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Further studies have demonstrated that a number of different high shear deformation processes can transform the near surface microstructure and generate an ultra-fine grain structure [9-11].
The higher magnification image shows the fine grains generated by grinding.
The high density of grain boundaries within the very fine grain structure of the deformed layers results in a highly superficial corrosion attack and fast lateral propagation of corrosion under paint films.
In the dark filed image, the hardening phase precipitates can be seen to be present in the large grain below the deformed surface layer, while no such precipitates are present within the very fine grains in the surface.
This may be achieved by using treatments that enhance the natural, protective oxide layer, e.g. anodising, or by a number of chemical conversion treatments.

· Eutectoid steels at clean austenite grain boundaries follow the Pitsch-Petch OR-RS between cementite and ferrite.
Orientation relationships: · Isaichev: (101)q//(112)α, [010]q//[111]α · Bagaryatskii: (001)q//(211)α, [100]q//[0-11]α, [010]q//[1-1-1]α · Pitsch-Petch: (001)q//(5-2-1)α, [100]q 2-3º[13-1]α, [010]q 2-3º[113]α Note: numbers in () denote planes of the crystal structures and number in [] denote crystallographic directions.
(d) shows cementite associated with alumina grains in the clogging deposit.
Figure 2 displays the phases present in the three pearlite islands measured and the different grain boundaries.
Black boundaries are fulfilling the Pitsch-Petch orientation relationship and blue are high angle grain boundaries. 4.

In addition, that the nano-particles adsorbed on the surface of grains will hinder the growth of grains and lead to refine grains and increase the grain boundaries, thus melting caused by slight changes in the temperature.
The microstructure of Sn-30Bi-0.5Cu after adding nano-Ag was shown in Figure 2, indicating a large number of Ag3Sn micro-nano particles were adsorbed on grain boundaries [22].
(2)The Grain boundary strengthening.
Due to the high melting point of these particles and no reaction with the matrix, the added inert nano-particles such as TiO2, Al2O3, ZrO2, and so on, may become the core of heterogeneous nucleation, to increase grain numbers, and particles adsorbed on grain boundaries will impede the migration of grain boundaries, refining grains.
The generated IMC adsorbed at grain boundaries and dispersed in the matrix, will hinder the migration of grain boundaries, refining grains.

After the deformation, the lines were still well-visible and changed their relative orientation according to the number of turns (e.g. they kept their relative orientation for an integer number of turns).
Grain refinement is no major effect of the deformation process since the grain size is still in the order of magnitude of microns.
The APB causes local disorder, so a large number of APB reduces the degree of order significantly.
One difference to our experiments is, apart from the different SPD method, the grain size of the initial material.
Due to melt spinning prior to ball milling, their initial grain size was about 80nm, while our grains were several microns large.

The preferred ratio is defined as the number of cells in the preferred direction to the number of cells in the other (in two dimensions the preferred ratio is 2).
For each cell, a randomly allocated orientation number, q, was assigned to each grain.
The orientation number indicates primarily the orientation of a cell and maximum number of q was 936, which represents 936 texture components, which were equally distributed in orientation space.
The misorientation is obtained from the q numbers of the neighbouring grain where ∆q is the difference between orientation numbers of two adjacent grains and 10 < ∆ ≤ q q (12) In the present study, an adjustment of the nucleation criterion used in Raabe's study [28] was adopted.
The recrystallised grain grows continually until it impacts on the other growing grains.

Effect of grain statistics In a simple situation we could assume that the orientation of different grains are stochastically independent and thus cor(X(gi), X(gj)) = 0 for gi and gj measured on different grains, while the orientation within the grain is approximately constant and thus cor(X(gi), X(gj)) ≈ 1 for gi, gj measured on the same grain.
Consequently for N grains with mk, k = 1, . . . , N measurements on grain number k we get n = NX k=1 mk4 andccor = 1 n nX i=1 nX j=1 cor(X(gi), X(gj)) = 1 n NX k=1 m2k = 1 m PN k=1 m2k 1 m PN k=1 mk = m2 ¯m = ¯m + (mk − ¯m)2 ¯m where ¯m denotes the arithmetic mean of mk.
Thus with equisized grains the statistical error behaves like having one measurement on each grain.
• Misorientation across grain boundaries, called grain misorientation in the following
Depending on grain size, number of actual measurements, calculated quantity and band width of the kernel estimator the precision can vary several orders of magnitude.

Fatigue crack growth in polycrystalline metals is governed by a number of interacting mechanical effects at the crack tip, such as the deformation inside a plastic zone and contact between the crack faces over part of the loading cycle.
Here, we report results for two batches of AISI 316 stainless steel with different grain sizes (Fig. 2).
Effect of gauge volume and grain size.
Furthermore, a representative selection of those grains must be sampled by the diffraction technique used.
Rather, as different hkl peaks arise from different grains, a method that considers many peaks is thus increasing the total number of grains that are measured, thereby better approximating the continuum elastic behaviour.

However, the TFTs with single grain-like polycrystalline channel under the recent fabrication technology frequently demonstrate non-uniform electrical characteristics because of the grain boundary traps, bulk grain traps, interface states and some defects on channel region [4].
The location of grain traps and grain boundary traps has indeed and randomly disturbed the TFT performance.
Additionally, grain boundary traps also affects the electron mobility.
This phenomenon is that the amount of grains in polycrystalline structure permutes the inner-atom of each grain which generates some dislocation in structure.
According to the experimental results, we also found the moving carriers colliding with lattices could generate a number of traps, which deteriorated the carrier velocity.

The effect of current density on the preferred orientation of grains Some literatures proposed that there may be correlation between whisker formation and grain orientations, while some people argued about that [7].
Figure 3.5 shows the results of the measured grain orientations of the as-plated samples.
Also, it can be seen that current density (in the range 1.5-3.0 A/dm2) has an effect on the preferred grain orientation of coatings.
However, the formation of dislocations can end this phenomenon, and a new preferred orientation of grains may form [6].
However, there is no obvious evidence that can explain the relationship between whisker formation and grain orientations.

A number of theories have been developed to explain these effects [2-4] .
(b) grain boundary between two grains(S1).
(c) (d) (c) triangle shape grain boundary(S2) (d) grain boundary between two grains (S2).
Fig.6 TEM micrographs of (S1) and (S2) triangle shape grain boundary and grain boundary between two grains.
The TEM micrographs of (S1) and (S2) triangle shape grain boundary and the grain boundary between two grains are shown in Figs.6 (a) and (b) and Figs.6 (c) and (d) respectively.