Electron Microdiffraction

Spence, John C. H.; Carpenter, R. W.

doi:10.1007/978-1-4899-2037-9_9

Cited by 94 publications

(133 citation statements)

References 69 publications

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“…In combination, the symmetry elements in this patternsuggest adiffraction group of 6 R . [44,45] Continuing to Figure 3(b),t he perpendicular mirror lines observed in both the ZOLZ and whole patterns give two possibled iffraction groups,2 mm or 2mm1 R . [44,45] Figure3 (c) shows only twofold symmetry in the ZOLZ pattern( which represents the projected crystal symmetry).…”

Section: Resultsmentioning

confidence: 94%

Electron microscope studies of Al-Fe-Si intermetallics in an Al-11 Pct Si alloy

Kral

Nakashima

Mitchell

2006

Metall Mater Trans A

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Al-Fe-Si intermetallic particlesinboth unmodified and highly modified sand-cast eutectic Al-11.7pct Si alloys were characterizedusing scanning and transmission electron microscopy,energy-dispersive X-ray spectroscopy,and convergent beam and selected area electron diffraction. The only twoAl-FeSi intermetallics observed in this particulara lloy are (1) ''Chinese-script''m orphology,c onsistent with ad escription of body-centered cubic a -Al 19 Fe 4 MnSi 2 and (2) plate-shaped, consistent with tetragonal d -Al 3 FeSi 2 .T he authors are unaware of any otherc haracterization of d -Al 3 FeSi 2 using convergent beam electron diffraction (CBED) and selected area diffraction (SAD) techniques.

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Section: Resultsmentioning

confidence: 94%

Electron microscope studies of Al-Fe-Si intermetallics in an Al-11 Pct Si alloy

Kral

Nakashima

Mitchell

2006

Metall Mater Trans A

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“…The thickness of thin foils may be determined by a variety of methods using a TEM, including the use of the projected width of inclined stacking fault images, a wedge-shaped sample, and the convergent beam electron diffraction (CBED) method. [16] Methods involving a cleaved sample provide the most accurate thickness calibration, but this method does not suit the present case because the areas of interest were not in the regions showing thickness fringes. The error involved with the CBED method can be up to 10 pct, [16] and so thickness measurements by CBED are often used as a rough estimation for computer simulations of defects.…”

Section: Methodsmentioning

confidence: 97%

“…[16] Methods involving a cleaved sample provide the most accurate thickness calibration, but this method does not suit the present case because the areas of interest were not in the regions showing thickness fringes. The error involved with the CBED method can be up to 10 pct, [16] and so thickness measurements by CBED are often used as a rough estimation for computer simulations of defects. More accurate thickness can be obtained from a computed micrograph showing contrast variation along a dislocation line and comparing this with the experimental image obtained under identical electron beam conditions.…”

Section: Methodsmentioning

confidence: 97%

On cells and microbands formed in an interstitial-free steel during cold rolling at low to medium reductions

Chen

Duggan

2004

Metall Mater Trans A

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The cold-rolled microstructure formed in an interstitial-free (IF) steel from low to medium reductions has been investigated by using transmission electron microscopy. Dislocation cells formed early in the process and reduced in size until a critical strain was reached, beyond which they remained at a constant size of ϳ1-m diameter. The critical strain coincided with the formation of microbands, and it is proposed here that microbands carry all the deformation from their creation, rendering cell refinement unnecessary. Furthermore, since the dislocation densities of meshes and cells are almost identical and the stored elastic energy E cell is always less than E mesh , it is proposed that cells are derived from the dislocation mesh structure. Microbands grow quickly to a length that is limited by grain boundaries. The thermodynamic condition favoring microband formation is (∂E MB /∂) Ͻ (∂E Cell /∂), and the microbands are not derived from cell structures but from dislocation sheets or walls on which deformation is concentrated.

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“…For sub-nanometer probes, the illumination may take the form of a coherent aberrated spherical wave. However, for perfectly crystalline slabs, the variation of intensity in the CBED rocking curve is then the same as for the incoherent case provided the orders do not overlap (Spence & Carpenter, 1986). A source point such as P gives rise to a set of scattered waves which reach the detector at a family of points such as P'.…”

Section: (S)mentioning

confidence: 96%

On the accurate measurement of structure-factor amplitudes and phases by electron diffraction

Spence¹

1993

Acta Cryst Sect A

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139

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A review is given of research into the measurement of crystal structure-factor amplitudes and phases by transmission electron diffraction. Accuracies for amplitudes are commonly a fraction of a percent (after conversion to X-ray structure factors) while phases may now be measured in favorable cases using three-beam electron diffraction to an accuracy of much better than 1 °. Following a brief review of theory, the main techniques are outlined. These include quantitative convergent-beam electron diffraction, the critical-voltage method, the intersecting K_ikuchi-and HOLZ-Iine methods and methods based on weak high-order reflections in wide-angle patterns. Enantiomorphs and polarity are discussed. Summaries are given of measurements of the mean inner potential and of structure factors generally. A brief review of the implications of this work for studies of crystal bonding and ordering in alloys is given, and its use to test ab initio computations of charge density. The mean inner potential is found to be the quantity most sensitive to the bonding distribution of valence electrons and sensitively constrains accurate X-ray structure-factor measurements. Electron diffraction techniques are to be preferred for studies of individual microcrystals or artificially formed structures and for the very accurate measurement of structure-factor phases in acentric crystals with small unit cells.

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Electron Microdiffraction

Cited by 94 publications

References 69 publications

Electron microscope studies of Al-Fe-Si intermetallics in an Al-11 Pct Si alloy

Electron microscope studies of Al-Fe-Si intermetallics in an Al-11 Pct Si alloy

On cells and microbands formed in an interstitial-free steel during cold rolling at low to medium reductions

On the accurate measurement of structure-factor amplitudes and phases by electron diffraction

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