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Therefore, the grain size becomes more and more uniform and thin, and the (SDAS) of aluminum alloy are more and more small.
While solidification pressure is 400 KPa, the grain size reduces further and the average of SDAS is 27.7 mm.
When solidification under 450 KPa, the number of grain is much more than others and the average of SDAS is 20.7μm.
So the dendrite may be broken as long as the feeding forces higher than strength of dendrite, which can make the number of the grain increase.
Acknowledgements This research was financially supported by Aeronautical Science Foundation of China (grant number: 2009ZE56015), and Jiangxi Education Department Science and Technology Project of China (grant number: GJJ10508).

With the roles of above two interactions, some EBSD characteristics such as the packet size and the number fraction of high angle grain boundaries all have a peak present at 740℃ Introduction HSLA100 steel has been developed widely in recent years owing to an excellent combination of high strength, good toughness and excellent welding performance.
Fig.3f shows the number fraction of HAGBs (≥15°) in the test samples quenched at different temperature in the 2-phase region.
With the quenching temperature increasing, the number fraction of HAGBs increase gradually to peak at 740℃ and then decrease gradually, and finally the fraction of HAGBs fluctuate slightly above 800℃.
With the roles of above two interactions, some EBSD characteristics such as the packet size and the number fraction of high angle grain boundaries all have a peak present at 740℃ (Fig.5).
With the roles of above two interactions, some EBSD characteristics such as the packet size and the number fraction of high angle grain boundaries all have a peak present at 740℃ References [1] E.J.

Harvesting grain directly has been the development trend of modern maize combine harvester.
The type of most maize harvester in our country is self-propelled maize harvester or mounted maize harvester, which efficiency is lower than the foreign [1].The technique of plucking, threshing, separating, cleaning and gathering is used in a little number of maize combine harvesters, whilst it also has some problem.
After threshing and separating, maize grain falls to the cleaning device through concave grate.
When cleaning grain is completed, it fall to spiral conveyer at the bottom of the harvester, then it is transported to grain container by lifter.
Meanwhile, the grain fell to the cleaning device through concave grate.

The occurrence of size effects in cobalt was examined by the analysis of mechanical properties of samples with thickness t, in a large range of grain size d giving a number of grains across the thickness t/d.
The influence of size effects on the mechanical properties of metals can be analyzed through the number of grains (of diameter d) across the thickness (t) parameter t/d.
For smaller grains, the deformation is assisted by dislocation gliding whereas for the biggest grains, twinning is the main straining mechanism.
Geers, Size effects from grain statistics in ultra-thin metal sheets, J.
Hug, Hall–Petch behaviour of Ni polycrystals with a few grains per thickness, Mater.

During each extrusion, besides the large simple shear plastic deformation in a thin layer of a workpiece by moving through a die, the cross-section of the sample remains unchanged and consequently this procedure can be repeated a great number of passes, resulting in the accumulation of large strains of alloy.
Therefore, compared with the grain size pressed for 4 passes, the grains (Fig.2 (b)) grow up and trend to be coarse, at the same time the boundaries are more distinct and the grain are more equiaxed.
Recrystal grains grow up slightly and grain boundary is distinct owing to high tensile temperature and long tensile time.
The recrystal grains in Fig.4 (a) are finer than grown grains in Fig.4 (b).
The formation of fine-equiaxed grain consumes distortion energy, reduces dislocation density, loosens stress concentration caused by grain-boundary sliding [5-7], provides new slidable large angle grain boundaries and benefits grain-boundary sliding.

Again, when grain growth ceases it is widely assumed that each grain present arose from a single nucleus.
The numbers are staggering, it is simple arithmetic to show that, in Fe-Si, for example, the abnormal Goss oriented grains must have consumed ~100,000 of their neighbors.
The final grain size was ~30µm.
Grain EG1 in Fig. 2b could have arisen from three such grains as shown in Fig. 2a.
The critical length for a process similar to SIBM is observed to be 3-5 subgrian diameters, i.e. 3- 5µm Acknowledgement It is a pleasure to acknowledge financial support for this work for the Research Grants Council of Hong Kong Special Administrative Region of China, numbered RGC 7067/97E.

Softening level depends on both ARB temperature and number of cycles.
Fig. 2 shows the variation of ultimate strength and elongation with increasing number of ARB cycles at temperatures from 250°C to 350°C.
Fig. 2 Variation of ultimate strength Rm (a) and elongation (b) with number of ARB cycles of samples processed at 250 to 350°C.
It was found out that recrystallization and grain coarsening occurs during heating before ARB and by this the grain size keeps constant with increasing number of cycles.
Non-uniform grain size with coarser grains at bonded interface is observed in 0 30 60 90 0 1 2 3 4 5 6 7 number of ARB cycles I2 [%] positrons at defects (b) 0 60 120 180 240 300 0 1 2 3 4 5 6 7 number of ARB cycles lifetime [ps] free positrons at defects (a)samples processed by 2 ARB cycles.

Grain Refinement by High Temperature Plane-Strain Compression of Fe-2%Si Steel P.
After 75% reduction the equi-axed grains exhibited an average size of 10 µm which represents a strong grain refinement with respect to the initial size of 80 µm prior to PSC.
At isolated sites in this lamellar band structure a number of equi-axed grains can be observed.
Because these grains are associated with a sharper Kikuchi band contrast it may be readily assumed that they represent highly recovered or even recrystallised grains.
Average misorientation of recrystallised grains vs. temperature.

In production of superfine-grained grades, one of the main obstacles is to retard and control the grain growth during sintering [3-5].
The WC grain sizes in specimens added with Pr6O11 were fine and their average grain sizes were lower than 0.5um, without abnormal growth of WC grain found in them.
In specimen VI with 3.5% of Pr6O11 doping content, some nearly quadrate large-size grains, which were the undissolved Pr6O11 grains, were found.
Studies have shown that the flexural strength will increase with the reduction of WC grain size when WC grain size reaches the superfine-grained range for WC-Co cemented carbide.
This means that a large number of pores appeared in the sinter.

Fig. 2 Schematic of marked grain boundaries (TD is parallel to horizon) Figs. 3 show the measured results of angle of grain boundaries with increasing local strain.
The twinned bands are usually surrounded in grains and all twinned bands end at grain boundaries.
In this zone the twinning occurred very early and the twinned band number 2 is the first one.
The number 6 is a grain boundary which is a turning joint and a target to suffer collision of twinning bands.
Grain boundary turning is an apparent characterisation of crystal grain turning, the later is an essential mechanism for plastic deformation process in magnesium alloy; the grain boundaries turn to parallel loading direction. 2.