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Higher T1 temperature and extended soaking time caused larger grain size, which accompanied with the Ostwald ripening of the grain and led to non-uniformity of grain size distribution.
This was mainly because of the pinning of the grain boundary by MgO as the second phase, which inhibited the grain growth to get grain refinement.
So there were more residual pores in the grain, and the grain heterogeneity was obvious.
With the increase of the soaking time, it could be seen from Fig.5 (b) and Fig.5 (c) that the small grains were gradually disappeared and the number of the grain with larger size increased, which also proved that the Ostwald ripening phenomenon occurred in the long soaking time.
The grain boundary was pinned by MgO as the second phase, resulting in hindrance of grain growth and grain refinement

Equal channel angular pressing (ECAP) is one of the most efficient SPD processes, which allows a grain size of about 1µm to be achieved [1].
The results of the EBSD analysis indicated that the average grain size and misorientation angle are about 120µm and 21 o , respectively.
Many dislocations are visible inside the grain.
The grain size and subgrain size were measured to be about 1µm and 200nm, respectively.
The sizes of the grain and subgrain did not change significantly and the dislocation density inside the grain remained high.

Introduction In the production of metals and alloys, control of grain size is a key to improve the mechanical performance.
Adopting per unit area grain number represent grain size, A 100mm2 piece sample was sectioned along the center point, and calculated the ratio of 100 in the area of grain number, and the hardness and cooling curve is obtained via microsclerometer (HVS-1000) and temperature recorder.
When the pulse voltage is 700V, the sample is similar to 300V, the average grain size is 31/mm2.
The result agrees with the previous Fig.2; on the other hand, the platform shows grain growth time on the curve, the grain growth time is different depending on different pulse voltages, EPM is most effective on grain refinement when it is applied 500 V.
The result indicates the supercooling increased nucleation rate, the grain growth time is shortened in the meantime.

As shown in Fig.2, during the traditional lapping (TL) process material removal rate increases along with the lapping speed, which is involved from that the bigger linear velocity makes the friction between workpiece and oilstones intense per unit time and number of effect grains increase.
And the effect of the acoustic cavitation of cooling emulsion and peening of detached grains contributes to material removal.
Influence of Grain Size on Surface Roughness.
In ultrasonic lapping the influence of grain size on surface roughness keeps to the same rule in traditional lapping.
It is clear that the surface quality using W5 grain is superior to that using W20 grain and it is improved with ultrasonic assistance.

In this study, the WL zones formed in fine grain to fine grain RR1000 welds are examined.
This image was taken by using a double diffraction spot generated from the inclined grain boundary (see the insert) where the grain A and grain B were overlapped.
The number density is very high in the WL zone.
The spherical morphology and the very high number density of the reprecipitated g¢ in the WL zone are shown in Figs. 7a.
The number density is very high.

Overall features are explained qualitatively by a model in which tensile stress makes the number of effective pinning sites which have appropriate activation energies for discontinuous motion of domain wall more, while annealing process makes just the number of pinning sites such as defects and grain boundaries less.
The magnetic Barkhausen noise measurements have been reported and discussed in relation to heat treatment, grain size, strain, and hardness [1,2].
The distortion makes the local crystal magnetically anisotropic and the easy axis of the magnetization is not continuous anymore near crystal defects or grain boundaries.
The number of effective pinning sites which have sufficient Fig.2.
The annealing process makes just the number of defects and grain boundaries less.

This paper presents a fractal analysis of the self-sharpening phenomenon of the grain cutting edges in cBN grinding.
Representative single crystal cBN grain was used for cBN wheel.
And then, the number of cubes intersected with 3D-profile N(r) is counted.
If there is a fractal nature in this 3D-profile, the relationship between N(r), r and fractal dimension DS is given by () SD rrN − ⋅=α (1) where α is constant number.
As shown in Fig. 2 (a), square grid with mesh size r1 is set on a 3D-profile of the top surface of grain cutting edge.

These incompatibility stresses, adding to the resolved shear stress due to the applied load, result in a total stress at the grain boundaries considerably higher than that experienced by the matrix of the grain.
Hence, the region near grain boundary flows plastically prior to the matrix.
Therefore, the dislocations concentrated near the grain boundary.
The propagation of dislocations to the matrix is easiest when the maximum shear stress in grain is parallel to longitudinal grain boundaries by applying the external stress in the 45° direction of elongated grain structure.
Acknowledgements It is a project supported by natural science foundation of shanxi province China (project number: 2009011028-1; 2011011021-1).

Significant grain refinement was achieved using high deformation degree per pass (> 30 %).
final thickness [mm] number of passes pass reduction [%] Schedule 1 1.25 1 46 1 56 Schedule 2 1.25 2 ≤ 30 1 ≤ 35 Schedule 3 1.25 3 ≤ 26 1 ≤ 30 The rolling speed of finish-rolling was 80-120 m/min with a rolling temperature in the range of 270-360°C depending on number of rolling passes and final thickness.
According to [4] a fine grained region would develop at former grain boundaries of large grains.
The homogenized condition with an inhomogeneous microstructure provides the grain grow in the initial large grain boundaries after the roughing.
Finish-rolling The influence of deformation on the process stability and properties of the final strip was examined by means of variation for the number of rolling passes and pass reductions (see Table 2).

With increasing particle concentration, it is much more fine grain due to increasing the number of nucleation core at 6% TiB2/7075 composites.
It makes TiB2 be good grain refiner of Al alloy.
It was nearly spherical grains under the boundary layer.
The more particles content, the smaller grain size was at the corresponding parts.
Acknowledgements This work was supported by the Scientific Research Staring Foundation of Chongqing University of Technology as Project number 2012ZD12 and Project Supported by Scientific and Technological Research Program of Chongqing Municipal Education Commission (Grant No.