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The refinement and uniformity of grains must be on the basis of reducing the “grain inheritance” and making use of complete austenitizing process [6].
It also reduces the number of residual austenite, and reduces or avoids grain inheritance.
Two times normalizing Two times normalization is to eliminate the nonuniform microstructure and mixed grains, and to refine grains.
Meanwhile, recrystallization generates new grain boundaries, and the harmful elements deposited on grain boundaries may be rearranged to reduce the segregation on grain boundaries.
Pre-treatment increases nucleating of austenite in recrystalization and decreases the number of residual austenite, which refines grains primarily and reduces grain inheritance.

In order to determine the number, size and distribution of pores, two rheocasting alloys were investigated using computed tomography (CT).
Number, size and distribution of pores were thus determined using the software package Volume Graphics Studio Max 3.3.
S11)), indicating that a significant grain growth occurs during T6.
The number density is only 0.024 mm-3.
The number density is 0.7 mm-3.

It was found that the secondary phase TiN grains, which formed from TiO2 and AlN, distributed in grain-boundary phase throughout the sintered body.
Furthermore, the smaller TiN grains in the composite are, the better the wear-resistance is [7,8].
Thus the size and morphology of TiN grains in Fig.1 XRD of Si3N4-TiN composite.
Bright TiN grains were homogenously distributed in a darker matrix Si3N4, all TiN grains were of a submicron average size.
However, their number decreased with increasing amount of ammonium citrate at 0.20 g, the microstructure was homogeneous with almost no agglomerates (Fig.3d), in which the average grain size of TiN was from 0.2 µm to 0.3 µm.

The average grain size of sample 1 is the greatest of all the samples.
And the fully recrystallized grain is the main structural feature for sample 1.
Since it is difficult to distinguish high-angle grain boundary and the low-angle grain boundary in optical microscope, further observation is conducted with EBSD.
For grain boundaries with grain boundary misorientation that is more than 15 degrees are defined as high-angle boundary.
Fig. 3 Grain boundary map of 7055 aluminum alloy samples in various conditions obtained by EBSD: (a) sample 1; (b) sample 3; (c) sample 4; (d) sample 5 Table 2 Fraction and length of different grain boundaries measured by EBSD Sample Number Fraction and length of different grain boundaries 2°～5° 5°～15° 15°～180° Fraction Length (cm) Fraction Length (cm) Fraction Length (cm) 1 0.321 4.98 0.225 3.49 0.454 7.03 3 0.324 3.78 0.216 2.51 0.460 5.35 4 0.359 5.45 0.200 3.04 0.441 6.69 5 0.302 4.42 0.199 2.91 0.499 7.29 Relation between fracture toughness and microstructure.

It can be seen that the precipitate formed on the grain boundary and hindered the growth of the grain.
Optical microstructure of specimens (a) without Sb, (b) with 0.12% Sb, (c) with 0.22% Sb Table 2 Average grain size of the specimens with different Sb conent Sample number 1# 2# 3# Average grain size(μm) 98.7 93.6 72.8 (b) (a) Fig. 2.
Table 3 Magnetic properties of test steel Sample number Average P15/50(W/kg) Average B50（T） 1# 3.699 1.768 2# 3.798 1.790 3# 4.202 1.760 Fig. 6.
For a certain volume grains, the grain boundaries will decrease with increasing of grain size, accordingly, the energy of magnetic domain moving will become lower and the magnetic hysteresis loss is less [7].
The decrease of grain-boundary energy, which could be achieved by the segregation of antimony on the grain boundaries, is considered to be the driving force for the grain growth.

Typical Journal Title and Volume Number (to be inserted by the publisher) 3 microstructures and pole figures from EBSD analysis are presented in Figure 3 for the three steels after hot torsion at 900 and 1050°C and a strain rate of 1 s-1.
At the onset of straining, sub-boundaries form near the original grain boundaries.
Above this temperature range, the energy stored by deformation is lower (higher recovery) and the pinning effect by precipitates ( NbCN, TiN or TiC) Journal Title and Volume Number (to be inserted by the publisher) 5 is also observed [6].
Moreover, after the plateau, the grains and subgrains with D2 orientation grow and the overall grain and subgrain size increase.
Jonas: Acta Metall., vol. 32, 1984, p. 2077 Journal Title and Volume Number (to be inserted by the publisher) 7 [5] J.

However, few phases still remain near grain boundaries.
However, the grain size of new grains become a little larger with the temperature increase.
At the lower strain rate, e.g. 0.001s-1 and 0.01s-1, in this temperature, a number of fine grains are formed near grain boundaries and around some coarse phases, as shown in Fig. 4c and Fig.5a.
Fig. 8 (a) SEM microstructure of the sample deformed to a strain of 0.6; (b) EBSD microstructure (GB+IPF-Image) showing a number of fine grains from DRX took place nearby the original boundaries (site A), coarse particles (site B), and deformation bands (slip bands here, site C); (c) misorientation profiles obtained in (b) along the arrow with dot line.
Grain misorientation increased with lattice rotation during hot deformation, gradually resulting in formation of new grain boundaries.

The main result obtained by the application of such technique is that the hyperbolic flow of grains is the nature way during deformation, as well; this hyperbolic motion is assisted by dislocations dynamics and self accommodation of grains.
The grain size of 42.10 µm was measurement by using the mean linear intercept technique [8].
Here twelve grains were selected and identified with a number in order to follow their trajectory during deformation process.
As it is shown in the Figure 2, in all pictures in the Figure 1, twelve grains were selected and identified with a number in order to follow their trajectory during deformation process.
Also, it is obvious that the displacement of each grain is a function of their position.

Therefore, the GOS value of a recrystallized grain is expected to be small as compared to GOS value of a deformed grain.
To investigate the relation between critical strain and GOS at different deformation conditions, the number of DRX grains (in percentage form) at each condition has been plotted against the corresponding critical strain.
This is supported by the presence of several pancaked (elongated) grains surrounded by fine grains in Fig. 5a.
The increase in temperature may favour DRX kinetically, but due to insufficient thermal activation, the number of nucleating grains is limited.
This can be attributed to the greater number of nuclei available for recrystallization at these elevated temperatures.

The segregation at the free surface was found to be stronger than the segregation at the grain boundary.
Cu bicrystals containing deliberately made internal cavities at the grain boundary were doped with Bi, annealed at temperatures between 1073 and 1223 K, and broken along the grain boundary in an ultra-high vacuum chamber for AES.
Using the equilibrium Bi vapour pressure and applying the ideal gas equation, the number of Bi atoms present in a cavity at a certain temperature can be estimated.
Conclusions Using a special method to produce Cu bicrystals, containing a grain boundary with cavities at the grain-boundary face, the segregation of Bi in Cu simultaneously at the grain boundary and at the free surface (of the cavities) was investigated under identical experimental conditions.
McLean: Grain boundaries in metals (Clarendon, Oxford 1957), p. 116