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Most grains had high-angle grain boundaries with some boundaries exhibiting non-equilibrium characteristics.
Instead, a large number of ultrafine grains (50-150 nm, about 30 vol.%) were revealed to uniformly distribute at the triple grain junctions, leading to a fully dense bimodal microstructure.
On the other hand, instead of copious dislocations, deformation twins with a spacing of several tens of nanometers were revealed to form in a limited number of ultrafine grains (marked by the black arrow in Fig. 2 (d)).
Compared with the 1-pass sample, a prominent feature in the 3-pass sample was the formation of deformation twins within a large number of ultrafine grains of 50-150 nm, as shown in Fig. 3.
grain refinement.

For the final extrusion the opposite punch was removed, the cumulated true strain is calculated by the equation[2]: d n D ln)12(2 −=ε , where n is the number of extrusion passes.
Although many grains are already significantly refined after only 1 pass, the grain structure is inhomogeneous with fine grains of 1-2µm as well as coarse grains of greater than 8µm.
Equiaxed grains are formed in both samples with an average grain size of 1.2µm and 0.8µm, respectively.
It is evident from the curve that there is a significant increase in hardness with the number of extrusion passes.
Further investigation is required to underpin this point. 60 65 70 75 80 85 90 HV (Kg/mm2 ) 15P 7P 1P ex-extruded Number of Extrusion Passes 100 150 200 250 300 350 400 Compressibility (%) Stress (MPa) Number of Extrusion Passes AZ61: CEC at 573K Yield Stress Compressive Stress 15 20 25 30 35 40 15P 7P 1P ex-extruded Compressibility Conclusions (1) CEC process can refine the grains of AZ61 Mg alloy effectively.

In this case, the main scientific and technological tasks are: 1) to ensure that the recrystallization starts in a large number of centers; 2) to limit the growth of recrystallized grains during superplastic deformation (SPD).
Cold hydrostatic extrusion was used for grain refining.
Dispersoids restrict grain growth during recrystallization.
Grain size was determined in two directions (LL – grain size along the rolling direction, LT - grain size in the transverse direction).
The grain structure of the samples obtained by the second regime consists of finer and more equiaxed grain (Fig. 5 b, Table 3) with the grains form factor about 1.0 – 1.4 (Fig. 5 b).

The number of the cutting and contacting abrasive grains was calculated.
The statistical research on the number of grains The probability distribution functions about the height of grains.
The number of the smallest abrasive grains and the largest was very small, while the number of adjacent to the average abrasive grains was the most on the surface of grinding wheel.
The number of the grains in grinding arc area.
The number of abrasive grains in contacting and the number of abrasive grains in acting cutting is determined analytically.

The increasing number of coal-fired power plant in Indonesia, then the amount of fly ash waste will also increase. 3.3 million tons is resulted the in 2009[7].
Orthogonal Array (OA) OA selection criteria standards to be used is determined by the number of degrees of freedom (degree of freedom) factors experiments, where the number of experiments on standard OA selected must be greater than or equal to the number of degrees of freedom experimental factors.
The number of degrees of freedom experimental factors calculated by the following eq. 1: The number of DOF = Average number + [number of factors (number of level-1)] (1) Result and Discussion Brinell’s hardness number (HB) is obtained by making a load of 62.5 kg and 2.5 mm diameter indenter.
Grain size is the importance factor that is influence of Aluminum/5% fly ash with sintering temperature 550 oC.
Whereas, more small of grain size can increase of alloy hardness. 3.

At a given time, different from one (original) grain to another, some (sub)grains start to grow following an 'abnormal grain growth' pattern.
Journal Title and Volume Number (to be inserted by the publisher) (a) ED ND (b) ED ND Fig. 2.
The grain size distribution is bimodal, with all grains larger than 15µm belonging to the fraction of large grains.
ND ED Journal Title and Volume Number (to be inserted by the publisher) Table 1 Measured properties of EBSD scans from an 8pass ECAE sample for given annealing times.
The dislocation density inside the grains decreases, (sub)grain boundaries get a more equilibrated structure and some (sub)grain coarsening occurs.

Thermally stimulated current (TSC) measurement provided the relative number of oxygen vacancies both on the cathode/ceramics interfaces and the grain boundaries.
At first glance, this result can be understood as an increase in the number of oxygen vacancies.
They also correlated the TSC peaks with two types of space charge formed by the electro-migration process of oxygen vacancies: within-grain (accumulation of oxygen vacancies on the grain boundaries) and across-grain (accumulation on the cathode/ceramics interfaces).
According to the Takeoka's report [7], these peaks can be assigned to the within-grain space charge and the across-grain space charge, respectively.
Therefore, in sample 3, both within-grain and across-grain space charges existed, implying that the electro-migration of oxygen vacancies is restricted by the grain boundaries.

At the same time, significant grain refinement down to ~100 nm in diameter takes place in aluminium phase.
On the other hand, there are a number of possibilities to improve the mechanical properties of Al-Si alloys by micro-alloying and heat treatment [2-3].
After HE the grain size decrease to 119 nm and 109 nm, respectively.
The processing leads to significant grain refinement and particle redistribution.
Acknowledgment This work was supported by the Polish Ministry for Science and Higher Education (grant number 3T08A 06430).

The results indicate that a great deal of ultra-fine grains appear in CNTs/AZ31 Alloy Composites just after one pass of ECAP; With the increase of pass number, the proportion of ultra-fine grain increases.
Coarse grains with a few fine grains in the composites prior to ECAP were shown in Fig. 3(a).
As is presented in Fig.4, with different number of ECAP passes, the grain size evolutes.
Since the grain size decreased monotonously with the number of passes, other factors, besides grain sizes, should be considered.
With increasing the number of ECAP passes, the initial coarse grained structure in the as-extruded material is transformed gradually into an ultrafine-grained microstructure with an average grain size of 2µm by 4 ECAP passes

It is influenced by grain boundary plane; one of twelve {110}β planes in the neighboring β grains, which is most parallel to the grain boundary plane, is preferentially chosen as the close packed plane for the K-S relation.
The interfacial sliding occurred and a large number of cavities were formed at the interface (2) / 'β γ while coherent interface (1)/ 'β γ was stable against deformation even at high temperature.
Figure 4 shows change in the number of irrational ( / ')β γ boundaries in Ni-36at%Al Fig. 2 Variation in fracture stress with K Sϕ −∆ at ( (2)/ ')β γ interface boundary.
The dynamic recrystallization accompanied by the bulging of grain boundaries occurs at high Z and small new grains are formed by pinching-off from the serrated parts of initial grains.
In contrast, at low Z the equiaxed fine grains surrounded by high angle boundaries are homogeneously formed due to the geometric dynamic Fig. 4 Number of irrational / 'β γ boundearies with deviation angle from the K-S relation in Ni-36at%Al annealed at 1123K.