I. Energy calculations for pure metals

Zinkle, S.J.; Seitzman, L. E.; Wolfer, W.G.

doi:10.1080/01418618708209803

Cited by 113 publications

(36 citation statements)

References 52 publications

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“…On the other hand, when the SFT is approached by a mobile twin boundary from its base as shown in the lower case of Fig. 3b, a 18 . The two scenarios predicted by MD simulations are consistent with our in situ observations.…”

Section: Discussionmentioning

confidence: 99%

“…Stacking-fault tetrahedra (SFTs) are a dominant type of vacancy cluster in various irradiated fcc metals with low-tointermediate stacking fault energy (SFE) 4,17,18 in the absence of noble gases in the materials. SFTs, once formed via collapse of vacancy clusters 19,20 , are typically very stable, and their removal requires annealing at very high temperature 21 , incorporation of interstitials via radiation 19 or mobile dislocations 22 .…”

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confidence: 99%

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Removal of stacking-fault tetrahedra by twin boundaries in nanotwinned metals

et al. 2013

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Stacking-fault tetrahedra are detrimental defects in neutron-or proton-irradiated structural metals with face-centered cubic structures. Their removal is very challenging and typically requires annealing at very high temperatures, incorporation of interstitials or interaction with mobile dislocations. Here we present an alternative solution to remove stacking-fault tetrahedra discovered during room temperature, in situ Kr ion irradiation of epitaxial nanotwinned Ag with an average twin spacing of B8 nm. A large number of stacking-fault tetrahedra were removed during their interactions with abundant coherent twin boundaries. Consequently the density of stacking-fault tetrahedra in irradiated nanotwinned Ag was much lower than that in its bulk counterpart. Two fundamental interaction mechanisms were identified, and compared with predictions by molecular dynamics simulations. In situ studies also revealed a new phenomenon: radiation-induced frequent migration of coherent and incoherent twin boundaries. Potential migration mechanisms are discussed.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Removal of stacking-fault tetrahedra by twin boundaries in nanotwinned metals

et al. 2013

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“…If a resolved shear stress is imposed on the slip plane, the actual width of the SF may change as a result of the difference in the shear factors of the two partial dislocations [1,4]. In addition to activities of partial dislocations, SFs can also be formed during crystal growth [5] or by condensation of excess point defects (vacancies or interstitials) produced by irradiation [6][7][8][9] or by large strain plastic deformation [10,11], normally on close-packed planes. After collapse of the lattice near the vacancy discs, sessile dislocation loops or SF tetrahedra are formed.…”

Section: Introductionmentioning

confidence: 99%

Non-equilibrium basal stacking faults in hexagonal close-packed metals

Zhang

Liu

2015

Acta Materialia

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“…The faulted loop on ͑111͒ planes is, in fact, the predicted morphology/configuration in continuum elastic energy calculations to be the most stable for small Al clusters ͑e.g., Ͻ ϳ 1000 vacancies͒. 22 The transition between faulted and perfect loops in Al occurs at a loop diameter of ഛ15 nm ͑2500 vacancies͒, overcoming an energy barrier for the unfaulting process. 23 The loop sizes in our Al are generally below this size, and these loops are therefore expected to be faulted ones, consistent with all previous reports for quenching or irradiation by electron, ion, or neutron.…”

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confidence: 99%

Vacancy clusters in ultrafine grained Al by severe plastic deformation

2007

Applied Physics Letters

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Bulk nanostructured metals are often formed via severe plastic deformation ͑SPD͒. The dislocations generated during SPD evolve into boundaries to decompose the grains. Vacancies are also produced in large numbers during SPD, but have received much less attention. Using transmission electron microscopy, here we demonstrate a high density of unusually large vacancy Frank loops in SPD-processed Al. They are shown to impede moving dislocations and should be a contributor to strength. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2794416͔ Bulk ultrafine-grained ͑UFG͒ and nanostructured ͑NS͒ metals are often prepared via severe plastic deformation ͑SPD͒, 1,2 which refines the originally large grains. The highangle and low-angle grain boundaries ͑GBs͒, as well as the subgrain dislocation structures stored, are usually taken as the only microstructural features responsible for the macroscopic strength/ductility properties of the UFG/NS metal obtained. However, SPD also introduces into the material another nanoscale feature in large numbers. That is, the aggregates of point defects generated throughout the SPD process. 3,4 For example, the movement of a screw dislocation with a jog should result in the creation of a row of either interstitial atoms or vacancies. 3 The vacancies are dominant because the energy to form a vacancy is smaller than that to form an interstitial. A high density of vacancies is expected for SPD, because of the intense dislocation interactions and tremendous plastic strain characteristic of SPD. The vacancy population present during and after SPD depends on the deformation rate, SPD route, temperature, etc.Point defect clusters are known to be very important in controlling the strength, toughness, and stability ͑such as swelling͒ of irradiated ͑nuclear͒ metals and alloys. [5][6][7] For point defects produced via deformation, evidence for vacancy concentration of the order of 10 −4 , close to the equilibrium value at the melting temperature ͑T m ͒, has been provided by differential scanning calorimetry, electrical resistivity measurements, and x-ray Bragg profile analysis. 8,9 However, the nanoscale entities formed by vacancies and their effects on the properties of the SPD-processed UFG/NS metals have not drawn adequate attention. For example, the stacking faults ͑SFs͒ observed in UFG/NS metals have all been attributed to dislocation dissociation or partial dislocation emission. 10 Little consideration is given to the vacancy clusters that may form SFs. It is therefore the goal of this letter to call attention to these vacancy-type defects produced by SPD. Their size, density, thermal stability, and effects on strength will be evaluated in the following using Al as an example.High-purity Al ͑99.999%͒ specimens were subjected to equal channel angular pressing ͑ECAP͒ for four passes ͑true shear strain of ϳ4͒ via route B C at room temperature ͑RT͒. No storage of vacancy-type clusters was observed in the transmission electron microscopy ͑TEM͒ after such ECAP. This is because for a metal like A...

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I. Energy calculations for pure metals

Cited by 113 publications

References 52 publications

Removal of stacking-fault tetrahedra by twin boundaries in nanotwinned metals

Removal of stacking-fault tetrahedra by twin boundaries in nanotwinned metals

Non-equilibrium basal stacking faults in hexagonal close-packed metals

Vacancy clusters in ultrafine grained Al by severe plastic deformation

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