A mechanism for the origin of screw dislocation sequences, giant screw dislocations, and polytypism in platelet crystals
| Autor: | Dhananjai Pandey, P. Krishna, D. Kuhlmann-wilsdorf |
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| Rok vydání: | 1980 |
| Předmět: |
Materials science
Physics and Astronomy (miscellaneous) Condensed matter physics Metals and Alloys Crystal growth Condensed Matter Physics Electronic Optical and Magnetic Materials Shear (sheet metal) Crystal Crystallography Lattice constant Buckling Cylinder stress General Materials Science Dislocation Crystal twinning |
| Zdroj: | Philosophical Magazine A. 42:527-550 |
| ISSN: | 1460-6992 0141-8610 |
| DOI: | 10.1080/01418618008239374 |
| Popis: | Several workers have observed growth spirals of very large step heights on platelet crystals, sometimes associated with polytypism. These are attributed to spiral growth round a sequence of similar screw dislocations in a close planar array or a single giant screw dislocation. Polytypism can be (but is not necessarily) caused by such giant growth steps. The origin of the dislocations giving rise to them has remained obscure. It is proposed that they are due to radial impurity gradients which cause the lattice parameter to change gradually away from the centre. The hoop stresses which thus arise may be relieved by elastic buckling, twinning, glide or brittle fracture. Since the hoop stresses produce no shear on either the basal plane or the prismatic planes of a crystal growing parallel to the basal plane, as long as the crystal remains planar, the hoop stresses may build up until the platelet buckles, cracks or twins, if those are the only active slip planes in the material. In all cases the disl... |
| Databáze: | OpenAIRE |
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