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Introduction Practical solution of a number of problems of high energy physics and thermonuclear energetics requires creation of various devices for obtaining high magnetic fields, such as International Thermonuclear Experimental Reactor (ITER), Large Hadron Collider, Demonstration Power Plant (DEMO), etc.
Moreover, the previously formed Nb3Sn grains can grow under the following diffusion annealing which can cause the overall grain coarsening and thus decreasing of the pinning force, which directly depends on the total amount of grain boundaries [7].
However, in the longitudinal sections studied by TEM the areas of three types, fine equiaxed grains, coarse grains and elongated (columnar) grains, are observed in all the samples (Fig. 6).
The Nb3Sn layers in sample 7: a- fine equiaxed grains; b- coarse grains, wide grain-size scattering; c – columnar grains For the quantitative estimation of the Nb3Sn grain structure all images obtained after the diffusion annealing of the samples were statistically treated using the computerized SIAMS600 program, and the results of this treatment are given in Table 2.
Three types of Nb3Sn grains morphology are observed – fine equiaxed grains, coarse grains with wide size scattering and elongated grains.

The results showed that, Y was an effective element strengthening Mg-Zn-Zr alloy, a large number of Mg3Zn6Y phase was formed due to the addition of Y.
It can be seen form the figure1, the grain size of 1# alloy is larger and its grain boundary is broader.
The addition of Y element decreased the grain size and grain boundary width significantly.
When the temperature decreased a lot of Mg3Zn6Y appeared in the grain boundary.
Ultrafine grain metal (National Defence Industry Press, Beijing 1982)

Prates and Biloni [4] showed that increasing the roughness of the mould surface (using abrasive papers) led to an increase in the heat transfer coefficient and also the number of pre-dendritic nuclei and hence, grains.
They were numbered from 1 to 6 in order of decreasing cooling rate (see table 2).
For sample number 3, where there is a clear segregated layer, the DAS was measured separately for areas with and without the layer.
The grain structures of some of the samples are shown in Figure 5 (no grain refiner was added prior to casting).
Grain structure of: (a) Sample 1, (b) Sample 2 and (c) Sample 3.

The wear test was performed in the hip joint simulator according to ISO standard 14242 in bovine serum and over a total number of 2 million cycles; n = 2 couplings were tested in each case [9].
Fig. 6 Comparison volumetric wear rates on heads of the tested pairings The roughened surface area of the ceramic heads and liners show for alumina ceramic grain pullouts and sharp edged in comparison to the dispersion ceramic relatively coarse grains.
At the surface of the ATZ-samples the mixture of alumina grains (dark) and zirconia grains (bright) is visible (Fig. 7 - 9).
There is not so much grain pull-out as for alumina detectible.
Jobbins: Ceramic bearing surfaces in total artificial joints: resistance to third body wear damage from bone cement particles; Journal of Medial Engineering & Technology, Volume 15, Number 2, (March/April 1991), 63 - 67 [4] A.

Because of the low sintering temperature, the original morphology of TiB2 grains produced by the compaction can be clearly seen.
A number of voids and small flaws existed in the specimen, due to a loose connection between the TiB2 grains.
The weak interface strength in porous TiB2 ceramic sintered from T32 compacts originated from TiB2 grains and their poor connections (Fig.1 (a)).
Because of the progress of densification and grain growth, highly packed regions densified faster than the less-dense regions, as shown in Fig.2 (a) and (b), where the ceramic grains clearly have grown in neck area but the connections between the particles are still the porous structures.
The loose connections between the TiB2 grains in T32 compact led to a nonuniform microstructure, and a number of small flaws existed in the sintered porous body (arrows in Fig.1 (a)).

However this thermal treatment reveals furrows along the grain boundaries several hundreds of nm deep [5].
The mean grain radius was estimated at 9 µm from microscopy observations of their surface.
However, a very small fraction of the sample surface was concerned by these observations and the number of pink halos and exfoliated areas did not visibly increase with the annealing temperature.
NRA microanalyses have shown that helium is mostly over-concentrated in grains in which the pink halos are observed.
However there are a number of differences between the two situations.

Both the grain size and lamellar structure inside grains were significantly refined with the addition of Er in as-cast alloys.
The beta transus-temperature of ingots marked with number 1#, 2#, 3# and 4# alloy were 1045℃, 1039℃, 1041℃ and 1040℃, respectively.
The element area scanning analysis indicated that the Er mainly existed in the form of compounds that were distributed both in the grain boundary and inside grains.
Conclusions (1) With increasing rare earth Er, the average grain size decreases.
The Er in the alloy mainly exists in the form of compounds that are distributed both in grain boundary and inside grain.

Fig. 6 (b) shows the microstructure is uniform, grain size is smaller, grain boundary is clean at 1900ºC.
Some holes of pull-out of the grains can be seen in Fig. 6 (b) and Fig. 6 (c).
Therefore, in the process of crack propagation, crack propagated along the grain boundary (or phase boundary) with the weak combination under the condition of relatively small grain.
When the grain size is larger, trans-granular fracture will occur.
When this stress field encounters applied stress, crack propagation is blocked, the number of rough crack surface increases, the crack propagation energy consumption increases, leading to a higher fracture toughness.

Tab.1 Relationship between wheel linear speed and spool surface roughness at workpiece shaft rotational speed 50r/min Tab.2 Relationship between wheel linear speed and spool surface roughness at workpiece shaft rotational speed 90r/min Tab.3 Relationship between wheel linear speed and spool surface roughness at workpiece shaft rotational speed 130r/min Tab.4 Relationship between wheel linear speed and spool surface roughness at workpiece shaft rotational speed 170r/min Fig.6 Spool sample 4 Surface roughness influence factors analysis The grinding surface roughness has relationship with unit area abrasive grains numbers, abrasive grains distribution, cutting mark, chemical composition and metallurgical structure of the workpiece, workpiece diameter, wheel characteristics, trimmed condition, attrition rate, grinding wheel and workpiece speed, feed rate, no-spark grinding times, grinding depth and grinding fluid.
Because of the wheel speed increasing makes single grain undeformed cutting thickness reduced, workpiece surface roughness decrease.
Increasing the workpiece shaft rotation speed causes the workpiece surface roughness increases, because to increase the workpiece speed will decrease the number of contacts between grinding wheel surface abrasive grains and a certain point on the workpiece surface, the thickness of the single grain undeformed cutting is increased, the number of cutting grains in the unit area of the workpiece surface is reduced.
The grinding depth is increased to cause a single grain undeformed cutting thickness is increased, the grinding force is increased, thereby to make the surface roughness increased.
The more the number of no-spark grinding times, the more the contact times between abrasive gains and outline hump when the grinding depth ap>0.

The resistive sintering furnace are easier to manufacture, to manipulate the atmosphere during sintering, and allow the processing of a greater number of samples simultaneously, thus reducing the cost of processing [15].
However, often leads to heterogeneity in the microstructure and grain growth and abnormal non-uniform.
On the other hand, sintering using microwave energy enables to accelerate the kinetics of the process without driving the formation of microstructural heterogeneities as abnormal grain growth or development of microstructures with grain size distribution multimodal [16].
However, despite having obtained grain size less than 0.5 µm in both sintering conditions, we found that the sample sintered in a microwave oven (Fig. 2b) resulted in a microstructure with average grain size of around 50% larger relative to the grain size of the sample sintered in a conventional oven.
This behavior is explained by the grain size of 50% higher than the grain size of the sample sintered in a conventional oven.