. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. Dislocations and Their Movcnwnl in Mclal Foils 313. Fig. 3(«). An example of a square cross-grid of screw disloca- tions forming a iwist boundary on (100). Dislocations come to an end on the surface at A. Magnification 100,000. Fig. 3(ft). A hexagonal network of dislocations. Magnification 200,000. Fig. 4. Fast dislocation slip trace showing cross-slip. Ihc dislocation penetrated the boundary at C. CD is another slip trace with the dislocation held up at D. Magnification 60,000. (c) Some of th
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. Dislocations and Their Movcnwnl in Mclal Foils 313. Fig. 3(«). An example of a square cross-grid of screw disloca- tions forming a iwist boundary on (100). Dislocations come to an end on the surface at A. Magnification 100,000. Fig. 3(ft). A hexagonal network of dislocations. Magnification 200,000. Fig. 4. Fast dislocation slip trace showing cross-slip. Ihc dislocation penetrated the boundary at C. CD is another slip trace with the dislocation held up at D. Magnification 60,000. (c) Some of the arrangements of lines can be explained readily on dislocation theory (see below), but not on any other basis known to the authors. (d) On tilting the illumination or the specimen through small angles, the lines remain fixed in posi- tion, although the contrast changes. This shows that the lines are a definite property of the specimen. (c) When working with large beam current den- sities the lines are observed to move; the movement occurs along straight lines parallel to the traces of (111) slip planes, fig. 4. Contrast mechanism.—The diflFerences in contrast between one subgrain and another are due to differ- ences in intensities of Bragg refiections caused by the small misorientation angles. This is easily dem- onstrated by tilting the object in a stereo holder through an angle of 1° or 2'', when it is possible to illuminate grains which were originally dark and vice versa. The thickness of the foil is sufficient (about 500 A) for the scattering of electrons to be dy- namical, and depending on the orientation much inten- sity may be abstracted from the direct beam and the Obiect Ezzz Ezzzzz; czza Len s. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original European Regional Conference on Electron Microscopy
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