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It was found the grains of pure iron were significantly refined to the submicron size range by an HPT process, and the Vickers hardness of HPT-processed specimens increased with increasing number of turns and distance from the center due to the grain refinement.
Particularly effects of the number of turns in the HPT process and the counter materials in the wear tests were studied.
The number of turns (N) was varied in five conditions; N = 1/4, 1/2, 1, 5 and 10.
Fig. 2 Variation of Vickers hardness with distance from the center (r) for HPT-processed disks through different numbers of turns.
Summary The grains of pure iron were significantly refined to the submicron size range by an HPT process, and the Vickers hardness of HPT-processed specimens increased with increasing number of turns and distance from the center due to the grain refinement.

Fig. 10- Variation of the hardness as a function of ECAP pass number.
Fig. 11- Variation of the yield stress as a function of ECAP pass number.
Fig. 12- Variation of dislocation density as a function of ECAP pass number.
Fig. 13- Variation of average boundary spacing as a function of ECAP pass number.
Fig. 14 - The calculated and experimentally measured flow stress as a function of the pass number.

During deformation, the number of low angle boundaries increase, in contrast to DRV, because of transformation from low to high angle boundaries.
These occur inside the grains.
Measurements of these grains have shown that the grain size here is like the initial grain size.
The numbers of elements changed from 8,000 at the beginning up to 18,000 at the end of the process.
A look at the grain shape reveals that the grains in the dead metal zone are still equiaxed.

Zhan[7] studied high-angle symmetric tilt Σ5 (310) Ag nanowires with varied amount of grain boundaries and the influence of grains sizes.
His work mainly discussed the quantitative relationship between natural frequency and number of grain boundaries.
Our study will highlight the importance of grain boundary misorientation angles and the associated grain boundary energy as the generated grain boundaries is likely to be of metastable structures instead of the stable ones.
Firstly, (310) is chosen as the grain boundary orientation of interest, and the tilt axis is set as x axis and the grain boundary (GB) plane is locating in the x-y planes.
Additionally, asymmetry in number of atoms arises by only deleting the atoms in one of the grains; to address the issue, same number of atoms must be deleted in both grains for atoms beneath the cut-off radius.

Note that only GBs between in-cavity solidified grains are shown for the HPDC sample because the number of GBs between ESCs is not sufficient for statistical validity.
In-grain misorientations (misorientations within the same grain) were measured in most of the primary grains in every sample.
The number of low-energy GBs formed by crystal collisions therefore depends on the number of collisions.
Increasing the number of collisions results in an increase in the number of low-energy GBs.
This is attributed to the increased number of crystal collisions during HPDC which promotes crystal agglomeration. 3.

When adding 0.02 wt% nanometer magnesium oxides, the number of bainite increases significantly in the cast microstructure, which is mostly distributed at the boundary of the ferrite grains.
The number of bainite is largest in the cast microstructure, most of which is distributed at the boundary of the ferrite grains, when the 0.02 wt% MgO is added.
The nanometer oxides also segment the austenite grains, with making the grains fine and uniform.The second-phase particles prevent the growth of the austenite grains by pinning the austenite grain boundaries.
Thus, when the number of the particles increases and the size becomes smaller, the pinning force to the original austenite grains becomes greater.
The number of bainite, which is mostly distributed at the boundary of the ferrite grains, increase significantly in the cast microstructure.

The ferrite grain size number is 11.
The requirements of Nb microalloyed H beam are as fellow: yield strength is great than 365 MPa, ferrite grain size number is great than 9, charpy impact energy at -20°C is greater than 34 J.
Austenite grain size affects ferrite grain size of product.
When heating temperature are 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, the corresponding austenite grain size number is 4.5, 4, 3.5, 3, 2, 1, respectively.
The microstructure consists of ferrite and pearlite, and the ferrite grain size number is 11 (see Fig 4).

The initial bonding between several particles becomes the combination of a number of particles, so the examined results at macro level display area shrinkage ratio enlarging and metallization happening, at micro level quantities of bonding boundaries evolve into symmetrical boundaries as networks which are not continuous and incomplete.
From 1833K to 1953K, a great many recrystal grains come into being, at this time, the new grains’ sizes are very small, impurity such as O is swept away by hydrogen from grain boundaries.
At 2073K, the grains grow up quickly and the bending three branches grain boundaries become smooth, the bigger grains devour the smaller ones, two or more grains combine together into a big one, during the process, the porosities in three branches grain boundaries are closed into big grains.
The porosities in grain boundaries disappear, but the porosities inside of grains remain when the grains around three branches boundaries join into a big grain, at this time, the three branches grain boundaries disappear.
Acknowledgements This work was financially supported by the Shaanxi ‘13115’ Science and Technology Innovation Project (project number: 2008ZDKG-41) and the experiment was carried out under the help of JDC Technology Centre.

The surface of the grains is uneven.
Sylvinite acquires a milky white color due to a large number of gas-liquid or halite inclusions.
The study of the specific nature of the destruction process of milky white sylvinite reveals a number of successive changes in its shape.
Fracturing along the cleavage is more frequent, and the surface of the mineral becomes spongy due to the large number of cavities.
Clear transparent colorless halite grains and its grains with blue spots, as well as grains, which contain halopelite, are almost not destructed when heated.

The grain density of WA grains in the slurry was set at 60 wt%.
The number of abrasive grains on the tool working surface and the protrusion height of abrasive grains from the bond face increased as the truing condition shifted from area C to area A.
As regards the tool radius of the hemispherical tool with a mesh size of #1000, the number of diamond grains on the tool working surface decreased markedly when the tool tip was shaped to have a radius of 50 µm.
The decrease in the toughness of diamond grains caused by impurities in the grains increases with an increase in grain size [6]; thus, diamond grains on the tool working surface were successfully flattened at the same level as the bond face.
It was unavoidable to obtain flattened grains with slightly rounded edges, but the flattened area remained on the grains.