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Introduction A grinding wheel is composed of abrasive grains, bond material and pores.
When viewing normal to the wheel surface the number of distinct wear-flat areas per unit area on the wheel surface may be counted and is sometimes interpreted as the cutting-edge density.
Detailed information can be obtained concerning the abrasive grains and even details on a particular grain in the wheel surface.
Depth measurement using stylus or optical methods allows the number of grains to be related to the radial depth below the wheel surface.
Fine surface detail can be detected including adhesive loading of grains.

In case of composite nanofilms the grain system obtained in the course of deposition contributed to good Pt grain refining, and due to that mostly particles from 3 to 9 nm in conventional diameter were formed.
On the other hand, the number of particles exceeding 20 nm was vestigial.
However, larger particles are a residuum of platinum being part of spheroidal grains, where Al fraction was smaller, which was conducive to the process of Pt coagulation.
In case of (Pt+Al) composite films, the grain system obtained in the course of deposition is conducive to good Pt disintegration, and owing to that particles with conventional diameters from 3 to 9 nm were obtained.
Joining of crystals of this oxide with crystals of the oxide growing from substrate (hybridisation) is conducive to displacement of Pt grains.

The Alsoft model The Alsoft model is based on a two-parameter description of the as-deformed sub-structure after cold/hot deformation where the microstructure is characterized by an average sub-grain size d and a dislocation density ri inside the sub-grains.
The average sub-grain size after deformation can be obtained from experiments or from adequate models [10].
During annealing of the as-deformed state recovery will take place through sub-grain growth and by annihilation of the sub-grain interior dislocations.
As far as possible experimentally measured relevant material parameters (e.g. alloy composition, as-cast grain size) and microstructure parameters (size and number density of primary particles and dispersoids) have been used as input.
Table 3 Calculated and experimentally measured grain sizes (circle area equiv. diameter) Alloy/condition Anneal. temp.

The maximum grain size and the average width were 687μm and 31μm.
The grains were also beginning growth from the outer to inner.
In primary structure, PF showed a linear growth along the grain boundary, which outlined original austenite grain.
As PF had done, feathery UB was nucleated from the grain boundary and stretched within the grain.
Although there were a certain proportion of PF, FSP and UB at columnar grain and equiaxed grain boundaries of weld, these organizations accounted for a very small proportion of the grain size and grain remained a large number of AF.

Therefore, the alloy exhibits less average grain size and more recrystallization grains in the extrusion direction.
When DRX occurs, new fine recrystallization grains can form along original grain boundary.
Finally, fine grains with large angle form [14].
Improving the deformation degree can increase the dislocation density within the grains and strengthen the crystal lattice distortion, thus the nuclei number of new grains increases.
Average grain size is at the range from 6 mm to 8 mm for extruded rods, while the extruded plates exhibit much large grain size and fine micro-particles.

For the 4P 1050/ 6082 and 4P 6082/1050 FSPed joints, table 2 summarizes the average grain size measurements of the mean grain sizes, standard deviations, minimum and maximum grain sizes of the surfaces depicted in Figure 3.  
The 4P 1050/6082 mean grain size joint ranged from 5.381 to 9.120 µm, while the 4P 6082/1020 mean grain size ranged from 1.744 to 1.193 µm.
Dynamic recrystallization occurred as the number of FSP passes increased, causing grain size refinement.
The following conclusions were reached based on results archived; findings are as follows: · The grain sizes were decreased as the number of passes were increased.
The 4P 6082/1050 had substantially finer grains than the 4P 1050/6082

Fully dense Ho:YAG ceramics with the average grain size of ~ 10 μm were obtained after vacuum sintering at 1780 ℃ for 8 h.
The microstructures including grain boundary, grain size and residual pores are considered as the main factors affecting the transmittance [11].
As shown in Fig. 3 (a), the Ho:YAG transparent ceramic exhibited homogeneous grains and the average grain size was about 10 µm.
Obviously, no grain-boundary phase or residual pores can be observed in the microstructure of the sample.
The ceramic exhibited homogeneous grains and the average grain size was about 10 µm.

The austenitic grains would be refined for the extra-product of ferrite above the Ar3.
The eutectoid reaction was induced on the grain boundaries of ferrite and non-transformed austenite and deformation bands with the increasing volume of deformation.
As can be seen from Figure 4, deformation induced ferrite occupy most of the ferrite austenite grain boundaries ,forming a network structure precipitate along with austenite boundaries.
When the strain reach to 1.0, the process of dynamic ferrite transformation has been basically completed, pearlites elongate along the deformation direction, and a considerable number of lamellar pearlite have been spheroidized into cementite particles.
[4] Park J, Song D H, Lee D,Choo W Y: Ultrafine Grained Materials Ⅱ，Settle:The Minerals,Metals & Materials Society, p. 275,(2002) [5] Storojeva L,Kaspar R,Ponge D:Mater Sci Forum, p. 426-432,(2003) [6] Kotobu Nagai: Second Phase of Ultra Steel Project at NIMIS.

Binomial equation and power equation can describe the relationships of gasoline and diesel oil volatilization coefficients with mean grain size respectively.
Table 1 Grain size distribution and physical properties for porous media samples Porous media CS1 CS2 CS3 CS4 CS5 CS6 Fraction [%] 30.8 33.3 25.5 6.3 2.8 1.3 Main grain size[mm] 1.532 0.671 0.386 0.243 0.152 0.086 Specific surface area[m 2/g] 1.41 4.69 5.23 5.62 6.17 8.21 Organic carbon content[g/kg] 0 0 0 0 0 1.72 Bulk density[g·cm -3] 1.60 1.60 1.54 1.54 1.51 1.51 Table 2 Physical-chemical properties of oils Oils 93#Gasoline 0 # Diesel oil Density[g/cm 3]（20℃） 0.750 0.848 Viscosity[mPa·s]（20℃） 0.45~0.65 3.56~4.05 Boiling range[℃] 40~200 180~370 Hydrocarbon Number C4~C12 C9~C28 Experimental design.
The volatilization mass of diesel oil becomes more with the decrease of the mean grain size.
When the mean grain size is 0.086mm, the volatilization mass of diesel oil in porous media exceeds that with no underlying material.
Fig.3 was drawn with the volatilization coefficient of oil as ordinate and mean grain size of the six underlying materials as abscissa.

The extent of grain growth in the YSZ films increased with substrate temperature and the YSZ films had nano-structured morphology with small average grain size less than 100nm.
Since the electrical conductivity of the film was nearly constant in oxidizing atmosphere, ionic transference number (σion/(σion+σe)) of YSZ film is thought to be close to unity.
This can be explained by the microstructure change that the grain size increased with deposition temperature.
Since the electrical conductivity of the nano-structured YSZ films by EB-PVD is controlled by grain boundaries, YSZ film at 600 o C with more grain boundaries shows lower electrical conductivity.
It was found that the grain size increased with deposition temperature between 600 and 800 o C.