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The light gray color contrast phase of as cast 7075 Al alloy was matrix-a(Al) and the dark gray color contrast phase was grain boundary (GB) of eutectic phase (a-Al + h-MgZn2), Al2Mg3Zn3, Al2CuMg, Mg2Si, and Fe-rich phase, as shown in Fig.1(a).
However, solution heat treatment time was over 4h resulted in coarse black particles formation at grain boundary, as seen in Fig. 1(d) and (e).
In addition, Mg, Cu, Al, Si, and Fe atoms are lower diffusion coefficient than Zn atoms resulted in these atoms segregated grain boundary to form Al-Cu-Fe (gray phase).
As-cast specimens, high content of grain boundary phase particles in the microstructure, obtained discontinuous film and severely intergranular corrosion at grain boundary, as clearly seen in Fig 2(a).
The continuous oxide film formed on 4h solution treated specimens, as shown in Fig.2(c), which they had a minimum number and small size of secondary phase particles.

In the structural elements obtained with the technology of strength hardened alloy AlMgSi (containing 0.57 wt.% Si), the formed microstructure consists of grains of solid solution a-Al and evenly spaced dispersion phases of silicon.
Occurring on the cross-section in the rod φ 9.5 mm inhomogeneity in grain size was the cause for the delamination of the material under the influence of external static compressive stress.
In contrast, in the rod φ 4.0 mm after exceeding the yield point there were only a few microcracks, especially on the border of the three grains. 3.
Taken external static load led always to initiate a number of transverse microcracks in the initial phases of eutectic silicon participles of conifers shape.
Both analyzed technologies: · The strain hardening technology of AlMgSi alloys (containing 0.58 wt.% Mg and 0.57 wt.% Si), shapes microstructure so that after applying external static compression loads, cracks are initiated, mainly at grain boundaries of the solid solution

a) b) Fig.4 SEM-picture of diamond films on substrates of different positions From Fig.4 (a) we could seen that the diamond films represented rough and the grain size reached 10µm.
It could be seen clearly from Fig.4 (b) that the grain size of diamond films was about 5µm.
Obviously, the grain size shown in Fig.4 (b) was much smaller than that shown in Fig.4 (a).
Obviously, the grain size of diamond films deposited on substrates placed on the central region of workbench was very big.
However, the grain size of diamond films deposited on substrates placed on the corners of workbench was much smaller.

And it can change the recrystalization of austenite and inhibit the growth of austenitic grain bringing grain refinement.
The variation of RHF is shown in Fig.1, and on this condition, the defects of transverse corner cracks on casting slab (left-side and right-side) are shown in Table 3 （a） （b） Fig. 1 Variation of RHF Table 3 Statistics of transverse corner cracks on casting slab (left-side and right-side) Heat flux in left-side/ heat flux in broad-side Numbers of transverse corner cracks Heat flux in right-side/ heat flux in broad-side Numbers of transverse corner cracks （a） 0.90~1.10 35 0.75~0.85 9 （b） 0.75~0.83 10 0.85~1.00 29 It is indicated from Fig.1 and Table 3 that there is close relationship between RHF and transverse corner cracks on casting slab for 510L steel.
Table 4 Physical properties of mold powder CaO/% SiO2/% F-/% Al2O3/% Na2O+K2O/% C/% Li2O/% Basicity Melting temperature/℃ Viscosity/ Pa•s Before optimization 32±4 32±4 8±1.5 ≤5 6±2.5 3±1.5 0.8 1.02 1056 0.20 After optimization 32±4 31±4 9±1.5 ≤5 8±2.5 3±1.5 1.0 1.04 1057 0.16 Table 5 Effect of mold powder on transverse corner cracks Size of cracks/mm Number of cracks Lift-side of slab Right-side of slab Before optimization 8~40 9~51 9~45 After optimization 2~10 3~18 2~16 (a) Before he optimization (b) After the optimization Fig.3 Transverse corner cracks on slab before and after the optimization Casting speed.
Table 6 Effect of casting speed on transverse corner cracks Casting speed Size of cracks/mm Numbers of cracks Lift-side of slab Right-side of slab Big fluctuation 4~16 3~11 3~9 Stable 1~3 0~5 0~6 Stabilization of caster.

