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Multiple grain reorientation as the distinguishing feature of ECAP.
Fragmentation of grains under ECAP.
The longer is the trajectory of grain reorientation, the higher misorientation accumulates within grains due to their non-uniform deformation and the more intense is resulting grain fragmentation.
A probability of grain fragmentation with formation of high-angle boundaries increases with the number of ECAP passes.
These displacements of grains result in their accidental rotations.

There are a large number of dislocation tangles which distribute near the grain boundaries that form the sub-grain although the cellular substructure is not too clear.
When the extrusion ratio reaches 50, quite a number of dislocation tangles distribute around the second phases.
In this case, the number and the size of recrystallized grains are both increase (Fig.5(c)).
When the deformation is low (λ=12, 25), a large number of intra-crystallinedislocationsform the dislocation wall through the dynamic response at first.
The crystal orientation of sub-grain which are exist in this area do not match each other so that there are a large number of dislocations around the second phase particle which could supply the more driving force to dynamic recrystallization as the proceeding of hot extrusion compared with other place [18, 19].

Values of E were obtained from compression and tension parallel to grain, and static bending tests.
Brazilian Code ABNT NBR 7190: Design of Timber Structures [6], in its Annex B, specifies three tests in order to determine the longitudinal modulus of elasticity: compression parallel to grain; tension parallel to grain and static bending.
After static bending tests, specimens were extracted for testing in compression parallel to grain (15cm × 5cm × 5cm) and tension parallel to grain (45cm × 5cm × 2cm), both performed obeying the requirements of Brazilian Code ABNT NBR 7190 [6].
Fig. 1 Extraction of specimens for tension and compression parallel to grain tests Table 1 shows the number of specimens tested in static bending, tension and compression parallel to grain, for the six wood species used in this study, totalizing 297 tests.
Table 1 Number of specimens per species of wood and type of test.

After 390℃ extrusion the alloy grain size（as shown in Fig. 3-d） is significantly larger than the that extruded at other temperatures grains of alloy extruded at 290℃ very unevenly, mainly for coarse grains within a partial area, while in other regions, grains are particularly small (Fig. 3-a), the grain sizes not the uniformity which will usually result in the unevenness of the material properties.
With increasing post extrusion temperature grain gradually becomes uniform.
Therefore, for thermal deformation at a lower temperature, the grains will have a large number of the twin tissues (Fig. 3-a).
There are a large number of large and deep dimples on the fracture surface(Fig. 5-b).
The interior of the crystal grains of the alloy in the post extrusion exist a large number of twinned organizations, which is reduced with extrusion temperature rising. 3) The aging treatment can further improve the Mg-6Zn-Si-0.25Ca’s mechanical properties after the post extrusion.

A large number of investigations [1-3] show that NS metallic materials produced by severe deformation techniques exhibit a marked structure-heterogeneity effect.
Every so often bimodal grain-size distribution is observed.
The former grains account for ∼40 % of the specimen area.
Equiaxial grain structure with average grain size d ~ 1 µm is formed in the alloy subjected to ECAP [23].
Zabudtchenko in: Ultrafine Grained Materials IV, edited by Y.T.

Effect of Silicon on the Grain Size and Grain Morphology of AZ91E.
The grain size measurements were based on two samples and a minimum of 100 grain measurements was taken across each sample.
The average grain size of AZ91E was 103 ± 25 μm.
Effect of silicon on the average grain size of AZ91E.
The dendrites in the unrefined alloy are large and highly branched, while the grain structure in AZ91E with Si additions consists of smaller, less developed (less number of secondary dendrite arms) dendrites.

One of the reasons is that many microstructural factors near grain boundaries contribute to the mechanical properties, e.g. the width of PFZ, size of grain boundary precipitates and so on.
On the grain boundaries, furthermore, grain boundary precipitates are observed in all the investigated alloys.
The quantitative analysis in Fig.4 reveals that whereas the addition of Ag results in a high number density in the later stage, in the Cu-added alloy the number density is higher than in the Al-Zn-Mg ternary alloy in the early stage and subsequently decreases.
Ag-added Cu-added Al-Zn-Mg ternary 10 0 10 1 10 2 A.Q. 0 5 10 15 20 Number density, N ×1023 /m3 Aging time, t /ks Fig.4 Changes in number density of nanoclusters and η' precipitates formed in the grain interiors of the Al-Zn-Mg ternary, Ag-added and Cu-added alloys aged at 433K.
The quantitative analysis of the 3DAP results reveals that whereas the addition of Ag results in a high number density in the later stage, in the Cu-added alloy the number density is higher than in the Al-Zn-Mg ternary alloy in the early stage and subsequently decreases.This is in agreement with the hardness results, and suggests that Cu increases the rate of nucleation, while Ag increases the density of nucleation sites.

Monte Carlo simulation, of recrystallization and grain growth [1, 2].
Monte Carlo simulation of recrystallization and grain growth.
A number termed as Si was assigned to each lattice site.
Following the Saito and coworker’s research on the basis of diffusion-controlled mechanism of grain growth to convert simulation time (MCS) to real time (sec) [10-12], one can write: (8) where DGB is the grain boundary diffusion coefficient, d, the simulation lattice constant considered to be 5 µm in this simulation, and Q the number of all orientations in the simulation.
Acknowledgments This research was carried out under the project number MC 4.04203 in the framework of the Research Program of the Materials Innovation Institute M2i (www.m2i.nl), the former Netherlands Institute for Metals Research.

the grain boundaries of cermets, which strengthened the grain boundaries and improved the mechanical properties of Ti(C, N)-based cermets.
In addition, a great number of nanoparticles distributed at the grain boundaries, some of them without clear rim were observed.
With increasing nano TiC and TiN additions, the average grain size reduced, so the number of grains acting as crystal nucleus during sintering increased.
As a result, grains grew up in partial regions.
Furthermore, the nano particles distributing at the grain boundaries of cermets strengthened the grain boundaries (as shown in Fig. 2 b, grains 1 and 2), inhibited the crack propagation along the grain boundaries, and hence, improved the mechanical properties of the cermets.

For lower strains when the grain size is still small enough, the plastic flow governs by twinning and probably grain boundary sliding.
We suppose that this could be explained by the development of grain boundary sliding for the lower grain sizes which requires lower stresses than a transfer of shear from one grain to another via dislocation mechanism.
Variation the crystallite size and microstrains with increasing of numbers of HPT cycles.
Strain-induced grain growth.
Further deformation has led to strong grain growth in shear direction and to formation of elongated grains.