Low angle boundaries

Figure 10.5 Real-time image, with no computer processing, of magnetic domains and low-angle boundaries in iron-silicon taken using the Bede Scientific HI-RES detector at Daresbury Laboratory. The white radiation topograph was taken with X-rays of fundamental wavelength 1 A...

The lattice constants for undoped GaN and the highly conductive Ga Zn and GaN Ca bulk crystals vary slightly for different crystals as well as for different areas of the individual crystals [26,28], This is caused by the differences in free electron concentration and can lead to certain strains in the crystals. For the Mg-doped crystals, there are no free electrons and therefore the lattice parameters are uniform for individual crystals and the same for different samples [28], Elimination of the strains in the GaN Mg crystals is the reason for the improvement of their structure. The rocking curves are narrower and no low angle boundaries are observed even for 8 mm single crystalline GaN Mg platelets. The strains in the undoped GaN crystals are extremely small (<0.02%) but their presence can adequately explain the wider rocking curves than for the Mg-doped samples. 

H. C. GATOS (M. I. T.) What is the sensitivity of the anodic oxidation technique in determining low angle boundaries ... 

The diffraaion effects directly attributable to periodic arrays of dislocations that form low-angle boundaries in olivine have been studied by Ricoult and Kohlstedt (1983). Figure 8.35 shows an edge-on tilt boundary approximately parallel to (100) and its associated SAD pattern. The extra... 

Dislocations of the same Burgers vector climb into stable arrays of parallel dislocations, forming low-angle boundaries between subgrains of relatively low dislocation density. 

Huang, Y. and Humphreys, F. J., Subgrain growth and low angle boundary mobility in aluminium crystals of orientation 110 (001), Acta Mater., 48, 2017-30, 2000. 

The arrangement of these dislocations is parallel and they are positioned in different basal planes, one under another, so that the entire arrangement is normal to the basal planes and constitutes a low-angle boundary (a). Contrast analysis (b and c) reveals that the wall is composed of edge and mixed dislocations. For information on the various dislocation configurations observed during RT deformation, refer to the work of Barsoum et al. [14]. 

Figure 7.7 Dislocation array at an asymmetric low-angle boundary in Zr02- The individual lattice planes are distinguished in this high-resolution transmission electron micrograph. Each arrow indicates the termination of a lattice plane in an interfacial dislocation. 

The mechanical properties of a metal or alloy are determined by the microstructore of toe material. This is the so-called microstructure-prop-erties relationship. Microstructoral features that affect mechanical performance include grain size, sub-grain structure (low-angle boundaries, cells, etc.), the distribution of matrix and particle phases, the atomic structure of the matrix phase (e.g., single element or solid solution), disloca-... 

Figure 6.1 (a) Schematic microstmcture of a tempered martensitic steel, for example, steel grade 91 [14], Low-angle boundaries are drawn in dashed lines (in practice disorientation angle less than 5 degrees) while the other boundaries are shown by continuous lines (block boundaries, packet boundaries, former austenitic boundaries) (b) Initial microstmcture (TEM) [18],... 

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