Nanoscale modulated structures by balanced distribution of atoms and mechanical/structural stabilities in CoCuFeMnNi high entropy alloys

Shim, Sang Hun; Oh, Seung Min; Lee, Jeongkuk; Hong, Sung-Tae; Hong, Sun Ig

doi:10.1016/j.msea.2019.138120

Cited by 40 publications

(18 citation statements)

References 56 publications

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“…Ni cannot be concluded to segregate to either from this profile. This data qualitatively agrees with the segregation behavior reported for the arc-melted alloy 8 and most non-equilibrium solidified materials in the MnFeCoNiCu system 7,[9][10][11][12][13] . Note that the average secondary dendrite arm spacing ( ) is measured to be approximately 800 nm for the re-solidified material.…”

Section: Resultssupporting

confidence: 89%

“…Several studies have proposed Cu to be responsible for compositional segregation in as-solidified MPCAs, due to its positive binary enthalpy of mixing with other common constituent elements 3,7,[9][10][11][12][13][14][15] . The mechanism for such segregation behavior, however, remains unclear, as there are limited accounts of in situ research in MPCA solidification.…”

mentioning

confidence: 99%

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In situ synchrotron diffraction and modeling of non-equilibrium solidification of a MnFeCoNiCu alloy

Schneiderman

Chuang

Kenesei

et al. 2021

Sci Rep

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The solidification mechanism and segregation behavior of laser-melted Mn35Fe5Co20Ni20Cu20 was firstly investigated via in situ synchrotron x-ray diffraction at millisecond temporal resolution. The transient composition evolution of the random solid solution during sequential solidification of dendritic and interdendritic regions complicates the analysis of synchrotron diffraction data via any single conventional tool, such as Rietveld refinement. Therefore, a novel approach combining a hard-sphere approximation model, thermodynamic simulation, thermal expansion measurement and microstructural characterization was developed to assist in a fundamental understanding of the evolution of local composition, lattice parameter, and dendrite volume fraction corresponding to the diffraction data. This methodology yields self-consistent results across different methods. Via this approach, four distinct stages were identified, including: (I) FCC dendrite solidification, (II) solidification of FCC interdendritic region, (III) solid-state interdiffusion and (IV) final cooling with marginal diffusion. It was found out that in Stage I, Cu and Mn were rejected into liquid as Mn35Fe5Co20Ni20Cu20 solidified dendritically. During Stage II, the lattice parameter disparity between dendrite and interdendritic region escalated as Cu and Mn continued segregating into the interdendritic region. After complete solidification, during Stage III, the lattice parameter disparity gradually decreases, demonstrating a degree of composition homogenization. The volume fraction of dendrites slightly grew from 58.3 to 65.5%, based on the evolving composition profile across a dendrite/interdendritic interface in diffusion calculations. Postmortem metallography further confirmed that dendrites have a volume fraction of 64.7% ± 5.3% in the final microstructure.

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Section: Resultssupporting

confidence: 89%

mentioning

confidence: 99%

In situ synchrotron diffraction and modeling of non-equilibrium solidification of a MnFeCoNiCu alloy

Schneiderman

Chuang

Kenesei

et al. 2021

Sci Rep

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“…Many HEA researchers have demonstrated that the formation of HEAs is not highly dependent on the maximum configurational entropy via equiatomic ratios of elements. In addition, they reported that entropy is not the most dominant factor in the strength of solid solution-strengthened HEAs [15,18,19]. These arguments led to more active research on non-equiatomic HEAs, compared to equiatomic HEAs [20].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Evolution and Mechanical Properties of Non-Equiatomic (CoNi)74.66Cr17Fe8C0.34 High-Entropy Alloy

et al. 2022

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In this study, we manufactured a non-equiatomic (CoNi)74.66Cr17Fe8C0.34 high-entropy alloy (HEA) consisting of a single-phase face-centered-cubic structure. We applied in situ neutron diffraction coupled with electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) to investigate its tensile properties, microstructural evolution, lattice strains and texture development, and the stacking fault energy. The non-equiatomic (CoNi)74.66Cr17Fe8C0.34 HEA revealed a good combination of strength and ductility in mechanical properties compared to the equiatomic CoNiCrFe HEA, due to both stable solid solution and precipitation-strengthened effects. The non-equiatomic stoichiometry resulted in not only a lower electronegativity mismatch, indicating a more stable state of solid solution, but also a higher stacking fault energy (SFE, ~50 mJ/m2) due to the higher amount of Ni and the lower amount of Cr. This higher SFE led to a more active motion of dislocations relative to mechanical twinning, resulting in severe lattice distortion near the grain boundaries and dislocation entanglement near the twin boundaries. The abrupt increase in the strain hardening rate (SHR) at the 1~3% strain during tensile deformation might be attributed to the unusual stress triaxiality in the {200} grain family. The current findings provide new perspectives for designing non-equiatomic HEAs.

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“…Spacial variations in the chemical composition have been commonly observed experimentally in MPEAs and are described as local chemical ordering (LCO) or local short range order (SRO) for the short and medium ranges and is said to lead to the increase in the yield strength and hardening due to size and modulus mismatches [3,12,13]. Depending on the specific alloy composition, LCO can promote complex dislocation dynamics characterized by sluggish dislocation glide and complex dislocation interactions [4,14]. Furthermore, for some face-centered cubic (FCC) MPEAs intense cross-slip was observed, which was explained by the resistance against dislocation glide on primary slip systems caused by sluggish dislocation motion [13,15].…”

Section: Introductionmentioning

confidence: 99%

The effect of local chemical ordering on dislocation activity in multi-principle element alloys: a three-dimensional discrete dislocation dynamics study

Sudmanns,

El-Awady

2021

Preprint

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The exceptional combination of strength and ductility in multi-component alloys is often attributed to the interaction of dislocations with the various solute atoms in the alloy. To study these effects on the mechanical properties of such alloys there is a need to develop a modeling framework capable of quantifying the effect of these solutes on the evolution of dislocation networks. Large scale three-dimensional (3D) Discrete dislocation dynamics (DDD) simulations can provide access to such studies but to date no relevant approaches are available that aim for a complete representation of real alloys with arbitrary chemical compositions. Here, we introduce a formulation of dislocation interaction with substitutional solute atoms in fcc alloys in 3D DDD simulations that accounts for solute strengthening induced by atomic misfit as well as fluctuations in the cross-slip activation energy. Using this model, we show that local fluctuations in the chemical composition of various CrFeCoNi-based multi-principal element alloys (MPEA) lead to sluggish dislocation motion, frequent cross-slip and alignment of dislocations with solute aggregation features, explaining experimental observations related to mechanical behavior and dislocation activity. The developed method also provides a basis for further investigations of dislocation plasticity in any real arbitrary fcc alloy with substitutional solutes.

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Nanoscale modulated structures by balanced distribution of atoms and mechanical/structural stabilities in CoCuFeMnNi high entropy alloys

Cited by 40 publications

References 56 publications

In situ synchrotron diffraction and modeling of non-equilibrium solidification of a MnFeCoNiCu alloy

In situ synchrotron diffraction and modeling of non-equilibrium solidification of a MnFeCoNiCu alloy

Microstructural Evolution and Mechanical Properties of Non-Equiatomic (CoNi)74.66Cr17Fe8C0.34 High-Entropy Alloy

The effect of local chemical ordering on dislocation activity in multi-principle element alloys: a three-dimensional discrete dislocation dynamics study

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