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An experiment, in which a lengthy number billet at a temperature of 500 °C rolled from a diameter of 30 mm to a diameter of 15 mm in the mill SVP-08, was conducted.
All industrially used metal materials have a coarse-grained structure with grain-crystallite dimensions of the order of 20-80 μm or more.
The periphery of the rod is an equiaxial ultrafine-grained structure with grains size 300-600 nm.
In the initial state, titanium grade VT-1 has a coarse-grained structure with an average grain size of 70-80 µm.
Acknowledgments This work was partially supported by Ministry of Science and Education Republic of Kazakhstan, grant number AP05131382 - “Development and research of the technology for producing ultrafine-grained materials with improved mechanical properties and increased radiation resistance for using them as materials of the first wall of fusion reactors and in nuclear energy” (2018-2020).

Also specimens with the mean grain size of 1, 7 and 30 mm were obtained by controlling annealing of ultrafine-grained preforms produced by the isothermal multiaxial forging [6] at 480, 600, 700 and 800°С, respectively to check the effect of initial grain size on twinning.
The intensity of twinning in HCP metals is controlled by a number of factors [7].
a b Figure 4 - The influence of the initial grain size on the fraction of twinned grains in 10% cold rolled CP titanium (a) and the microstructure of titanium with the initial grain size of 1mm after rolling to 10% (b).
The investigation of the microstructure of CP titanium with different grain size rolled at room temperature to e=10% have shown that activity of twinning increased with increase in grain size reaching maximum fraction of twinned grains at grain size of 15¸30mm.
To intensify the formation of the ultrafine-grained structure due to twinning, a CP titanium with relatively low level of impurities and with grain size ³15mm should be used.

The eutectic phase is characterized and quantified in terms of the development of eutectic cells size and number of eutectic cells.
Quantitative measurements were carried out on the fraction of solidified primary austenite (fγ), Secondary Dendrite Arm Spacing (SDAS), number of primary grains, eutectic cells (EC) size and number of EC.
To obtain the number of primary crystals, pictures of the etched DAAS sample were taken keeping the position of the camera and the sample fixed and varying the orientation of the light source in every shot to get the reflections of all grains.
The CET was identified and the number of and equiaxed grains obtained.
The number of EC per unit volume is in the range of those presented in the literature [13,14].

Effect of Ppm Level Dopant on Ductility of Ultrafine Grained Gold Wires E.
In Fig. 3a, the red lines delineate the boundaries of grains.
Second, it is also known that SFE reduction is more effective with elements of higher valency, i.e. having higher numbers of electrons in the outermost energy level of an atom [14].
Lavernia would like to acknowledge support by the Office of Naval Research (Grant number N00014-08-1-0405) with Dr.
Chew: PhD thesis on Micro-doping in Ultrafine-grained Gold Bonding Wires.

Some important results are obtained: with the increasing of ageing time, the size of platelet shaped (known as Guinier-Preston (G-P) zones) precipitates and spherical shaped η' precipitates increased, the number of platelet shaped precipitates increased too, while the number of η' precipitates decreased; the precipitates with almost the same size distributed continuously and uniformly along the grain boundary with quite narrow precipitate free zones (PFZs) at 5 hours of ageing time, when the ageing time increases to 8 hours, the distribution of the precipitates along the grain boundary becomes discontinuous and the PFZs gets wider, while with the further increasing of the ageing time, the precipitates distributed continuously again along the grain boundary and the PFZs become more wider.
It can be seen from Fig. 2 that the number and size of platelet-shaped precipitates increase gradually with creep aging time.
Precipitates free zones (PFZs) at grain boundary are larger than Fig.1 (b) and the distribution of the precipitates along the grain boundary becomes continuous again.
The number of the second phase particles η' phases becomes fewer than the former.
Some important conclusions can be obtained as follows: (1) As ageing time increases from 5 h to 20 h, the number and size of platelet shaped precipitates increased, but the number of η′{TTP}8242 precipitates decreased at 120 ℃/ 250MPa. the precipitates with almost the same size distributed continuously and uniformly along the grain boundary with quite narrow precipitate free zones (PFZs) at 5 hours of ageing time, when the ageing time increases to 8 hours, the distribution of the precipitates along the grain boundary becomes discontinuous and the PFZs gets wider, while with the further increasing of the ageing time, the precipitates distributed continuously again along the grain boundary and the PFZs becomes more wider

However, a bimodal character of the microstructure for RT processed sample with some significantly larger grains presented in the sample, and many non-equilibrium grains with low angle boundaries formed in larger grains (white lines in Fig. 1d).
It can be seen that the grain sizes of Mg were reduced to around 0.8 µm, including some smaller grain sizes of ~0.2 µm, as shown in Fig. 4.
Also, there are abundant dislocations are visible within grains, and some tangled dislocations near grain boundaries.
With an accumulation strain of around 4, almost all the twin boundaries were evolved to HAGBs, without twin formation in ultafined grain, and some dislocation sinks were accumulated by increased the number of grain boundaries [21].
In this study, the high fraction of {10-11}-{10-12} double twins deformation mechanism would give a large number of {10-11} variant interfaces, which can contribute to dynamic recovery at RT and absorb dislocations.

If the fracture stresses in a set of brittle specimens are arranged in size order, the probability of survival of a given sample can be given by the following approximation: 1+ = �n Psurvival (1) Where n is the rank number of the sample and � is the number of the samples in the set (� = 20 in this case).
The EBSD grain orientation map (right) shows failure occurred across a grain rather than at a grain boundary.
A light etch was used to reveal the grain boundaries.
The EBSD grain orientation map (right) indicates a Σ = 19 grain boundary with misorientation 38.3˚ vicinity of grain boundaries.
Fracture toughness of grain boundaries in mc-Si as a function of grain misorientation.

Implications for grain boundary engineering are mentioned.
The number of papers containing data on different grain boundaries is very limited.
A large number of good quality bicrystals is needed for such measurements and their preparation is a requisite condition for systematic research.
(I) Since the Burgers vectors belong to two different crystals separated by the interface, the expression above indicates only the number and types of dislocations but not the specific crystallographic directions.
Watanabe, T.: in Grain Boundary Engineering, ed.

Due to changing the deformation axis, the fraction of severely deformed areas increases with increasing number of passes and very high cumulative strain becomes possible [16,17].
The number of deformation bands was rose owing to increasing a cumulative strain from 3 to 6.
Grain growth led to increasing the grain size in a fine grained area from 5.3 to 8.2 µm in the samples pre-deformed at 400 °C.
The mean grain size in a fine-grained area increased from 10.2 µm to 10.9 µm and fraction of fine recrystallized grains decreased from 54% to 32%.
Bimodal grain structure with 40 % of coarse grains and 60 % of fine grains was formed after 4 cycles.

Grain refinement was achieved in both steels after all rolling schedules.
The initial austenite grain size, D0, and the average recrsytallised grain size, Drex were measured from quenched specimens immediately after soaking or after roughing.
Austenite Grain Size.
As expected, Drex decreases with increasing εapp due to the increased number of nucleation sites.
Li, Static recrystallized grain size of coarse-grained austenite in an API-X70 pipeline steel, Journal of Materials Engineering and Performance 22(12) (2013) 3626-3630