10.1016/j.scriptamat.2019.12.009. S2CID 213782769.
- ^ Akrami, S.; Edalati, P.; Fuji, M.; Edalati, K. (October 2021). "High-entropy ceramics: review of principles, production and applications". Materials Science and Engineering: R. 146: 100644. doi:10.1016/j.mser.2021.100644. S2CID 242759639.
- ^ Anandkumar, Mariappan; Bhattacharya, Saswata; Deshpande, Atul Suresh (2019-08-23). "Low temperature synthesis and characterization of single phase multi-component fluorite oxide nanoparticle sols". RSC Advances. 9 (46): 26825–26830. Bibcode:2019RSCAd...926825A. doi:10.1039/C9RA04636D. ISSN 2046-2069. PMC 9070433. PMID 35528557.
- ^ Padamata, Sai Krishna; Yasinskiy, Andrey; Yanov, Valentin; Saevarsdottir, Gudrun (2022-02-11). "Magnetron Sputtering High-Entropy Alloy Coatings: A Mini-Review". Metals. 12 (2): 319. doi:10.3390/met12020319. hdl:11250/3051725. ISSN 2075-4701.
- ^ a b c d e f Li, Wei; Liu, Ping; Liaw, Peter K. (2018-04-03). "Microstructures and properties of high-entropy alloy films and coatings: a review". Materials Research Letters. 6 (4): 199–229. doi:10.1080/21663831.2018.1434248. ISSN 2166-3831. S2CID 139286977.
- ^ a b Baptista, Andresa; Silva, Francisco; Porteiro, Jacobo; Míguez, José; Pinto, Gustavo (2018-11-14). "Sputtering Physical Vapour Deposition (PVD) Coatings: A Critical Review on Process Improvement and Market Trend Demands". Coatings. 8 (11): 402. doi:10.3390/coatings8110402. hdl:10400.22/15871. ISSN 2079-6412.
- ^ a b c d e Hsu, Ya-Chu; Li, Chia-Lin; Hsueh, Chun-Hway (2019-12-18). "Effects of Al Addition on Microstructures and Mechanical Properties of CoCrFeMnNiAlx High Entropy Alloy Films". Entropy. 22 (1): 2. Bibcode:2019Entrp..22....2H. doi:10.3390/e22010002. ISSN 1099-4300. PMC 7516440. PMID 33285777.
- ^ a b c d Hsu, Ya-Chu; Li, Chia-Lin; Hsueh, Chun-Hway (2020-10-15). "Modifications of microstructures and mechanical properties of CoCrFeMnNi high entropy alloy films by adding Ti element". Surface and Coatings Technology. 399: 126149. doi:10.1016/j.surfcoat.2020.126149. ISSN 0257-8972. S2CID 225592198.
- ^ a b c Fang, Shuang; Wang, Cheng; Li, Chia-Lin; Luan, Jun-Hua; Jiao, Zeng-Bao; Liu, Chain-Tsuan; Hsueh, Chun-Hway (2020-04-15). "Microstructures and mechanical properties of CoCrFeMnNiVx high entropy alloy films". Journal of Alloys and Compounds. 820: 153388. doi:10.1016/j.jallcom.2019.153388. ISSN 0925-8388. S2CID 213937088.
- ^ a b c Huang, Tzu-Hsuan; Hsueh, Chun-Hway (2021-08-01). "Microstructures and mechanical properties of (CoCrFeMnNi)100-xMox high entropy alloy films". Intermetallics. 135: 107236. doi:10.1016/j.intermet.2021.107236. ISSN 0966-9795. S2CID 236239363.
- ^ a b Liang, Yu-Hsuan; Li, Chia-Lin; Hsueh, Chun-Hway (2021-12-14). "Effects of Nb Addition on Microstructures and Mechanical Properties of Nbx-CoCrFeMnNi High Entropy Alloy Films". Coatings. 11 (12): 1539. doi:10.3390/coatings11121539. ISSN 2079-6412.
- ^ Braeckman, B. R.; Boydens, F.; Hidalgo, H.; Dutheil, P.; Jullien, M.; Thomann, A. -L.; Depla, D. (2015-04-01). "High entropy alloy thin films deposited by magnetron sputtering of powder targets". Thin Solid Films. 580: 71–76. Bibcode:2015TSF...580...71B. doi:10.1016/j.tsf.2015.02.070. ISSN 0040-6090.
