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The results indicated that, after aging and dynamic precipitation at the grain boundaries of dynamically recrystallized grains, fine precipitates formed and the strength of the alloy improved [2].
When the temperature was 300ºC, new grains have been formed from big grains in magnesium alloy because of the influence of stress.
Since the pinning of the black second phase on the grain boundary can prevent the grains from growing big, the grains became finer, which accounts for the increasing of tensile strength.
When the temperature reaches 390ºC，it can be seen from Fig.2 that the diffusion precipitation inside the grains begins to substitute the intermittent precipitation along the boundary of the grains.
When the extrusion ratio was 60, the grain has the smallest size (being about 3-5μm), the second phase in diffusion precipitation refines gradually and increases in number, and the tensile strength reaches to its highest.

The results of experiments were described on graphs of the fatigue crack length „a” versus numbers of cycles N.
The microstructure heavily dominated by elongated grains of the solid solution α of various sizes, and a width of about 50 μm.
Between large elongated grains are also visible cluster very small equiaxed α phase grains in the system band.
Precipitations phase Al2Cu occur mainly in the chain system on grain boundaries of the solid solution, and their size does not exceed 5 mm [11].
At the same time, the number of load cycles N was recorded.

It is evident that increasing the SiC content reduces the area fraction of pullout, fpo, and that this reduction accrues both through a reduction in the number of pullouts per unit area, and through a reduction in the diameter of the individual pullouts.
Figure 9 shows the effect of moving some of the SiC particles in composites containing 2% SiC from within the grain to the grain boundary.
The resulting lack of grain growth removes the mechanism by which SiC particles are enveloped within the grains (Fig. 10).
Plot of %po vs. % of SiC particles on the grain boundary for 2% SiC composites with grain and particle sizes shown. 2 µm2 µm2 µm Figure 10.
Acknowledgements Some of this work was supported by the Mexican Government through the National Council for Science and Technology (CONACyT) with grant number 70668/118089.

The ECAP is very often used for the improvement of strength properties of aluminium alloys by converting the conventional coarse grained metals into ultra-fine grained materials.
A grain size of 40-60 mµ was revealed before processing.
The experimentally measured stress and microhardness values are presented in Fig. 2 as a function of the ECAP pass numbers.
It is seen that briefly a high value of maximal value of stress (and hardness) in each pass will be achieved by the ECAP processing. 0,00 200,00 400,00 600,00 800,00 0 2 4 6 8 10 pass number σmax 0 30 60 90 120 150 microhardness stress microhardness Fig. 2. a) Values of maximal stress and microhardness as a function of ECAP pass number, and b) the TEM microstructure after ECAP processing through 10 passes.
Finally after fourth stage the average size of the grains is between 1 and 3 mµ .

When the extrusion temperature is up to 390°C, the grain size increases significantly, but the second phase precipitation along grain boundaries transforms into continuous and uniform-distribution precipitation within the grain.
When the temperature is 300ºC, big grains in magnesium alloy form new grains under the influence of stress, at the same time, relative rotation among grains causes imperfect dynamic recrystallization of the deformed structure, which eventually forms fine particles.
At 330ºC, some black second phase begin to precipitate along the boundary of the grains.
Since the pinning effect of the black second phase on the grain boundary prevents the grains from growing big, the grains becoming finer, which accounts for the increase of tensile strength.
When the extrusion ratio is 60, the grain has the smallest size (being about 3-5µm), the second phase in diffusion precipitation refines gradually and increases in number, and the tensile strength reaches to its highest.

However, increasing the number of grains leads to longer computational time.
The VPSC-FLD predictions based on the IF steel texture represented by various numbers of grains, i.e., spanning from 100 to 20000, are demonstrated in Figure 3.
As shown in the previous Section, the predicted FLD is affected significantly by the number of sampled grains in the statistical population.
Results shown in Figure 5b also indicate that the computational speed reduces when increasing the number of CPU cores in use (in this case a population consisting of 100 grain was used for 10 different ψ0 for 7 paths.
Note that the re-0 5000 10000 15000 20000 Number of grains in the population 0 5 10 15 20 25 30 35 40 Computation time [hour] (a) Various numbers of grains in the population (b) Number of CPU cores in use 0 10 20 30 40 50 Number of CPU cores in use [N] 0 2 4 6 8 10 12 14 Speed-up Time(1)/Time(N) 100 grains with 70 independent runs (c) Linear scaling of the results in (b) Fig. 5: Computation time spent for VPSC-FLD calculation sults illustrated in Figure 5a may be significantly sensitive to the technical specifications of computing hardware.

These grains are 4- 7µm thick which is equal to the 2-4 grains thickness at this reduction level.
The recrystallized grains predominantly form at the grain boundaries in 30% rolled material, figure3b.
At 80% rolling, the recrystallized grains formed inside the microbanded grains and become larger by consuming the deformed material of the parent grains.
These shear bands covered several grain widths instead of being confined inside a single grain.
In a detailed investigation of partially recrystallized warm rolled 75% IF steel it was found that double sets shear banded grains which are small in number, were missing in the 8% partially recrystallized stage and replaced by some grains which were completely recrystallized.

Many numbers of experimental studies and simulation models have been conducted in order to understand the texture development in pure magnesium and its alloys [4].
However, it was showed a large change of grain size and texture in extruded AZ80 magnesium alloy at stress of 15-20MPa.
The grain boundaries with a misorientation higher than 15° are expressed by the black lines.
The uniform grain structure is shown in specimen before deformation, and the grain size is about 42μm.
Also, although not shown here, the grain size increases with an increase of true strain.

The number of electropulses (N) was either 50 or 100, while the applied current (I), pulse duration (t) and frequency (f) were kept constant.
Vicker's hardness vs. number of applied electropulses.
Conrad, Colony (grain) size-reduction in eutectic pb-sn castings by electropulsing Scr.
Wang, Grain refinement by means of phase transformation and recrystallization induced by electropulsing, Trans.
Guo, Grain refinement and formation of ultrafine-grained microstructure in a low-carbon steel under electropulsing, J.

Alloy properties after aging treatment were related to the number of θ’ and θ” phases.
With the increase of addition amounts, a large number of Al3Zr or Al3Y particles generated that increased resistance to dislocation motion.
It can be seen from Fig. 12(a) that the particles with large size and a certain number of dimples appear on whole surface morphology of the as-cast Y-containing alloy.
After T6 heat treatment, not only the number and size of cavities and cracks are greatly reduced, but also the structures of tear ridges and a certain number of dimples emerged, which are small and distribute uniformly, and the proportion of alloy ductile fracture increases.
Further discovery through contrasting with alloys added additions of Y and (Zr+Y) was that there existed changes of grain size and number and shape of θ phase, which was an important factor of alloy properties change.