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Morawiec1, a 1 Polish Academy of Sciences, Institute of Metallurgy and Material Science, PL-30-059 Kraków, Poland a nmmorawi@cyf-kr.edu.pl Keywords: Grain boundaries; Interfaces; Twin grain boundary; Tilt grain boundary; Coincidence site lattice.
There are a number of classifications of homophase grain boundaries.
Since the accuracy depends on applied experimental methods, the data below are listed for a number of particular tolerances.
[9] Viewpoint set number 41: 3D Characterization and Analysis of Materials.
Conf. on Grain Growth, edited by H.

)exp(DH oG ε−= Static and Dynamic Grain Growth in Single-phase Aluminium H.
From such maps, a number of microstructural parameters were determined, and figure 3 shows the crystallite size measured for samples of different initial grain size and deformed to various strains under different deformation conditions.
However, the effect has been noted in a number of aluminium alloys deformed to large strains at room temperature [4,7,8], and has also been found during deformation at elevated temperatures [9], and it is clear that it is a general phenomena.
The grain aspect ratio as a function of strain for all deformation conditions in 3µm grained material.
Conf. on Recrystallization and Grain Growth.

Grain boundary diffusion in the ultrafine-grained Ni is found to be significantly faster than in the coarse-grained Ni, which indicates a 'non-equilibrium' (deformation-modified) state of grain boundaries in the former.
Introduction To date, a number of various techniques of severe plastic deformation (SPD) has been developed [1], and equal-channel angular pressing (ECAP) worked out by Segal [2] is one of the most widely used.
In a number of studies it was demonstrated that non-equilibrium boundaries are characterized by enhanced energy, excess free volume and accelerated diffusion [5]-[7].
On the other hand, the non-equilibrium boundaries are the ultra-fast diffusion paths, as shown in a number of studies [13]-[16].
Micro-strains in Ni versus the number of passes by DCAP and ECAP We found that SPD processing via both methods increases the level of micro-strains by a factor of 2.5, and a noticeable growth of the micro-strains is observed only up to 2 passes.

The research is also carried out in areas of abnormal grain growth simulation, anisotropy, grain growth for two-phase steels, or grain growth for sintered polycrystalline materials.
Thermodynamic driving force for grain growth is the decreasing of surface energy of grain boundaries at increased temperatures smaller grains are gradually absorbed by growing grains therefore total number of grains is decreasing.
Further the grain growth can be controlled by e. g. diffusion together with precipitation phase in growing grains (m=3), or the effect of precipitation and diffusion occurs along grain boundaries (m=4) [5].
Fig. 3a shows the grain size into HAZ of real weld and Fig. 3b shows numerically calculated grain size in Sysweld program.
Table 3 Comparison of the grain size results calculated numerically and formed experimentally Distance from the melting boundary [mm] 0.5 1.0 1.5 2.0 2.5 3.0 5.0 Middle grain size [mm], experiment 0.0906 0.0847 0.0783 0.0701 0.0651 0.0663 0,0642 Middle grain size [mm], calculation 0.0883 0.0811 0.0749 0.0686 0.0614 0.0614 0.0614 Grain size number G, ISO 643 stand.

The number of counted grains was more than 200.
In the present simulation, the number of possible orientations Q was 48 for both the ordered and disordered phases.
A further reduction in grain size was observed when the thickness of carbon layer was decreased, i.e. by increasing the number of carbon layer from n = 1 to n = 4.
The more important point, however, is that all the grains of disordered phase come to be, at least on one side of grain, in contact with the grains of ordered phase and vise versa.
This means that the grains of two phases are well inter-mixed and the sides of their grains are inter-locked one another by the presence of inter-phase, at least, on one side of each grain.

Four experiments with an increasing number of passes were conducted on the Gleeble MAXStrain system in order to obtain various effective strain levels.
Introduction The consequence of severe plastic deformation (SPD) is the crystal fragmentation of a large number of metallic alloys to an ultrafine or even nano-grained dimension.
Four different tests were conducted with different number of passes (4, 8, 16 and 32).
Estimated total values of the effective strain at the centers of compressed samples Number of passes 4 8 16 32 Total effective strain 2.1 3.8 6.2 9.1 STEM examinations.
A new local high-angle boundary grain appeared with the diameter of 300 nm (Fig. 4d).

The formation of the grain microstructure of precision castings is a result of creation and growth of grains nuclei.
According to the nucleation law (1) the number of grains in the casting increases with a growth of undercooling.
Undercooling in front of columnar grains growth is too small for the liquid metal to form equiaxed grains whose growth can block the development of columnar grains layer.
Equiaxed grains block the growth of columnar grains in the airfoil/blade root transition area (Fig. 4 b).
The number of grains in the blade root is significantly lower in comparison to the airfoil.

Determination of GB diffusion parameters based on Fisher model and radiotracer data The classical Fisher model is described and analyzed in a number of reviews and monographs [9-11].
Diffusion proceeds only along grain boundaries.
From the values of the spectral lines relative intensities in the low-temperature sections the segregation factors were determined using formula (32) for a number of temperatures, and based on these values the following expression was obtained for the temperature dependence of grain-boundary segregation factor of Co in W:
Based on the relative intensities of spectral lines in this temperature range the segregation factor was determined by formula (32) for a number of temperatures, and the following expression was obtained for the temperature dependence of this parameter:
The numbers 1 and 2 indicate the spectrum components In the system under consideration the segregation factor increases with the increasing temperature.

The number N of the straight cut grains was counted.
If the distribution of the grains were uniform and isotropous, N grains were cut in the line segment of the length L, which was perpendicular to the direction of AB.
Therefore, there were N2 grains in the area of L2.
So, the mean length of the grain was: a=
Table 2 The grain size measured results Number Measured value a1 (mm) Measured value a2 (mm) Measured value a3 (mm) average value a (mm) no nano-oxides addition 0.875 0.583 0.583 0.644 0.01 wt% MgO 0.438 0.875 0.583 0.632 0.02 wt% MgO 0.583 0.438 0.292 0.438 0.05 wt% MgO 0.875 0.583 0.875 0.778 0.01 wt% CaO 0.438 0.583 0.350 0.457 0.02 wt% CaO 0.292 0.583 0.292 0.389 0.05 wt% CaO 0.583 0.583 0.292 0.486 Conclusions Nanometer calcium and magnesium oxides were added into molten steel by the carrier method in the experiment.

The plate was heat-treated at 730K for 4h to obtain 100~200µm grain size by recrystallization and grain growth.
The grid points without data exist in the map due to fewer numbers of strains measured points than the number of grid.
These are affected by grain microstructure.
A lot of grains reach to the sample surface.
Acknowledgement The SR experiment was performed with the approval of JASRI through proposal numbers 2005B0019, 2007B1213, 2008A1498 and 2009A1554.