Atomic-size effect and solid solubility of multicomponent alloys

Wang, Zhijun; Huang, Yunhao; Yang, Yong; Wang, Jincheng; Liu, Chang

doi:10.1016/j.scriptamat.2014.09.010

Cited by 374 publications

(142 citation statements)

References 17 publications

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“…Strictly speaking, Al 2 CrFeMnTi 0.25 , Al 3 CrFeMnTi 0. 25 , and Al 4 CrFeMnTi 0.25 alloys do not meet the HEA definition (HEAs consist of 5 or more elements between 5 and 35 atomic percent (at.%).) proposed by Yeh et al [2].…”

Section: Methodsmentioning

confidence: 99%

“…The trial-and-error approach that has been used for traditional alloys design is costly and time-consuming for the discovery of new HEAs because of the vast compositional space that they occupy. As a consequence, efforts have been made to study HEA phase-formation rules to accelerate the discovery process [4,[16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Taking advantage of the phase-formation rules, the constitutive phases in HEAs can be controlled and adjusted to improve mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

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Design of Light-Weight High-Entropy Alloys

Feng

Gao

Lee

et al. 2016

Entropy

191

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High-entropy alloys (HEAs) are a new class of solid-solution alloys that have attracted worldwide attention for their outstanding properties. Owing to the demand from transportation and defense industries, light-weight HEAs have also garnered widespread interest from scientists for use as potential structural materials. Great efforts have been made to study the phase-formation rules of HEAs to accelerate and refine the discovery process. In this paper, many proposed solid-solution phase-formation rules are assessed, based on a series of known and newly-designed light-weight HEAs. The results indicate that these empirical rules work for most compositions but also fail for several alloys. Light-weight HEAs often involve the additions of Al and/or Ti in great amounts, resulting in large negative enthalpies for forming solid-solution phases and/or intermetallic compounds. Accordingly, these empirical rules need to be modified with the new experimental data. In contrast, CALPHAD (acronym of the calculation of phase diagrams) method is demonstrated to be an effective approach to predict the phase formation in HEAs as a function of composition and temperature. Future perspectives on the design of light-weight HEAs are discussed in light of CALPHAD modeling and physical metallurgy principles.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design of Light-Weight High-Entropy Alloys

Feng

Gao

Lee

et al. 2016

Entropy

191

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“…Many others have since followed this methodology, using the same parameters or others that provide measures of the same key effects. 163,204,252,253,255,258,[263][264][265][266]271 138,272 have used VEC alongside compositional considerations to predict σ formation in HEAs, while others have compared instances of ordered phase formation (including topologically close-packed phases, TCPs) against the average value of the d-orbital energy level 262,273 and Dx. 274 It has been suggested that Dx it is also an indicator of elemental segregation on casting.…”

Section: Phase Prediction and Alloy Selection In Heasmentioning

confidence: 99%

High-entropy alloys: a critical assessment of their founding principles and future prospects

Pickering

Jones

2016

International Materials Reviews

697

299

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High-entropy alloys (HEAs) are a relatively new class of materials that have gained considerable attention from the metallurgical research community over recent years. They are characterised by their unconventional compositions, in that they are not based around a single major component, but rather comprise multiple principal alloying elements. Four core effects have been proposed in HEAs: (1) the entropic stabilisation of solid solutions, (2) the severe distortion of their lattices, (3) sluggish diffusion kinetics and (4) that properties are derived from a cocktail effect. By assessing these claims on the basis of existing experimental evidence in the literature, as well as classical metallurgical understanding, it is concluded that the significance of these effects may not be as great as initially believed. The effect of entropic stabilisation does not appear to be overarching, insufficient evidence exists to establish the strain in the lattices of HEAs, and rapid precipitation observed in some HEAs suggests their diffusion kinetics are not necessarily anomalously slow in comparison to conventional alloys. The meaning and influence of the cocktail effect is also a matter for debate. Nevertheless, it is clear that HEAs represent a stimulating opportunity for the metallurgical research community. The complex nature of their compositions means that the discovery of alloys with unusual and attractive properties is inevitable. It is suggested that future activity regarding these alloys seeks to establish the nature of their physical metallurgy, and develop them for practical applications. Their use as structural materials is one of the most promising and exciting opportunities. To realise this ambition, methods to rapidly predict phase equilibria and select suitable HEA compositions are needed, and this constitutes a significant challenge. However, while this obstacle might be considerable, the rewards associated with its conquest are even more substantial. Similarly, the challenges associated with comprehending the behaviour of alloys with complex compositions are great, but the potential to enhance our fundamental metallurgical understanding is more remarkable. Consequently, HEAs represent one of the most stimulating and promising research fields in materials science at present.

