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This area is filled with fine columnar grains.
Inside of the Al matrix, a number of dispersoids are distributed as shown in Fig. 3 (b).
In this area, single constituent particles are present along the grain boundaries/cell boundaries as well as inside of grains.
Fig. 4 (c) shows the one on the grain boundaries.
The agglomerated particles are considered to consist of a number of particles.

The number of forging steps depended on the recrystallization kinetics.
The number of forging steps also depended on the phase composition.
This condition determined the number of forging steps at each temperature.
Dislocation Absorption Properties of Grain Boundaries A number of questions arise from the results presented above.
The achievement of submicrocrystalline structure in sheet rolling preforms enables the rolling of the Ti-22.9Al-22.7Nb-2.4(Zr,V,Si,C) alloy to be performed at relatively low temperatures which retains a high number of grain boundaries. 2.

A UFG structure produced by ECAP has a large volume fraction of grain boundaries, as compared with a coarse-grained (CG) structure, and is also characterized by a high concentration of defects (point and linear ones) in grain boundaries and in their vicinity, with a decreasing number of dislocations inside grains [1].
(5) A decrease in the density of a substance participating in the mass transfer can take place due to an increase in the number of dislocations and vacancies.
Their average grain size was 15, 0.3 and 0.1 µm, respectively (fig. 2).
Their average grain size was 50 and 0.3 µm, in the initial condition and in the ECAP-processed condition, respectively.
The smaller is the grain size and the higher is the contact temperacture, the stronger is this effect.

The carrier concentrations, hall mobilities and grain sizes of the AZO samples were measured.
Table 1 The test results of AZO samples number n[cm-3] μ [cm2V-1s-1] ρ[Ω·cm] Grain size[nm] 01 1.46×1019 1.407 3.03×10-1 28.5 02 2.23×1019 1.23 3.0×10-1 23.7 03 3.402×1019 5.076 3.615×10-2 65.4 04 4.837×1019 3.225 4.0×10-2 38.0 05 7.35×1019 3.5 2.19×10-2 60.0 06 8.42×1019 4.17 1.5×10-2 58.5 07 2.65×1020 3.1 7.6×10-3 81.8 08 4.34×1020 2.03 6.34×10-3 85.3 09 5.63×1020 1.47 8.08×10-3 80.8 10 7.82×1020 1.32 9.2×10-3 81.5 11 8.06×1020 1.25 9.45×10-3 54.6 The effect of the carrier concentration on the hall mobility.
In addition, even if a small amount of carriers arrived to the grain boundaries, they would pass through the grain boundary barrier because of the quantum tunnelling effect, so the influence of grain boundary scattering on carrier mobility was very small.
The grain boundary scattering and ionized impurity scattering coexisted for when the carrier concentration was a magnitude of 1019 for the samples ( number 01-05).
The carrier mobilities increased with the grain sizes increasing and the carrier concentration decreasing.

Compared with traditional metal processes, ECAP has a number of advantages such as introducing exceptional high strain without changing the cross section of workpiece.
Annealed at the lower temperature 923 K, the primary α grains were different in size and not well globularized (Fig. 3b).
While annealed at the higher temperature 1073 K (Fig. 3e), the equiaxed α grains showed pronounced growth.
It attributed to the increase in number of grain boundaries, which balanced the decrease in density of dislocations due to annealing softening.
Increasing energy input introduced by longer annealing time led to more complete recovery and recrystallization, and longer annealing time caused grain growth and consequent decrease in number of grain boundaries.

It is now well established that processing by ECAP has the capability of producing materials where there is a reasonably large number of grain boundaries having high-angle misorientations [12,13].
It is also apparent that the maximum elongation is displaced to a faster strain rate with increasing number of pressings from 6 to 8 passes where this is due to the higher fraction of high-angle grain boundaries that are anticipated in the sample processed to higher numbers of passes [13].
This procedure gave an ultrafine-grained structure with an average grain size of ~0.5 µm.
This procedure refined the grain structure to a grain size of ~0.8 µm.
By contrast, to date there are only a limited number of reports evaluating the role of grain boundary sliding in the ultrafine-grained materials processed by ECAP.

In the fig1(a), the ferrite grains are coarse，the grain boundary is not clear, and ferrite grains is shown as polygon and particle.
In the Fig1(c)，ferrite grain is distributed irregularity，the shape of ferrite grain are particle，polygon or block，and the grain boundary is clear.
The numbers of the island and fibrous martensite are few.
At the same time the number of precipitated second phase particles is significantly increasing with increasing reduction，and is the one of reason to restrain the growth of ferrite grain in the further.
It is found that the number of precipitated second phase particles are significantly increasing，the precipitated second phase particle is fined with increasing reduction.

The coarse-grained alumina specimen, TM7, was selected for additional testing, in the hope of analysing the effect of incident wave shaper with regards to strength results.
Influence of grain size on the dynamic response behavior of alumina.
SHPB stress-strain curves for alumina ceramics with different grain sizes It is well known that microstructural inhomogeneities caused during material preparation (e.g. inclusions, grain boundary impurities, secondary phases, porosity, etc.) are the main cause of cracking and can lead to material fracture.
As the applied load increases rapidly, the inertial effect of accelerated crack expansion prevents the initial stage of material fracture from occurring, and microcracks are generated in large numbers but do not converge, the material remains integral at this point and therefore ceramic materials exhibit a high compression strength under high strain loading.
The fine grain alumina ceramic SH3 exhibited a high dynamic compressive strength of 3.80±0.25 GPa, as compared to the SHPB experiments conducted on the alumina ceramic materials.

Fig. 3: Grain size distribution in all samples.
Significant grain growth occurred in all annealing cycles.
The fact that the grain sizes increased so drastically during magnetic annealing suggests that the field had a considerable effect on grain boundary migration and hence the grain growth kinetics.
The grain size increased with increasing field strength, suggesting that the magnetic field accelerates grain growth under these conditions.
Acknowledgments This work was supported by the MRSEC Program of the National Science Foundation under award number DMR-0079996.

The number of free electrons activated from valence electrons increase, which make excess electrons show up in the bottom of conduction band, and the carrier concentration of the internal crystal increase accordingly.
With the increase of doping content, number of free electrons and carrier density, the conductivity of powder decreases[5-9].
SEM image of Al3+-doped tin oxide gel grains The microstructure and distribution of Al3+-doped ZnO gel grains were shown in Fig.1.
It was found that the grains varied in size from 10 to100nm and evenly distributed during the formation of gel, which revealed that polyethylene glycol (PEG) could effectively prevent ZnO gel grains from agglomerating.
Polyethylene glycol (PEG) could effectively prevent ZnO gel grains from agglomerating during the formation of the gel.