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The iron-containing intermetallic compounds in type 319 aluminium casting alloys were investigated using convergent beam electron diffraction (CBED) and electron backscatter diffraction (EBSD). The Chinese script α-phase was identified as having the cubic Im space group consistent with the Al19Fe4MnSi2 phase reported in the literature. However, the atomic ordering of this phase results in complex Kikuchi lines in the CBED and EBSD patterns, which makes phase and orientation identification difficult. In fact, it is shown that the EBSD patterns in the scanning electron microscope and Kikuchi patterns in the transmission electron microscope from this phase are closely related to the structurally similar m icosahedral quasicrystals that form in numerous aluminium–transition metal alloys by both conventional and rapid solidification. The other iron-containing phase in these alloys was determined to be plate shaped and to have the orthorhombic Cmcm space group consistent with the β-Al5FeSi phase, which has some...

Samples of Ti–6 wt% Al–4 wt% V and Timet 550 (Ti–4 wt% Al–4 wt% Mo–2 wt% Sn–0.5 wt% Si wt%), which have been deformed at a strain rate of 5 s−1, were annealed after thinning so that the visibility of dislocations in transmission electron microscopy could be compared before and after annealing. It has been found that imaging with g = 0002 produces clear images of dislocations before and after annealing, but that imaging with other diffracting vectors gives reasonable dislocation images only after annealing to at least 700°C. The sharpness of Kikuchi lines in diffraction patterns obtained from fully annealed samples, deformed at 10−1 and 5 s−1, has been examined. The lines are sharp for all planes in the fully annealed samples, but become more diffuse in samples deformed at 10−1 s−1. However, in samples deformed at 5 s−1 the Kikuchi lines from (0002) planes are sharp but the lines from all other planes are diffuse. These observations are interpreted in terms of the presence of a high density of defects, whi...

The first electron back-scattered diffraction Kikuchi patterns and grain orientation maps were captured for pure n-phase (fcc) Ce. The sample preparation technique used for electron back-scattered diffraction orientation mapping of this surface-reactive metal included ion sputtering the surface using a scanning Auger microprobe followed by vacuum transfer of the sample from the scanning Auger microprobe to the scanning electron microscope. The effect of ion sputtering on the microstructure as well as preliminary electron back-scattered diffraction microstructural characterization is presented. Based on the sputtering data, the room-temperature diffusivity of O in n-Ce was estimated.

Transmission electron microscopy (TEM) observations were carried out for examining the as-formed and post-deformed microstructures in a variety of electroformed copper liners of shaped charges. The deformation was carried out at an ultra-high strain rate. Specifically, the electron backscattering Kikuchi pattern (EBSP) technique was utilized to examine the micro-texture of these materials. TEM observations revealed that these electroformed copper liners of shaped charges have a grain size of about 1-3 w m. EBSP analysis demonstrated that the as-grown copper liners of shaped charges exhibit a d 1 1 0 ¢ fiber micro-texture which is parallel to the normal direction of the surface of the liners of shaped charges. Having undergone plastic deformation at ultra-high strain rate (10 7 s m 1 ), the specimens which were recovered from the copper slugs were found to have grain size of the same order as that before deformation. EBSP analysis revealed that the d 1 1 0 ¢ fiber texture existed in the as-formed copper li...

Kikuchi bands observed in transmission electron microscopy of crystalline approximants to quasicrystals differ from those observed from the quasicrystals only in small details. They reveal the relationship between the two phases and in the past have provided some information about the small distortions of atomic clusters that occur on going from one phase to the other.

In this review, I describe how low-energy (typically below 500eV) electron diffraction spectra can be inverted to produce three-dimensional coordinates of atoms neighbouring a reference atom with no prior knowledge of what type or types of atom are present. The reference atom may be one of many equivalent near-surface atoms from which a core-level photoelectron is excited or, in the case of diffuse low-energy electron diffraction, one of many equivalent adsorbate atoms (lacking in long-range order) on the surface of a crystalline substrate. Other variants apply to low-energy electron diffraction, Kikuchi electron diffraction and time-reversed versions in which the wavenumber (energy) and direction of the incident beam are varied. I show that, for such low-energy electron diffraction spectra, the relative phases between the reference wave and scattered waves have a known geometric form if the spectra are taken from within a small angular cone in the near-back-scattering directions. By using the back-scatte...

