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The morphology of ultrafine grains formed is different from that of aluminum alloys.
The as-received copper showed a recrystallized structure with the average grain size of 63 µm in diameter.
This structural evolution of oxygen free copper with the number of ARB cycles is similar to the results of some aluminum alloys processed by the ARB [6, 7, 10].
It is found that the UFGs with grain diameter of about 250 nm have relatively equiaxual appearance.
The inhomogeneity in hardness for 1-cycle ARBed sample is 0 1 2 3 4 5 6 7 0 100 200 300 400 500 0 10 20 30 40 50 60 70 80 Elongation (%) UTS / MPa � Equivalent strain� UTS Elongation 0 1 2 3 4 5 6 7 0 100 200 300 400 500 0 10 20 30 40 50 60 70 80 Elongation (%) UTS / MPa � Equivalent strain� UTS Elongation Fig. 3 Changes in mechanical properties of the copper with the number of ARB cycles. 500nm Fig. 3 Dark field image of ultrafine grains developed in high purity copper by ARB process

The numbers 0~8 in the figures correspond to each other, and refers to the different deformation stages.
The numbers correspond to those in Fig. 4.
Numbers 0-4 correspond to those in Fig. 4.
� � Matrix Journal Title and Volume Number (to be inserted by the publisher) 5 473K, 10-3s-1.
Besides the matrix, two DRX grains were observed, grains A and B.

In the specimen under consideration the diffusion layers mostly demonstrate areas of fine equiaxed grains, with minor grain size scattering (Fig. 3a).
The layers also mostly consist of fine equiaxed grains with minor grain size scattering.
Only in some electron diffraction patterns, the relative number of which is not big, there are additional super-structural reflections forming weaker Debye rings along with the main rings of this phase (see, for example, Fig. 4c, in which these super-structural reflections are indicated by arrows).
Parameters of the grain size distribution of the Nb3Sn grains Wire diameter, mm 0.8 0.5 Minimal grain size, nm 30 30 Maximal grain size, nm 160 130 Average grain size, nm 70 60 RMS deviation, nm 17 15 Conclusion Nanocrystalline structure of the Nb3Sn layers forming in multifilamentary Nb/Cu-Sn composites, the external diameters of 0.8 and 0.5 mm, after the two-staged diffusion annealing of 575°С, 150 h + 650°С, 200 h has been studied by SEM and TEM.
In the wire of smaller diameter the structure of the diffusion layers is more perfect, namely, both the average grain size and the grain size scattering are smaller.

Part of the cell walls formed grain boundary and then small angle subgrain formed.
With the increase of current density, the number of the dislocation cell increases and the size decreases.
The dislocation cell has a tendency to move to the grain boundary.
With the increase of current density, the number of the dislocation cell increases and the size decreases.
The dislocation cell has a tendency to move to the grain boundary.

We have reported in this paper, the effect of grain size in Nd0.6Sr0.4MnO3 .We have investigated the effect of grain size on metal-insulator transition and Curie temperature.
Variation of sintering temperature changes the grain size.
We have employed the Debye Scherer formula to calculate the grain size.
The grain surface contains large number of defects and magnetic spins become pinned there.
The reduction of grain size reduces TP and TC quite appreciably.

It is generally accepted that β-sialon tend to develop into elongated grains, while α-sialon usually occurs in equiaxed grains.
However, some recent experimental results show that α-sialon with elongated grains can also be obtained by controlling the nucleation and grain growth properly and the toughness is improved considerably [5-8].
It is clear that increasing N2 pressure results in larger grains.
In the sample Yb1510-S2, most grains occur in elongated morphology and the average aspect ratio of the elongated grains is between 3 and 5.
But on the other hand, excessive addition of seeds results in a large number of α-sialon nuclei which have not adequate space and sufficient materials to develop into elongated grains.

This is the very simple processing that only bar-shaped material is twisted, and then torsion worked material is twisted in the opposite direction for the number of times.
Experimental Results 3.1 Control of grain size Fig.2 shows that the annealing time versus the grain size of the material to control a grain size.
The grain growth stopped though grains grew soon after annealing the material, once again grew rapidly.
The grain size of the material under test was 15μm.
And it is found that grains extended in the direction of it.

Grain refinement and superplastic deformation behavior of Zn-Al alloys were investigated in this study.
There have been an extensive number of reports on superplasticity the various classes of materials including metallic materials, ceramics, and amorphous alloy. [4-8] Zn-Al alloys have also been reported to exhibit an excellent superplasticity. [9] Equal channel angular pressing (ECAP) is very effective way to obtain a fine grain size in crystalline materials by imparting severe plastic shear deformation. [10] In the present work, it was attempted to obtain a fine grain size in Zn-0.3Al alloy by employing ECAP and to evaluate the superplastic characteristics of the alloy.
It is apparent that in the as-cast specimen grains are very coarse and irregular and the grain size of warm rolled specimen was observed to be about 30 mm.
The strain imposed in the ECAP process can be expressed as the following equation (2), where N is the number of passages and are described in Fig. 1. [14] In the present study, the strain after a pass of ECAP is calculated as 0.62 and the strain rate as about 1.3´10-1 s-1.
Conclusions To obtain fine grain size in Zn-0.3Al alloys, ECAP process was successfully employed in this study.

Figure 1 shows shapes of the analyzed grains (Grains 1 to 8).
For example, the grain boundary between Grains 1 and 2 is denoted as GB 1/2 in this report.
The grains involved with the crack growth are denoted as the numbers from 1 to 8.
Fig.5 ECC images of dislocation structure formed in (a) Grain 8 and Grain 5 near GB 8/5.
GB 4/5 GB 8/5 primary slip system conjugate primary slip system Grain 4 Grain 5 Grain 5 Grain 8 Grain 5 εx -0.297γ4 -0.258 γ5 0.110 γ5c -0.040 γ8 -0.151 γ5 εy 0.374 γ4 0.377 γ5 0.124 γ5c 0.377 γ8 0.377 γ5 γzx 0.116 γ4 -0.168 γ5 0.548 γ5c -0.303 γ8 -0.236 γ5

The principle of emerging two-dimensional Voronoi crystalline grain structure is: (1) in certain area, some geometry points are sown some points of geometry to define the grain embryo at random.
According to the grade characteristic of crystalline grains in national standard GB/T6394-2002，when grade of crystalline grain is offered，for the calculating formula: (1) we can obtain density of crystalline grains, that is number of crystalline grains on an area equaling to 1,by which we can simulate polycrystal models through Voronoi algorithm.
Fig.4.Metallographic picture of aluminum alloy The shape and area of the crystalline grain, as the visualized indices of the character, can reflect detailed geometry view of material structure; therefore, the side number and area of the every polygon under different grades from 2 to 4 of crystalline grain are statistical analyzed.
Mean value of the side number of every grain under different grades of crystalline grain is shown in Table 1.
Table 1.Statistic of crystalline grain polygon Project Grade 2 Grade 3 Grade 4 Mean value 5.314 5.322 5.346 Theory value 5.148 Above all ,we can conclude that the meso-scale model based on Voronoi algorithm has met the metallurgy principle through the mathematical information and geometric simulation，and have good consistency with actual structure in main characters such as grain shape, side number, area, etc, which can offer the good structural form for meso-scale calculating.