Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo

Niu, Chunyao; Zaddach, A.J.; Oni, A.; Sang, Xiahan; Hurt, J. W.; LeBeau, James M.; Koch, Carl C.; Irving, Douglas L.

doi:10.1063/1.4918996

Cited by 186 publications

(120 citation statements)

References 25 publications

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“…Although this can be a good approximation for some alloys (e.g. in HEAs [112]), short range order (SRO), i.e. correlations between the chemical occupancy of the atomic sites, can exist in materials.…”

Section: Solid Solutions As Random Alloysmentioning

confidence: 99%

Solute strengthening in random alloys

et al. 2017

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Random solid solution alloys are a broad class of materials that are used across the entire spectrum of engineering metals, whether as stand-alone materials (e.g. Al-5xxx alloys) or as the matrix in precipitatestrengthening materials (e.g. Ni-based superalloys). As a result, the mechanisms of, and prediction of, strengthening in solid solutions has a long history. Many concepts have been developed and important trends identified but predictive capability has remained elusive. In recent years, a new theory has been developed that builds on one historical model, the Labusch model, in important ways that lead to a well-defined model valid for random solutions with arbitrary numbers of components and compositions. The new theory uses first-principles-computed solute/dislocation interaction energies as input, from which specific predictions emerge for the yield strength and activation volume as a function of alloy composition, temperature, and strain-rate. Being a general model for materials that otherwise have a low Peierls stress, it has broad application and has been successfully applied to Al-X alloys, Mg-Al, twinning in Mg alloys, and recently fcc High-Entropy Alloys. Here, the new theory is presented in a general and systematic manner. Approximations and limiting cases that reduce the complexity and facilitate understanding are introduced, and help relate the new model to various physical features present among the historical array of models. The quantitative predictions of the model in the various materials above is then demonstrated.

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Section: Solid Solutions As Random Alloysmentioning

confidence: 99%

Solute strengthening in random alloys

et al. 2017

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“…Further DFT studies revealed strong element-specific magnetic moment fluctuations in fcc FeCoNiCr, which are ultimately rooted in local electronic structure effects [20][21][22]. In particular anti-ferromagnetic Cr plays a crucial role [20]. By mixing ferro-and anti-ferromagnetic elements, significant element-specific local lattice fluctuations can be expected.…”

Section: Introductionmentioning

confidence: 99%

“…Density-functional-theory (DFT) calculations for FeCoNiCr and FeCoNi revealed that electronic charge transfer causes a local atomic pressure on the individual constituents, which could result in local volume fluctuations [19]. Further DFT studies revealed strong element-specific magnetic moment fluctuations in fcc FeCoNiCr, which are ultimately rooted in local electronic structure effects [20][21][22]. In particular anti-ferromagnetic Cr plays a crucial role [20].…”

Section: Introductionmentioning

confidence: 99%

Lattice Distortions in the FeCoNiCrMn High Entropy Alloy Studied by Theory and Experiment

Leyson

et al. 2016

Entropy

178

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Lattice distortions constitute one of the main features characterizing high entropy alloys. Local lattice distortions have, however, only rarely been investigated in these multi-component alloys. We, therefore, employ a combined theoretical electronic structure and experimental approach to study the atomistic distortions in the FeCoNiCrMn high entropy (Cantor) alloy by means of density-functional theory and extended X-ray absorption fine structure spectroscopy. Particular attention is paid to element-resolved distortions for each constituent. The individual mean distortions are small on average, <1%, but their fluctuations (i.e., standard deviations) are an order of magnitude larger, in particular for Cr and Mn. Good agreement between theory and experiment is found.

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“…[4][5][6][7][8][9][10] Up until recently, this class of high entropy material was restricted to metals and refractory ceramics [11][12][13][14] with relatively simple crystal structures within which all of the lattice sites are part of the entropic phase. In a recent set of experiments, Rost et al demonstrated a new class of material in which entropy drives the free energy landscape, an entropystabilized oxide (ESO).…”

Section: Introductionmentioning

confidence: 99%

Charge compensation and electrostatic transferability in three entropy-stabilized oxides: Results from density functional theory calculations

Rak

Rost

Lim

et al. 2016

Journal of Applied Physics

117

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Density functional theory calculations were carried out for three entropic rocksalt oxides, (Mg0.1Co0.1Ni0.1Cu0.1Zn0.1)O0.5, termed J14, and J14 + Li and J14 + Sc, to understand the role of charge neutrality and electronic states on their properties, and to probe whether simple expressions may exist that predict stability. The calculations predict that the average lattice constants of the ternary structures provide good approximations to that of the random structures. For J14, Bader charges are transferable between the binary, ternary, and random structures. For J14 + Sc and J14 + Li, average Bader charges in the entropic structures can be estimated from the ternary compositions. Addition of Sc to J14 reduces the majority of Cu, which show large displacements from ideal lattice sites, along with reduction of a few Co and Ni cations. Addition of Li to J14 reduces the lattice constant, consistent with experiment, and oxidizes some of Co as well as some of Ni and Cu. The Bader charges and spin-resolved density of states (DOS) for Co+3 in J14 + Li are very different from Co+2, while for Cu and Ni the Bader charges form continuous distributions and the two DOS are similar for the two oxidation states. Experimental detection of different oxidation states may therefore be challenging for Cu and Ni compared to Co. Based on these results, empirical stability parameters for these entropic oxides may be more complicated than those for non-oxide entropic solids.

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Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo

Cited by 186 publications

References 25 publications

Solute strengthening in random alloys

Solute strengthening in random alloys

Lattice Distortions in the FeCoNiCrMn High Entropy Alloy Studied by Theory and Experiment

Charge compensation and electrostatic transferability in three entropy-stabilized oxides: Results from density functional theory calculations

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