“Treasure maps” for magnetic high-entropy-alloys from theory and experiment

Körmann, Fritz; Ma, Duancheng; Belyea, Dustin D.; Lucas, M. S.; Miller, Casey W.; Grabowski, Blazej; Sluiter, Marcel H. F.

doi:10.1063/1.4932571

Cited by 88 publications

(55 citation statements)

References 53 publications

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“…5,6 In contrast to the addition of Mn, ferromagnetic FeCoNi alloys can become paramagnetic at RT by adding Cr or CrMn in an equiatomic composition, resulting in a significant reduction of the Curie temperatures (T C ) from 868 K to 156 K for the Cr addition and 23 K for the CrMn addition in simulation. 7 It was observed that the T C increased to 355 K and 640 K when Al and Ge, respectively, were added to the FeCoNiCr alloy. 8 The change in T C was accompanied by structural decomposition into a mixture of FCC and BCC solid solution phases.…”

Section: Introductionmentioning

confidence: 98%

Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

Na¹,

Yoo

Lambert

et al. 2017

AIP Advances

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High-entropy alloys (HEAs) containing multiple principle alloying elements exhibit unique properties so they are currently receiving great attention for developing innovative alloy designs. In FeCoNi-based HEAs, magnetic behaviors strongly depend on the addition of alloying elements, usually accompanied by structural changes. In this work, the effect of non-magnetic components on the ferromagnetic transition and magnetic behaviors in equiatomic FeCoNiCrX (X=Al, Ga, Mn and Sn) HEAs was investigated. Alloy ingots of nominal compositions of HEAs were prepared by arc melting and the button ingots were cut into discs for magnetic measurements as functions of magnetic field and temperature. The HEAs of FeCoNiCrMn and FeCoNiCrSn show typical paramagnetic behaviors, composed of solid solution FCC matrix, while the additions of Ga and Al in FeCoNiCr exhibit ferromagnetic behaviors, along with the coexistence of FCC and BCC phases due to spinodal decomposition. The partial phase transition in both HEAs with the additions of Ga and Al would enhance ferromagnetic properties due to the addition of the BCC phase. The saturation magnetization for the base alloy FeCoNiCr is 0.5 emu/g at the applied field of 20 kOe (TC = 104 K). For the HEAs of FeCoNiCrGa and FeCoNiCrAl, the saturation magnetization significantly increased to 38 emu/g (TC = 703 K) and 25 emu/g (TC = 277 K), respectively. To evaluate the possibility of solid solution FCC and BCC phases in FeCoNiCr-type HEAs, we introduced a parameter of valence electron concentration (VEC). The proposed rule for solid solution formation by the VEC was matched with FeCoNiCr-type HEAs.

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Section: Introductionmentioning

confidence: 98%

Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

Na¹,

Yoo

Lambert

et al. 2017

AIP Advances

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“…These include their use as protective coatings owing to their good corrosion and wear resistance 1,80,84,115,170,171,[219][220][221][222][223][224][225][226][227][228][229][230][231] (see review of laser-deposited HEA coatings by Zhang et al 232 ), as alloys for bulk metallic glasses, 11,[233][234][235][236] and even as materials for hydrogen storage 237 and diffusion barriers. 1,181,182 There has also been interest in their magnetic 1,10,97,[238][239][240][241][242][243] and thermoelectric properties. 244 These properties and applications, and others, are discussed in more detail in the reviews by Zhang et al 14 and Tsai et al 6 The authors consider one of the most promising potential applications for HEAs is as structural materials, and this is addressed specifically in the following text.…”

Section: A Route For Alloy Developmentmentioning

confidence: 99%

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

Pickering

Jones

2016

International Materials Reviews

672

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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“…The solution may be to consider the electronic structure, the effects of which are not fully captured by the empirical approaches. To access such information, the Density Functional Theory (DFT) formalism21 can be used, such as in investigating enthalpies22 and entropies23 of formation for HEAs within spin-polarised electronic structure calculations. One simplification of the DFT approach is the Rigid Band Approximation (RBA), originally proposed for non-magnetic metallic alloys, which assumes that the energy difference between two phases is given entirely by the difference in band-structure energy24252627.…”

mentioning

confidence: 99%

The Effect of Electronic Structure on the Phases Present in High Entropy Alloys

Leong

Wróbel

Dudarev

et al. 2017

Sci Rep

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Multicomponent systems, termed High Entropy Alloys (HEAs), with predominantly single solid solution phases are a current area of focus in alloy development. Although different empirical rules have been introduced to understand phase formation and determine what the dominant phases may be in these systems, experimental investigation has revealed that in many cases their structure is not a single solid solution phase, and that the rules may not accurately distinguish the stability of the phase boundaries. Here, a combined modelling and experimental approach that looks into the electronic structure is proposed to improve accuracy of the predictions of the majority phase. To do this, the Rigid Band model is generalised for magnetic systems in prediction of the majority phase most likely to be found. Good agreement is found when the predictions are confronted with data from experiments, including a new magnetic HEA system (CoFeNiV). This also includes predicting the structural transition with varying levels of constituent elements, as a function of the valence electron concentration, n, obtained from the integrated spin-polarised density of states. This method is suitable as a new predictive technique to identify compositions for further screening, in particular for magnetic HEAs.

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“Treasure maps” for magnetic high-entropy-alloys from theory and experiment

Cited by 88 publications

References 53 publications

Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

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

The Effect of Electronic Structure on the Phases Present in High Entropy Alloys

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