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An average size of original grains was 17 mm.
The fraction of these grains is about 0.2.
The elongation of original grains and the development of strain-induced grain boundaries results in decreasing the transverse grain size.
In contrast to central area, the screw rolling to 63% reduction in area leads to the formation of a number of new fine grains on the sample edge (Fig. 3b).
In the present study, any bulging of original grain boundaries, leading to new grain development was not revealed in spite of frequently observed grain boundary serrations.

Not only the number of particles on heterogeneous nucleation is increased, but also it can control the growth of grain.
When addition content of Al-Ti-C-Ce is 0.2%, grain size had a new phenomenon what is local grain coarsening, but the number of second phase particles were decreased.
The number of equiaxed grains decreased.
At the same time, the number of point structure decreased.
However, when addition content is 0.3%, as shown in Fig. 3(d), the number of second phase particles which precipitated from the grain boundary were increased.

Some Remarks on the Magnitude of the Chemical Diffusivities at Moving Grain Boundaries Paweł Zięba Polish Academy of Sciences, Institute of Metallurgy and Materials Science 25 Reymonta St., 30-059 Cracow, Poland nmzieba@imim-pan.krakow.pl Keywords: Grain boundary diffusion, grain boundary movement, discontinuous reactions Abstract.
The number of atoms, which have to diffuse across the boundary increases with the further boundary movement giving a contribution to the formation of the solute profile.
After a certain time, the number of atoms becomes so large that it may cause the stop of the boundary to enable all the excessive atoms to enter the solute depleted α lamella.
Gust: in Fundamentals of Grain and Interphase Boundary Diffusion (John Wiley & Sons Ltd.
Kolobov: Did you observe the formation of dislocations on the grain boundaries during the process of migration of grain boundaries.

The number of serial sections was 96 and the area of each scanned section was about 50 2 µm2.
The number of neighboring pixels contributing to the calculation of average disorientation was one for this case.
The number of nearest neighboring pixels included in the calculation of Eq. (1) is one.
The grains adjacent to the edge of the reconstructed region were excluded from the calculation and the total number of bulk grains was 1018.
This work was supported primarily by the MRSEC program of the National Science Foundation under Award Number DMR-0520425.

Results and Discussion Table 1 gives the initial dislocation density inside sub-grain and the mean diameter of sub-grain of the single crystal specimen annealed for various times (S1-S5).
The relationship between the cyclic hour of annealing and the dislocation density is not always linear in five specimens, because the number of grown-in dislocations for each specimen is different by the effect of mechanical polishing before annealing.
Annealing Specimen number First [h] Cyclic [h] Dislocation density [cm-2] Diameter of sub-grain [µm] S1 40 200 1.86×105 75 S2 40 50 2.01×105 65 S3 40 25 2.31×105 50 S4 40 200 9.31×104 105 S5 40 120 4.20×104 165 Table 2 Nominal stress, critical resolved shear stress (CRSS) and shear stress of the main slip system for each specimen.
Nominal stress Shear stress Specimen number σ0.1 [MPa] σ0.5 [MPa] σ1.0 [MPa] CRSS τ0 [MPa] τ0.5 [MPa] τ2.0 [MPa] Diameter of sub-grain d [µm] d -1/2 [µm-1/2] S3 3.1 3.9 5.1 1.16 1.35 1.76 50 0.141 S2 2.5 3.4 4.2 1.02 1.20 1.48 65 0.124 S1 1.7 3.0 4.4 0.83 0.89 1.40 75 0.115 S4 1.7 3.0 5.2 0.70 0.85 1.54 105 0.098 S5 1.3 2.3 3.3 0.54 0.66 1.11 165 0.078 Mecking and Bulian [7] have reported that the values of τ0 ranged from 0.80 to 0.39�MPa for mean sub-grain sizes from 120 to 370�µm in 19 single crystals of different orientations of 5 N high purity copper.
It was seen that dislocations piled�up against sub-grain boundaries.

To solve this problem it is advisable to perform the experiments in conditions where the number of ‘free parameters’ influencing the (near)cube grains formation during annealing is strongly limited.
The numbers of correctly indexed points was always above 98%.
In homogeneously (less) deformed matrix the recrystallized areas were composed of single isolated grains or small chains of grains surrounded by deformed/recovered matrix.
Most of the grains were elongated along specific directions.
However, only one set of elongated grains shows the (near)cube orientation.

In order to distinguish resin-bonded diamond grinding wheels with metal-bonded diamond grinding wheels, the prefix R and M are added respectively before the corresponding numbers of grain size, such as R100 represents a resin-bonded diamond grinding wheel of size number 100, and MW10 represents a metal-bonded diamond grinding wheel of size number W10; dressing methods are elliptical ultrasonic vibration dressing, longitudinal ultrasonic vibration dressing and ordinary dressing, respectively represented by ED, LD and TD.
It can be found that there are potholes coming from the shedding of abrasive grains on the surface of diamond grinding wheel surface with the observation under microscope, and the bonding agent, particularly bronze, is squeezed flat, overlaying most of diamond abrasive grains, and the protrusion height of diamond abrasive grains over binding agent in low and the number is limited, and dressing must be done on those wheels.
Figure 4b shows the broken condition of abrasive grains dressed by diamond stylus, and due to it is sharper than GC abrasive grains, part of the diamond abrasive grains are locally broken by impact crushing.
The wear mechanism of abrasive grains on grinding wheel can often be attributed to the following three forms of grain wear, crushing and shedding.
The less shedding of abrasive grains dressed by the two dressing methods demonstrates the strong holding capacity between bronze bonding agent and abrasive grains.

With the increase of the number of ECAP-C passes to 4 in accordance with the specified regimes the most part of boundaries of fragments/grains remained non-distinct and wavy.
The view of electron-diffraction patterns with a big number of spots, arranged in the circumference, testifies to formation of a UFG structure with high-angle grain boundaries.
d UTS UTS, MPа d, % Number of passes Fig. 4.
With the increase of the number of passes to 4 the structure is transformed into a UFG structure and there high-angle grain boundaries appear.
With the further increase of the number of passes to 6 the structure is not changed, but the grain size decreases to 250 nm. 3. 

A grain refinement to a mean grain size of 10 to 15 µm is achieved by using this process.
The most important limitations of introduced methods are the small size of the product and the large number of steps needed to reach the desired texture.
Pure copper bars were pre-stretched in a tension test machine and then deformed by torsion to a specific number of turns in a torsion test machine.
By increasing the number of torsion turns in a specific length of the wire, a higher degree of refinement due to the higher equivalent strain could be achieved (Fig. 7e).
It is shown that at a low strain (εeq<2), the original grains are deformed and start to be fragmented into sub-grains or grains.

Because the twin nucleates at the grain boundary, stress concentration is necessary to be accommodated by dislocation absorption into the grain boundary at low strain rates.
Extrinsic grain boundary dislocations move and engender grain boundary sliding (GBS) with low thermal assistance.
If the basal slip system is activated at low stresses, then the number of the independent slip system is only two, where the von Mises condition is violated and where it might engender low formability.
Therefore, SRS for AZ31 Mg alloy can be described as follows: (1) lattice dislocations move toward grain boundaries; (2) they pile up at grain boundaries; (3) dislocation absorption occurs time-dependently to accommodate stress concentration there; (4) grain boundaries slide by the motion of extrinsic grain-boundary dislocations.
The Role of Grain Boundaries, phys. stat. sol.