- ^ Xian, Xin; Zhong, Zhi-Hong; Lin, Li-Jing; Zhu, Zhi-Xiong; Chen, Chang; Wu, Yu-Cheng (2018-11-20). "Tailoring strength and ductility of high-entropy CrMnFeCoNi alloy by adding Al". Rare Metals. 41 (3): 1015–1021. doi:10.1007/s12598-018-1161-4. ISSN 1001-0521. S2CID 139318962.
- ^ a b c Huang, Ping-Kang; Yeh, Jien-Wei (2009-03-25). "Effects of nitrogen content on structure and mechanical properties of multi-element (AlCrNbSiTiV)N coating". Surface and Coatings Technology. 203 (13): 1891–1896. doi:10.1016/j.surfcoat.2009.01.016. ISSN 0257-8972.
- ^ a b c Cheng, Keng-Hao; Lai, Chia-Han; Lin, Su-Jien; Yeh, Jien-Wei (2011-03-01). "Structural and mechanical properties of multi-element (AlCrMoTaTiZr)Nx coatings by reactive magnetron sputtering". Thin Solid Films. 519 (10): 3185–3190. Bibcode:2011TSF...519.3185C. doi:10.1016/j.tsf.2010.11.034. ISSN 0040-6090.
- ^ a b c Chang, Zue-Chin; Liang, Shih-Chang; Han, Sheng; Chen, Yi-Kun; Shieu, Fuh-Sheng (2010-08-15). "Characteristics of TiVCrAlZr multi-element nitride films prepared by reactive sputtering". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 268 (16): 2504–2509. Bibcode:2010NIMPB.268.2504C. doi:10.1016/j.nimb.2010.05.039. ISSN 0168-583X.
- ^ a b c Liu, L.; Zhu, J. B.; Hou, C.; Li, J. C.; Jiang, Q. (2013-04-01). "Dense and smooth amorphous films of multicomponent FeCoNiCuVZrAl high-entropy alloy deposited by direct current magnetron sputtering". Materials & Design. 46: 675–679. doi:10.1016/j.matdes.2012.11.001. ISSN 0261-3069.
- ^ Liao, Wei-Bing; Zhang, Hongti; Liu, Zhi-Yuan; Li, Pei-Feng; Huang, Jian-Jun; Yu, Chun-Yan; Lu, Yang (2019-02-04). "High Strength and Deformation Mechanisms of Al0.3CoCrFeNi High-Entropy Alloy Thin Films Fabricated by Magnetron Sputtering". Entropy. 21 (2): 146. Bibcode:2019Entrp..21..146L. doi:10.3390/e21020146. ISSN 1099-4300. PMC 7514628. PMID 33266862.
- ^ Shaginyan, L. R.; Britun, V. F.; Krapivka, N. A.; Firstov, S. A.; Kotko, A. V.; Gorban, V. F. (2018-09-01). "The Properties of Cr–Co–Cu–Fe–Ni Alloy Films Deposited by Magnetron Sputtering". Powder Metallurgy and Metal Ceramics. 57 (5): 293–300. doi:10.1007/s11106-018-9982-0. ISSN 1573-9066. S2CID 139253120.
- ^ a b Braic, V.; Vladescu, Alina; Balaceanu, M.; Luculescu, C. R.; Braic, M. (2012-10-25). "Nanostructured multi-element (TiZrNbHfTa)N and (TiZrNbHfTa)C hard coatings". Surface and Coatings Technology. Proceedings of Symposium K on Protective Coatings and Thin Films, E-MRS 2011 Conference. 211: 117–121. doi:10.1016/j.surfcoat.2011.09.033. ISSN 0257-8972.
- ^ a b c d Chen, T. K.; Shun, T. T.; Yeh, J. W.; Wong, M. S. (2004-11-01). "Nanostructured nitride films of multi-element high-entropy alloys by reactive DC sputtering". Surface and Coatings Technology. Proceedings of the 31st International Conference on Metallurgical Coatings and Thin Films. 188–189: 193–200. doi:10.1016/j.surfcoat.2004.08.023. ISSN 0257-8972.
- ^ a b Ren, Bo; Shen, Zigang; Liu, Zhongxia (2013-05-25). "Structure and mechanical properties of multi-element (AlCrMnMoNiZr)Nx coatings by reactive magnetron sputtering". Journal of Alloys and Compounds. 560: 171–176. doi:10.1016/j.jallcom.2013.01.148. ISSN 0925-8388.
- ^ a b Lai, Chia-Han; Lin, Su-Jien; Yeh, Jien-Wei; Chang, Shou-Yi (2006-12-04). "Preparation and characterization of AlCrTaTiZr multi-element nitride coatings". Surface and Coatings Technology. 201 (6): 3275–3280. doi:10.1016/j.surfcoat.2006.06.048. ISSN 0257-8972.
