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The microstructure was formed by equiaxed grains of alfa-Al with Si as spheroidaltype particles in the intergranular region and inside the grains.
These two regions were not observed for large particles because they solidified under lower undercooling and therefore the number of nucleation sites is large, such as observed in the figures 1d-e that shows equiaxed dendritic microstructure.
The figures 3c-e (magnifications of regions B, C and D in Fig. 3a) shows that the microstructures in those regions consisted of α-Al equiaxed grains and Si particles.
The average grain size in each region was ~5 µm (region B), ~19 µm (region C), and ~25 µm (region D).
The spray formed deposit showed α-Al equiaxed grains and Si particulates.

The specimen having a defect was rejected to the SP tests regardless of the number and size of defects.
Their grain sizes were very similar and estimated to be 20-40µm.
These grain boundary precipitates were identified as M6C and M2C-types carbides by X-ray diffraction (XRD) analyses.
The cavities and microcracks were also formed along the grain boundaries of the aged steel.
The scanning electron microscope (SEM) observation of the fractured specimens revealed that some cracking seemed to initiate at large grain boundary carbides and they passed through grain interiors.

In some cases, it is necessary to limit the content of impurities that promote grain growth upon heating.
For example, in some magnesium alloys, modification results in grain growth.
Pre-eutectoid ferrite is formed at the boundaries of dendritic grains.
There are no non-metallic inclusions inside ferrite grains.
Figures show a large number of non-metallic inclusions (marked with blue arrows) and pores (marked with a red arrow), which are the cause of brittle constituent in the fracture.

Nowadays, the materials of micro-cutting tool mainly are high performance high-speed steel, fine grain and ultra-fine grain cemented carbide, PCBN, PCD and Monocrystalline diamond, etc.
With regard to the widely using stainless steel 1Cr18Ni9Ti, three kinds of tool materials were selected: superb quality of high-speed steel M42, cemented carbide YG8 and ultra-fine grain cemented carbide XF30.
In contrast, XF30 had the best resistant to wear and adhesive because of its higher hardness, fine grain, and uniform distribution.
But when the velocity increased to a critical value, the larger area of the contact zone and the large number of the heat created in friction aggravated the effect of adhesive.
For XF30 (Fig.5b), few flake of grain happened, from the picture could found craze on the grain, that caused the crush of grain and resulted abrasive wear.

Recently, increasing numbers of studies investigate stone grinding and polishing with diamond abrasive tools [10-11], but they focus mainly on the machining process itself and the optimization of operating parameters rather than the removal mechanisms for stone materials.
For investigating the fracture tendency of brittle materials in grinding, a relevant parameter to consider is the average normal force exerted on each diamond grain [12], which is related to the maximum grain depth of cut (also referred as undeformed chip thickness) taken, on the average, by an abrasive grain as it passes through the cutting zone [13].
Actually, many previous qualitative studies related to the wear of diamond segments indicated that an excessive load on individual diamond grains causes excessive fracture, thereby making the cut less efficient.
Similarly, a load that is too light causes only attrition and dulling of the grains, leading to sawblade glazing and poor cutting.
Coupled with the measurements of cutting forces, the different removal mechanisms for granite under different grinding conditions were found to be closely related to the average normal force exerted on each diamond grit, which is mainly governed by the maximum grain depth of cut taken by an abrasive grit.

Elongated β-Si3N4 grains are present in the Si3N4- TiC0.5N0.5 composites, as shown in Fig. 1.a.
The present investigation indicates that the TiC0.5N0.5 as well as TiN particles influence the preferred orientation of the β-Si3N4 grains.
This directly results in an anisotropy of the fracture toughness since the crack resistance is larger when the crack propagates perpendicular to the elongated β-Si3N4 grains.
The elongated β-Si3N4 grains have a preferred orientation after hot-pressing at 1650°C, resulting in a toughness anisotropy.
Acknowledgement This work was supported by the Flemish Institute for the Promotion of Scientific and Technological Research in Industry (IWT) under contract number GBOU-IWT-010071.

Furthermore, Fig.9 (c) shows that the path turn of corrosion fatigue crack of CFB/M is apparent and the number of branches increases significantly.
In the CFB/M steel, the lower bainites precipitating beforehand in the austensite grains separate the austenite grains and cause refinement of martensite plate. while the thin filmy retained austenite forms in the prior austenite grain boundaries, in the lath bundle boundaries of the lower bainite and martensite and in sub-lath boundaries [7].
Meantime, the fine microstructure increases phase boundaries and grain boundaries obviously that raises the intensity of hydrogen traps.
In addition, the large effectual grain size reduces the intensity of hydrogen traps and increases hydrogen brittle sensitivity.
The retained austenite films existing in phase boundaries and grain boundaries in the CFB/M steel could reduce the effectual grain size and make the tip of corrosion fatigue crack blunt. 4.

In the analysis of fatigue, a clear distinction is usually introduced between high-cycle and low-cycle fatigue problems, depending on the number of cycles typically leading to the failure of the considered component/structure.
A boundary cohesive grain element formulation for modelling intergranular microfracture in polycrystalline brittle materials.
An enhanced grain-boundary framework for computational homogenization and micro-cracking simulations of polycrystalline materials.
A grain boundary formulation for crystal plasticity.
Grain-boundary modelling of hydrogen assisted intergranular stress corrosion cracking.

According to DLVO theory, an increase in Ca2+ concentration increases the deposition of particles onto grain surfaces as the electrostatic double layer repulsion between particles and grains is expected to decline due to the compressed electric double layer [29].
Darlington et al found that the transport of aluminum NPs in Lakeland sand decreased as the number of PV increased [13].
Figure 5 shows direct evidence about the distribution of Zn/ZnO NPs in soil grains.
Acknowledgment This material is based upon work supported by the National Science Foundation and the Environmental Protection Agency under Cooperative Agreement Number DBI-0830117.
The authors also acknowledge the USDA grant numbers 2008-38422-19138 and 2011-38422-30835 and the NSF Grant # CHE-0840525.

They can also recombine or disappear on fix sinks (dislocations, surfaces or grain boundaries).
In order to limit the number of parameters Bi niE , extrapolation can be used for large clusters.
The reaction rate for the elimination of defects on surfaces or grain boundaries has been given by Bullough et al [13].
The large number of parameters entering in this kind of modeling is often an object of criticisms.
Figure 4: Evolution of the stationary number density of interstitial loops of radius larger than 1nm in normal iron.