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When the electromagnetic frequency is 20Hz, the grains with developed secondary dendrites trend to be eliminated, and the grains are mainly the short rod or rosette-shaped structures, shown as Fig.3 (b). when the electromagnetic frequency is 30 Hz, the microstructure of the billet is composed of the homogeneous and fine rosette-shaped equiaxed grains, and the distribution of grains is more homogeneous, the size of grain is refined obviously, shown as Fig.3 (c).
The conditions for forming a large number of grain nuclei in the melt are provided.
The resistance of grain growth from the surface tension of the ‘grain bud’ could not be eliminated by the small constitutional undercooling at the solid-liquid interface of growing grain[9].
The grains would be tended towards the rosette-shaped growth.
In the process of moving, the nuclei bump and frictionate each other, which is helpful for the formation of rosette-shaped grains.

Table.2 Microhardness of the coating Sample The value of each test (HV0.1) The average value (HV0.1) Equivalent value (HRC) 572 911 1113 678 683.62 Cr3C2-NiCr 639.40 570.441 599.34 852.35 950.19 756.946 61.8 Grain-abrasion performance analysis.
Wear test experiment was done with MLS-225 wet sand rubber wheel grain-abrasion equipment.
Hard ceramic particles in the coating have good wear resistance property and could stop grinding crack expansion during grain-abrasion wearing process.
The extent of plastic deformation at the sample's surface is lesser than that of the sample after grain-abrasion wear.
The other is the number of hard particles in the coating.

Introduction In the last decade, a large number of studies were devoted to analyzing the effect of Sc and Zr on the formation of the ultrafine grain structure in aluminium based alloys [1-5], including studying the influence on Zr and Sc on superplastic behavior [6-8].
The grain structure after annealing of cold rolled sheets was studied in polarized light using an Axiovert 200 MMAT “Carl Zeiss” light microscope (LM).
Dispersoids heterogeneously nucleated after one-step annealing mode A; precipitates are formed on dislocations and low angle grain boundaries.
Grain structure of sheets after 20 minutes of annealing at 540 °C: (a) mode A; (b) mode B; (c) mode C Sheets treated in two-step mode B exhibited the largest fraction of unrecrystallized grains (Fig.4 b) in compare to other treatment modes.
Langdon, Influence of scandium and zirconium on grain stability and superplastic ductilities in ultrafine-grained Al–Mg alloys, Acta Materialia 50 (2002) 553–564

In the Primary Shear Zone (PSZ), ferrite grains appear as really elongated (Fig. 3b).
If the latter is broken up (splitting of the perlite lamella and dispersion of the carbides), the ferrite grains, with an initial grain size of 10 to 20 µm (Fig. 1), are here found to be considerably refined with a diameter smaller than 1 tm.
The subsurface layer (I) is formed by nanometric grains, perfectly equiaxed and smaller than 200 nm.
It can be seen as an equivalent number linking strain rate to temperature via an activation energy.
The SEM and EBSD analyses performed on the collected chips highlighted, in the main intensive deformation zones, a drastic grain refinement leading to grain size lower than 200 nm.

When the annealing temperature was at 730 degree, zonal structures in the steel substrate disappeared, but there were some un-equiaxed grains and some small grains, that meant the recrystallization was almost finished, but the grains grew not very well.
When the annealing temperature was at 760 degree, the grains were equiaxed and small grain numbers decreased, that meant recrystallization were finished completely.
Many small particles precipitated at 730 degree, and these particles distributed along with grain boundary and sub-grain boundary.
The grains were equiaxed and when the annealing temperature was above 760 degree, the grains hardly grew up
(3) When the annealing temperature increased, many small particles precipitated, and these particles distributed along with grain boundary and sub grain boundary.

