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Importance of grain boundary atomic structure in superplastic ceramics In fine-grained ceramic materials, the combination of grain boundary sliding, grain switching and grain rearrangement accommodated by diffusion can be regarded as the main mechanism of superplastic deformation [22].
Dispersion of second phase particles is highly effective to suppress initial grain size and dynamic grain growth.
When initial grain size and the number of fine pores in the sintered body is at similar levels, the failure process, and hence the tensile ductility, are mainly controlled by the cavity nucleation [22].
Nanocrystallization should improve the tensile ductility in superplastic ceramics, because the flow stress can be lowered owing to nanocrystallization, and because cavity nucleation is suppressed owing to increased number of grain boundaries,.
The combination of the decreased grain size, increased grain boundary diffusivity and decreased grain boundary energy is likely to be responsible for the improved ductility of PX172-G.

Today is a lack of such data due to the limited number of the measuring methods.
The average grain size was 115 µm.
These data resemble the Shyshkovsky isotherm for a dilute solution [11] (2) where γ0 is the surface tension of pure solvent, γS is the surface (S) tension of solution, γGB is the grain boundary (GB) tension of solution, T is the temperature, R is the gas constant, z is the number of adsorption sites at the surface (grain boundary), b is the constant of adsorption equilibrium and c is the solute concentration in at. %.
It is possible to evaluate the number of sites in surface (grain boundary) monolayer A A m N N V n 3 2 max −       = , (3) where Vm is the solute molar volume and NA is the Avogadro number.
Experimental values of surface and grain boundary tension.

Al3Ti except for Ti powder sample (200 mesh) Almost can not be found, Most of the Al3Ti is the block in the others sample （2）From the view of TiC distribution, TiC are small and scattered, but with the reduce of the TiC powder particle size, TiC size slightly decreased and the number also increased
Besides, with the reduce of the grain size of C powder, the distribution of Al3Ti in the master alloys is more dispersed and the numbers are increasing.
When the grain size of C powder is reduced, the grain size of TiC is also reduced.
When the grain size of C powder is 1200 mesh, the grain is homogeneous equiaxed crystal.
Conclusions （1）Refinement is the result of the interaction of refinement phase Al3Ti and TiC in the master alloy （2）When the grain size of Ti is much smaller，the TiC and Al3Ti particles in the master alloys that is formed by Contact Reaction Method is fine and scatter , and when the more large its number is, the more complete the reaction of the Ti powder is.

The differences of surface topography and chip morphology of Inconel 718 machined by single diamond grain and single CBN grain were evaluated.
The space between the sawteeth narrows and the number of sawtooth increases while the grinding speed ranges from 20m/s to 150m/s.
Normally, the grinding forces of single-grain are small.
(2) The morphologies of the grooves machined by single diamond grain and single CBN grain show no big difference, are all relatively smooth.
With the increase of grinding speed, the space between inter-sawteeth of the chip narrows, the number of sawtooth increases

Introduction Grain boundaries (GB) are planar defects where two grains of different orientation meet.
The interaction between solute and migrating GBs has been studied by a number of researchers since the 1950's [3, 8-37].
To begin, one simple microstructure is considered: a shrinking spherical grain embedded inside a cubic grain driven by curvature, to mimic grain growth in single-phase materials.
Fig. 1 Composition profile along a line across the center of a spherical grain embedded in a cubic grain.
Therefore, this study provides a solid base for performing 3D simulations of grain growth of a large-scale microstructure with a statistically meaningful number of grains that will be performed in the near future.

The results show that the microstructure which contains a number of cake shaped grain can be refined and homogenized by the feasible annealing holding time.
The most of these grains are irregular in nature.
But some recrystallized grains and caked grains can be easily observed in these micrographs in Fig.1(b).
A bimodal grain size distribution consisting of larger and finer grains has been observed after full recrystallization in Fig.1(d).
Conclusions 4.1 It is found that the ferrite grain size is grown up with longer annealing holding time at 850 ℃.The ferrite grains are fully recrystallized with 150s annealing holding time, the microstructure which contains a number of cake shaped grain can be refined and homogenized by the feasible annealing holding time. 4.2 It is known that the recrystallization can largely be effect by the annealing time .The change of strength for test steel is small when the annealing time is up to 150s.

Silicon grains have multiplied.
Number of particles per unit area.
The intermetallics initially grow, but their number diminishes.
In the first stage, a rapid decrease of the number of β-AlFeSi-particles is observed, coupled with a significant increase of their size.
Their number decreases only slowly, as is expected for a process of gradual dissolution.

Our recent previous work already achieved a phase-field model to simulate the grain growth process of AZ31 Mg alloy during recrystallization in real time and space, and the simulated results are agreed well with the experiments [10, 11] by introducing a new concept of grain boundary range, where the term of the grain boundary is to explain the physical backgrounds of the order parameter gradients at grain boundary and the diffusion grain boundary.
The temporal evolution of microstructure can be determined by evaluating the time-dependent Allen-Cahn equation and Cahn-Hilliard diffusion equations as follows [12, 13]: (p=1, 2, 3,…,n) (1) where L and M are the structural relaxation and chemical mobility parameters, respectively, ηp(r, t) is the long-rang orientation parameters, used to distinguish the different orientations of the grains, c(r, t) is a concentration field variable, p is the possible number of the grain orientations in the system, and it is taken as 32 as suggested in reference [14].
However, if the the sizes of the particles are 100 nm, 200 nm, 300 nm, the initial state is changed that the unit grid are refined to 0.1μm, the total number of grids are chosen as 1024×1024, and the unit time is 0.075s, the other parameters are the same with reference [10].
The average grain sizes are close to each other at the early stage of grain growth though the contents of the particles are different.
Wu, A physical model to express grain boundaries in grain growth simulation by phase- field method, Acta Phys.

And finer grains with the high angle grain boundaries (HAGBs) and disperse second-phase particles could be obtained in AZ61 and AZ91 after 8 passes of ECAE. 1.
The figure shows that there are low angle grain boundaries (LAGBs) with misorientaion<15r and high angle grain boundaries (HAGBs) with misorientation>15 rin the two alloys.
Fig. 3 TEM morphology and misorientation angles of AZ61 (a, b) and AZ91 (b, c) Mg alloy after ECAE 8 passes at 225°C 3.2 The effects of second phase on grain refinement The microstructure evolution of AZ61 and AZ91 Mg alloy during ECAE showed that the grain size decreased with the pass number increasing.
In the AZ61 and AZ91 Mg alloy, Mg17Al12 particles would precipitate during ECAE deformation as pass number increasing.
During ECAE, dislocations are arranged into dislocation boundaries and sub-grain boundaries and then these sub-boundaries evolve to high angle grain boundaries (LAGBs) and high angle grain boundaries (HAGBs).

Many grain and oil depots have been established.
One group is composed by grain depots, oil depot, delicate railway and dock, deep processing for the grain and oil factory, test office.
Low load-carry ability of grain and oil depots construction.
The arrangement of sand drains are quincunx with diameter of 0.4 m ,distance between drains of 2.5 m ,length of 18m and the total number of sand drains is 283.
A large number of practical projects show that the ground bearing capacity of the region can improve 15 to 30 kPa by vacuum preloading method.