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And there were no traces of He bubble at grain boundary.
As a result, crack didn't occur because He bubble didn't grow at the grain boundary of low alloy steel by heat cycle of repair welding.
Number of porosities with low alloy steel was much than one of weld metal.
It was assumed that there cracks were induced by He bubble which grow at grain boundary.
Heinisch, The effects of grain boundary structure on binding of He in Fe, J.

Especially, nano-sized grains are easily obtained, so that the deposited particle sizes and the contact area between the ion and electron conducting particles of the electrode or electrolyte could be easily controlled.
(4) where, nt is number of particles per unit volume, nel and nio are the fraction number of electron and ion conducting particles, which are related with to the volumetric fraction of electron conducing particles (φ).
Z is the total average particle coordination number in electrode equal to 6.
For calculation in this work, the typical grain size of 20 nm [3] and the typical thickness of 0.7 µm [16] were used.
Oshima, Estimation of the co – ordination number in a multi – component mixture of spheres, Powder.

In the production of self-compacting concretes, it may be necessary to ensure a number of conflicting factors that contribute to the non-segregation of the mixture and its high-quality compaction.
In this case, the theoretical increase in the density of the volume-centered cubic packing of the multicomponent system will be 8.09%, and the coordination number will increase to 8%.
For example, a study of the microstructure of a cement matrix of fine-grained concrete containing carbon nanofibers in an amount of only 25 g / m3 showed its very high density (Fig. 2).
Microstructure of the cement matrix of fine-grained concrete (drawings by Prof.
On the surface of the concrete mixture, uniformly distributed grains of coarse aggregate are observed, confirming the above-mentioned properties (Fig. 7).

It can be seen that the grain size decreases as indium content increases, which is in agreement with previous studies that indium is a grain refiner for zinc[38].
Increasing alloying concentration tend to increase the amount of surface active sites because it generally causes increasing inhomogeniety of the crystal structure, more displacement sites, vacant sites and misaligned regions such as grain boundaries.
The fact that grain size decreases with indium concentrations is an indication that the amount of irregular lattice sites is increased at the density of grain boundaries, where the atoms are poorly aligned, per area is increased.
Small amount of indium addition results in a reduction of grain size or number of grains per unit area. 2.
The exchange current for zinc reaction increase with addition of indium because the surface becomes more active with addition of small amount of indium as the number of active sites increases with indium. 5.

During the milling, by repeated fracture and cold welding of the powder particles, new surfaces and grain refinement are generated.
The gas pressure during milling was measured by a strain gauge type transducer, and the instant number of absorbed N atoms per Hf, HfRTn PVn ∆= 2 was evaluated from the pressure change ∆P (Pi = 0.20MPa), the gas constant R, the temperature T and the number of Hf moles nHf.
After 1h of milling, only Hf2Fe reflections are observed, but with a considerable broadening associated with the grain refinement.
These interstices are then well adapted to allocate absorbed N atoms in a number of 0.25 per Hf atom, giving rise to the η structure.
In this way, the kinetic acceleration can be related with the increment in the number of octahedral interstitial per Hf atom, from 0.25 to 1.

The second has been to use a phenomenological approach pioneered by Kocks and Mecking [5] to discuss the concurrent processes of dislocation accumulation and annihilation in the pure matrix material and to add or modify terms to describe the role of additional features such as grain size, solute, hard particles etc
Microstructural Aspects One approach to optimizing the microstructure is to consider the various elements of the microstructure (e.g. grain boundaries, shearable particles, hard particles, dispersoids or inclusions, solute atoms) and ask first how they may change the rate of dislocation accumulation or annihilation and over what range of strain or temperature.
In precipitation hardening reactions we need to consider the evolution of the size and volume fraction of particles but also the amount of solute remaining in solution, precipitation events at grain boundaries or at dispersoids, i.e. several microstructural elements may act in concert to generate the overall macroscopic response.
Solute Elements In the very comprehensive review by Neuhauser and Schwink [8], the authors deal with the superposition of solute hardening and work hardening and demonstrate that in a number of systems a regime of linear additivity exists while in contrast when solutes are mobile and interact strongly with dislocations, a number of more complex situations arise.
Summary If we consider the schematic diagram in Fig. 2 we can see that it provides a simplified way of rationalizing a number of microstructural elements and thus an initial step toward microstructural design.

The wavelength used as a standard value for zero stress was obtained either by averaging over a large number of spectra from well-annealed samples or from a powder sample.
Unfortunately, a simplifying assumption has to be made that the crystallographic distribution of grains or glass clusters is random.
If the probed volume from which the luminescence band originates is sufficiently large to probe a statistically meaningful number of grains or clusters, elastic anisotropy of the material can be neglected and an average stress value, σav, can be defined which is calculated from an average line shift, ∆λav, as follows: ∆λav=Πσav (2) Note that in eq.(2), as an additional simplification, the residual stress is considered to be equi-dimensional (e.g., hydrostatic if three dimensional) within the probed volume, the piezo-spectroscopic coefficient, Π, and σav being merely the traces of the respective tensors.
Mott's rule can be expressed as follows: nN−=Κ 8 (3) where KN is the coordination number and n is the number of electrons taking part in the chemical bond.
The number of valence electrons for Si, O and N are 4, 6 and 5, respectively.

The resultant microstructure of the ingot is columnar grains with a central equiaxed portion.
The fineness of the equiaxed particles or number of particles or dendrites depends on the number of nuclei present from which the equiaxed zone can start to form.
Results The principal objective of the cooling slope vibration was to increase the number of nuclei available by fragmentation or stimulation of free nucleation in the liquid.
For an ingot produced with slope vibration, the numbers of aAl particles per mm2 ranged from about 175 particles /mm2 to 130 particles /mm2 and the grain size varied from ~74 mm to ~88 mm.
The number of aAl particles per unit area is higher in the ingots produced with slope vibration than without vibration by about 40 particles /mm2.

In this method, a grain of the tool traces double trochoidal trajectory.
The difference of the polishing traces was quantified by calculating the number of white pixels in the binary images.
Polishing trace differences depending on the lighting direction Postion number Postion number Postion number α＝45° α＝90° α＝0° Polishing trace area pixel Polishing trace area pixel Polishing trace area pixel Fig. 5.
Relation between lighting direction and polishing trace area In vibration finished surfaces, as circular trace patterns of grains are crossing mutually, the number of shorter hairlines increases, and the directions of them become random.
PCA involves a mathematical procedure that transforms a number of possibly correlated variables into a smaller number of uncorrelated variables called principal components.

Crevice corrosion (CC) was investigated for a number of selected corrosion resistant alloys in natural seawater containing microorganisms for up to 18 months under stagnant conditions.
Interestingly, grain structures were observed at the crevice former boundaries on 316L exposed to NSW (Fig 3.c).
(c) 316L showing grain structures and localized attack and (d) pitting concentrated at the outside edges of the crevice former).