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Corrosion resistance of ultrafine-grained pure Cu D.R.
The results show that the corrosion rate of the ultrafine-grained Cu decreases, in comparison with the coarse-grained Cu.
The number of ECAP passes is 4.
In contrast, TEM image of the ultrafine-grained sample is shown in Fig. 2 (b).
It is obvious that the anodic current density of the ultrafine-grained Cu decreases and the corrosion potential of the ultrafine-grained Cu becomes more positive, in comparison with the annealed Cu.

These reactions are driven by the local stresses in the grain boundaries, presumably much higher in magnitude and dispersion than those in the grain interiors.
Since the homogenization scheme does not provide local information on and hence, the resulting RSS values on the variants, it was assumed that the RSS values at the grain boundaries can be estimated by adding a local fluctuation term to those obtained by projecting the grain average stress tensor on the variants i.e. where is the RSS on the variant using the grain average stress (obtained by VPSC), r is a random number between 0 and 1, is the fluctuation term and is the estimate of the RSS on the variant at the grain boundary.
In each grain, the inner 6 x 6 x 6 block of voxels was considered as part of the grain interior and the layer of voxels close to the grain boundary as the grain boundary zone (Figure 1c).
Figure 1: a) (0001)basal pole figure of the initial texture of pure Mg; b) 3D polycrystal with cuboidal grains used in the FFT calculations; c) 2D schematic showing the “grain interior” and the “grain boundary” zone in one grain.
The results show that the average RSS is basically the same for interior and grain boundary zones and, as expected, the dispersion in the grain boundary zone is generally higher compared to the grain interior zone.

But after increasing numbers of turns the hardness increases in the center to the extent that there is a reasonably homogeneous distribution of hardness values across the diameter after a total of 10 turns.
This type of behavior is termed without recovery and it is typical of a large number of metals where the hardness increases with equivalent strain and then essentially saturates [12].
It was observed that agglomerations of the second phase particles may take place at the early stage of processing [19] but an increase in the number of turns promotes homogenization.
Langdon, The strength-grain size relationship in ultrafine-grained metals, Metall.
Zhu, Producing bulk ultrafine-grained materials by severe plastic deformation, JOM 58(4) (2006) 33-39

Normal grain growth with stationary size distributions of grains was also predicted for the two mechanisms.
A number of investigations have also been conducted in order to take the matrix volume fraction into account for the growth kinetics controlled by diffusion [3-7].
Method of Grain Growth Calculation In a system with a large number of grains in a matrix, the driving force for the growth of a grain is proportional to the difference in curvature between the grain and the critical size grain, which is neither growing nor dissolving [1,2,20].
An individual grain has its own driving force and the largest grain has a maximum ∆gmax, as schematically shown in Fig. 2.
AG: abnormal grains; SGG: stagnant grain growth.

Introduction Equal channel angular pressing (ECAP) is the representative technique of severe plastic deformation refining the grain size of metallic materials down to the submicrometer level, so called ultrafine grained (UFG) materials.
In addition to a near-equiaxed UFG structure, high angle grain boundaries are another necessary condition to achieve LTS.
The combined process of ECAP and conventional cold rolling is anticipated not only to reduce the number of ECAP passage but also to fabricate UFG sheets or plates.
There was no significant difference in the apparent (sub)grain size between the two samples, ~ 0.3 �.
The band width was comparable to the (sub)grain or cell size of the ECAP sample.

When brewing liquor, large amounts of distiller grains (DG) are left over, which are as the byproduct in liquor production.
They investigated the changes in crystallinity, crystallite size, grain size distribution and morphological features of the MCC particles.
distillers grains(DG)(×2000) distillers grains(DG) (×1000) DMCC (×2000) DMCC (×1000) LowaPH102 (×2000) LowaPH102 (×1000) Fig.1 SEM graphs of distillers grains (DG), DMCC and LowaPH102 However, the fibrillar structure of DG was destroyed and changed into small irregular particles during acid hydrolysis.
DMCC fibers were more distorted, consisted of a number of deposits on the surface of fibers and pores with different sizes.
In contrast the LowaPH102 had short rod-shaped particles which were formed by a number of swollen fibrils and appeared to be a dense network structure, which agrees with the data reported by Mohamed E[10].

Through the example of many metals and alloys it has been demonstrated that the HPT processing of disk-shaped coarse-grained billets can lead to an intense grain structure refinement to the sizes of 100 nm and smaller, and also promotes the formation of predominantly high-angle grain boundaries in combination with a high level of internal stresses.
Fig. 1 – Schematic of the HPT process The shear strain γ imposed on the disk specimens can be estimated from the following relationship [5, 6]: γ=2πNrh , (1) where h and r denote the thickness and the radial distance of the deformed specimens, respectively, and N is the number of HPT turns.
The mean size of the grain structure for HPT1 was about 100 nm.
In the case of HPT2, the mean grain size was about 150- 200 nm.
In the fatigue tests, samples in the CG state were tested, having a structure where the mean α-phase grain size was (8±3µm).

Enhanced Ductility in Ultrafine-Grained Al Alloys Produced by SPD Techniques Ruslan Z.
To date, a number of procedures and strategies were suggested to enhance ductility of nanostructured metals by keeping high strength.
Average grain size was estimated from more than 250 grains measurement.
Slight amount of very fine Zn grains (grain size of 5 to 15 nm) is also present inside the Al-grains.
Valiev: in Ultrafine Grained Materials IV. ed.

Length and volume are expressed in number of grid points (gps) and time in the time steps (ts).
The total number of orientation field variables for the two phases were 36.
As the grain boundaries move and grains grow, the pores tend to break away from the grain boundaries.
It is also noted that the relative green density affects not only the average grain size but also the distribution of the grain size in the ceramics [14].
In the final stage, when boundary diffusion becomes dominant, the ZrO2 grains may serve as second phase particles to impede the growth of the Al2O3 grains due to its lower grain boundary energy than that of Al2O3.

The lattice rotations of 176 grains could be followed, with approximately 3000 orientation measurements per grain.
The polycrystal morphology was modelled as a 1000-grain 3D Voronoi tessellation. 176 inner grains were assigned the initial average experimental grain orientations.
The grains were finely meshed into 600 elements on average, thus enabling in-grain orientation spreads to develop.
Taking N for the total number of disorientations, the 3 × 3 covariant S, of components Sij, can be obtained as: with which is symmetric and can be diagonalized.
Acknowledgements The simulation part of this work has been achieved during the postdoctoral position of R.Q. at Cornell University, for which partial support has been provided by ONR, under grant number N00014-09-1-0447 and N00014-05-1-0506.