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Introduction It is technically important to solve problems on fatigue strength of metals containing various metallurgical discontinuities such as grain boundaries, inhomogeneous phase, nonmetallic inclusions and so on.
These studies suggest that the equations of the equivalent stress ratios based on the hypothesis of plastic adaptation are also applied to microscopic problems on fa-tigue strength of metals containing various metallurgical discontinuities, such as grain boundaries, phase inhomogeneties, nonmetallic inclusions, dispersed fine carbides and so on, presupposing that the effects of metallurgical discontinuities on fatigue strength of metals are reasonably characterized and pertinent mechanical parameters are introduced into the equation of the equivalent stress ratios.
Fatigue strength σw1 is regarded as the stress at which metallurgical micro-structure-dependent cracks (such as slip band cracks, grain boundary cracks, debonded inclusion cracks and so on) are unified into a mode I crack proper to fatigue.
A number of fatigue strength data of metals have been rearranged by diagraming relations between the equivalent stress ratios REQ and the notch root stress ranges ∆σNR .

The number of pores reduces and the size of pores increases obviously with the decrease of impulse frequency.
Lots of rough micro convex objects of layer surface are rubdown, and form plenty of abrasive grain and abrasive dust near wear scar.
Micro convex objects are abraded, bring plenty of abrasive grain and abrasive dust which are transferred to micropore holes or low-lying part of wear scar surface in dry friction movement.
Abrasive grains continue to concerned with friction, and have effect of mirco cutting to wear scar surface in friction processing, forming abrasive wear.

The bright fields on the images are WC grains, the dark areas cobalt and the bright gray phase are eta phase of Co.
Results and discussion Microstructural analyses Comparison of the as-sprayed and annealed coated samples shows that new phases has been produced in the previous amorphous area and that WC grains have been partly dissolved and mixed with the cobalt matrix to produce new crystalline and dendritic phases.
Likewise, decreased grain size and increase in porosity in the annealed microstructural properties compared to as-coated are observed.
Relatively large errors result from the lever rule applied and error propagation, so that ratio between the error in coating (~118 MPa) and an individual error in substrate (~10 MPa) are related by a factor , where Nsubs is the number of measurement points taken in the substrate.

For their high melting point, high thermal conductivity and excellent mechanical properties, it was demonstrated in a number of studies that showed ZrB2 and HfB2 ceramics could be best candidates to use in aerospace application, such as sharp wing leading edges, nose tips and so on[1, 2, 3].
Since the composites were not completely densified and the existing intergranular oxidation may weaken the grain boundary, and finally decrease the strength.
However, the vickers’ hardness is best for its grain particles size were smallest.
Basu, et al, Dynamic compression behavior of reactive spark plasma sintered ultrafine grained (Zr,Hf)B2-SiC composites, Ceram.

Murayama’s reagent attacks WC grains and roughens the substrate surface, thus, favoring the adhesion of the diamond coating by mechanical interlocking.
For the characterization, the scanning electron microscopy (SEM) is adopted to characterize the surface morphology, microstructure and grain size.
The slight shift from 1332cm-1 in wave number is considered to the presence of the residual compressive stress.
The SEM study shows highly crystallized diamond films, with the grain size of 4-5μm, is uniformly deposited on the substrate surface.

Since the original grain boundary structures remained in the oxide scales, the scale was considered to have inwardly grown by inward diffusion of oxidizer.
It was also found that a number of grains dropped off.
In contrast, at 800ppm of oxygen, a thin oxide film formed and no grain boundary attack was found.

Table 2 Orthogonal experimental results Experimental number Influence factor Experimental results Solution temperature /℃ Holding time /h HRC 1 520 6 12.48 2 520 7 12.52 3 520 8 12.95 4 530 6 15.70 5 530 7 15.73 6 530 8 15.00 7 540 6 18.52 8 540 7 20.83 9 540 8 17.92 HRC 37.95 46.70 46.43 49.10 57.27 45.87 R 9.68 1.68 Range analysis shows that, the order of primary and secondary of the degree for effect of two factors on hardness was solution temperature> holding time.
But when the holding time of 8h, the temperature was increased to 540 ℃, the eutectics further roughened, and roundness of the part of the organization deteriorates, while the size of the difference in between the grains becomes large.
However, when the holding time of 8h, the temperature was increased to 540 ℃, further roughened eutectic silicon, and wherein part of the eutectic silicon roundness deteriorates, while the difference in size between the eutectic silicon grains larger, the degree of uniformity of the particle declined.
At the same time of eutectic structure graining, tiny eutectics particles becomes smaller, or even disappear and the thick of eutectic structure or not fusing of plate-like eutectic structure is coarsening.

The electrical conductivity of SnO2 depends on the number of impurity atoms adsorbed from the environment by the surface of crystallites.
According to the authors, this is due to the increase in the concentration of the amorphous phase in the films after annealing forming the fine crystalline phase and having a developed grain boundary surface, which provides high gas-sensitivity.
The high gas-sensitivity of such film structures is due to their developed grain boundary surface.
According to the authors, for the specimens of this group after reaching the critical thickness and crystallization the further growth of the film is accompanied by grain densification.

The irradiation conditions were as follows: energy density in the electron beam ES = (40…90) J/cm2; electron-beam pulse duration t = 150 μs; the total number of applied pulses N = 15; pulse repetition frequency f = 0.3 s-1.
With increasing the energy density in the electron beam, the grain sizes in the surface layer of the material showed a decrease.
For instance, for ES = 40 J/cm2 the grain sizes varied in the interval (4…10) µm, whereas for ES = 70 J/cm2 it varied in the interval (2…5) µm.
The structural micro-level of the surface layer in the electron-beam irradiated hard alloy involves solidification cells that formed the sub-grain structure of the material (Fig. 5).

Number of passes employed was four to cover the thickness of 7 mm.
Fig. 1 Micro structures of weld and parent metals The microstructure of KC20WN revealed irregular grains with twins in the solution treated condition as shown in Fig. 1.
Equiaxed grains containing lath martensite was observed on the 15-5PH parent metal region as shown in Fig. 1d.
The heat affected zone on the 15-5PH contained recrystallized grains leading to higher hardness.