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By using combustion synthesis under high gravity, TiC-TiB2 fine-grained composite ceramics with hypoeutectic, eutectic and hypereutectic microstructures were prepared through rapid solidification.
The FESEM and EDS results showed that TiC spherical grains constituted the matrix of the hypoeutectic ceramic composites, as shown in Fig. 2(a), while a few of TiB2 platelets were embedded in the TiC matrix, and there were also a few of white (Cr,W,Ti)3B2 phase were filled in between TiC spherical grains and TiB2 platelets.
By referring to TiC-TiB2 eutectic composition ceramics with 50mol% TiB2, the fine-grained TiB2 platelets with grain size less than 1 µm were embedded in the TiC matrix, as well as the uniform distribution of (Cr,W,Ti)3B2 phase could be observed in Fig. 2(b) .The TiC-TiB2 hypereutectic composition ceramic matrix with 60mol%TiB2, consisted of a number of TiB2 platelets grains and a few of irregular TiC grains distributed in between TiB2 platelets, whereas a few of coarse TiB2 platelets were observed in Fig. 2(c).
With the nucleation and growth of TiC solids, W atoms substitute a few Ti atoms, and a few of (Ti,W)C1-x solid solution with the crystal lattice similar to TiC were formed, subsequently, TiB2 nucleated adhering to TiC spherical grains and grew into platelets due to its AlB2-type structure of a P6/mmm space group, and were distributed in between TiC spherical grains.
Meanwhile, the highest bending strength of TiC-TiB2 eutectic composite benefited from the fined-grained microstructure, high fracture toughness and small-size flaw of the ceramics.

If the new orientation is accepted, the site may belong to other grain, otherwise the site belongs to the old grain.
Effect of Fabrication Temperature on Grain Growth.
The migration velocity (v) of grain boundaries can be given by the following equation [7] 2 2 2 exp exp m a a a AZV S Q v h R RT r γ   ∆    = −           (1) where A is the accommodation probability, Z is the average number of atoms per unit area at the grain boundary, Vm is volume of specific mol, a is Avogadro's number, h is Planck's constant, R is the gas constant, T is absolute fabrication temperature, aS∆ is the activation entropy, aQ is the activation energy, γis grain boundary energy, and r is grain boundary curvature radius.
The simulation time is expressed in term of the number of Monte Carlo Steps (MCS).
So, the atoms at the grain boundary diffuse faster and the rate of grain growth is also higher at the higher temperature.

A number of thermomechanical aspects such as plastic deformation, heat transfer between the material and the container, heat generated by friction, and cooling process after the extrusion are involved in the extrusion process and result in changes in temperature and microstructure parameters subsequently.
More generally, the distribution of grain orientation, grain size, and grain shape, will result in anisotropic behavior.
In contrast to mesh refinement, this method helps us to improve the quality of mesh and decrease the number of elements during the simulation.
coarser subgrain finer subgrain I: Dead zone II: Shear zone III: Deformation zone IV: Die exit    The distribution of non-dimensional grain size in Fig. 3 (right) shows that in the areas where the deformation is smaller (in DMZ and in the middle of the block close to the ram) the grain size is not changing during the extrusion and has almost the original grain size of the material before deformation, whereas in the die exit, MDZ and SIZ, the size of grains gets smaller.
The evolution of non-dimensional subgrain size in the DMZ is very slow and the size of grains remains almost unchanged.

The ECAE was carried out at the pass number of 4 times and at 623 K.
Although there was a little difference in microstructure between 4-pass and 8-pass specimens, the grain size was decreasing with increasing the pass number.
The α-Mg grain size of 4-pass specimen processed at 623 K was about 6.5 µm.
Although the yield strength and elongation were increased with increasing the number of passes, the tensile strength was saturated at the pass number of 4 times.
(2) Refinement of α-Mg grains and dispersion of the LPSO phase was caused by the ECAE process.

Mishra et al.[2] prepared the grain size of nano-fine grain aluminum alloy, and the strength and ductility of the obtained aluminum alloy have greatly improved.
Therefore, when extrusion number of times is low, as shown in Fig. 2(a) and Fig. 2(b), CNTs in the copper matrix do not flow fully, the distribution areas are small, emerge more serious agglomeration of CNTs.
The one of possible reasons is that extrusion too much makes the grain deformation, with the presence of grain boundaries, the dislocations of the deformation grains were blocked in the grain boundary, the slip bands of each grain were also ended in the grain boundary.
Grains in compound region suffered from the tool strong stirring and intense friction bring in local high temperature during FSP, resulting in a large number of broken grains, the broken grains occurred dynamic recrystallization, along with the flow of plastics metal driven by the tool, the CNTs were evenly spread out in copper matrix.
The grain refinement introduced a large number of grain boundaries, while the presence of large number grain boundaries can significantly increase the scattering of electrons, thereby reducing the conductivity of the composite.

Meanwhile, the pore number decreases.
The size and shape of pores change with grain growth.
Simulated images of grain growth and pore evolution.
Conclusions The images of pore evolution are obtained for practical ceramics during the grain growth, including the number, shape and size of pores.
The pore shape changed from interconnected channels to isolated sphere and pore number decreased during grain growth process.

Most of the publications in the topic of SPD are devoted to the dependence of mechanical properties on a strain degree (number of repetitions) at SPD processing [2].
Commercial pure aluminum AD1 (99.3%) and pure electrolytic copper M1 (99.9%) with a coarse-grained (CG) and ultrafine-grained (UFG) structure are considered.
The aluminum with coarse-grained structure was delivered in the form of an annealed plate with a thickness of 16 mm.
The billets were compressed to the required pressure (6 GPa), then the torsion with a given number of turns (10) was conducted under conditions of hydrostatic pressure.
Maex, Influence of surface and grain-boundary scattering on the resistivity of copper in reduced dimensions, Appl.

In the 1970s, Bailey et al. had classified the different diamond grain wear forms, which consist of grain wear, grain broken, grain pullout and bond broken [3,4].
(a) The hexagon or quadrangle exposed area grain; (b) The fracture grain; (c) The covered grain; After the tool wear.
(a) The attrition wear grain; (b) The part fracture grain; (c) The whole fracture grain; (d) The pullout grain; For the (a) attrition wear grain and (b) part fracture grain, we consider the wear mechanism is frictional wear.
From the above grain forms counting results, we can see that the numbers of different grain forms are changing with the material removal in Fig. 16.
Fig. 16 The number of grains with different forms Fig. 17 The TWR vs. material removal Depending on the above grain forms, we measure the wear areas of each grain with different forms and draw the graph to reflect the relationship between material removal and TWR.

The high frequency semicircle can be attributed to the grain property of the material arising due to parallel combination of grains resistances Rgb and grains capacitances Cgb of the bulk material as shown in Fig. 1(b) inset.
These double semicircles of YIG: Bi sample is likely to result from its pretty high resistances of both grains and grain boundaries.
In such a mechanism, the number of the charge carrier is dominated by a factor that increases with temperature exponentially.
From Fig. 2(b) it can be seen that the slope of the line for grain boundaries is greater than that for grains.
The difference of activation energy (barrier height between hopping sites) in the interior of grains and at grain boundaries is quite probably because the interior of grains and grain boundaries possess a different chemical environment.

At the microscale, a small number of grains are directly involved in the forming process, so that size, orientation, and position of a single grain can influence the process[1-2].
The repeat number was 22.
The grains of the larger pin are more elongated while the grains in the smaller one are more rounded.
As recrystallization tends to round the grains, the grains in the smaller pin were rounded rather than elongated.
The grains in the larger pin were elongated, while the grains in the smaller one had rounded shapes.