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By a qualitative analysis of the figures, one can observe a material with a large number of pores, besides the coexistence of open and closed pores.
This large number of pores is due to the processing and is responsible for the low mechanical resistance of the compound, making it very fragile.
For the sample MB#2 it can be observed that the annealing propitiated a significant increase in the number of pores, along with an apparent growth of the grains.
The Rietveld analyses showed that the MB#1 sample possesses 89.3% of MgB2 and 10.7 of MgO phases, while for the MB#2 sample the numbers were 88.6% of MgB2 and 11.4% of MgO phases.
The authors cite traces of another relaxation process located in high temperatures, probably due to the grain-boundaries motion, but it was not possible to observe it owing to experimental limitations.

The standard does not define the number of compaction layers.
It is recommended adjusting the number of layers depending on the consistency of the concrete and the height of the mold to achieve proper compaction.
The grain size distribution curve is shown in the Figure 1.
Fig. 1 Grain size distribution curve Ordinary Portland cement CEM I 42.5 R was used in the concrete mixes.
Acknowledgements This paper was prepared thanks to the financial support of Testing methods and application of cement composites, project number SGS20/109/OHK1/2T/11 and Durability of concrete structure and assessment of its life cycle, project number SGS19/149/OHK1/3T/11.

According to optical and TEM microscopy the average grain size was refined considerably from ~80 μm to ~1 μm.
It is well known that, severe plastic deformation (SPD) process introduces large number of GBs in materials [7, 8].
Equal-axial coarse grains (CG) dominate the morphology of microstructure.
For multiple ECAP processing, a total number of eight passes process has been applied on the CP tungsten rod with a diameter of 15 mm.
The microstructure of multiple ECAP tungsten is not homogeneous, there’re equal-axial and elongated grains distributed in the field.

The paper presents an overview of a number of unusual phase transformations which take place in pearlitic steels in conditions of the severe deformation, i.e. combination of high pressure and strong shear strain.
(1) where: R = distance from sample centre, N = number of anvil rotations, h = sample thickness.
The image displays two grains overlapping along the interface.
The right hand grain is <111>oriented ferrite and the left hand one is <110>-oriented austenite, which can be determined from Fourier transforms taken in areas of each grain (Fig. 6a, inserts, Fig. 6b).
Valiev, in: Ultrafine Grained Materials III, (TMS (The Minerals, Metals & Materials Society), 2004 , p. 31) [14] X.

Rated load on counterbody was 10 N; finite number of sample rotation - 5000.
Namely, it contains separately located point reflections belonging to α-phase (solid on the base of bcc lattice of iron) and a large number of thin diffraction rings belonging, most likely, to nano-dimensional particles of carbide and oxycarbide phases.
First, the lamellar pearlite grains in which the ferrite grains are divided to disoriented areas are revealed.
The similar structure forms in the grains of ferrite-carbide mixture as well.
Second, the pearlite grains and grains of ferrite-carbide mixture with partial or complete dissolution of cementite plates are determined.

Due to the high vibration frequency of the system, the sample surface was struck repetitively by a large number of balls, resulting in a progressive refinement of coarse grains into the nanometer scale.
It can be seen that the plastic deformation degree decreases with increase of the depth and the original coarse grains in the surface layer are severely refined into ultrafine grains, in which grain boundaries could not be identified.
The microstructures in the treated layer change gradually from ultrafine-grained structures in the topmost layer to the undeformed grains in the matrix.
Firstly, high number density of grain boundaries and triple junctions in nanocrystalline materials can provide rapid mass transport paths [16,17], which is believed to be the primary diffusion mode of Fe and Cr elements.
Grain growth is mostly attributed to the grain boundary migration and grain boundary is the primary channels for accommodating solute atoms.

The results show that the corrosion rate of the ultrafine-grained alloy decreases, in comparison with the coarse-grained alloy.
The number of ECAP passes is 4.
After four passes, remarkable grain refinement occurs by repeated shear deformation, and the grains of the alloy were refined to submicron level after four passes.
In that way, grain size is an important factor for improving corrosion resistance.
The pits on the coarse-grained sample surface (0P) are much larger and darker than those of the ultrafine-grained sample (4P).

In this case, a section or a projected image is enough provided that the number of objects containing by the section is enough statistically.
Similarly to it the PP quantity (point relation) can be derived as PP = P /P, where the P� in the numerator means the number of points being in the microstructure shape, while the P in the denominator represents the total number of points of the investigated sample.
the number of steps.
The histogram of porous grain can be seen in the Fig. 10, while the histogram of compact grain can be seen in Fig. 11.
PVC-grains of different compactness.

of atom) Bond angle variance : s2=Smi=1(fi-f0)2/(m-1) (fi: Bond angle, f0: Bond angle of regular body, m: number of face) Fig. 5.
The same analysis was performed to separate grain and grain boundary conductivities.
The grain boundary conductivity seems to be directly related to Mg carrier concentration in the vicinity of grain boundary.
Three to four resistance components attributed to grain, grain boundary and electrode interface were successfully separated.
For undoped sample, grain and grain boundary conductivities were 1.7 x 10-3 and 1.9 x 10-5 S/cm at 600oC, respectively.

The work indicates that the recrystallized grains, which migrate into the deformed grains, are mainly with the high misorientation angles.
The large percentage of the recrystallized grains, whose misorientation angles with deformed grains exceed 15°, are corresponding to the {111} transformation texture.
From picture, we can see that almost all the recrystallized grains and deformed grains were separated by high angle boundaries (>15°).
The {110} grains have the highest stored energy, but since this texture component is very weak, the number of nuclei produced is small.
(3) The migration of recrystallized grains into deformed grains is difficult to proceed if the misorientation angles are less than 15°.