Lattice Images at θ’ Precipitates in Al-3%Cu Alloy

1975 ◽  
Vol 33 ◽  
pp. 272-273
Author(s):  
V. A. Phillips
Keyword(s):  
Imaging Technique ◽  
Phase Identification ◽  
Lattice Imaging ◽  
Electron Microscopic ◽  
Cu Alloy ◽  
Solution Treated ◽  
Intermediate Phases ◽  
Resolution Electron ◽  
Slice Orientation ◽  
Lattice Images

As part of a high resolution electron microscopic study of the precipitation sequence at 130°C in aluminum - 3% copper alloy, we studied G. P. [1], G. P. [2] or θ”, and θ’ precipitates by the lattice imaging technique. This approach proved valuable for phase identification and distinction. Examples of cros sed-lattice and c-plane lattice images at θ’ platelets will be presented here.Slices were spark cut nearly parallel to {001} from a melt-grown single crystal of aluminum -3.0 wt. % copper, previously solution treated at540°C and water quenched. Slices were aged at 130°C in argon and hand ground. Discs were chemically, electrolytically or in one case ion thinned, and examined at 100 kV in a slightly modified Philips EM 300 microscope.In the aluminum-copper system, the intermediate phases (G. P. zones and θ’) separate parallel to cube matrix planes, so that the slice orientation chosen resulted in two sets of platelets being parallel and one set normal to the beam.

Mapping the composition of materials at the atomic level

1992 ◽  
Vol 50 (2) ◽  
pp. 1474-1475
Author(s):  
A. Ourmazd ◽  
F.H. Baumann ◽  
Y. Kim ◽  
C. Kisielowski ◽  
P. Schwander
Keyword(s):  
Imaging Techniques ◽  
Atomic Level ◽  
Objective Lens ◽  
Lattice Imaging ◽  
Electron Microscopic ◽  
Lattice Image ◽  
Crystalline Materials ◽  
Transmission Electron ◽  
Lattice Images ◽  
Compositional Changes

This paper briefly outlines how transmission electron microscopic lattice imaging techniques can be used to map the composition of crystalline materials at the atomic level.Under appropriate conditions, a conventional lattice image is a map of the sample structure, because the dominant reflections used to form lattice images are relatively insensitive to compositional changes in the sample. Such reflections may be termed “structural”. In many cystalline materials, compositional changes occur by atomic substitution on a particular subset of lattice sites. In these systems, compositional changes are accompanied by the appearance of reflections, which we name “chemical”. Such reflections, for example the (200) in the zinc-blende structure, owe their existence to chemical differences between the various atomic species present on the different lattice sites. For fundamental reasons these reflections are often weak; they come about because of incomplete cancellation of out of phase contributions from different sublattices. “Chemical lattice imaging” exploits dynamical scattering to maximize the intensity of such reflections, and uses the objective lens as a bandpass filter to enhance their contribution to the image.

High Resolution Electron Microscopy of Grain Boundaries in Silicon

1981 ◽  
Vol 5 ◽  
Author(s):  
B. Cunningham ◽  
D. Ast
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Imaging Technique ◽  
Coincidence Site Lattice ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Lattice Imaging ◽  
Site Lattice ◽  
Resolution Electron

ABSTRACTThe lattice imaging technique has been used to study grain boundaries in annealed, chemically vapor deposited (CVD) silicon. The majority of the grain boundaries are Σ*=3, 9 or 27, i.e. they are all twin related, and have boundary planes which coincide with high density planes of the appropriate coincidence site lattice (CSL). Asymmetric Σ=27 boundaries are found to be dissociated on an atomic scale into faceted Σ=3 boundaries and Σ=9 boundaries. No dissociation of the Σ=27 boundaries is observed when the boundary planes are symmetric.

Study of TE Puke Halloysite by a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 200-201
Author(s):  
T. R. McKee ◽  
J. B. Dixon ◽  
U. G. Whitehouse ◽  
D. F. Harling
Keyword(s):  
Basal Spacing ◽  
X Ray Diffraction ◽  
Lattice Imaging ◽  
Direct Examination ◽  
Electron Microscopic ◽  
Electron Diffraction Investigation ◽  
X Ray ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Diffraction Effects

Clay minerals normally exhibit platy morphology with basal spacings parallel to the surface of an aggregate and registering characteristic x-ray diffraction effects. For the same reason the majority of the electron microscopic lattice imaging has been accomplished using embedded and ultrathin sectioned clays, allowing the basal spacing to be correctly oriented with respect to the electron beam. Yada has observed lattice spacings in chrysotile (a tubular mineral) by direct examination.Halloysite is a type of kaolin clay mineral that usually exhibits curved layers as tubes and spheroids which reduces the x-ray diffraction intensities from preferred orientation mounts while exposing the basal spacing for electron diffraction investigation and lattice imaging.

