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Much research was conducted using the HPT process to achieve grain refinement in a number of metals and alloys, including Al, Cu and their alloys [3-5].
Thus, since the initial grain sizes for the Al6061-O and Al6061-T651 were ~200 µm and 50 μm, it appears the initial grain size is not important for the final grain size obtained by HPT but it may influence the grain boundary misorientations.
Langdon, in: Ultrafine Grained Materials III, edited by Y.T.
Langdon, in: Ultrafine Grained Materials III, edited by Y.T.
Buchanan, in: Ultrafine Grained Materials III, edited by Y.T.

Grain coarsening.
Discussion Goss grains after Deformation.
Nucleation of Goss grains in microshear bands was expected to take place with a higher frequency and a growth advantage compared to the γ-fibre grains, because they were already surrounded by high angle grain boundaries after deformation.
However, the Goss-oriented grains have an advantage.
In addition to their higher number, a lot of them are larger than nuclei of other orientations.

The equiaxed primary α grains tended also to be elongated along the hot-rolling direction.
Within each column prior β grain, there were a number of α′ laths with various orientations, which were shown in different colors.
Obviously, most of the grain boundaries were HABs and only sporadic LABs were interspersed within some grains.
Furthermore, an increase in the number of variants came with the increasing of the cooling rate [12, 20].
It formed a very weak texture in the FZ, and most of grain boundaries were HABs.

Cu additive increased the average grain size and film roughness.
Film compositions were adjusted by the numbers of the Cu and Pt chips on Fe target.
The Nb crystallines, marked by arrows in firgure 2(d), plays a imporant role on the reduction of grain size of the FePt grains.
The later limits the grain growth of FePt grain during high temperature annealing.
Nb atoms also form nanocrystallines between FePt grains.

To increase the numbers of core limb assemble will reduce the efficiency of transformer.
There are several materials that use of transformer core such as cold rolled grain oriented (CRGO).
Flux changes the direction by 90̊ when the layers are mitered 45̊. [5] Grain oriented along the length of the laminations in the horizontal and vertical directions.
Figure 8 The flux flows in the core Conclusion In this paper the performance of transformer affected by the number of limbs are presented.
Increase the number of core limb assembling will reduce the efficiency of transformer.

The nucleation at an initial stage of recrystallization was found at the high angle grain boundaries (HAGBs) and grain interiors.
The topology of grains is an important factor in static recrystallization as well as normal grain growth [9].
The anisotropic properties of grain boundary energy and grain boundary mobility were expressed as functions of grain boundary misorientation in the method.
Misorientation between grains or orientations has been extensively reviewed in [17].
Randle: The Measurement of Grain Boundary Geometry, UK: IOP; 1993.

The HE processes were characterized using: ε - accumulated strain, R - reduction of the sample cross-section, N - number of the extrusion cycles (see Table 2). 1) Billet - material to be extruded 2) Product - extruded material 3) Hydrostatic medium 4) Plunger 5) Operational chamber 6) Die 7) Die sleeve 8) Die plate Changes of the rod diameter [mm] Accumulated strain (ε) Total cross-section reduction (R) Numbers of extrusion stages (N) Ø33→Ø5 3,77 43,56 12 Ø20→Ø3 3,79 44,44 12 Table 2.
The grain size distribution is shown in Fig.3. 12 16 2621 9 610 0 20 40 60 80 100 5 10 15 20 25 30 35 d2 [µm] Grain fraction [%] Fig.2.
Grain size distribution in the 5mm diameter rod.
Clearly, in the 20mm rod with a starting grain size markedly higher than the 33mm rod, the grain refinement was much more intensive.
Grain size distribution in the 3mm diameter rod.

Fig. 3(b) shows that after deformation at 1150ºC and e = 0.3, the recrystallized grain size is slightly refined (D = 70 µm).
Recrystallized Grain Size.
(a) Comparison of the experimental recrystallized grain sizes with the predictions of several equations found in the bibliography; (b) Effect of strain on the recrystallized grain size.
However, the grain size increase is overestimated by some of the published equations.
Acknowledgments The authors acknowledge the RCFS number RFSR-CT-2013-00012 for financial support.

They concluded that creep is controlled by grain boundary sliding accommodated by grain boundary diffusion.[12] Schneider et al. studied creep on SiC ceramics with Y2O3-AlN sintered in N2 atmosphere at 1920-1970ºC e by hot isostatic pressing at 2000ºC.
After creep tests, the sample surfaces were investigated by XRD (Philips X'Pert - PW1380), using Cu Kα radiation and SEM (LEO-435 VPi), with backscattered electron mode, to observe contrast relative to atomic number.
Results and Discussion The sintered ceramics presented equiaxial grains morphology and micrometric grain size average.
The microcracks observed in this work, after creep, seems to be originated from triple points junctions of grain boundary.
At 1350ºC, grain boundary sliding will prevail, still accommodated by diffusion.

(2) Impact action of abrasive grains caused by the ultrasonic vibration: The rotation movement of abrasive grains driven by a rotating tool can be modeled as a grinding process, namely abrasive action and polishing effect which are generated by ultrasonic vibration and rotational motion of tools simultaneously
In ordinary grinding machining, as abrasive grains scratch pieces of linear grinding cracks on the surface to be machined, the material volume removed by a single abrasive grain in ordinary grinding is shown as follows: (3) In which, —scratching distance of abrasive grain in a certain time in an ordinary grinding process ; ;- radius of abrasive grain.
In ultrasonic-vibration grinding, the scratching distance of abrasive grains is as follows[7]： (4) Thus, the equation of the material volume removed by a single abrasive grain in ultrasonic vibration grinding: (5) As the ultrasonic-vibration has a predetermined circle, it should be more reasonable that the study on the material volume removed by a single abrasive grain was carried out within one cycle.
§ 3 Mathematical model of grinding force in rotary ultrasonic grinding According to the equation (4), the average chip cross-sectional area of single abrasive grain in rotary ultrasonic grinding is easy to be obtained: (10) In which, - contact length between wheel and workpiece, , plus sign is used fro up grinding while minus sign is used for down grinding; as for surface grinding, the ratio of is very small due to a larger difference between and , and ; - the number of abrasive grain at a unit width of all grinding carried out at the same time.
In which, - the proportion coefficient related to the number of static sharpening, and ;- related to the distribution of the abrasive grains in the circumference of grinding wheel, and in general ; - related to the distribution of the abrasive grains in the circumference of grinding wheel, and in general; - the equivalent diameter of grinding wheel[8]; - half-angle of projection of abrasive grains [10], if average value , ; - the coefficient related to the sharpening density and shape of grinding wheel; .