Effects of electro-negativity on the stability of topologically close-packed phase in high entropy alloys

Dong, Yong; Lu, Yiping; Jiang, Li; Wang, Tongmin; Li, Tingju

doi:10.1016/j.intermet.2014.04.001

Cited by 231 publications

(101 citation statements)

References 35 publications

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“…The values of δ, ∆H mix , and Ω for the current alloy are listed in Table 3. In addition, the valence electron concentration (VEC) and Pauling electronegativity difference (∆χ) are also used to predict the formation of solid solution versus intermetallic phases in HEAs [42][43][44]. The VEC and ∆χ for multi-component alloys can be defined as:…”

Section: Phase Formationmentioning

confidence: 99%

MoNbTaV Medium-Entropy Alloy

Yao

Qiao

Gao

et al. 2016

Entropy

113

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Abstract:Guided by CALPHAD (Calculation of Phase Diagrams) modeling, the refractory medium-entropy alloy MoNbTaV was synthesized by vacuum arc melting under a high-purity argon atmosphere. A body-centered cubic solid solution phase was experimentally confirmed in the as-cast ingot using X-ray diffraction and scanning electron microscopy. The measured lattice parameter of the alloy (3.208 Å) obeys the rule of mixtures (ROM), but the Vickers microhardness (4.95 GPa) and the yield strength (1.5 GPa) are about 4.5 and 4.6 times those estimated from the ROM, respectively. Using a simple model on solid solution strengthening predicts a yield strength of approximately 1.5 GPa. Thermodynamic analysis shows that the total entropy of the alloy is more than three times the configurational entropy at room temperature, and the entropy of mixing exhibits a small negative departure from ideal mixing.

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Section: Phase Formationmentioning

confidence: 99%

MoNbTaV Medium-Entropy Alloy

Yao

Qiao

Gao

et al. 2016

Entropy

113

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“…where VEC is the average valence electron concentration; VEC i is the valence electron concentration of element i; ∆χ is the Pauling electronegativity difference; χ i is the Pauling electronegativity of element i [34]; c i , r i , and χ i are the atom fraction, radius, and electronegativity of the i-th element, respectively; and r a and χ a are the average radius and electronegativity of the elements in the alloys, respectively. Table 3 presents the corresponding values of δ, ∆H mix , ∆S mix , T mix , Ω, VEC, and ∆χ for the Al x CrFeNiV alloys (x = 0.3, and 0.5).…”

Section: Discussionmentioning

confidence: 99%

The Al Effects of Co-Free and V-Containing High-Entropy Alloys

Xia

Yang

Chen

et al. 2017

Metals

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Abstract:In this study, five-component high-entropy alloys (HEAs) Al x CrFeNiV (where x denotes the molar ratio, x = 0, 0.1, 0.3, 0.5, 0.75, 1, and 1.5) were prepared using an arc-melting furnace. The effects of the addition of the Al on the crystal structures were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Also, two non-equiatomic ratio HEAs, Al x CrFeNiV (x = 0.3, and 0.5), were systematically studied through the use of various characterization methods in the as-cast state. The Al 0.3 CrFeNiV alloy displayed typical duplex body-centered cubic (BCC) structures, including disordered BCC (A2), and NiAl-type ordered BCC (B2) phases. Meanwhile, in regard to the Al 0.5 CrFeNiV alloy, this alloy was found to contain an unknown phase which was enriched in Cr and V, as well as the coherent A2/B2 phases. Both of these alloys displayed very high yield and fracture strengths. However, their compression fracture strains were approximately 10%. Also, the fracture surfaces showed mainly cleavage fracture modes.

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“…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. 257 DS mix is not particularly useful differentiator, since it is uniformly high for HEAs.…”

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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Effects of electro-negativity on the stability of topologically close-packed phase in high entropy alloys

Cited by 231 publications

References 35 publications

MoNbTaV Medium-Entropy Alloy

MoNbTaV Medium-Entropy Alloy

The Al Effects of Co-Free and V-Containing High-Entropy Alloys

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

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