Symmetrical tilt boundaries

Figure 3-9. Grain boundary energies in aluminum. Rotation axis of the (symmetric) tilt boundary is <110) [after G. Hasson, C. Goux (1971)].

Figure 9.9 Calculated atom jumps in the core of a E5 symmetric (001) tilt boundary in b.c.c. Fe. A pair-potential-molecular-dynamics model was employed. For purposes of clarity, the scales used in the figure are [130] [310] [001] = 1 1 5. All jumps occurred in the fast-diffusing core region. Along the bottom, a vacancy was inserted at B, and subsequently executed the series of jumps shown. The trajectory was essentially parallel to the tilt axis. Near the center of the figure, an atom in a B site jumped into an interstitial site at I. At the top an atom jumped between B, I and B sites. From Balluffi et al. [14],...

Figure 13.1 Motion of small-angle symmetric tilt boundary by means of glissile motion...

Solution. Using Eq. 11.2, the force per unit length on each dislocation is /CT = [Pg.326]

Figure B.2 Symmetric large-angle (113)(TlO] tilt boundary in A1 viewed along the [110] tilt axis by high-resolution electron microscopy. The tilt angle is 50.48°. The inset shows a simulated image [4], Reprinted, by permission, from K.L. Merkle, L.J. Thompson, and F. Phillipp, Thermally activated step motion observed by high-resolution electron microscopy at a (113) symmetric tilt grain-boundary in aluminum," Philosophical Magazine Letters, vol. 82. pp. 589-597. Copyright (c) 2002 by Taylor and Francis Ltd., http //www.tandf.co.uk/journals.

Figure B.4 (a) Singular large-angle symmetrical tilt boundary in f.c.c. structure viewed...

Figure 8.15 Symmetric small angle tilt boundary (drawn after [339]).

Thus, the value of the CSL-E value is obtained for symmetric tilt boundaries between cubic crystals as follows ... 

A series of studies in Ni have been made for tilt boundaries that elucidate the role of misorientation in boundary structure. The case study of interest to our present discussion (Rittner and Seidman 1996) involved the use of a pair functional description of the total energy to investigate 21 distinct symmetric tilt boundaries with a (110) tilt axis. Representative examples of the relaxed structures are shown in fig. 9.45 and the corresponding grain boundary energies are shown in fig. 9.46. 

Fig. 9.45. Series of grain boundary structures for (110) symmetric tilt boundaries as computed using a parr functional description of the total energy (adapted from Rittner and Seidman (1996)).

Use the Johnson potential to simulate the structure of a S5 symmetric tilt boundary with a (001) rotation axis. In particular, find the relaxed structure associated with the S5 boundary shown in fig. 9.41. 

The structural unit model has been used successfully to predict the structures of grain boundaries in perovskite structured SrTiOs bicrystals [11.31-11.34]. The structural units observed for symmetric SrTiOs [001] tilt boundaries are shown in Fig. 11.8. In a similar manner to the isolated dislocation cores in YBCO, the structural units also appear to contain atomic positions where the cations are too close together. Again, depending on the structural unit, the close separation of the atomic columns can occur for either of the sub-lattice sites,... 

Fig. 12.12. A symmetrical tilt boundary where the bright 11.7 A c-axis lattice fringes appear staggered rather than matched at the boundary. This is a typical appearance for such boundaries (see also Fig. 12.2(a)) and may be a lower energy configuration than one with perfect matching.

Fig. 9. Symmetrical tilt boundary, which has but one type of edge dislocation.

Two niobium specimens were used in this study. Both of them were directly grown from the melt with bicrystal seeds using a technique described by Pande et al f]. The grain boundary in each case was a symmetric tilt boundary with [111] tilt axis. The details of the specimens and their surface treatments are given in Table I. The resistivity ratios in the table are the ratios of the room temperature resistivity... 

A symmetric twin boundary can also be described as a twist boundary or a tilt boundary—the difference depends on which aspect of the symmetry we think is most important. Not all twin boundaries are parallel to a mirror plane. 

Figure 3.4. Schematic of the variation of grain boundary energy for symmetric tilt boundaries with tilt angle.

Monl] Monzen, R., Takada, N., Nanometer Sliding of (001) Symmetric Tilt Boundaries in Copper With Boundary Precipitates , Mater. Sci. Eng. A, A234—236, 202-204 (1997) (Experimental, Meehan. Prop., 13)... 

Figure 4.6 The formation of a symmetric tilt boundary. (This figure appeared originally in J. Weertman and J. R. Weertman, Elementary Dislocation Theory (Oxford Oxford University Press, 1992) and is reproduced by permission of Oxford University Press.)...

The geometry of the non-symmetric tilt boundaries which form when the two crystals are not mirror images of each other is more complex and must be described in terms of two arrays of edge dislocations [6]. 

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