Insights into the phase diagram of the CrMnFeCoNi high entropy alloy

Laurent‐Brocq, Mathilde; Akhatova, A.; Perrière, Loïc; Chebini, Siham; Sauvage, Xavier; Leroy, Éric; Champion, Yannick

doi:10.1016/j.actamat.2015.01.068

Cited by 317 publications

(131 citation statements)

References 30 publications

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“…33, Reports have often upheld CrMnFeCoNi as being stable as a single solid-solution phase, a characteristic that has made its mechanical properties of great interest, and a number of studies with a focus on phase stability have confirmed this. 19,22,[58][59][60] However, it has recently been shown that exposures below 800 W C trigger precipitation in the alloy, most notably of the Cr-rich σ phase. [33][34][35] Hence, CrMnFeCoNi can no longer be thought of as stable as a single face-centred cubic ( fcc) phase below its solidus.…”

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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“…Nevertheless, the formation of microcracks at the highest testing temperature of 1073 K leads to a deterioration in ductility at this temperature. In addition, the testing temperatures used to achieve superplasticity in this investigation are >0.5T m based on the CoCrFe-NiMn phase diagram where T m  1613 K [41].…”

Section: Significance Of the Strain Rate Sensitivity In This Alloymentioning

confidence: 99%

“…41 GPa and with a very low ductility of ~4% at room temperature. No systematic investigations have been conducted to evaluate the high temperature mechanical behavior of this nanocrystalline CoCrFeNiMn alloy prepared by HPT.…”

Section: Introductionmentioning

confidence: 99%

Evidence for superplasticity in a CoCrFeNiMn high-entropy alloy processed by high-pressure torsion

Shahmir

Liu

et al. 2017

Materials Science and Engineering: A

106

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A CoCrFeNiMn high-entropy alloy was processed by high-pressure torsion to produce a grain size of ~10 nm and then tested in tension at elevated temperatures from 773 to 1073 K using strain rates in the range from 1.0 × 10 -3 to 1.0 × 10 -1 s -1 . The alloy exhibited excellent ductility at these elevated temperatures including superplastic elongations with a maximum elongation of >600% at a testing temperature of 973 K. It is concluded that the formation of precipitates and the sluggish diffusion in the HEA inhibit grain growth and contribute to a reasonable stability of the fine-grained structure at elevated temperatures. The results show the activation energy for flow matches the anticipated value for grain boundary diffusion in nickel but the strain rate sensitivity is low due to the occurrence of some grain growth at these high testing temperatures.

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“…In reality, the microstructure of alloys of multiple principle elements is usually more complicated and can consist of a mixture of different phases including intermetallic ones [2]. Among many proposed HEA compositions, CoCrFeMnNi alloy indeed has a single phase disordered fcc microstructure [3][4][5]. Due to such a 'model' structure, this alloy is currently one of the most studied HEAs so far.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures

Zherebtsov

Stepanov

Ivanisenko

et al. 2018

Metals

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High-pressure torsion (HPT) is applied to a face-centered cubic CoCrFeMnNi high-entropy alloy at 293 and 77 K. Processing by HPT at 293 K produced a nanostructure consisted of (sub)grains of~50 nm after a rotation for 180 • . The microstructure evolution is associated with intensive deformation-induced twinning, and substructure development resulted in a gradual microstructure refinement. Deformation at 77 K produces non-uniform structure composed of twinned and fragmented areas with higher dislocation density then after deformation at room temperature. The yield strength of the alloy increases with the angle of rotation at HPT at room temperature at the cost of reduced ductility. Cryogenic deformation results in higher strength in comparison with the room temperature HPT. The contribution of Hall-Petch hardening and substructure hardening in the strength of the alloy in different conditions is discussed.

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Insights into the phase diagram of the CrMnFeCoNi high entropy alloy

Cited by 317 publications

References 30 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

Evidence for superplasticity in a CoCrFeNiMn high-entropy alloy processed by high-pressure torsion

Evolution of Microstructure and Mechanical Properties of a CoCrFeMnNi High-Entropy Alloy during High-Pressure Torsion at Room and Cryogenic Temperatures

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