So dynamic effective grains number in unit time and undeformed chip thickness decrease both as mill-grinding speed increasing, which leads to decreasing of surface roughness.
Moreover, the undeformed chip thickness increases with feed rate increasing, and the dynamic effective grains number unit length of workpiece decreases during mill-grinding process.
The undeformed chip thickness increases with feed rate increasing, and the dynamic effective grains number unit length of workpiece decreases during mill-grinding process.
For one thing, the increment of mill-grinding depth causes the increment of undeformed chip thickness of mill-grinding and the mill-grinding depth of single grain.
So the trench marks caused by grains becomes deeper.

If it can be used to replace special soils, not only the construction costs will be effectively reduced, but also the construction period will be greatly shortened. 1 the Materials Application of Replacement with Gobi desert method The rules asked: the replacement materials must be clean, there are no such impurities as plant residue, rubbish, etc, mud content to 5%, organic matter content to 5%, good gradation, maximum grain size to 5cm.
Table 1: Statistical Results about the Grain Analysis of the Gobi Desert (Average Value,%) Name of the Grain Group Egg Granules[mm] Gravel Grain[mm] Sand [mm] Silt [mm] Range of Particle Size >60 60-40 40-20 20-10 10-5 5-2 2-0.5 0.5-0.25 0.25-0.075 0.075-0.01 Percentage Content 18.3 20.9 17.0 15.7 9.4 2.6 5.2 5.2 5.2 0.5 2 Evaluation on Reinforcement Effect of the Replacement with Gobi desert method 2.1 Bearing Capacity of the Cushion and its Construction Quality Control In order to ensure construction quality, it should be conduct some tests about materials application before construction, such as mud content test, organic matter content test and grain analysis, etc.
The treatment place is constructed by 15T vibrating roller whose exciting force is no less than 200kN.The compaction speed and the number of compactions should be determined by experimental rolling.
Generally, the compaction speed is usually no more than 2km/h, the number of compactions is no less than 8.
The heavy cone dynamic penetration test are conducted after finishing the construction of the whole cushion, the number of the test points no less than 3, the test depth no less than 5m. 2.2 Evaluation on Reinforcement Effect In this project, there are about 2931m2 soft soils using replacement method to strengthen.

SEM images show that the density and grain size of the composite ceramics increases with sintered temperature increasing.
It can be seen that the grain sizes become larger as the temperature increases.
Composite samples sintered at 1250°C have asymmetrical grain size, high porosity and low density, whereas when the sintered temperature rises up to 1350°C, the grains grow enormously in size coupled with the phenomenon of over-sintering.
It is known that La can scatter electrons much more effectively than Mn, Ni and Ca, for the atomic number of the former is much larger than those of the latter.
That makes the ion pair number of different valence states (Mn2+/Mn3+, Mn3+/Mn4+) decrease, then the electrical conduction of the composite weakens.

By this procedure, an optimum set of dressing parameters such as coarse dressing depth, number of coarse dressing, fine dressing depth, number of fine dressing, non-feeding dressing, and dressing feed speed will be found.
A critical stage that prepares for the grinding wheel after each grinding operation is dressing or sharpening abrasive grains.
This leads to increased fracturing of the grains and whole-grain pull out.
It can be seen that, the fine dressing depth (af), the number of fine dressing (nf), the number of non-feeding dressing (no), the number of coarse dressing (nr) are considered with three levels, but the coarse dressing depth (ar) and the feed speed (Sd) are only two levels are considered for both figures.
- The surface roughness will be max when using Fine dressing depth at level of 2, Number of Fine dressing at level of 3, Number of non-feeding dressing at level of 4, Number of coarse dressing at level of 3, Coarse dressing depth at level of 2, and dressing feed rate at level of 1

The most serious negative features of such ordered intermetallics are their grain boundary brittleness.
One of them is by reducing long-range ordering or grain size of intermetallic compounds [1, 2].
The average grain sizes of the milled powders were estimated based on XRD peak broadening by the Scherrer equation.
The mean grain size was estimated to be 13 and 8.6 nm for the Ni and Ti solid solution respectively after 30 h of MA.
After MA for 30h, Ni and Ti solid solution were formed with mean grain size of 13 and 8.6nm, respectively.