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The grain size of primary Al plays an important role in the final properties of the casting.
For the grain refiner master alloy to act as an effective dopant, the physical nature (shape, size morphology or number density) of the pre-existing phases in the master alloy play a key role in the microstructural development during casting [5].
Chakraborty, Grain refinement of aluminium and its alloys by heterogeneous nucleation and alloying, Int.
Zhang, Revisiting the role of peritectics in grain refinement of Al alloys, Acta Mat. 61 (2013) 360–370
StJohn, An analysis of the relationship between grain size, solute content, and the potency and number density of nucleant particles, Metall Mater Trans A, 36A (2005), 1911-1920

In Fig. 3c and 3d, the dendrites have a clear growth direction, showing a small columnar grain.
From the region of the substrate to the region of the top, number of layers increases, the heat input becomes larger and the cooling rate decreases.
The growth tendency of the grains becomes stable and single.
So the liquid metal of this part produces a large number of nuclei and forms a layer of fine grain area manifesting as fine and “messy” dendrites [10].
With the number of layers gradually increasing, the rate of cooling decreases and the direction of heat dissipation becomes apparent along the direction of accumulation of the material, the columnar grains appear parallel to each other, and the primary dendrite arm space and the secondary dendrite arm space become wider as well.

The results from these studies have lead to a number of conflicting findings depending on the deformation mode used to study the strain path.
The final grain size is smaller at the surface of the slab, probably due to the quenching effect of the rolls on the slab during rolling with a peak in grain size at 0.8 of the sample half thickness with the remaining material showing a homogenous grain size.
The 180° sample had the largest sub-grain size and aspect ratio.
As the stored energy in a materials is inversely proportional to the sub-boundary separation or sub-grain size [9] there is a correlation between the sub-grain sizes seen and the recrystallisation response of the materials where the larger sub-grain sizes seen in the 180° and 90°(FCD) samples is a result of a stored energy and hence slower recrystallisation kinetics and a larger recrystallised grain size.
Table 2: Sub-grain sizes and aspect ratios for the samples deformed though the strain paths in Fig.2 0°(F)ε=0.15 0°(CD) ε=0.15 90° (CDF) 90° (FCD) 180° Grain size A (µm) 1.50 1.72 1.09 1.61 1.30 Grain size B (µm) 1.80 2.2 1.19 1.49 2.26 Aspect Ratio 1.2 1.28 1.09 1.3 1.74 Conclusions The strain path by which the material is deformed affects the flow stress, recrystallisation kinetics and recrystallised grain size.

The density analysis shows almost 98% of density and microscopy reveals some precipitates of α phase and presumably ω phase at the grain and grain boundaries.
The microstructure consists of relatively large grains of phase β with grain boundary α precipitates.
In addition, some amount of intra-granular α precipitation is also visible within β grains.
It is possible that the same precipitate would be formed into the grain boundary.
At β matrix, and even at grain boundary, precipitates were found, presumably α and/or ω phase.

After analyzing the change of CT numbers for the same specimen, the relational expression between CT numbers and deterioration variable was established.
Primary materials and mix proportions for tests Primary materials for tests After crushing and processing the waste reinforced concrete, the recycled coarse aggregates can be acquired with the grain size ranging from 5mm to 20mm.
Results and analysis of spiral CT tests CT scanning images was 512×512, image resolution was 0.15mm and each pixel point in the image was attaching with CT numbers stored with 12-bit number that had 4096 orders.
For the same centre of the circle, the CT numbers of damage region and failure region at each loading stage with same radius were analyzed by statistics, average CT numbers and standard deviation of each image can be acquired, as shown in Tab.2~Tab. 4 Table 2 CT numbers of damage zone in R0 specimen with different stress Stress(MPa) 0 37.6 37.0 36.5 36.0 CT numbers 2080 2078 2075 2039 1978 standard deviation 339.7 351.2 364.0 377.0 457.9 Table 3 CT numbers of damage zone in R50 specimen with different stress Stress(MPa) 0 35.9 35.6 35.1 34.8 34.4 CT numbers 1981 1983 1966 1933 1910 1884 (standard deviation) 324.7 344.7 350.7 357.3 372.9 404.6 Table 4 CT numbers of damage zone in R100 specimen with different stress Stress(MPa) 0 34.6 34.2 33.7 33.2 32.8 CT numbers 1853 1821 1802 1782 1742 1721 standard deviation 378.2 380.6 387.0 396.7 405.0 442.0 From Tab.2~Tab. 4, we can see that with the increase of mixing amount of recycled coarse aggregate, the CT numbers decreased which
The relation between average CT numbers and stress Fig. 5.

Fig. 1 Voltage-ampere characteristics curves for electrode combination of (a)WCe-WCe, (b)WCe-WLa and (c)WCe-WY, in which “1” and “2” stand for lamp number, and “+” means the anode is WCe and “-” the opposite.
And there are grains and sheet peeled off the surface of cathode WLa, and those area may be the stress concentration zone caused by the machining.
According to the principle of metallography[5], the grain boundary often has lower melting point, so the melting process usually begin from the grain boundary.
And also the atoms around the grain boundary be in a unstable state and has a higher corrosion rate than other area.
Because of the presence of grain boundary, the doping element will be easy migrate and escape down the grain boundary which is useful to improve the electron emission property of cathode. 3 Summary Experimental result indicates that the tungsten electrode doped with rare earth element Yttrium oxide has good performance while be used as cathode of pulsed xenon lamp.

In this study, the corrosion property of three types of AZ31 alloys specimens with different grain size and texture was investigated.
The grain size of the extruded rod, hot rolled sheet and extruded sheet specimens is ~ 8.8 µm, 7.0 µm and 20.4 µm, respectively.
The extruded sheet specimens with a basal texture and comparative large grain size exhibited the slowest weigh loss rate during almost all the days of immersion.
After three days' immersion in SBF, the weight loss rate of the extruded rod and hot rolled sheet, which have comparable initial grain sizes, was close.
Acknowledgements This research is supported by the National Key Basic Research Program of China (grant number 2007CB613703).

Larger particles can also be obtained by changing the number of pulses.
Its grains are uniform and vertically oriented, and their spherical shape shows good dispersion.
All produced films had their surface roughness, grain size, and root mean square roughness value evaluated using a specific program; the findings are shown in Tab 2.
The grain size also matches the XRD test results.
Fig. 4. 3D AFM image and grain aggregation distribution diagram of a thin film of SeO2 nanoparticles produced using different laser pulses 250P, 300P.

But after annealing at 200°C for 1h, grain boundary could be clearly observed, the fine grains were formed among the large grains and the average grain size was 6.04μm.
This is mainly because the static recrystallization has begun to occur when annealing at 200°C and the fine grains were static recrystallized grains.
After the annealing temperature rose to 300 and 350°C, the grains grew up and the average grain sizes were 11.16 and 11.19μm, respectively.
The slender grains suppressed the grain boundaries sliding [8], which resulted in the larger tensile strength.
Grain refinement will increase the number of obstacles to dislocation motion and reduce the length of groups of dislocations within the grain, resulting in increased yield strength.

Grain of substrate grows along the direction to thermal diffusion.
Grain growth has the directions, but is not obvious.
As the substrate material is different, its microstructure, grain size, growth direction is very different from Figure 3 and 4.
With the increase of number of impact, specimen occur distortion, hardening or softening, cracking and subsidence caving deformation.
Acknowledgements The authors gratefully acknowledge the foundation by Hunan Provincial Natural Foundation with the project number 02JJY2072 References [1] Yunchang Fu, A.