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The difference in the number of adsorption centres, especially obvious for GBs in zinc, gives rise to a number of effects.
Experimental Grain boundaries of twin.
Grain boundaries of mechanical twin.
Fabricated twin grain boundaries.
According to [8] of special interest is the nature and number of adsorption sites at GB.

Although a complete characterization of the grain boundary remains as a complex problem, since both grain boundary crystallography and boundary plane are necessary, the use of geometrical criteria for grain boundary classification has proved useful for technological development.
Nevertheless, a number of works[14,15] have shown the relation between dislocation and CSL boundaries, attesting for its specialty.
In this sense, grain boundary engineering becomes the search for different ways of altering the crystallographic nature of grain boundaries.
The possible ways through which the crystallography of a grain boundary may be altered are[16]: twining, grain growth, grain rotation, local lattice rotations, rotation and recovery of the grain boundary.
It is interesiting to notice that random grain boundaries has almost completely disappeared from neighbouring grains.

Molecular dynamics (MD) simulation was performed to study the stress induced grain boundary migration caused by the interaction of dislocations with a grain boundary.
A y z x [110] (a) z x y Grain boundary B [110] (b) Journal Title and Volume Number (to be inserted by the publisher) 3 Fig. 2.
The figure suggests that the atoms in the second grain moves downward by the reaction of dislocations at the tube with atoms interfacing the grain boundary in the second grain.
This appears a special case of the high angle grain boundaries and further studies with non-symmetric high angle grain boundaries are necessary for the complete understanding of the stress induced grain boundary migration.
This unusual phenomenon of stress-induced grain boundary migration of a high angle grain boundary is attributed to the symmetrical atomic arrangement of the � = 5 (210) grain boundary.

Under fatigue loading, the number of cycles to failure and its associated scatter increase when the loading level decreases.
The High-Cycle Fatigue (HCF) regime is thus characterized by a large scatter in the number of cycles to failure [1].
- This grain is surrounded by 6 surface grains and 7 sub-surface grains.
The grains exhibit a high crystalline anisotropy.
The distribution of the numbers of cycles to crack initiation widens as the loading decreases, as experimentally observed.

It is found when the processing number of the ECP treatment is not greater than four times, the grains are refined and more homogenized, and the texture intensity obtained from the (0002) pole figure appears an obvious enhancement from 11.22 to 22.88.
However, increasing the repeated ECP processing number will cause the coarsening of grain size and the decreasing of the texture intensity.
By adjusting the pass number of ECP at the same current density, the microstructural evolution was investigated, and the related mechanism was also discussed.
With the increasing the repeated ECP processing number, the grain orientation has an apparent rotation and the intensity of basal-type texture presents an enhancement until the processing number to 4´ECP.
From Fig. 2 and Fig. 3, it can be found that when the repeated ECP processing number greater than 4´, the grains become coarsening and the texture intensity becomes weaken.

They significantly delay the austenite grain coarsening temperature, refine grains and prevent the abnormal growth of austenite grains.
They affect austenite grain growth significantly.
The grain coarsening temperature is 1100°C.
These second-phase particles pin austenite grain boundary and effectively prevent austenite grain growing in heating process.
That large grains swallowed small grains leaded to the number of grain boundaries are reduced and grains increased.

Therefore, in that work, the specimens were performed with large grains.
Meanwhile, the number decreased gradually.
To further study the fine carbonitrides in the experimental steel, a large number of smaller precipitates were found to appear in the shape of spherical.
The volume fraction of precipitates can be determined by [15]: (2) where N is the number of precipitates per area, S is the specific area for estimation, D is the equivalent dimameter of precipitates, r is the equivalent radius of precipitates.
The influence of grain boundaries on mechanical properties, Metall.

Pittsburgh, Pennsylvania 15213-3890, USA Keywords: Grain Boundary Character Distribution; Grain Boundary Planes; Stereology; Spinel.
In this case, the local maxima are clearly split into two peaks; one is a {111}-type orientation and the other is a complementary plane 40° away.Journal Title and Volume Number (to be inserted by the publisher) 3 MRD Figure 1. l(n), the relative areas of grain boundary planes in spinel, in multiples of a random distribution, plotted in stereographic projection along [001].
In each case, the reference frame is the same as used in Fig. 2 and the circle with the x shows the position of the misorientation axis.Journal Title and Volume Number (to be inserted by the publisher) 5 Discussion The high populations of {100} grain boundary planes in MgO and SrTiO3 have been quantitatively compared to the measured surface energies, which show minima at these orientations [5,6].
For example, since the average number of faces on a grain (13-14) is greater than the multiplicity of the {111} planes, and grain boundaries always have some curvature, it is necessary to introduce non-habit planes in the interfacial network.
Acknowledgment This work was supported by the MRSEC Program of the National Science Foundation under award number DMR-0079996.

Effect of grains boundaries self-orientation caused by grains deformation can be identified on metallographic cut.
In undeformed state (Fig. 1a) the structure is isotropic, the grains have isometric dimension and grain boundaries are not oriented.
It is very difficult to describe actual shape of the grain [5], therefore an idealized grain shape is used in the model.
From the relative number (number to unit of length) of parallel test lines intersections with grain boundaries (PL)P and perpendicular lines ones (PL)O was total relative surface area (SV)TOT of grains estimated according Eq. 3.
This model of conversion of grain boundary degree orientation to grain deformation is independent on the initial grain size – strain depends only on shape of grain and it does not depend on grain dimensions.

Marked values show the number of pores and intermetallics.
Overall, the number density and the volume fraction of the pores increase with increasing strains.
A significant drop of both the number density and the volume fraction of the intermetallics is observed for 1.33% strain compared to the initial state (Table 1).
Statistics, including number density (ρ), spherical equivalent diameter (EqD) and volume fraction (fV) of pores and intermetallics at different strain states.
Statistics show that the number of grains increases from 69 to 427 and the average grain size decreases from 104.9 to 32.9 µm.