Phase formation in mechanically alloyed AlxCoCrCuFeNi (x = 0.45, 1, 2.5, 5 mol) high entropy alloys

Sriharitha, R.; Murty, B.S.; Kottada, Ravi Sankar

doi:10.1016/j.intermet.2012.08.015

Cited by 149 publications

(50 citation statements)

References 21 publications

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“…3,21,[61][62][63][64][65][66][67][68][69][70][71][72][73][74] Part of the Al x CrFeCoNiCu series of alloys, which have received a great deal of attention, 1,64,73,[75][76][77][78][79][80][81][82][83][84][85][86] initial reports appeared to suggest that Al 0.5 CrFeCoNiCu was stable as a single face-centred cubic ( fcc) solid-solution phase. 3,[62][63][64]75,76,78 Subsequent studies, however, found that this not the case, and have 17,31,35,62,69,73,[85][86][87]97,107,113,125,…”

Section: Entropic Stabilisationmentioning

confidence: 99%

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

Pickering

Jones

2016

International Materials Reviews

736

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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Section: Entropic Stabilisationmentioning

confidence: 99%

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

Pickering

Jones

2016

International Materials Reviews

736

299

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“…In addition to the above-mentioned unique structural and compositional characteristics, HEAs possess promising mechanical, magnetic and electrochemical properties, such as high hardness, high strength, high thermal stability, excellent wear resistance and outstanding oxidation resistance [11][12][13][14][15][16][17], etc. In the literature, various experimental techniques have been utilized to prepare HEAs, e.g., arc-melting [11,18], copper mold casting [14], mold-clamp casting [19], fluxed water quenching [20], melt spinning [21], injection casting [22], induction melting [23], mechanical alloying (MA) [24], reactive DC sputtering [25] and laser cladding [26], etc. However, review of the literature shows that casting is the most widely used method for processing HEAs, especially copper mold casting and arc-melting.…”

Section: Introductionmentioning

confidence: 99%

“…However, review of the literature shows that casting is the most widely used method for processing HEAs, especially copper mold casting and arc-melting. To overcome the potential segregation and inhomogeneous microstructure generated by casting, MA has been developed to prepare HEAs with better homogeneity of microstructure at room temperature [24,[27][28][29][30]. In addition, the process of MA tends to form nanocrystalline grains in the alloyed powders.…”

Section: Introductionmentioning

confidence: 99%

“…Inspection of the literature reveals that most of the reported HEAs which are prepared by MA followed by densification have equi-atomic concentrations [24,[27][28][29][30], and that there have been very few reports on medium-entropy alloys prepared by MA [30,32]. Fe, Ni, and Co with similar atomic radii can form solid solution easily, and moderate concentrations of Al and Ti with larger atomic radii are usually added into some HEAs with the aim of achieving excellent mechanical properties [14,30,31].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Ti addition and sintering method on microstructure and mechanical behavior of a medium-entropy Al 0.6 CoNiFe alloy

Chen

et al. 2014

Materials Science and Engineering: A

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“…In addition, we predict numerous potential single-phase alloy compositions and provide three tables with the ten most likely five-, six-, and seven-component single-phase alloys to guide experimental searches. The term high-entropy alloy (HEA) has come to signify nontraditional alloy systems composed of five or more elements at, or near, equiatomic ratio that form random, single-phase solid solutions on simple underlying facecentered-cubic (fcc) and body-centered-cubic (bcc) lattices [1][2][3][4][5][6][7][8][9][10][11]. HEAs stand in sharp contrast to traditional metal alloys that are typically based on one or two primary elements and where addition of further alloying elements often leads to the formation of new phases.…”

mentioning

confidence: 99%

Criteria for Predicting the Formation of Single-Phase High-Entropy Alloys

et al. 2015

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High-entropy alloys constitute a new class of materials whose very existence poses fundamental questions regarding the physical principles underlying their unusual phase stability. Originally thought to be stabilized by the large entropy of mixing associated with their large number of components (five or more), these alloys have attracted attention for their potential applications. Yet, no model capable of robustly predicting which combinations of elements will form a single phase currently exists. Here, we propose a model that, through the use of high-throughput computation of the enthalpies of formation of binary compounds, predicts specific combinations of elements most likely to form single-phase, highentropy alloys. The model correctly identifies all known single-phase alloys while rejecting similar elemental combinations that are known to form an alloy comprising multiple phases. In addition, we predict numerous potential single-phase alloy compositions and provide three tables with the ten most likely five-, six-, and seven-component single-phase alloys to guide experimental searches. The term high-entropy alloy (HEA) has come to signify nontraditional alloy systems composed of five or more elements at, or near, equiatomic ratio that form random, single-phase solid solutions on simple underlying facecentered-cubic (fcc) and body-centered-cubic (bcc) lattices [1][2][3][4][5][6][7][8][9][10][11]. HEAs stand in sharp contrast to traditional metal alloys that are typically based on one or two primary elements and where addition of further alloying elements often leads to the formation of new phases. Clearly, the existence of HEAs poses important questions regarding the driving mechanism for their unexpected stability and how to identify the specific combinations of elements that are most likely to form a single-phase HEA.Although there are several proposals regarding the stability of HEAs, much of the existing work uses semiempirical approaches based, for example, on HumeRothery rules, thus focusing on the differences of the atomic sizes (δ), electronegativities (Δχ), and electron-toatom ratio (e=a) [12][13][14][15][16][17]. Some approaches utilize calculation of phase diagrams methods [18], while others consider δ, the enthalpy of mixing (ΔH mix ), and the ideal entropy of mixing of the alloys to develop criteria for the phase stability [1,12]. For example, in the work of Guo et al. [14], the use of δ and ΔH mix as independent variables clearly separates solid-solution phases from amorphous phases but does not necessarily isolate intermetallic compounds from either one of these phases. In addition, in the work of Otto et al. [11], there are atomic substitutions to the solid-solution CrMnFeCoNi alloy that are specifically chosen to follow the Hume-Rothery rules in respect of δ, Δχ, and crystal structure yet do not form a single-phase solid solution. Useful as many of these attempts to encapsulate features of the underlying bonding mechanisms have been, it is clear that a model that can robustly predict, out ...

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Phase formation in mechanically alloyed AlxCoCrCuFeNi (x = 0.45, 1, 2.5, 5 mol) high entropy alloys

Cited by 149 publications

References 21 publications

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

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

Influence of Ti addition and sintering method on microstructure and mechanical behavior of a medium-entropy Al 0.6 CoNiFe alloy

Criteria for Predicting the Formation of Single-Phase High-Entropy Alloys

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