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The morphology of the grains in Sr0.5Ba0.5Bi4Ti4O15 thin films was elliptoid and the grain size was about 90 ~ 100 nm.
A number of them, SrBi2(Nb,Ta)2O9 (m = 2), Bi4Ti3O12 (m=3), SrBi4Ti4O15 (m = 4) have been investigated from the point of view of both structural and electric properties [6-8].
When pH value and solution concentration of the precursor was 3.5 and 0.35M respectively, the morphology of the grains in Sr0.5Ba0.5Bi4Ti4O15 thin films was elliptoid.
The growth of crystal grain was smooth and uniform, and the grain size was about 90 ~ 100 nm.
The morphology of the grains in Sr0.5Ba0.5Bi4Ti4O15 thin films was elliptoid and the grain size was about 90~100nm.

Through near isothermal forging at 960 °C/0.001s-1/40 % coarse columnar grains have been broken, fine recrystal grains have been gotten, but trace of β grain boundaries yet can be seen obscurely (Fig1b).
At the meantime recrystalization occur at pile-up dislocations, new grains generate.
For weldment of Ti2AlNb/TC11 dual alloy in proper temperature scope second phase, such as o or α2, can precipitate in grains when content of elements meet demand due to diffusion, but it is difficult to fine grains.
(2) For bonding interface of fusion welding evolving of structure is from coarse columnar grains to fine two phase grains with β grain boundaries discontinuously, to equiaxed and/or strip shape fine two phase at coupling action of heat and force
[2] Klotz, U.E.; Henderson, M.B.; Wilcock, I.M.; Davies, S.; Janschek, P.; Roth, M.; Gasser, P.; McColvin, G.; .Materials Science and Technology, Volume 21, Number 2, February 2005, 218

Pouring temperature determines the cooling rate, nucleation, controls the size of formed grains during growth, the grain morphology and the distribution of alloying elements within the matrix[3].
Two types of castings were made: untreated and AlTiB grain-refined LM6 alloys.
The mould was prepared by filling unbonded unbounded silica sand with AFS grain fineness number 70.
The effect of adding the grain refiner (TiB) is illustrated in Fig. 7, which shows the microstructures of castings produced at a constant pouring temperature of 780oC for the 3, 12, and 24 mm sections, with and without the addition of TiB grain refiner.
(magnification100X) Effect of pouring temperature, section thickness and grain refiner on eutectic spacing is tabled in Table 2.

Long stirring time could reduce dendrites and liquid phase, and made the non-dendritic grains well spheroidized.
It can be seen that the morphology of primary a-Mg gives priority to rosette-like, and a few globular-like and particle-like grains with coarse size.
The broken fragments from primary dendritic crystal grow up the new drifting grains at suitable temperature to realize drifting grain multiplication and to increase the number of the grains.
Conclusions (1) There is an important effect of stirring temperature on the grain morphology and the grain size of the primary a-Mg in AZ31 magnesium alloy.
(2) Long stirring time could reduce dendrites and liquid phase, and made the non-dendritic grains well spheroidized.

The impedance spectrum of Gd-doped sample indicates that consist of semiconducting grain and moderately insulating grain boundary regions.
Generally, the formula of doped bismuth titanate is (Bi2O2)2+(Am–1BmO3m+1)2– , where A means mono-, di-, or trivalent ions, or a mixture of them; B means quadri- or quinquevalence ions, such as Ti4+, Nb5+, Ta5+; and m means integer number > 1.
Gd-doped sample exhibits randomly oriented and plate-like grains, and the average grain area of the sanple was approximately 10×10μm2, and thickness was less than 2μm in general.
In general, the capacitance C of grain and grain boundary are typically of the order of pFcm–1and nFcm–1, respectively.
The Gd-doped bismuth titanates consist of grain and grain boundary regions.

