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After 25% reduction the grains elongate in the direction of rolling.
The majority of grains contain twins (Fig.1b) which grow through the whole grain interior and interacting with each other refine the microstructure.
With strain the number of the twinned grains increases and the initial grain boundaries become less distinct.
The number of such fragments increases with strain (Fig. 1d), so that after 96% rolling the microstructure of the sheet is mainly homogeneous with the mean size of the fragments of about 0.15 µm (Fig. 1e).
At further strain the size of grains decreases gradually.

Introduction The attractive application potential of the materials with nanometer-sized grains is anticipated from a high fraction of grain boundaries (GBs) and triple junctions (TJs) between grains in these materials.
In spite of a considerable progress in our understanding of diffusion in nano-crystalline materials, a number of fundamental problem remains still unresolved: to which extent do GBs in nanocrystalline materials differ from the relaxed boundaries in coarse grained materials and to which extent are the various types of grain boundaries in a the same material different; what is the relation between the GB structure and the corresponding energetic and kinetic properties; could one apply the concept of an 'averaged grain boundary' in a nanomaterial; what is the effect of the production route?
One can conclude that in the nanocrystalline material (the grain size d ~ 100 nm) the GB structure is well relaxed and is similar to that in the coarse-grained material.
The grain size after SPD lies typically in the range of about 150 to 350 nm, although a considerably smaller grain size could be reached, too [31].
As a result, a gradient microstructure is produced which evolves from a nano-scaled layer to ultra fine grained, fine grained and finally to the coarse grained matrix.

Chain-liked M23C6 phase precipitated along the grain boundary cause the chromium depletion zone along the grain boundary.
Around the grain boundary, the enrichment of chromium also causes the presence of the chromium depletion zone along the grain boundary.
A large number of tear ridges and dimples appear on the upside of impact fracture.
The precipitation of a large number of precipitates at the grain boundary causes the chromium depletion zone along the grain boundary.
The transmission calibration shows that a large number of M23C6 phases appeared at the grain boundary of the HR3C base metal after the service.

In a previously proposed model [5] it was discussed that the growth rate of crystallographic planes is influenced by the number of nearest neighbours that a metallic adatom encounters at the growing surface.
The crystallographic plane that offers the highest number of nearest neighbours to a metallic adatom will have the highest growth rate.
Calculating the number of nearest neighbours, it was predicted that the [002] direction will be the resulting out-of-plane orientation in case of YSZ (a fluorite structure) [5].
As such, the grains that catch the largest number of metallic adatoms will be able to overgrow the others.
The higher grains will shadow the other grains more efficiently when the substrate is tilted.

The TiNi alloy was exposed to HPT in the new die-set at a pressure of 6 GPa, and the number of rotations was n = 5.
(1) where r - the distance from the specimen axis, n - the number of rotations, h - the final height of the sample.
An average grain size after annealing at 400°С (1 h) was 20 nm as well; thus, there was no noticeable grain growth after a one-hour annealing.
The grains are equiaxed and possess sharply defined boundaries.
Annealing at a temperature of 550°С (1 h) leads to more intense grain growth and formation of a structure with the mean grain size of about 300 nm (Fig. 2 d).

A number of SPD techniques have been developed up to now.
For grain the tolerance angle was less than 15˚.
The grain size distribution is wide (from 1.4 to 56 µm) with average grain size of 5.6 µm.
Grains are heavily dislocated.
Ni/N is number fraction of grain boundaries with misorientation in the interval Analysis of the dependencies of microhardness, microstress, grain and subgrain sizes on annealing temperature reveals significant contribution of internal stresses to the strengthening of Mo by MF due to high dislocation density in the core of grains and to non-equilibrium state of grain boundaries [13].

Y2O3 could act as an inhibitor to the growth of ZnO grains when working with Sb2O3.
With the increase of Y:Sb ratio, a new phase of Y-Sb-O would be formed, which is a more effective inhibitor to the growth of ZnO grains, so the mean size of ZnO grains further decreased.
And the calculated mean sizes of ZnO grains in the corresponding samples (h).
However, without doping of Sb2O3, due to the abnormal growth of ZnO grains and the segregation of the doped Y2O3 at the grain boundaries, the densification of the samples was inhibited and the number of pores increased quickly.
However, without Sb2O3, the densification of samples decreased, the number of pore in them increased, and lots of the doped Y2O3 would segregate at the grain boundaries, resulting in increased carrier concentration there.

In order to simplify of calculations, the thickness of the film is expressed in number of monolayers.
The recent studies show that the excess chemical potential of the surface relative to grain boundaries produces a net flow of adatoms into the grain boundaries which generates compressive stress within the grains [8,9].
The nucleation of dislocations and glide in grains result in the plastic deformation and fragmentation of grains and in the formation of “slip-steps”.
If dislocation movement, which occurs at the grain boundaries, is prevented the formation of subgrains within the original grain structure takes place.
The oxidation rate changes as the number of grain boundaries available for the atomic transport across the oxide scale changes.

Thermal Stability of Ultrafine Grains in Al-Fe-Mn-Si Foils Prepared by ARB and Subsequent Rolling P.
UFG sheets exhibit enhanced strength and very fine grain structure.
No significant difference in the hardness changes due to annealing is observed between the ARB foils differing by the number of cycles (4 or 6 cycles).
Such an unusual phenomenon is attributed to the decrease of the number of dislocation sources during annealing that is observed in highly deformed alloys.
It is well known that CReX occurs in materials of small grain size after large strains [8,9,10].

For each grain, one Voronoi site is assigned; then the grain boundaries are drawn in such a way that any point within the grain is the closer to its own Voronoi site than to any other Voronoi site in the microstructure.
Fig. 1 Flow chart of the integrated model algorithm to simulate intergranular crack propagation (N=number of Monte Carlo iterations, n = number of microstructures to be simulated, Lavg = average of the maximum crack length) The Markov Chain theory.
That is, a grain boundary can be cracked if and only if the previous grain boundary is cracked.
Hirano; Grain boundary fracture strength in Ni3Al bicrystals, Philos.
Abe, Misorientation dependence of grain boundary fracture strength and grain boundary energy for molybdenum <001> symmetric tilt boundaries, J.