Vacancy Mechanism of High Oxygen Solubility and Nucleation of Stable Oxygen-Enriched Clusters in Fe

Fu, C. L.; Krčmar, Maja; Painter, G. S.; Chen, Xing-Qiu

doi:10.1103/physrevlett.99.225502

Cited by 172 publications

(128 citation statements)

References 15 publications

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“…In order to understand the formation and stability of these nanoclusters, we performed first-principles energy band calculations [11], solving the density-functional equations in the generalized gradient approximation [12] and using the ultrasoft pseudopotential method [13,14]. The vacancy mechanism of high oxygen solubility and nucleation of stable oxygen-enriched nanoclusters in Fe has been discussed previously [11].…”

Section: Resultsmentioning

confidence: 99%

Vacancies as a constitutive element for the design of nanocluster-strengthened ferritic steels

Miller

Krčmar

et al. 2008

Front. Mater. Sci. China

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The existence of nanoclusters that are thermodynamically stable at elevated temperatures is truly intriguing because of its scientific implications and potential applications. Highly stable nanoclusters have been observed by atom probe tomography in iron-based alloys at temperatures close to 1400°C (0.92T m ) that appear to defy the stability constraints of artificially created nanostructured materials. The~4-nm-diameter Ti-, Y-and Oenriched nanoclusters are identified in the new form of a highly defective material state with vacancies as the critical alloying component and with (Ti + Y):O ratio different from the stable TiO 2 and Y 2 Ti 2 O 7 oxides. Vacancies play an indispensable role in enhancing the oxygen solubility and increasing the oxygen binding energy in the presence of Ti and Y, resulting in the stabilization of coherent nanoclusters. Atom probe tomography characterizations and theoretical predictions indicate that vacancies can be exploited for the first time as a nanoscale constituent to design materials with far superior high temperature properties.

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Section: Resultsmentioning

confidence: 99%

Vacancies as a constitutive element for the design of nanocluster-strengthened ferritic steels

Miller

Krčmar

et al. 2008

Front. Mater. Sci. China

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“…15 In this context, an oxide "particle" can be as small as a fewÅngströms, correponding to just a couple of atoms. 10,12 While size of these "nanofeatures" 3 can be below the resolution obtainable in transmission electron microscopy, they nonetheless contribute to He sequestration due to their sheer number and very large effcetive interface area.…”

Section: Introductionmentioning

confidence: 99%

“…7-9). They are characterized by a fine distribution of a) Electronic mail: erhart@chalmers.se nanometer-sized oxide particles [10][11][12] that act as obstacles for dislocation motion and are metastable up to very high temperatures. The oxide particles and even more so the oxide-matrix interfaces are expected to act as sinks for He interstitials.…”

Section: Introductionmentioning

confidence: 99%

A first-principles study of helium storage in oxides and at oxide–iron interfaces

Erhart¹

2012

Journal of Applied Physics

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Density-functional theory calculations based on conventional as well as hybrid exchange-correlation functionals have been carried out to study the properties of helium in various oxides (Al 2 O 3 , TiO 2 , Y 2 O 3 , YAP, YAG, YAM, MgO, CaO, BaO, SrO) as well as at oxide-iron interfaces. Helium interstitials in bulk oxides are shown to be energetically more favorable than substitutional helium, yet helium binds to existing vacancies. The solubility of He in oxides is systematically higher than in iron and scales with the free volume at the interstitial site nearly independently of the chemical composition of the oxide. In most oxides He migration is significantly slower and He-He binding is much weaker than in iron. To quantify the solubility of helium at oxide-iron interfaces two prototypical systems are considered (Fe|MgO, Fe|FeO|MgO). In both cases the He solubility is markedly enhanced in the interface compared to either of the bulk phases. The results of the calculations allow to construct a schematic energy landscape for He interstitials in iron. The implications of these results are discussed in the context of helium sequestration in oxide dispersion strengthened steels, including the effects of interfaces and lattice strain.

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“…The ultrafine grains in NFAs remain unusually stable with little or no grain growth, coarsening or recrystallization up to 800-900°C. Although nanoclusters (NCs) and precipitates that are embedded in the grains and along the grain boundaries 4,5 , together with solute segregation of W and Cr to the grain boundaries, are widely recognized to account for the excellent creep resistance 2,4,[6][7][8] , the ultrafine ferrite grains are also essential in promoting the mechanical strength, for example, via Hall-Petch hardening 9 . Thus, it is important to understand how the ferrite grains deform in response to stresses, particularly, at elevated temperatures.…”

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confidence: 99%

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Stoica

Miller

et al. 2014

Nat Commun

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Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersionstrengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-ofthe-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from lowtemperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation.

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Vacancy Mechanism of High Oxygen Solubility and Nucleation of Stable Oxygen-Enriched Clusters in Fe

Cited by 172 publications

References 15 publications

Vacancies as a constitutive element for the design of nanocluster-strengthened ferritic steels

Vacancies as a constitutive element for the design of nanocluster-strengthened ferritic steels

A first-principles study of helium storage in oxides and at oxide–iron interfaces

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

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