- ^ Zhang, W.; Tang, R.; Yang, Z. B.; Liu, C. H.; Chang, H.; Yang, J. J.; Liao, J. L.; Yang, Y. Y.; Liu, N. (2018-12-15). "Preparation, structure, and properties of high-entropy alloy multilayer coatings for nuclear fuel cladding: A case study of AlCrMoNbZr/(AlCrMoNbZr)N". Journal of Nuclear Materials. 512: 15–24. Bibcode:2018JNuM..512...15Z. doi:10.1016/j.jnucmat.2018.10.001. ISSN 0022-3115. S2CID 105282834.
- ^ a b Hsueh, Hwai-Te; Shen, Wan-Jui; Tsai, Ming-Hung; Yeh, Jien-Wei (2012-05-25). "Effect of nitrogen content and substrate bias on mechanical and corrosion properties of high-entropy films (AlCrSiTiZr)100−xNx". Surface and Coatings Technology. 206 (19): 4106–4112. doi:10.1016/j.surfcoat.2012.03.096. ISSN 0257-8972.
- ^ Kao, W. H.; Su, Y. L.; Horng, J. H.; Wu, H. M. (2021-01-01). "Effects of carbon doping on mechanical, tribological, structural, anti-corrosion and anti-glass-sticking properties of CrNbSiTaZr high entropy alloy coatings". Thin Solid Films. 717: 138448. Bibcode:2021TSF...717m8448K. doi:10.1016/j.tsf.2020.138448. ISSN 0040-6090. S2CID 229423367.
- ^ Yu, Xu; Wang, Junjun; Wang, Linqing; Huang, Weijiu (2021-04-25). "Fabrication and characterization of CrNbSiTiZr high-entropy alloy films by radio-frequency magnetron sputtering via tuning substrate bias". Surface and Coatings Technology. 412: 127074. doi:10.1016/j.surfcoat.2021.127074. ISSN 0257-8972. S2CID 233695035.
- ^ Zeng, Qunfeng; Xu, Yating (2020-09-01). "A comparative study on the tribocorrosion behaviors of AlFeCrNiMo high entropy alloy coatings and 304 stainless steel". Materials Today Communications. 24: 101261. doi:10.1016/j.mtcomm.2020.101261. ISSN 2352-4928. S2CID 219474551.
- ^ Sajid, Alvi. Synthesis and Characterization of High Entropy Alloy and Coating. ISBN 978-91-7790-395-6. OCLC 1102485976.
- ^ a b Liang, Shih-Chang; Tsai, Du-Cheng; Chang, Zue-Chin; Sung, Huan-Shin; Lin, Yi-Chen; Yeh, Yi-Jung; Deng, Min-Jen; Shieu, Fuh-Sheng (2011-10-15). "Structural and mechanical properties of multi-element (TiVCrZrHf)N coatings by reactive magnetron sputtering". Applied Surface Science. 258 (1): 399–403. Bibcode:2011ApSS..258..399L. doi:10.1016/j.apsusc.2011.09.006. ISSN 0169-4332.
- ^ Feng, Xingguo; Tang, Guangze; Ma, Xinxin; Sun, Mingren; Wang, Liqin (2013-04-15). "Characteristics of multi-element (ZrTaNbTiW)N films prepared by magnetron sputtering and plasma based ion implantation". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 301: 29–35. Bibcode:2013NIMPB.301...29F. doi:10.1016/j.nimb.2013.03.001. ISSN 0168-583X.
- ^ Sheng, Wenjie; Yang, Xiao; Wang, Cong; Zhang, Yong (2016-06-13). "Nano-Crystallization of High-Entropy Amorphous NbTiAlSiWxNy Films Prepared by Magnetron Sputtering". Entropy. 18 (6): 226. Bibcode:2016Entrp..18..226S. doi:10.3390/e18060226. ISSN 1099-4300.
- ^ Lai, Chia-Han; Lin, Su-Jien; Yeh, Jien-Wei; Davison, Andrew (2006-11-07). "Effect of substrate bias on the structure and properties of multi-element (AlCrTaTiZr)N coatings". Journal of Physics D: Applied Physics. 39 (21): 4628–4633. Bibcode:2006JPhD...39.4628L. doi:10.1088/0022-3727/39/21/019. ISSN 0022-3727. S2CID 62901267.