The coarse grained hard metals are mainly used in mining applications, the smallest grain size being about 3 µm and the minimum cobalt content 6 wt%.
The standard indicates with letters the classes of carbides after specific compositional limits while with numbers (0 to 50) it is indicated the degree of toughness / hardness.
High numbers correspond to higher toughness and lower numbers correspond to higher hardness.
Relation between carbide grain size and binder content (%wt.) [10] Grades with between 3 – 10% by weight of binder and grain size < 1 µm have the highest values of hardness and compressive resistance in combination with high wear resistance and good toughness.
Toughness in cemented carbides is directly proportional to the grain size; hardness instead is inversely proportional to both the size of the grain and the fraction of metallic binder.

With decreasing grain size the volume fraction of grain boundaries increases in the second order and the effect of grain boundaries become more pronounced.
This definition of atomic stress ij � � for atom �can be expressed as: ji ij i j 1,n 1 1 m v v r f 2 � � � � �� �� � �= � � � = + � � 
� � 
 (2) Theoretically, the above definitions are valid only for homogenous systems, though BDT stress gives a fair indication of the nature of stresses in systems with defects and has been used to study point defects and grain boundaries in a number of metallic systems.
Grain boundary energy is calculated as the difference between energy of all the atoms in the grain boundary region and a perfect crystal containing the same number of atoms, divided by the area of the grain boundary.
Variation of grain boundary sliding with grain boundary energy is shown in Fig 4.
Atomic simulation of grain boundary sliding indicates that extent of sliding and grain boundary energy are related in symmetric tilt grain boundaries.

Some of carbon atoms could be enriched at the grain boundaries or in the M-A constituents to form carbides and ferrite grain contain a relatively high dislocation density.
Meanwhile, quite a number of fine precipitates interacted with the polygonalization of dislocations and resulted in the pinning effect on the movable dislocations, indicating that the precipitation strengthening effect played an important role in improving the tempered strength of the low carbon microalloy steel.
Both average grain size and high angle grain boundary closely related to low temperature impact toughness.
The ductile brittle transition temperature (DBTT) can be expressed as [8-9]: (1) Fig.4 Distribution of grain boundary misorientation in the samples at different states (a) as-rolled, (b) tempered at 500°C, (c) tempered at 600°C Fig. 5 Average grain size and percentage of high angle grain boundary in different states specimens where the constant A refers to metallurgical factors other than the grain size, the coefficient K is independent of grain size, and d is the crystallographic ferrite grain size.
EBSD analysis identified that excellent toughness of the steel was attributed to the fine average grain and high percentage of high angle grain boundary References [1]J.R.

Currently, a large number of studies focus on the adjustment of alloying and thermal processing technology to control the microstructure to achieve property improvement.
Its main function is to refine the grain size during the casting alloy solidification.
Boride particles dispersed and boron segregated around colony boundaries can prevent the α grain form growing and refine the α2+γ lamellar colonies transformed from α grain.
Fig7 (a) is the back scattered electron (BSE) image of fatigue specimens C22 at 480MPa, a large number of secondary cracks initiated from the B2+ω phase segregation.
Acknowledgements This research was sponsored by the National Natural Science Foundation of China (project number 51201141).

Since the process gap between the two electrodes which is one of most important parameter in the electrochemical process is decided by the diameter of abrasive grains, the proper size grains must be chosen in the wire-combined tools.
Fig.3 and Fig.4 have simulated one single grain's trail and 100 grains' trail, respectively.
Observed single grain's trails in Fig.3, it can be found: (1) with shorter reciprocating period, there are more grains trajectories in the same x position, but the travel distance of grain trajectories in x-axis becomes smaller, which represent less grains grinding over the same x-position and the total trajectories in unit x distance will not increase; (2) with higher reciprocating speed, the travel distance of the grain trajectories in x-axis becomes lager while the trajectories in unite x distance are unchanged, and the increase of the total trajectories in one period means the rise of trajectories in unit x distance; (3) the larger T cannot increase the number of trajectories but more different diameter grains will be involved in unit x distance, so the uniformity of the whole processed surface can be improved.
Fig.3 the simulation of single grains on the different period Fig.4 the simulated trajectories of 100 grains Experiment and discussion Experimental conditions.
The material of abrasive layer is diamond and average diameter of the grains is about 20um .