Kikuchi patterns from single crystals of magnesium oxide have been studied by electron microscopy at various accelerating voltages between 500 kV and 1 MV. In each case, the incident beam falls on the crystal near a zone axis [012] so that many non-systematic reflections were either strongly excited or not excited. In this paper it is shown that the critical voltage effect is very sensitive to the crystal orientation and, even when accidental reflections are weakly excited, the second-order Kikuchi lines vanish at a very different voltage than in the systematic case. Apart from this new value, a minimum intensity along the second-order Kikuchi lines and a reversal of the asymmetric contrast of the mid-line can be observed. These effects appear in the diffraction pattern at various distances of the systematic row, depending on the accelerating voltage and the excitation of the non-systematic reflections. They can be understood from the many-beam dynamical theory, and the theoretical profiles of th...

Aluminium billets of two purities (99.999 and 99.7%) were extruded at 250°C using commercial equipment to produce 10 mm rod (extrusion ratio, 25:1). On air cooling, the resulting microstructures were investigated using optical and transmission electron microscopy, including Kikuchi line analysis. Thefine microstructure of the lower purity extrusion consisted of subgrains of about 2μm dia., formed by dynamic recovery. Although the microstructure of the higher purity extrusion appeared to be similar both in morphology and size, the misorientation measurements revealed that this extrusion was composed of small high-angle grains. These recrystallized grains were found to be stable and resulted in an associatedflow strength of50-62 MN/m2

It was stated by Thomas and Humphreys (1970) that the inelastic electron intensity in a direction K in transmission electron diffraction may be calculated by summing, with appropriate weight factors, the elastic intensities in directions K + g taking K as the incident electron wave-vector. Starting from first principles we derived an exact single-scattering inelastic intensity expression. From this intensity expression it is easily seen that, neglecting some interference terms, the inelastic intensity may be described approximately in the form given by Thomas and Humphreys. Analytical expressions are derived for the weight, factors introduced by these authors.

A method for determining the crystallographic orientation from an electron-diffraction Kikuchi line pattern is described. The method makes use of all the available information in a single analysis and allows the accuracy of the determination to be estimated.

Double diffraction from a bicrystal containing a near-coincidence 〈111〉 twist boundary is analysed in some detail. It is found that a method suggested recently (Schapink and Erlings 1978) for disti...

The use of Kikuchi lines is very familiar as a part of electron microscopic technique; it is not so widely recognized that bend contours may be used in the same way. The two techniques are in fact very similar and generally complementary. The differences between the methods are examined and the advantages of each discussed. The use of bend contours has a number of advantages of convenience, especially for complicated specimens.

Kikuchi diffraction patterns (K-patterns) from low index planes of various crystals were studied as a function of electron accelerating voltage and planar inclination to the beam of a 100 to 1100 kv electron microscope. These patterns, many of which are shown for the first time, are predicted semi-quantitatively by a simple theory that relates K-patterns to electron transmission rocking curves. Although intended mainly to account for the effects of many-beam systematic interactions at high voltages and multiple inelastic scattering important in relatively thick crystals, the theory also gives new insight into such features of conventional 100 kv K-patterns as excess-deficit K-line pairs, thickness oscillations of K-line contrast, and fine structure. It also predicts and explains in terms of electron transmission behaviour, the vanishing of K-lines at ‘critical’ voltages, a new critical voltage effect from (111) planes of diamond cubic crystals, and the characteristic behaviour of K-patterns accom...

Polydipropylsiloxane single crystals, grown from a dilute n-butylacetate solution, were characterized by electron microscopy and by selected-area electron-beam diffraction techniques. The electron diffraction study shows that the growth face was parallel to the (100) plane. Fracture of single crystals parallel to the fold plane takes place during the electron diffraction examination to give ribbon like lamellae about 300 A wide and 80 A thick. Fracture normal to the fold plane was also observed.

