X-ray micro-beam characterization of lattice rotations and distortions due to an individual dislocation

Hofmann, Felix; Abbey, Brian; Liu, Wenjun; Xu, Ruqing; Usher, B. F.; Balaur, Eugeniu; Liu, Yuzi

doi:10.1038/ncomms3774

Cited by 52 publications

(44 citation statements)

References 47 publications

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“…The effective thickness in nanomaterials is limited by the specimen size. As illustrated experimentally by Hofmann et al [27], a single dislocation line within a nanostructure induces a sharp change of the lattice rotation similar to a tilt boundary in a bulk specimen (see Fig. 6(a) and (b)).…”

Section: Number Of Stored Gndssupporting

confidence: 53%

Three-point bending behavior of a Au nanowire studied by in-situ Laue micro-diffraction

Ren

Cornelius

Leclère

et al. 2018

Journal of Applied Physics

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The elastic and plastic deformation of a gold nanowire tested in three-point bending configuration using the custom-built scanning force microscope SFINX was studied in-situ by Laue micro-diffraction. A new data treatment method, which bases on the integration of diffraction patterns recorded along the deformed nanostructure, is introduced visualizing both movement and shape of the diffraction peaks as a function of the measurement position. Besides bending, torsion is evidenced during the elastic deformation originating from a misalignment of the SFINX-tip of the order of 60 nm with respect to the nanowire center. As demonstrated by post-mortem Laue micro-diffraction maps, the plastic deformation is governed by the storage of geometrically necessary dislocations. Analyzing the shape of the diffraction peaks, the activation of two unexpected slip systems is found which does not coincide with the slip systems with the highest resolved shear stress. These unexpected slip systems are probably related to the dislocation nucleation process at the clamping point, which is influenced by the local curvature.

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Section: Number Of Stored Gndssupporting

confidence: 53%

Three-point bending behavior of a Au nanowire studied by in-situ Laue micro-diffraction

Ren

Cornelius

Leclère

et al. 2018

Journal of Applied Physics

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“…In particular the symmetry of the deformation fields is reproduced. Experimental data for the ɛxz and ɛyz components is noisy as the experimental configuration is relatively insensitive to these strain components (Hofmann et al, 2013). (Kartal et al, 2015) used HR-EBSD, on the free surface of a nickel sample, to extract the full residual elastic strain tensor resulting from differences in thermal expansivities between the nickel matrix and a carbide particle embedded within it.…”

Section: Residual Elastic Lattice Strains and Rotationsmentioning

confidence: 99%

Consistent determination of geometrically necessary dislocation density from simulations and experiments

Das

Hofmann

Tarleton

2018

International Journal of Plasticity

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119

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The use of Nye's dislocation tensor for calculating the density of geometrically necessary dislocations (GND) is widely adopted in the study of plastically deformed materials. The "curl" operation involved in finding the Nye tensor, while conceptually straightforward has been marred with inconsistencies and several different definitions are in use. For the three most common definitions, we show that their consistent application leads to the same result. To eliminate frequently encountered confusion, a summary of expressions for Nye's tensor in terms of elastic and plastic deformation gradient, and for both small and large deformations, is presented. A further question when estimating GND density concerns the optimization technique used to solve the under-determined set of equations linking Nye's tensor and GND density. A systematic comparison of the densities obtained by two widely used techniques, L 1 and L 2 minimisation, shows that both methods yield remarkably similar total GND densities. Thus the mathematically simpler, L 2 , may be preferred over L 1 except when information about the distribution of densities on specific slip systems is required. To illustrate this, we compare experimentally measured lattice distortions beneath nano-indents in pure tungsten, probed using 3D-resolved synchrotron X-ray micro-diffraction, with those predicted by 3D straingradient crystal plasticity finite element calculations. The results are in good agreement and show that the volumetric component of the elastic strain field has a surprisingly small effect on the determined Nye tensor. This is important for experimental techniques, such as micro-beam Laue measurements and HR-EBSD, where only the deviatoric strain component is measured.

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“…of Laue measurements 38,51 and high spatial resolution of HR-EBSD measurements 44,52 detect the far-field and near-field deformation respectively. In the unimplanted sample, a small zone of high GND density is seen close to the indent (Figure 6 (d…”

Section: Gnd Densitymentioning

confidence: 99%

Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten

Das

Tarleton

et al. 2019

SSRN Journal

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Tungsten is the main candidate material for plasma-facing armour components in future fusion reactors. In-service, fusion neutron irradiation creates lattice defects through collision cascades. Helium, injected from plasma, aggravates damage by increasing defect retention.Both can be mimicked using helium-ion-implantation. In a recent study on 3000 appm heliumimplanted tungsten (W-3000He), we hypothesized helium-induced irradiation hardening, followed by softening during deformation. The hypothesis was founded on observations of large increase in hardness, substantial pile-up and slip-step formation around nano-indents and Laue diffraction measurements of localised deformation underlying indents. Here we test this hypothesis by implementing it in a crystal plasticity finite element (CPFE) formulation, simulating nano-indentation in W-3000He at 300 K. The model considers thermally-activated dislocation glide through helium-defect obstacles, whose barrier strength is derived as a function of defect concentration and morphology. Only one fitting parameter is used for the simulated helium-implanted tungsten; defect removal rate. The simulation captures the localised large pile-up remarkably well and predicts confined fields of lattice distortions and geometrically necessary dislocation underlying indents which agree quantitatively with previous Laue measurements. Strain localisation is further confirmed through high resolution electron backscatter diffraction and transmission electron microscopy measurements on crosssection lift-outs from centre of nano-indents in W-3000He.

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X-ray micro-beam characterization of lattice rotations and distortions due to an individual dislocation

Cited by 52 publications

References 47 publications

Three-point bending behavior of a Au nanowire studied by in-situ Laue micro-diffraction

Three-point bending behavior of a Au nanowire studied by in-situ Laue micro-diffraction

Consistent determination of geometrically necessary dislocation density from simulations and experiments

Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten

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