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In a previous work [7], it was determined that a number of cracks observed in thin sheet AA7079-T6 fuselage skin from various in-service aircraft were the result of a combination of stress corrosion cracking and fatigue.
It is interesting to note that this thin sheet is made by rolling, resulting in pancake shaped grains whose grain boundaries are aligned parallel to the surface.
It is also known that the corrosion preferentially occurs along the grain boundary in this material.
As suggested earlier, the galvanic corrosion occurs preferentially along the grain boundaries in AA7079-T6.
This suggests that if the cycling frequency is less than 0.04 Hz, corrosion processes can weaken the material along the grain boundaries and the crack propagation can occur in mode II along the grain boundaries of rolled thin sheet structure.

As expected, it can be observed two semicircles which contain information from different regions of the ceramic sample, grain (GR) and grain boundary (GBR) resistivity [19].
(Numbers denote the logarithm of frequency).
From this plot was possible to calculate the activation energy for migration of the oxygen ions of the grain, grain boundary and total.
Arrhenius plots of the grain (GC), grain boundary (GBC), and total (TC) conductivity of the ceramics.
The impedance diagrams showed two semicircles that were attributed to the contributions of the grain and grain boundary.

The average grain size of the samples was about 2.5 µm.
Strain hysteresis loops of the samples cycled for (a) 0, (b) 10 6.5, and (c) 10 8 cycles number.
Figure 5(a) shows the microstructure of virgin samples, with some etch grooves within the grains.
A large number of etch grooves can be found within grains for the fatigued samples at 10 8 cycles, as shown in Figure 5(b).
A large number of etch grooves were observed in the polished-etched surfaces.

Also, voids in between the grains and large surface irregularities are observed.
Undoped SnO2 thin film has an average grain size of 80 nm.
The grain size increases with the addition of dopants as discussed in XRD analysis.
The diameter of these grains depends on the subsequent doping amount.
Moderate doping concentration may increase the number of allowed states near the conduction band due to the defects in nano-grained SnO2 thin films which in turn causes the decrease in bandgap [22].

Large number of tailings occupied abundant land, and very harm to the local environment.
Glass-ceramics also known as crystallite ceramics, it was prepared by certain basic glass, and according to definite heat treatment, it became to a crystal solid material contains glass phase system and large number of microcrystalline phase.
In order to get well-proportioned grain of ingredients, the raw materials be scrunched in earthen bowl to make the grains have -200mesh granularity, then mix them together.
Then a layer of water retie was formed on the surface of the quartz, which on one hand can help to dissolve the carbonate and borax that exist in the raw materials and conduce to the accomplishment of the melting process, on the other hand, after the surface of the raw materials grains being wetted the loss of ingredients will be reduced when adding material.
By the analysis of XRD, the main phase of glass-ceramics is wollastonite, so these acicular crystal grains should be wollastonite phase, agree with main phase of design, and achieve the intended purpose of the experiment.

But studies related to fatigue and fracture behavior of this category of steels are limited in number.
The short crack growth rate (da/dN) has been calculated by measuring the increment in crack length (a) in a specific time interval and then dividing it by the number of fatigue cycles (N) the specimen has been subjected to in that interval.
The amount of the total segmental crack lengths passing through grains/colonies” initially decreases followed by an increase with increasing bainite.
(FG-ferrite grains, FF-ferrite-ferrite interface, B-bainite colony, FB-ferrite-bainite interface, and BB-bainite-bainite interface).
Fatigue crack path in FBDP steels passes through ferrite grain, bainite region, and through the interfaces of ferrite-ferrite, bainite-bainite, and ferrite-bainite.

Next, it provides significant information on the overall texture of a rock in the microscopic scale (Fig. 1), number of layers of mica per one millimetre, average thickness of ten mica layers and the structure of mica layers.
Fig. 6 also displays the visualization of the largest discrete grain in sample No. 2.
Fig.5. 3D visualization of pyrite grains volume and distribution - slate sample No. 1 Fig.6. 3D visualization of pyrite grains volume and distribution - slate sample No. 2 The charts in Figs. 7 and 8 show the frequency of size occurrence of the individual pyrite grains in the analyzed slate.
Contrasting comparable sizes of pyrite grains in both samples of the analyzed slate (i.e. pyrite grains in the samples larger than 0.013 mm3), the pyrite inclusion volume in sample No. 2 is 0.14%.
Histogram of pyrite grain size in slate sample No.1 Fig.8.

(The number of moles of material (component B) that entered the left-hand side of the couple equals the number that disappeared from the right-hand side).
By definition, the molar volume, of a cubic B2 phase can be found in a straightforward way as: (11) where a is the lattice parameter [m], is the Avogadro number [mole-1] and is the number of atoms in the unit cell.
Owing to the high atomic number of thorium, these particles exhibit a distinct contrast on back-scattered electron images.
Such “duplex” grain morphology may sometimes develop inside diffusion-grown compound layers [6, 15].
Moreover, the protruding of the interphase interface does not specifically occur at the grain boundaries, which indicates that contribution of grain boundary diffusion to the growth kinetics of the γ’-Ni3Al product phase is insignificant.

Adjacent to the center, a large number of craters are discovered (Fig. 2c).
Secondly, it is captured that the grain boundary cracks are accompanied by the craters (Fig. 3j).
When the atomic number of the matrix is unchanged, the greater the angle of incidence is, the stronger electron scatters.
According to the references [8], grain size, orientation and shape of the inclusion may vary normal melting point.
The deposited energy can not release completely through the eruption of particles, however, the nucleus are grain boundaries, not defects.

It can be seen that different morphologies and grain sizes of oxide scale are exhibited according to the cooling rate.
As shown in Fig. 4a, slow cooled microstructure of oxide scale shows progressively larger grain size (mostly 10µm) coexisting with minor precipitates at its grain boundaries.
It has been observed that the grain size of oxide scale decreases with an increase of cooling rate.
Furthermore, surface roughness achieves more smooth and homogeneous to grain surface at higher cooling rate.
This is due to that, during the transition Fe1-xOàFe3O4, the number of oxygen ions per crystal volume remains constant, only iron being lost [6].