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Quantum-chemical Simulation of Silicon Grain Boundaries Contaminated by Oxygen And Carbon A.M.
As is known, the majority of silicon polycrystals contain a number of oxygen and carbon atoms (~ 1016 -10 18 cm -3) mostly grouped at or around the grain boundaries.
Si69 cluster with GB Σ5 θ = 37° [001]/(130) consisting of two sub-clusters (grains) I and II separated by tilt GB created by rotation of grains I and II around the common axis [001] (lying in GB plane normally to the scketch plane) at the angle θ = 37°.
The cluster presented in Fig. 1 was chosen as a basis for simulation of different configurations of the contaminant-containing complexes SiOmCn Angle θ Grain I Grain IIformed at GB "core".
The rest of the cluster (nonrelaxed) simulated the influence of the silicon grains surrounding the GB "core" on both sides.

These properties are determined by a number of factors and depend on the conditions for creating, processing and use.
Based on the fact that the existing model can not be applied to such tasks required the formulation of a number of other mathematical models that have step by step should be updated and supplemented by the accumulation of research in this area [7, 8].
In Figure 1, the grain boundary layer is gray.
Acknowledgment This work was supported by Russian Foundation for Basic Research, grant number 13-01-00444.
Valiev Grain boundaries in ultrafine grained materials processed by severe plastic deformation and related phenomena Mat.

Volume fraction Specimen Average grain size (µm) Goss 40˚<111> Other 84%, 873k/0.5h 0.78 0.06 0.80 0.13 95%, 873k/0.5h 1.03 0.22 0.56 0.23 Regarding the variant selectivity of the 40˚<111> rotated grains, we determined the volume fraction, number density, and the size of each variant.
It is noted that this ratio is almost the same irrespectively of the prior cold reduction level, though the values of the volume fraction and number density are different corresponding to the progress of grain growth.
Volume fraction, number density, and grain size of each variant.
Specimen Rotation axis of 40˚<111> Volume fraction Number density (mm -2) Grain size (µm) Slip plane normal?
This number ratio is in fairly good agreement with the observed variant selectivity.

High cube volume fractions can be predicted under a number of conditions, though a small surface energy advantage of just 2% for cube-oriented grains is required to match the texture strengthening to the grain size change.
Each simulation was carried out 5 times, using the same experimental starting microstructure in each case, but using different seed values for the random number generator.
Effect of initial experimental data set size There is a trade-off between the sample area that can be modeled and the number of model grid-points (hence the simulation speed).
If a large map step-size is used (giving a large area but a small number of map grid-points) the real boundary curvature is not accurately represented with many small "grains" modeled as regions of just one or two map-pixels.
For the Ni-tape material, the final grain size after grain growth is similar to the tape thickness (90µm), hence during grain growth the fraction of surface grains (with respect to the total number of grains) increases from ≈ 29% to 100%.

A large number of studies have been realised concerning the stabilisation of nanocrystalline grain structures in many materials and the number of factors influencing the grain boundary mobility in nanocrystalline alloys, like grain boundary segregation, solute drag, pore drag, second phase (Zener) drag and chemical ordering.
The high number of observed grains makes statistical analyses possible.
Number and arrangement of the lattice points regulate only the accuracy of the calculations.
The high number of small grains implies also a high number of small triple junction distances (compare Fig. 3a).
The data of vs. x for all grains with a certain number of faces s show a strict linear relationship.

The larger size of island grains is their dominant characteristic, and grains which become island grains may have been incipient abnormal grains.
These grains grow excessively, consuming the matrix grains, resulting in a bimodal grain size distribution.
Of the total number of island grains observed, around 75% possessed either low angle (<20o ) or high angle (>45o ) grain boundaries.
The number of low and high misorientations observed at these island grain boundaries is therefore substantially higher than the number found in the uniform structure.
The existence of a number of island grains with mid-range misorientations (20 o -45o ) to the abnormally large grain may be explained by the presence of a Σ5 (36.9 o <100>) boundary misorientation.

The elongation of the composite decreased gradually with the number of ARB cycles, became almost zero after 4 cycles.
Results and Discussion Changes in mechanical properties of the composite with equivalent strain (number of ARB cycles) are shown in Fig. 2.
The specimens after 2 and 3 cycles have dislocation cell structures, but the cell size become smaller with the number of cycles.
The change in microstructure with the number of ARB cycles is different from that of the monolithic 6061 Al powder.
The elongation of the composites decreased gradually with the number of ARB cycles, became almost zero after 4 cycles

The number of attached cells was found to be higher on the samples having more (0002) plane parallel to the surface regardless of their grain sizes.
The number of attached cells as well as cell proliferation was reported to be higher on the sample with the texture of (1010)║ND.
Cell attachment on the samples was evaluated by counting the number of attached cells after 60 and 120 minutes of incubation.
The number of attached pre-osteoblast cells per unit area (cell density) was calculated for both cuts (C and L) of each sample.
The samples are ordered based on their grain size.

For abnormal grain growth, the effective interface mobility function is first introduced by Apel et al [1], which is successfully applied to both grain-grain and grain-precipitates interactions during boundary migration.
S is the number of locally existing orientation, i.e.
Voronoi tessellation is used to generate large number of grains and initial radius of grains is set to be 10 μm.
At 1062.5℃, since the pinning force is relatively small, almost small grains are consumed by abnormal grains, normal grain growth happens.
Parameters used in multiphase-field model Number of grid Nx, Ny 384 Grid spacing ∆x 1.0μm Number of grains Q 470 Interfacial energy σij 0.4J/m2 Interface thickness η 5.0μm Intrinsic interface mobility μ0 120*exp-350000RTm4/Jsec Table 3.

The former austenite grain boundaries in the HY-TUF steel revealed by the thermal etching: a) 900 °C; b) 1000 °C Statistical analysis of the measured values of the austenite grain size and area showed that at a heating temperature 900...925 °C the largest fraction of the surface area of the sample (26 %) was occupied by the grains of the number 7 according to ASTM E112 [18] with the average area 1008 μm2 (Fig. 2).
It should be noted that the studied steel had the sufficient scatter of the grain size: a statistically significant fraction of the sample surface area (more than 10 %) was occupied by the grains with an average area from 252 to 4032 μm2 (grain number from 9 to 5).
The distribution of the austenite grains in the HY-TUF steel by the occupied area on the sample surface for different austenitizing temperatures The increase of the heating temperature from 925 to 950 °C led to the increase of the fraction of the surface area (up to 35 %) occupied by the larger austenite grains of number 6.
After heating up to 975 °C the more coarse-grained microstructure formed: almost equal fraction of the surface area (approx. 25 %) was occupied by the grains with the average area 1008, 2016 and 4032 μm2 [grain number from 7 to 5].
In case of heating of the studied steel up to 1000 °C mostly large austenite grains were formed: the fraction of the surface area occupied by the grains with the average area 4032 μm2 (number 5) was 43 %, and 20 % of the surface area was occupied by the grains with the average area 8065 μm2 (number 4).