- ^ Hsieh, Ming-Hsiao; Tsai, Ming-Hung; Shen, Wan-Jui; Yeh, Jien-Wei (2013-04-25). "Structure and properties of two Al–Cr–Nb–Si–Ti high-entropy nitride coatings". Surface and Coatings Technology. 221: 118–123. doi:10.1016/j.surfcoat.2013.01.036. ISSN 0257-8972.
- ^ Lai, Chia-Han; Tsai, Ming-Hung; Lin, Su-Jien; Yeh, Jien-Wei (2007-05-21). "Influence of substrate temperature on structure and mechanical, properties of multi-element (AlCrTaTiZr)N coatings". Surface and Coatings Technology. 201 (16): 6993–6998. doi:10.1016/j.surfcoat.2007.01.001. ISSN 0257-8972.
- ^ Chang, Zue-Chin; Liang, Jun-Yang (2020-04-22). "Oxidation Behavior and Structural Transformation of (CrTaTiVZr)N Coatings". Coatings. 10 (4): 415. doi:10.3390/coatings10040415. ISSN 2079-6412.
- ^ Zhang, Cunxiu; Lu, Xiaolong; Wang, Cong; Sui, Xudong; Wang, Yanfang; Zhou, Haibin; Hao, Junying (2022-04-30). "Tailoring the microstructure, mechanical and tribocorrosion performance of (CrNbTiAlV)Nx high-entropy nitride films by controlling nitrogen flow". Journal of Materials Science & Technology. 107: 172–182. doi:10.1016/j.jmst.2021.08.032. ISSN 1005-0302. S2CID 244583979.
- ^ Johansson, Kristina; Riekehr, Lars; Fritze, Stefan; Lewin, Erik (2018-09-15). "Multicomponent Hf-Nb-Ti-V-Zr nitride coatings by reactive magnetron sputter deposition". Surface and Coatings Technology. 349: 529–539. doi:10.1016/j.surfcoat.2018.06.030. ISSN 0257-8972. S2CID 103303702.
- ^ Fahrenholtz, W. G.; Hilmas, G. E. Ultra-High Temperature Ceramics: Materials for Extreme Environments. Scripta Materialia 2017, 129, 94–99. https://doi.org/10.1016/j.scriptamat.2016.10.018.
- ^ Peters, A. B.; Zhang, D.; Chen, S.; Ott, C.; Oses, C.; Curtarolo, S.; McCue, I.; Pollock, T. M.; Eswarappa Prameela, S. Materials Design for Hypersonics. Nat Commun 2024, 15 (1), 3328. https://doi.org/10.1038/s41467-024-46753-3.
- ^ Wyatt, B. C.; Nemani, S. K.; Hilmas, G. E.; Opila, E. J.; Anasori, B. Ultra-High Temperature Ceramics for Extreme Environments. Nat Rev Mater 2023, 1–17. https://doi.org/10.1038/s41578-023-00619-0.
- ^ Oses, C.; Toher, C.; Curtarolo, S. High-Entropy Ceramics. Nat Rev Mater 2020, 5 (4), 295–309. https://doi.org/10.1038/s41578-019-0170-8.
- ^ Feng, L.; Chen, W.; Fahrenholtz, W. G.; Hilmas, G. E. Strength of Single‐phase High‐entropy Carbide Ceramics up to 2300°C. J. Am. Ceram. Soc. 2021, 104 (1), 419–427. https://doi.org/10.1111/jace.17443.
- ^ Wyatt, B. C.; Nemani, S. K.; Hilmas, G. E.; Opila, E. J.; Anasori, B. Ultra-High Temperature Ceramics for Extreme Environments. Nat Rev Mater 2023, 1–17. https://doi.org/10.1038/s41578-023-00619-0.
- ^ Feng, L.; Chen, W.; Fahrenholtz, W. G.; Hilmas, G. E. Strength of Single‐phase High‐entropy Carbide Ceramics up to 2300°C. J. Am. Ceram. Soc. 2021, 104 (1), 419–427. https://doi.org/10.1111/jace.17443.
- ^ Suryanarayana, C. Mechanical Alloying and Milling. Progress in Materials Science 2001, 46 (1–2), 1–184. https://doi.org/10.1016/S0079-6425(99)00010-9.
- ^ Zhang, Y.; Guo, W.-M.; Jiang, Z.-B.; Zhu, Q.-Q.; Sun, S.-K.; You, Y.; Plucknett, K.; Lin, H.-T. Dense High-Entropy Boride Ceramics with Ultra-High Hardness. Scripta Materialia 2019, 164, 135–139. https://doi.org/10.1016/j.scriptamat.2019.01.021.