Polycrystalline elastic moduli of a high-entropy alloy at cryogenic temperatures

Haglund, Amanda; Köehler, Michael; Catoor, Dhiraj; George, E.P.; Keppens, Veerle

doi:10.1016/j.intermet.2014.11.005

Cited by 177 publications

(63 citation statements)

References 22 publications

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“…As seen in Fig. 4, when normalized by shear modulus, 36,37 the yield strengths at 0 K deduced by Wu et al 35 for these equiatomic ternary, quaternary and quinary alloys scale linearly with the square root of the average MSAD values and can be described by the following equation:…”

Section: -6mentioning

confidence: 87%

Atomic displacement in the CrMnFeCoNi high-entropy alloy – A scaling factor to predict solid solution strengthening

et al. 2016

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Although metals strengthened by alloying have been used for millennia, models to quantify solid solution strengthening (SSS) were first proposed scarcely seventy years ago. Early models could predict the strengths of only simple alloys such as dilute binaries and not those of compositionally complex alloys because of the difficulty of calculating dislocation-solute interaction energies. Recently, models and theories of SSS have been proposed to tackle complex high-entropy alloys (HEAs). Here we show that the strength at 0 K of a prototypical HEA, CrMnFeCoNi, can be scaled and predicted using the root-mean-square atomic displacement, which can be deduced from X-ray diffraction and first-principles calculations as the isotropic atomic displacement parameter, that is, the average displacements of the constituent atoms from regular lattice positions. We show that our approach can be applied successfully to rationalize SSS in FeCoNi, MnFeCoNi, MnCoNi, MnFeNi, CrCoNi, CrFeCoNi, and CrMnCoNi, which are all medium-entropy subsets of the CrMnFeCoNi HEA.

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Section: -6mentioning

confidence: 87%

Atomic displacement in the CrMnFeCoNi high-entropy alloy – A scaling factor to predict solid solution strengthening

et al. 2016

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“…Even though the elements in this five-element alloy possess different crystal structures, it crystallizes as a single-phase face-centered cubic (fcc) solid solution [6]. Its mechanical properties have been recently studied [7][8][9][10][11][12][13][14][15][16]. Among its interesting features is the observation that the alloy shows a strong increase of yield strength with decreasing temperature [7,9], especially in the cryogenic range, which is a characteristic of pure bodycentered cubic (bcc) metals and some binary fcc alloys but not pure fcc metals.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties, microstructure and thermal stability of a nanocrystalline CoCrFeMnNi high-entropy alloy after severe plastic deformation

et al. 2015

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Severe plastic deformation Compositionally complex alloys 3 dimensional atom probe tomography Microstructure a b s t r a c t An equiatomic CoCrFeMnNi high-entropy alloy (HEA), produced by arc melting and drop casting, was subjected to severe plastic deformation (SPD) using high-pressure torsion. This process induced substantial grain refinement in the coarse-grained casting leading to a grain size of approximately 50 nm. As a result, strength increased significantly to 1950 MPa, and hardness to 520 HV. Analyses using transmission electron microscopy (TEM) and 3-dimensional atom probe tomography (3D-APT) showed that, after SPD, the alloy remained a true single-phase solid solution down to the atomic scale. Subsequent investigations characterized the evolution of mechanical properties and microstructure of this nanocrystalline HEA upon annealing. Isochronal (for 1 h) and isothermal heat treatments were performed followed by microhardness and tensile tests. The isochronal anneals led to a marked hardness increase with a maximum hardness of 630 HV at about 450°C before softening set in at higher temperatures. The isothermal anneals, performed at this peak hardness temperature, revealed an additional hardness rise to a maximum of about 910 HV after 100 h. To clarify this unexpected annealing response, comprehensive microstructural analyses were performed using TEM and 3D-APT. New nano-scale phases were observed to form in the originally single-phase HEA. After times as short as 5 min at 450°C, a NiMn phase and Cr-rich phase formed. With increasing annealing time, their volume fractions increased and a third phase, FeCo, also formed. It appears that the surfeit of grain boundaries in the nanocrystalline HEA offer many fast diffusion pathways and nucleation sites to facilitate this phase decomposition. The hardness increase, especially for the longer annealing times, can be attributed to these nano-scaled phases embedded in the HEA matrix. The present results give new valuable insights into the phase stability of single-phase high-entropy alloys as well as the mechanisms controlling the mechanical properties of nanostructured multiphase composites.

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“…The reason for the temperature-dependent yield stress is still unclear, although a recent study of equiatomic lower-order alloys based on the elements in the CoCrFeMnNi HEA suggests that it may be related to changes in the dislocation width with temperature [19]. It can, however, be ruled out that it originates from a variation in the shear modulus, which depends only weakly on temperature in the range between 55 and 300 K [20].…”

Section: Introductionmentioning

confidence: 99%

Temperature dependencies of the elastic moduli and thermal expansion coefficient of an equiatomic, single-phase CoCrFeMnNi high-entropy alloy

Laplanche

Gadaud

Horst

et al. 2015

Journal of Alloys and Compounds

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360

112

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Temperature dependencies of the elastic moduli and thermal expansion coefficient of an equiatomic, single-phase CoCrFeMnNi high-entropy alloy, Journal of Alloys and Compounds (2014), doi: http://dx. AbstractThe equiatomic CoCrFeMnNi alloy is now regarded as a model face-centered cubic singlephase high-entropy alloy. Therefore, determination of its intrinsic properties such as the temperature dependencies of elastic moduli and thermal expansion coefficient are important to improve understanding of this new class of material. These temperature dependencies were measured over a large temperature range (200 -1270 K) in this study.

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Polycrystalline elastic moduli of a high-entropy alloy at cryogenic temperatures

Cited by 177 publications

References 22 publications

Atomic displacement in the CrMnFeCoNi high-entropy alloy – A scaling factor to predict solid solution strengthening

Atomic displacement in the CrMnFeCoNi high-entropy alloy – A scaling factor to predict solid solution strengthening

Mechanical properties, microstructure and thermal stability of a nanocrystalline CoCrFeMnNi high-entropy alloy after severe plastic deformation

Temperature dependencies of the elastic moduli and thermal expansion coefficient of an equiatomic, single-phase CoCrFeMnNi high-entropy alloy

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