Abstract Electron microscope studies of dislocation arrangements around SiO2 particles in strained single crystals of copper indicate that there are lattice rotations associated with the structure. These rotations can be seen when the crystal matrix is close to the exact Bragg position. Using a microscope incorporating a Le Poole lens, diffraction patterns can be accurately obtained from an area 3000 A in diameter. Measurements of Kikuchi line positions on these patterns enable the magnitude and direction of these local lattice rotations to be determined.

A standard unmodified three-stage electron microscope fitted with a double condenser is capable of being used as a low-angle electron diffraction camera. The first condenser is used at maximum excitation to produce a small primary source, which is then focused on the viewing screen by use of the diffraction and projector lenses; the objective lens is not energized. A greatly enlarged diffraction pattern is obtainable showing very high resolution in all parts of the pattern, in particular in the region close to the primary beam where the inherent resolution potential corresponds to several thousand angstrom units in Bragg spacing. Low-angle diffraction from specimens of stretched polyethylene have been studied and reflections corresponding to Bragg spacings of up to near 2000 a were recorded. With the aid of microscope imaging of the area of the specimen contributing to the diffraction pattern, a model for the mechanism of stretching of polyethylene is proposed.

A simple, analytical method of calculating unique, accurate orientations from selected area electron diffraction patterns which contain spots or Kikuchi lines from more than one zone is described. ...

Contrary to a common assumption that the Kikuchi line spacing should be the same as that of the corresponding Bragg spot pattern if diffraction geometry is properly considered, experimental results obtained by using high-purity silicon single crystal specimens at 100 kv show that the Kikuchi line spacing can be different from that of the corresponding Bragg spot pattern, depending on the specimen thickness. This result is explained on the basis of dynamical scattering of Kikuchi electrons.

The orientation of a single crystal determined from a transmission electron diffraction pattern containing reflections from only one zone is in general not unique. It is shown that this ambiguity may be removed by taking into account the intensity distribution of the diffraction spots, provided that the diffraction pattern contains at least one reflection from a second zone. The method is illustrated on a particular example, and the results are verified by comparison with an x-ray Kossel line pattern taken in the electron microscope from the same specimen before thinning. The analysis of spot intensities allows the orientation to be determined to within ±2°, without the use of Kikuchi lines or structural features in the specimen.

The reciprocity in electron diffraction is demonstrated in thin and thick crystals by using an electron microscope with scanning system. It is concluded that the experiment of electron channeling is identical with that of Kikuchi patterns. The diffraction patterns from thin and thick films of silicon, copper and gold are observed with a 1 MV electron microscope and the relations between the channeling and diffraction are studied along various crystal axes. The diffraction can be classified into flower and geometrical patterns. The former is observed for gold and for the axes in silicon and copper. In this case, the classical theory may be applicable, and the ratios between Lindhard's critical angle and the observed one are about 0.65. The relation between channeling and various well known phenomena in electron diffraction is discussed.

Epitaxial silicon layers have been grown by the pyrolysis of silane on silicon substrates cut parallel to the {110}. The stacking-fault density and the overall crystalline perfection of the layers have been determined as a function of layer growth rate. The density of stacking faults decreased with increasing rate, but the overall perfection, as indicated by the sharpness of Kikuchi lines in transmission electron diffraction, was found to deteriorate with increasing rate. The characteristics of point contact diodes made at a number of places on individual layers have been determined and compared with the degree of crystal perfection.

Orientation-dependant patterns, very similar in appearance to Kikuchi patterns, have been obtained using thick single-crystal specimens in a scanning electron microscope. The patterns are superimposed on the normal topographical image and are obtained with both the back-scattered-electron and specimen current modes of operation. The width of the Kikuchi-like bands is proportional to the wavelength of the incident electrons, and depends also on the angle through which the electron beam is scanned.

Kikuchi patterns have been observed as an etched, or re-sputtered, pattern in the sputtered deposit obtained by electron irradiation of sodium chloride.