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However, such methods of welding require significant clamping force and can be realized with limited number of structures.
Grain size in the overheating area makes DG = 20-60 μm , microhardness is also reduced by 7%, i.e.
Grain size is DG = 40-80 х 350-400 μm with coefficient of shape æ = 6-8 and HV(B-M) = 3360-4500 MPa.
HAZ grain size in overheating area is DG = 20-70 μm at HV increase on average per 5% (Fig. 4c).
The coefficient of grain shape virtually does not change.

Due to the high heterogeneity of these materials is relatively difficult to assess the impact of specific parameters (grain size, the content of Fe2O3, SiO2, CaO, amorphous phase, etc.).
Due to the experimental testing of a large number of different types of fly ash and their mixtures, it will possible to verify at least some principles based on experience with the production of ceramic body.
The creation of high-quality aggregate grain also puts the requirements for granulometry, micro structure and chemical composition on the fly ash.
If specific weight is evaluated, it is apparent, that high temperature fly ash contains higher percentage of cenospheres (hollow spherical grains).
It is caused by missing of spherical amorphous grains and higher content of CaO, which at firing weakens structure of ash body.

And many nucleuses had not yet grown up to a grain.
(a) (b) Figure 4 TEM Morphology of Particles Precipitated from tested Steel Deformed at 950 ℃(ε=30%,Strain rate is 1s-1, interval time is 50s) In addition, as shown in Fig.4, a large number of nano-sized Nb, Ti (CN) second-phase particles precipitated on dislocation lines and grain boundaries during isothermal deformation at 950 ℃ were observed under TEM.
These precipitates had strong migration to dislocations, grain boundaries and sub-grain boundaries.
When the deformation temperature was at 950℃, there had less fine grains at grain boundary of the coarse austenite.
When the deformation temperature was up to 1000℃, the tiny recrystallized grains appeared at the grain boundaries or the deformation zones of austenite.

Normally the interior of the nanocrystal is constrained and the distances between atoms located at the grain boundaries expanded.
A large number of experimental investigations on LaNi5, TiFe, ZrV2 - type compounds have been performed up to now in relation to their exceptional hydrogenation properties.
Discharge capacities as a function of cycle number of negative electrodes made from nanocrystalline powders prepared by MA followed by annealing LaNi4-xMn0.75Al0.25Cox (solution, 6 M KOH; temperature, 20°C).
XRD spectra of nanocomposite Mg2Ni/C (a), Mg2Ni/Cu (b) and Mg2Ni/Pd (c) materials Figs. 6 and 7 show the discharge capacities as a function of the cycle number for some of the studied nanocomposite materials.
Normally the interior of the nanocrystal is constrained and the distances between atoms located at the grain boundaries expanded.

The microstructure of the laser surface melted zone consists of fine dendrites with an average grain size of less than 10µm.
The above characteristics make them an appropriate choice in a number of demanding applications including automobile, aerospace, computer, mobile phones components, household equipment, etc [3].
The microstructure of as-received AZ91D is coarse with grain size in the range of 50-200µm, consists of coarse grains of α-Mg and β-Mg17Al12 precipitates along the grain boundaries as shown in Fig.1.
Fig.2b shows the microstructure on the top surface of the melted zone, the mean grain size is less than 10µm; the grain size is reduced by a factor of more than 10 as compared to the microstructure of as-received AZ91D in Fig.1.
The major results are summarized as follows: The microstructure of the laser surface melted zone consists of fine dendrites with an average grain size of less than 10µm, the grain size is reduced by a factor of more than 10 as compared to that of the substrate.

Nickel are homogeneously dispersed in HA matrix with grain size between 0.25-2µm after sintered at 1250oC.
Because the atomic number of Ni is far higher than HA, the scattering contrast results in a white feature for Ni grains and grey for HA grains.
From Figure 6(b), the micrograph clearly reveal that Ni grains are agglomerated, and located at thriple junctions and are homogeneously dispersed in HA matrix compare to pure HA micrograph (Figure (a).
The grain size of HA and Ni are between 2-4.5µm and 0.25-2µm respectively.A homogeneous bright spherical grains of Ni distributed within dark region of HA can be seen at lower magnification (700 x) as illustrated in Figure 6(c).
Conclusions From this work, the Ni deposited on HA powder was successfully prepared by electroless plating process without sensitization and activation treatment.The nickel deposition was confirmed by the EDX and XRD analysis and uniform nickel distribution within the HA grains improve the density after sintering.

Table 1 Compaction test results of both fillers Fillers Filler of the bottom layer Filler of the underlying embankment Sample Number 1 2 3 4 5 1 2 3 4 5 Moisture/% 4.18 2.35 2.81 3.57 4.71 8.83 4.22 7.59 6.10 4.67 Dry density/(g/cm3) 2.09 2.07 2.09 2.10 2.06 2.13 2.10 2.18 2.21 2.14 Fig. 2 Curves of compaction test 4.
Test of high-speed railway coarse grained filler of improved particle size distributions [J].Journal of Central South University:Science and Technology,2014
Engineering properties and application of coarse grained soil[M].
Experimental study of compaction character of coarse grained soil[D].
Large-scale test study on volumetric strain law of coarse-grain soil[J].Water Resources and Hydropower Engineering,2013,44(6).

In this study, the phase structure and the grain size of Fe-doped nano-TiO2 powder produced by the sol-gel method were studied.
The number of photogenerated electrons and holes in the photocatalytic reactions would be increased, resulting in an enhancement in photocatalytic activity.
The influence of calcination temperature on the anatase-rutile transformation and the nanocrystalline grain size were characterized.
According to Scherrer formula（d =ĸλ/β1/2cosθ）, the crystal grain size is 8.25 nm.
With increasing amount of Fe, the density of oxygen vacancy decreases, which retards phase transformation and crystal grain growth.

At the same time, numerous generating grains contribute to the grain frequent collision and agglomeration.
The M-O absorption peak at low wave number declined sharply or even disappeared.
It is divided into two steps to separate out the colloidal particles from the solution: nucleation and grain growth.
Thus the size and distribution of colloidal particle depend on the nucleation rate(V1) and grain growth rate(V2)
Large numbers of nucleus have formed in the solution but the grain growth is slow when V1 is much larger than V2 at lower temperature, which tends to form colorless transparent sol system.

An even increasing number of papers has described the structural evolution and properties of such materials and techniques for their production (see, e.g., the Proceedings of special Conferences devoted to this topic [1-4] or the review [5]).
Coarse grained dual phase metallic materials have not been investigated very often.
Lowe, editors: Ulrtafine grained materials II.
Lowe, editors: Ulrtafine grained materials III.
Proceedings of Ultrafine Grained Materials III TMS annual meeting (2004) 629-634