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In the AA1100 alloy sheets, the grains were elongated along RD and the thickness of the elongated grains gradually decreased with increasing the number of ARB cycles.
Specimen Annealed 2 Passes 4 Passes 7 Passes 10 Passes 13 Passes Grain Thickness (µm) 35 4.5 1.8 1.1 0.5 0.45 Grain Length (µm) 33 14 6.1 3.4 1.3 1.1 In the sheet ARB processed by 2 cycles, a number of dislocations were generated in the original grains and it made subgrain structures.
The fraction of the UFG regions increased with increasing the number of ARB cycles, i.e. strain.
With increasing ARB cycles the grains were elongated along RD and the thickness of the grains gradually decreased
(2) The reduction of the grains thickness and length was carried out with increasing the number of ARB cycles, i.e. strain

This phenomenon strengthens with a further increase in the number of passes and the grain structure almost vanishes after the fourth pass: the grains appear in the form of parallel lines (Figs. 8d and 8e).
At the same time, porosity between the grains also changes, circular pores can be observed between the initial equi-axial grains, while part of them close and cease to exist with the number of passes, and while those remaining become elongated.
For a sintered sample this is 1 or a value close to 1 due to the initial equi-axial grain shape (the number of the horizontal and vertical sections is nearly identical).
In the case of grains becoming more and more elongated with an increase in the number of passes, the value of anisotropy decreases, for the horizontal number of sections decreases and the vertical increases (Figs. 1c and 8e), i.e. the value of the fraction tends to zero.
The grain structure of the deformed samples follows a directional structure identical to the direction of the deformation, and develops gradually with increasing the number of passes. 3.

Size of microvoids deduced from τ2 is represented in the last column as corresponding number of vacancies nV (see text for details).
grain interiors, was found by TEM in UFG Cu and Fe as well.
A large number of vacancies is created during SPD.
Microvoids (small vacancy clusters) are formed inside grains.
Number of defects in HPT deformed sample decreases with depth in certain surface layer.

studied carefully the hardness of the alloy during aging and revealed the existence of softer regions near the surface and the grain boundary than the interior of the grain even after aging for a long time [1].
Specimens for hardness test, 10x50x1mm 3, were strain annealed for the grains to grow to about 5mm in average diameter.
Fig.3 (a) shows the hardness number measured at 0.25 to 98N of load when the various thickness of surface layer was removed by electropolishing for the binary alloy specimen aged for 120ks at 293K after quenching from 623K.
When no surface layer is removed (as aged), hardness number decreases with decreasing load less than 9.8N.
If the specimen was homogeneous in hardness from the surface inward, hardness number would not show the dependence on the load, which has been confirmed by measuring a reference specimen [1].

In recent years, people have proposed a number of model against RBAC, such as RBAC96[1], ARBAC97[2], ARBAC02[3], RHA4[4] and HARBAC[5] etc.
In Section 2 we present the proposed fine-grained RBAC model.
In this paper, we propose the fine-grained RBAC model as follows: 1.
Fine-grained RBAC requires fine-grained resources; therefore the proposed RPA can identify access control by URI resources.
Class diagram of fine-grained RBAC architecture.

Vickers Hardness Numbers (HV) calculated from a minimum of 240 indentations made across the SZ of each sample were presented as microhardness distribution contour maps.
Significant grain refinement can be observed in the SZ, as shown in Fig. 2b.
Table 3 Summary of the average grain sizes and mechanical testing results for AZ91 alloy.
Apart from that, the horizontal microhardness profiles plotted in Fig. 5 not only illustrate higher Vickers Hardness numbers within the SZ (dashed box region), but showed general uniformity in the microhardness across the SZ, as opposed to the high fluctuations observed in the outer, unstirred region.
Significant grain refinement from an average grain size of 123.1 μm to about 5.0 to 6.2 μm was achieved.

The results of microstructure shows that the second phase particles pinned on grain boundary not only can inhibited the grain growth, but also the grain can be fined during the heating and cooling course.
The numbers of precipitates decrease greatly in the center of sample.
Fig.3 The particle pinning on grain boundary The effect of the second-phase particles on the grain refinement.
The second particles which are shown on the fig.4(b) is dispersed on the matrix and present irregular ellipse, but the numbers of second particles is less than that of on the fig.4(a) .
On the other hand, the ferrite grain can be fined during cooling by the second-phase particles pinned on the ferrite grain boundary.

There are a fine-grain zone and coarse-grain zone in the cross section during milling.
Equiaxed grain occupied most.
The grain size gradually grew with the engineering strain from 30% to 90%, mixed equiaxed grain and deformed grain.
A small number of twins were also observed at the outlet.
Another difference is that deformation twins often contain large number of sub grain boundaries, but the annealing twins contains no distortion.

As shown in a number of papers, this results in acceleration of diffusion processes, and, consequently, the processes of structure transformation start at lower temperatures than in traditional coarse-grained materials.
Its initial grain size was 50 µm.
Subgrains are observed within coarse grains.
Note that the coarse grain size achieves 2 µm, and the volume fraction of grains, 1-2 µm in size, is 40%.
As a result, the activation energy of grains is decreased essentially and the additional stage of rapid grain growth appears on the grain size-temperature curve (Fig. 2).

Figure 2 Microstructures of the samples under different deformation temperatures (a) 900℃ (b) 950℃ (c) 1000℃ (d) 1050℃ (e)1100℃ As shown in figure 2, under the same strain rates and deformation dimensions, when the deformation temperature was 900°C, a large number of deformed austenitic grains appeared at the core-area of the sample, and a small amount of recrystal grains also appeared.
When the deformation temperature was 950°C, the number of small recrystal grains increased obviously.
Figure3 Microstructures of the samples under different strain rates (a) =1s-1 (b) =0.1s-1 (c) =0.05s-1 (d)=0.01s-1 As shown in figure 3, under the same deformation temperatures and deformation dimensions, when the strain rate was 1s-1, a large number of deformed austenite appeared at the core-area of the sample, and a small amount of recrystal grains also appeared, the grains’ size were 5~10mm.
When the strain rate was 0.1 s-1, the number of the recrystal grains increased, and the size of the grains also increased.
When the strain rate was 0.05 s-1, the recrystallization was almost completed, and the grains’ size was also uniform, about 20mm, a small number of deformed grains still existed.