But both of them suggested that gaseous bromine bubbles within the lamellar structure of the graphite crystal are considered to be analogous to Griffith cracks, and Olsen proposed that bisulfate compounds existed as "pockets" at grain boundaries, with much of the graphite remaining unaffected in a study[5].
Although there are many studies, most of them are just qualitative studies which involving a large number of experiments, and the quantitative analysis is inadequate.
Mass balance equation The number of moles of gas between the graphite layers with the number of interlayer diffusion of the gas into the environment should be equal to the number of of gas generated by the phase transition: (2) Here n is the mole density of gas in the graphite matrix and Q is the gas flow from the grain boundary phase into the environment (3) Where ΔP=PG-PE, PE is the environmental pressure; χ is the filtration coefficient; S is the filtration area, S=2πrh.

The grain size of α-Al2O3 powders was calculated by Scherrer equation.
In most of the studies reported in the literature, the sizes of grains have been determined by calculation XRD data using Scherer's equation: θ λ cos 89.0 B D = Where D is the crystallite size, 2/122 0 )( cBBB −= , Bc is the full width at half maximum (in 2θ), Bc is the correction factor for instrument broadening, θ is the angle of the peak maximum (in 2θ), and λ is the Cu Kα weighted average wavelength.
TEM and the calculation of XRD data results show that α-Al2O3 powders particles is nanocrystalline, and the grain size of the powders varied from 20 to 70nm.
Size (nm) rept.1 rept.2 0 70 140 210 280 350 420 490 Number % Fig.5.

Cutting distances were chosen depending on the number of passes.
The deacrease of the binder phase simplies the removal of the carbide grains.
Wear of WC-Co specimen in different cutting distances (left) and shortening of the length of the cutting nose tip of different materials at 4400 m The Fig. 4 (left) shows that in the WC-Co cemented carbide, the WC grains are not simply removed from the surface, but are crushed to smaller pieces, and then removed.
Cracks are visible in the larger grains near the tip.
The ability of WC grains to absorb fracture energy is related to their higher plasticity compared to TiC grains [12].

A number of techniques have been applied to produce thick ceramic coating on aluminum alloy substrate, including arc-discharge plasma, gas-flame spraying, vacuum deposition and high temperature glass enameling.
The surface of microarc oxidation coatings contains many grains with various sizes, and the grains contact with each other as shown in Fig.2 (a).
The microarc discharge over several times at the same position of sample would result in one large grain due to the deposition of eruptive melt from the discharge channel.
Fig.2 (b) shows one crater-like hole of several micrometers remained at center of grain.
The trace of rapid solidification of oxide melt can be clearly observed on this large grain surface around the center of the discharge hole.

The dark grains were Al, having a size distribution from a few to tens of microns.
The size and distribution of the Al grains and the Fe3O4 in the sample sintered at 700 o C were similar to those of the green sample, and no reaction product was observed.
With reference to the XRD results, it was apparent that the matrix, dark grains and white particles were FeO, Al and Al2O3, respectively.
It was noticeable that the Al grains disappeared and voids with size ~tens of microns were left in the FeO matrix.
The value of y was proportional to the number of Fe 2+ ions exchanged their sites with Al3+ ions.

It was observed that not only many chips were removed in front of the point by brittle fracture, but also that a substantial number of chips separated from the work-piece.
It is assumed that the grain acting as an indenter is subjected to a normal load.
Ceramics with very dense fine grains normally have high strength.
In the upper region of the cut, the main material removal mechanism was a simultaneous cutting of matrix and inclusion grains (transgranular).
In the lower region, the removal process was characterized by the removal of the binding matrix, followed by washing of the inclusion grains.