High resolution lattice images of aluminum-copper alloy containing Guinier-Preston zones

1978 ◽  
Vol 36 (1) ◽  
pp. 306-307 ◽  
Author(s):  
H. yoshida ◽  
H. Hashimoto ◽  
Y. Yokota
Keyword(s):  
High Resolution ◽  
Crystal Lattice ◽  
Atomic Structure ◽  
Resolving Power ◽  
Lattice Image ◽  
Cu Alloy ◽  
Resolution Electron ◽  
Focus Condition ◽  
Lattice Images ◽  
High Resolution Electron Microscope

Imaging of atomic structure of sinple crystals such as A1 and Au by the conventional high resolution electron microscope operated at 100 kV is still not very easy, because the lattice spacing of the crystals are smaller than about 2. 3 A, which equivalent to the resolving power of the microscopes. However, if the crystal lattice image is taken at the “Aberration Free Focus” condition(l), the fine structure of the crystal lattice can be photographed. Using this technique, atomic structure arround G.P. zone is studied in the present paper. Since local orientation in the specimen film disturbes the Bragg condition, we did not succeed to observe the atomic structure but could see the lattice fringes, which are formed by the systematic reflection from the crystal position. The fringe position obtained such condition corresponds to the position of atomic rows.Disc specimens were spark-cut from the sheet of an Al-3.97%Cu alloy.

One Million Direct Magnification Microscopy

1971 ◽  
Vol 29 ◽  
pp. 166-167
Author(s):  
J. A. Hugo ◽  
V. A. Phillips
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Illumination Level ◽  
Level Of Detail ◽  
Photographic Emulsion ◽  
Low Contrast ◽  
Fluorescent Screen ◽  
Resolution Electron ◽  
Lattice Images ◽  
Electron Microscopes

A continuing problem in high resolution electron microscopy is that the level of detail visible to the microscopist while he is taking a picture is inferior to that obtainable by the microscope, readily readable on a photographic emulsion and visible in an enlargement made from the plate. Line resolutions, of 2Å or better are now achievable with top of the line 100kv microscopes. Taking the resolution of the human eye as 0.2mm, this indicates a need for a direct viewing magnification of at least one million. However, 0.2mm refers to optimum viewing conditions in daylight or the equivalent, and certainly does not apply to a (colored) image of low contrast and illumination level viewed on a fluorescent screen through a glass window by the dark-adapted eye. Experience indicates that an additional factor of 5 to 10 magnification is needed in order to view lattice images with line spacings of 2 to 4Å. Fortunately this is provided by the normal viewing telescope supplied with most electron microscopes.

Lattice Imaging of Twin, Lath and α/Martensite Boundaries in Duplex Low Carbon Steels

1977 ◽  
Vol 35 ◽  
pp. 118-119
Author(s):  
J. Y. Koo ◽  
G. Thomas
Keyword(s):  
High Resolution Electron Microscopy ◽  
Ferrite Matrix ◽  
Carbon Steels ◽  
Bright Field Image ◽  
Low Carbon ◽  
Lattice Imaging ◽  
Bright Field ◽  
Lattice Image ◽  
New Information ◽  
Resolution Electron

High resolution electron microscopy has been shown to give new information on defects(1) and phase transformations in solids (2,3). In a continuing program of lattice fringe imaging of alloys, we have applied this technique to the martensitic transformation in steels in order to characterize the atomic environments near twin, lath and αmartensite boundaries. This paper describes current progress in this program.Figures A and B show lattice image and conventional bright field image of the same area of a duplex Fe/2Si/0.1C steel described elsewhere(4). The microstructure consists of internally twinned martensite (M) embedded in a ferrite matrix (F). Use of the 2-beam tilted illumination technique incorporating a twin reflection produced {110} fringes across the microtwins.

The High Resolution Appearance of Biological Substrates

1969 ◽  
Vol 27 ◽  
pp. 416-417
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Phase Image ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Resolution Electron ◽  
Discrete Structures ◽  
Large Phase ◽  
Biological Substrates ◽  
High Resolution Electron Micrographs

High resolution electron microscopic study of negatively stained macromolecules and thin sections of tissue embedded in a variety of media are difficult to interpret because of the superimposed phase image granularity. Although all of the information concerning the biological structure of interest may be present in a defocused electron micrograph, the high contrast of large phase image granules produced by the substrate makes it impossible to distinguish the phase ‘points’ from discrete structures of the same dimensions. Theory predicts the findings; however, it does not allow an appreciation of the actual appearance of the image under various conditions. Therefore, though perhaps trivial, training of the cheapest computer produced by mass labor has been undertaken in order to learn to appreciate the factors which affect the appearance of the background in high resolution electron micrographs.

Plastic deformation of θ ' in Al-4%Cu alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 576-577
Author(s):  
Shrikant P. Bhat
Keyword(s):  
Deformation Behavior ◽  
Room Temperature ◽  
Electron Microscopic Observation ◽  
Bulk Alloy ◽  
Electron Microscopic ◽  
Cu Alloy ◽  
Cu Alloys ◽  
Orowan Mechanism ◽  
The Subject ◽  
Cyclic Straining

deformation behavior of Al-Cu alloys aged to contain θ ' has been the subject of many investigations (e.g., Ref. 1-5). Since θ ' is strong and hard, dislocations bypass θ ' plates (Orowan mechanism) at low strains. However, at high strains the partially coherent θ ' plates are probably sheared, although the mechanism is complex, depending on the form of deformation. Particularly, the cyclic straining of the bulk alloy is known to produce gross bends and twists of θ '. However, no detailed investigation of the deformation of θ ' has yet been reported; moreover, Calabrese and Laird interpreted the deformation of θ ' as largely being elastic.During an investigation of high temperature cyclic deformation, the detailed electron-microscopic observation revealed that, under reversed straining conditions, θ ' particles are severely distorted--bent and twisted depending on the local matrix constraint. A typical electronmicrograph, showing the twist is shown in Fig. 1. In order to establish whether the deformation is elastic or plastic, a sample from a specimen cycled at room temperature was heated inside the microscope and the results are presented in a series of micrographs (Fig. 2a-e).

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