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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 small grains have sharp grain boundaries and are almost free of dislocation.
Visible numbers corresponds to values of individual areas misorientation ef=120 Fig.5.
Visible numbers corresponds to values of individual areas misorientation X A a) B b) A X B Fig.7.
Numbers 1-4 in Fig.8a correspond to Kikuchy patterns 1-4 for grains/subgrains; c) orientation of analized area The high-angle boundaries (HABs) marked in the Fig.7 have bulges characteristic for the continuous dynamic recrystallization (CDRX) [7,8].
The effect of the introduced, additional loading is the increase in the number of the dislocation boundaries that cross mutually.

In other grains, grain-grain interactions arise due to an imposed constraint from the neighboring grains on the shape change of the grain in question.
Out of the whole sample, four grains numbered from 1 to 4 were picked out to study the orientation evolution and grain-grain interaction after each deformation step.
It moves upwards in grain 1 while it goes downwards in grain 3 and grain 4.
Euler angles of grain 1: [185 31 218], grain 2: [280 46 79], grain 3: [8.6 31 35], grain 4: [5.2 31.5 35].
Acknowledgements—The authors gratefully acknowledge the financial support from the Belgian Science Foundation (FWO) under contact number G.0379.07 and the financial support from the Interuniversity Attraction Poles Programme—Belgian State-Belgian Science Policy (Contract P6/24) References 1.

The process of strain-induced grain formation can be categorized into the three stages irrespective of deformation mode and temperature: i.e. i) an incubation period for new grain evolution in low strain; ii) a grain fragmentation by frequent development of MSBs and subsequently new grains in medium strain, and iii) a full development of fine grains in large strain.
Fig. 2 Effect of MDF at 763 K on (a) the average grain size, dUFG and the minimal spacing of deformation and microshear bands in remained initial grains, (b) the average misorientation of (sub)grain boundaries, Qave , in the fine- grained regions and (c) the fraction of fine grains evolved, VUFG.
Fig. 2 shows changes in some microstructural parameters in the AA7475 with repeated MDF at 763 K, i.e. the strain dependence of (a) the ultrafine grain (UFG) size, dUFG, (b) the average misorientation of (sub)grain boundaries, Qave, in the fine grained regions and (c) the volume fraction of the new grains evolved, VUFG. [8].
In stage 2, the number and misorientation of the boundaries of MSBs rapidly grow with strain in e > ec , leading to fragmentation of original grains into different misoriented small regions, where UFGs are preferentially evolved.
As the results, the number of grains having MSBs can be gradually decreased at elevated temperatures [9,11,14,15] and then UFGs with HABs are hardly developed in original grain interiors.

A number of ultra fined grained (UFG) alloys produced by SPD exhibits favorable mechanical properties consisting in a combination of very high strength and significant ductility [2].
L and (l/L) values are plotted as function of number of deformation cycles are shown in Fig.2a.
Fig.2: Evolution of (a) grain size parameters (length and aspect ratio) as function of number of CARB and ARB [5] cycles and (b) grain boundary character distribution as function of number of CARB cycles of Fe-36%Ni (wt.%) alloy.
During ARB processing, the intensity of S and Copper components tends to increase with the cycle number.
· The estimated deformed volume fraction increased with increasing number of CARB cycles.

The accumulation of plastic deformation in the sample during multiple pressing can be assessed by εeff=1.16*n, where n is the number of GP cycles.
The average grain size is dav=12 µm.
The amount of large grains (d > 10 µm) is slightly more than that of average grains (2.5 µm < d < 10 µm).
Since the number of repeated pressing cycles increases, the relative number of grains with the size of d < 2.5 µm and 2.5 µm < d < 10 µm also increases.
The increase in the relative grain number (d > 2.5 µm) in comparison with that of ultrafine grains can confirm the dynamic recrystallization processes during higher pressing temperature (Fig. 3).

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.

Structure and Grain Boundaries of Ultrafine-Grained Nickel after Rolling and Forging at Cryogenic Temperature Evgeniy V.
For the grain (subgrain) size was taken to be the diameter of the circle whose area is equal to the grain (subgrain) area.
The authors of this work studied the effect of the number of passes during ECAP on the fraction of high-angle grain boundaries and the mechanical properties of this material.
Figure 2a shows the presence of a large number of extinction contours indicating high internal stresses in the material.
Small elongation of grains after rolling of UFG nickel in comparison with coarse-grained material [17] is due to the smaller grain size of ultrafine-grained material, which, in accordance with [1] is the reason for the smaller number of dislocations in the cluster in the shear plane and, as a consequence, less change in the shape of the grains.

Coarse-grained materials are used more and more widely in modern industry.
This method includes two main contents: Firstly, a number of Intrinsic Mode Functions (IMF) which could describe signal characteristics is calculated from the detection signal according to Empirical Mode Decomposition (EMD).
Firstly, whether the number of the extrema point and the zero crossing point in h(t) are equal or differ by at most one.
Conclusion Because of a large number of structural noise appeared in the ultrasonic test of coarse-grain materials, HHT is presented to process this kind of signal here.
The influence of grain size variation on metal fatigue.

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.