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Introduction A grinding wheel could be defined as a composite substance consisted of a large number of abrasive grains bonded together with the binder maintaining the specific porosity from 20% to 40%.
It plays a key part apart from abrasive grains.
,Si3O8] sanidine 2.38 7,60 <1000 As a result of combining the components [Tab.2], the composites marked with the following symbols were obtained: CD - grain of boron nitride + binder D CS - grain of boron nitride + binder S Table 2.
CBN abrasive grain bond CBN abrasive grain bond Fig.1.
bond CBN abrasive grain CBN abrasive grain bond Fig.2.

With K2CO3, SrCO3 and Nb2O5 starting materials, KSN lead-free piezoelectric ceramics were prepared by conventional ceramics technique and reactive templated grain growth (RTGG) method, respectively.
The KSN ceramics prepared by RTGG not only had higher degree of grain orientation but higher sintered density compared with that prepared by solid-state reaction.
Simultaneously, a large number of pores are observed in the KSN ceramics.
It is confirmed that KSN lead-free piezoelectric ceramics with higher degree of grain orientation and sintered density could be prepared successfully by RTGG methods.
The KSN ceramics prepared by RTGG technology not only had higher degree of grain orientation but also higher sintered density compared with that prepared by traditional solid state reaction.

A count of the number of MF and MS grains per unit area (NMF and NMS, respectively) confirms the qualitative observation that there is a higher amount of MgO-fused aggregates in the refractory B.
brick MS (%) MF (%) Matrix (%) NMF NMS area (mm2) B 5 39 56 69 23 277 C 34 17 49 40 56 308 Considering the analyzed area in each brick, the number of grains per unit area (1 cm2) of magnesia-fused aggregates (δMF) and magnesia-sintered aggregates (δMS) are calculated.
Fig. 2a shows a MgO fused grain (brick B), the presence of triple points (CaO/SiO2 ~ 0.7) within the grain is observed.
MgO fused grain in (a) brick B, and (b) brick C.
In micrograph of Fig. 4a, corresponding to brick B, disaggregated MgO grains and large number of smaller rounded crystals of magnesia are observed.

The insertion of SrTiO3 interlayer yielded BaTiO3 thick films with homogeneous and dense grain structure with the number of SrTiO3 layers.
There was no remarkable distortion in the BaTiO3 crystal structure for the thick films having various numbers of BaTiO3/SrTiO3 layers.
This suggests two phases coexisting in the film, and the ratio of the two phases can be artificially controlled by the number of coating.
A mixture of various grain sizes was evident for the BaTiO3/SrTiO3-7 heterolayered thick/thin films sintered at 1300 �, which showed very large grains coexist with very small ones.
It could be seen that the BaTiO3/SrTiO3-7 heterolayered thick/thin films with the number of coatings was also effective for increasing the grain size and improving the microstructure homogeneity.

These define limits for grain size and shape, grain boundary location and the misorientation between grains RD, Reference Direction RP, Reference Plane Figure 1.
Main grain (primary) orientation.
Grain boundary misorientation R-values.
The R-value, a number in units of angle (°), is used to assess grain ‘misorientation’ or, more correctly, ‘disorientation’, as it is the minimum angular displacement between adjacent grains.
If grains on either side of a boundary are designated A and B, the R-value represents a summary of the rotations required to align grain A with grain B.

Initially low angle grain boundaries are formed and with further pressing the subgrains will transform into high angle grain boundaries with flow of dislocations into the grain boundary from within the grain.
Elongated grains could be observed after first pass.
As a result, large numbers of very fine precipitates are formed.
The grain size after ageing is 23μm.
Sample Condition Grain Size µm Hardness BHN 1.

The structure of ZnO can be described as a number of alternating planes composed of tetrahedral coordinated O-2 and Zn+2 ions, stacked alternately along the c-axis.
Their sintered disks form grains with narrow size and narrow size distribution, pure grain boundaries and inherent stability against grain growth [16].
The dimension of ZnO grains was (0.5-2.26) µm and (80-119) nm for sample A and sample B respectively.
So upon pressing and sintering the compactness of the grains increases while the number of pores and voids decrease relative to sample A [16].
Since c1 is a measure to the temperature T (K) which the filaments can reach, then it is proportional to the grain dimensions, i.e. large grains with imperfections, defects and voids are heated more.

Grain Size Distribution.
Figs. 5 (a) and (b), and Figs. 5 (c) and (d) show the number fractions and the area fractions, respectively.
Fig. 4 Change in pole densities of the compression plane at {011} and {001} with an increase in strain under three kinds of strain rate at 723K 0 1 2 0 2 4 6 8 True Strain, ε Pole Density 1.0X10 -4 5.0X10 -4 Al-3mass％Mg, 723K 001 011 strain rate /s -1 1.0X10 -3 0 200 400 600 0 10 20 30 40 Grain Size, d/µm Al-3mass% Mg, 723K As annealed Number Fraction of Grains (％) Total number of grains:211 Average grain size:115µm 20.4％ 0 200 400 600 0 10 20 30 40 Grain Size, d/µm Number Fraction of Grains (％) Al-3mass% Mg, 723K ε =1.0×10-3 s-1 , ε =-1.0 Total number of grains:222 Average grain size:109µm 39.6％ 0 200 400 600 0 10 20 30 40 Grain Size, d/µm Al-3mass% Mg, 723K As annealed Area Fraction of Grains (％) Total number of grains:211 Average grain size:115µm 23.4％ 0 200 400 600 0 10 20 30 40 Grain Size, d/µm Area Fraction of Grains (％) Al-3mass% Mg, 723K ε =1.0×10-3 s-1 , ε =-1.0 Total number of
(a) and (b) show number fractions and (c) and (d) show area fractions.
The number in the figure is the strains estimated by assuming the homogeneous deformation.

In absolute numbers this means an increase of only a few percent of the overall composition.
The oscillary frequency was 300...2900 Hz with an overall number of 500,000 strokes.
A larger fraction of grain boundary phase is present, too.
The fraction of grain boundary phase increases, too.
This load had dramatic consequences during one test run with alumina parts where the piston broke before reaching the maximum number of 500,000 strokes.

For both values of the wall thickness the hardness increased with rotational speeds and the number of revolutions.
The grain refinement starts at the inner surface of the sample and the width of the grain-refined zone grows with the number of revolutions.
The level of distortion of these grains is also larger for the higher rotation speed.
For a larger number of revolutions, even for a lower rotation speed, the front of the grain-refined zone penetrates deeper, almost through the entire wall thickness, cf.
With the growing number of revolutions ultrafine grains were observed near both surfaces of conical strip.