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Initial material was composed of grains ranging between 5 mm and 65 mm with large numbers of annealing twins, and its average grain size was 33 mm, as shown in Fig. 2(a).
As a result, CR processed material showed the significantly refined grains than that of initial material, in which grains ranged from 0.2 mm to 3 mm, with average grain size of 1.3 mm, as shown in Fig. 2(b).
At CRR processed material, the grains were more refined than that of CR, consequently, average grain size showed 0.6 mm, as shown in Fig. 2(c).
Further, at all cold rolled specimens, large numbers of annealing twins were distributed in microstructures, in common.
At all conditions, the high angle grain boundaries of the grain boundaries occupied more than 90% in fraction, as shown in Fig. 4.

The grains of AlN film had a worm-like shape.
When the number of layers (and cycles) increased, the (100) and (110) oriented grains weakened and the structure of film changed into (002) and (101) oriented.
Worm-like shape grains of nano-size were developed after one cycle.
The long axis of these grains is parallel to the sub- strate surface.
The grains become smaller and change to homogeneous (in dimensions) grains at higher number of cycles (2 and 4).

Superplasticity of Ultrafine-Grained Aluminum Alloy Processed by ECAP and Warm Rolling R.K.
This UFG material was successfully rolled at temperatures of 330-370o C retaining small grain size and equiaxed grain structure.
The average grain size was measured according to the dark-field image, averaging by the number of values more than 100 measurements.
At that the grains had recrystallized form, as evidenced by numerous extinction contours at grain boundaries.
Besides, the anisotropy coefficient of the grain size amounted to 2.1.

Thermal Stability of Nanomaterials A number of material properties are related to the grain size.
The colour intensity indicate coordination number (number of nearest neighbours), which equals 14 for atom at the site in perfect BCC lattice.
The number of grains in each structure has been kept near constant and this implied the same mean grain size prior to grain growth.
structure type number of grains (N) Ed2 [pix] CVd2 homogenous 4000 67,69 0,39 inhomogeneous 4000 57,96 0,67 The grain growth proceeds by movement of grain boundaries.
In particular the average grain diameter and coefficient of variation of grains diameter have been obtained as function of time (number of iteration steps).

As one of severe plastic deformation processes, ECAP can improve materials’ mechanical properties by grain refinement [4, 5], and a large number of studies were carried out to identify it [6-8].
But at 300℃, the ɛave reduce by about 1/4, and it is not conductive to grain refinement.
The grain is elongated to be broken after one pass ECAP.
With the deformation goes on, the original grain and the big grain deform due to the dislocation caused by stress.
Because of the dynamic recrystallization, the grain is further refined.

The recrystallizing grains in these initial microstructures have a lognormal distribution and the recrystallized number density (grains/mm 2) decreased during annealing, with the initial microstructures affecting the degree of this decrease in number density.
The PF microstructures consists of polygonal ferrite (average grain size ~ 40 µm) decomposed from coarse austenite (grain size ~300 μm), with pearlite distributed at the ferrite grain boundaries.
There are a number of factors influencing the rate of recrystallization, such as original grain size, deformation microstructure, solutes, degree of cold rolling reduction and annealing temperature [8].
At the early stages of recrystallization, a large number of fine grains are generated.
While the grain size distribution remains log normal throughout recrystallization for all samples, there was a general decrease in the area density of recrystallized grains (number of recrystallized grains per mm2) (Fig. 5).

The deterioration of the tolerance characteristics of electrical degradation by the addition of Y was probably caused by an increase in the number of willemite (Zn2SiO4)-type particles or a decrease in the number of spinel (Zn2.33Sb0.67O4)-type particles, but this deterioration was reduced by adding Zr.
Moreover, the reduction in the average ZnO grain size due to the addition of Y was a major factor in the increased varistor voltage, and the ZnO grain growth was inhibited by the formation of an unknown compound after adding Y.
fluencing the increase in varistor voltage was the decreased average ZnO grain size.
Although the cause of the increase in the number of willemite-type particles with increasing Y is currently unclear, it is likely that the increase in the number of spinel-type particles or decrease in the number of willemite-type particles deteriorates the tolerance characteristics of the electrical degradation.
The decrease in ZnO grain size caused an increase in the total surface area of the ZnO grains.

Smaller grain sizes lead to stronger material, making the ultrafine-grained (UFG) alloys very promising to achieve record mechanical strengths.
During milling the great number of defects are created and nanoscaled domains are formed leading to an interfacial energy sufficiently high to overcome the positive heat of mixing of immiscible systems [58,59].
In this situation, the final microstructures (the number of precipitates, their density, distribution and volume fraction) are also relatively difficult to control because of the strong interaction between defects and solute atoms.
In UFG materials the proportion of grain boundaries is much larger than in conventional coarse-grained alloys.
The role of grain boundaries.

Homogenization annealing before cold rolling will lead the initial fine grains become to be larger, even abnormal grain growth takes place during that course.
All the grains are fine in uniform grain size of ~20 μm.
The abnormal grains are ~10 times of fine grains as pointed out in the red line regions in Fig. 2(a).
A lemon-shape abnormal grain is shown in the red circle region surrounded by a large number of fine grains, and it could cause inhomogeneous deformation at the region around that abnormal grain.
Therefore, it can be concluded that, grains with uniform size can make deformation homogeneous, no matter the grains are fine or coarse.

The grains are represented by vertices with position kr r , where Nk ...1= (N - number of vertices in structure).
Journal Title and Volume Number (to be inserted by the publisher) 3 Values of mobility mij and grain boundary energy ijσ depend on the misorientation angle φ between two adjacent crystallographic lattices.
The minimal distance ∆, allowed between adjacent vertices, is proportional to the mean size [8] defined as ><=∆ rα with: n A r total π 2 >=< (9) where Atotal is the area of the studied "sample", α=0.025 is a proportionality factor and n is the number of triple points in the examined structure.
Journal Title and Volume Number (to be inserted by the publisher) 5 Test of the model A preliminary test of the model consists in predicting the texture change during recrystallization.
The influence of grain boundary energy was also studied.