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Upon annealing, grain growth sets in.
Hence, there are still a large number of zero solutions (mainly at grain boundaries) where the measured patterns could not be identified unequivocally.
For example, grain 6 has to end at the given position of the dashed line to allow for a Σ3 boundary between grain 1 and 5.
It is therefore more likely that the non-indexed area belongs to grain 5 (or grain 1) instead of grain 6.
The observed structural units have in common that all involved grains are <110>-oriented parallel to GD, grain boundaries within the structural units are low-Σ boundaries, the structural units are larger than the surrounding grains, and that some grains show a gradient in orientation to accommodate strain.

For example, the interfacial energy of Σ = 3 twin grain boundaries in copper changes with changing inclination of the grain boundary plane from the {111} symmetrical tilt grain boundary.
Solid lines represent non-coincidence grain boundaries (Σ ≥ 51), dashed lines are the Σ = 3 twin grain boundaries.
Nevertheless, the remaining networks of the original non-coincidence grain boundaries are still partially preserved but the number of the twin grain boundaries is substantially increased due to low stacking fault energy in silver. 5500 µµµµµµµµmm It is apparent from Fig. 2 that there is an extended intergranular failure of the object.
In Fig. 4, the non-coincidence (Σ → ∞) grain boundaries terminate exclusively at the Σ = 3 special grain boundaries.
These grain non-coincidence grain boundaries are heavily corroded.

Its goal is to provide an ultrafine-grained (UFG) structure in metals and alloys (with grain sizes in the range of 10~1000nm)[4-6].
It can be seen the initial size of grains is coarse in the solid solution treated 7055 samples before ECAP (Fig.1a).
From the further observations (Fig.1d), it can be seen that the elongated micrometer-sized grains along the shearing bands form during ECAP, and most of the grain sizes are less than 1 μm after two passes of ECAP.
With the number of ECAP increasing, the scattering intensity of samples increases.
In case of 7055 alloys, the atomic numbers of aluminum and magnesium, zinc and copper are very close.

Another mechanism of new grains formation is continuous dynamic recrystallization.
Improvement of mechanical properties through grain refinement has contributed to the rapidly expanding field of materials engineering, in which ultrafine-grained materials with the grain size less than 0.5-1 mm are produced using severe plastic deformation (SPD).
Unlike cubic metals with their large number of slip systems (e.g., twelve for fcc metals), hexagonal metals have far fewer deformation modes with which arbitrary imposed strains can be accommodated within polycrystalline aggregates.
The limited number of slip systems in hcp metals may result in the formation of unstable walls of edge dislocations rather than stable dislocation boundaries [6] such as high-angle deformation-induced boundaries.
The microstructure of the rod was homogeneous with a mean grain size of 35 mm.

However, magnesium alloys exhibit poor room temperature ductility and formability because of hexagonal close-packed (hcp) crystal structure with limited number of operative slip systems [3], in comparison to other materials currently widely used such as steel and Al alloys.
It is indicated that a significant grain refinement was achieved during the first stage of rolling and the average grain size measured is about 4µm.
On the other side, the AZ31 alloy exhibits a bimodal grain size distribution after the first processing stage (ARB1), and a moderate fraction of relatively coarse non-subdivided grains coexist together with the newly formed fine grains.
Mechanism of Grain Refinement TEM observation (shown in Fig.2) further revealed the mechanism of DRX induced grain refinement in AZ31 alloy.
These submicro grain boundaries probably formed initially and locally at the as-received coarse grain boundaries in the shape of zigzag, and gradually developed toward the interior, then finally covered the whole grain.

Introduction Nanometals, defined as pure metals or alloys having grain size reduced to below 100 nm, have been recognized as prospective for a number of structural applications due to their superior mechanical properties comparing to their conventional microcrystalline counterparts.
As a consequence, they have been a subject of extensive research which resulted in the development of a number of fabrication routes.
It should be noted that a number of SPD techniques, which allow obtaining unconventionally large strain, have been developed and successfully employed for grain size refinement in various metallic systems.
It should be noted large numbers of precipitates are uniformly distributed in the matrix.
Nano-consolidation produces larger grains (~500 nm in diameter) but more than 90% of grain boundaries are of high angle type.

Due to relatively high sensitivity of superplastic properties to a grain size, the superplastic forming is normally applicable to ultrafine-grained (UFG) materials only.
The HAB fraction was measured to be 84% of total grain boundary area.
The microstructure also consisted of nearly equiaxed grains with high proportion of HABs but the mean grain size was measured to be ~2 mm.
Effect of superplastic deformation and static annealing on mean grain size Characteristics Superplastic conditions 300 °C 3.3×10-3 s-1 350 °C 8.3×10-3 s-1 400 °C 3.3×10-3 s-1 Mean grain size in grip section on base material side, μm 2.1 2 10 Mean grain size in grip section on stir zone side, μm 2 >100 >100 Mean grain size in near-necking region, μm 2 2.1 20 At 350oC, the mean grain size of the base material was measured to be ~2 mm (Table 1, Fig. 6a), i.e. the grain growth behavior was nearly unchanged.
Acknowledgements This work is supported by the Ministry of Education and Science of the Russian Federation under the agreement №14.584.21.0023 (ID number RFMEFI58417X0023).

Effect of hot-deformation on micro-texture in ultra-fine grained HSLA steel S.
(d) Grain boundary misorientation histograms of SP-samples showing UFF grains.
EBSD measurement revealed that majority of the UFF grains in the SP-samples (63-75%) and MP-samples (60-80%) were surrounded by high angle grain boundaries.
In general, the investigated samples represented random texture, Fig. 1 and Fig. 2, however, quantitative analysis has been carried out to determine the fraction of different texture components from statistically significant number of grains (at least 1000 grains) in each sample.
Cube component in a-grains comes after the transformation of recrystallised g-grains and is known to cause delamination problem in the steel [4, 5, 8].

It is found that the thin film grain size present quantum state with the increasing of annealing temperature. 2.
The grain size is biggest crystallized at 900°C for 2h by FA, an average grain size of 30nm or so is obtained Fig.2 the sample annealed at 8400C by FA The SEM of Fig.2 shows crystallization by FA, from the Raman spectra an average grain size of 30nm has been obtained, however, the SEM of crystallization shows that grain size is 300nm or so.
This perhaps means that large particle group made there exists the grain boundary between their grains.
It is noted that the grain size means average grain size in the paper.
The transitions between quantum states with different quantum numbers should forced by the certain energies corresponding to the proper temperatures. 4.

Meanwhile, some small grains maybe deform by grain rotations.
This indicates there is a great number of grains with high angle boundaries.
The rings as marked by number one to six correspond to (102) and (110) planes of Cu4Y, (111), (200), (220), (220) and (311) planes of α-Cu.
Therefore, a considerable number of extinction fringes exist in most small grains.
Otherwise, the small grains maybe deform by grain rotations.