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“…There are some associated errors with this model [29] but more concerning is that it only represents an ideal solution and assumes a 50/50 mixture will yield the largest magnitude in the enthalpy of mixing [30]. Nevertheless, a ratio of the two contributions to the Gibbs free energy was proposed by Yang et al [31]:…”

Section: Current State-of-the-artmentioning

confidence: 99%

Predicting the formation and stability of single phase high-entropy alloys

King

Middleburgh

McGregor³

et al. 2016

Acta Materialia

317

120

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Abstract:A method for rapidly predicting the formation and stability of undiscovered single phase high-entropy alloys (SPHEAs) is provided. Our software implementation of the algorithm uses data for 73 metallic elements and rapidly combines them -4, 5 or 6 elements at a time -using the Miedema semi-empirical methodology to yield estimates of formation enthalpy. Approximately 186,000,000 compositions of 4, 5 and 6 element alloys were screened, and ~1,900 new equimolar SPHEAs predicted. Of the 185 experimentally reported HEA systems currently known, the model correctly predicted the stability of the SPHEA structure in 177. The other sixteen were suggested to actually form a partially ordered solid solution -a finding supported by other recent experimental and theoretical work. The stability of each alloy at a specific temperature can also be predicted, allowing precipitation temperatures (and the likely precipitate) to be forecast. This combinatorial algorithm is described in detail, and its software implementation is freely accessible through a webservice allowing rapid advances in the design, development and discovery of new technologically important alloys. , and re-iterated by others since then [1,12], defines a HEA as any alloy consisting of 5 or more elements between 5 -35 at. %. As such, this type of HEA will usually possess a microstructure consisting of two or more distinct phases, some of which are likely to be brittle intermetallic compounds. Although, multiphase strengthening is sometimes desirable in alloys, a large amount of any brittle phase will generally make an alloy unusable as a structural material and such HEAs are therefore mundane. However, as will be discussed shortly, in a few special cases, the additional entropy of the multi-element composition will stabilise a microstructure consisting of either (i) a single solid solution having one of the simple close-packed crystal structures (FCC, HCP or BCC) or (ii) a duplex microstructure consisting of two such simple solid solutions. Generally, it is these non-trivial examples of HEA that interest investigators.This is because the resulting random solid solution(s) will exhibit a combination of ductility coupled with significant solid solution hardening. We recommend use of the term single 2 phase high-entropy alloy (SPHEA) as a more restrictive term to differentiate the rare and desirable single phase type of HEA from generic examples of multiphase HEAs.Combining Yeh's compositional limits [7] with the requirement for a single phase solid solution, we can define a SPHEA as an alloy with  4 alloying elements, at least 4 of which with a molar ratio between 0.33 -1 to that of the highest contributing element. These alloys must be able to display a single phase of simple, random, close-packed structure below the solidus.We return now to the factors that might stabilise a SPHEA. The prevailing hypotheses were (i) that the simple crystal structure or structures are thermodynamically stabilised, relative to possible intermetallic compounds, by the inc...

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Atomic-size effect and solid solubility of multicomponent alloys

Cited by 374 publications

References 17 publications

Design of Light-Weight High-Entropy Alloys

Design of Light-Weight High-Entropy Alloys

High-entropy alloys: a critical assessment of their founding principles and future prospects

Predicting the formation and stability of single phase high-entropy alloys

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