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This kind of particle can penetrate a surface and locate itself in the grain boundaries and other defects of materials.
Several types of sites have been found to trap hydrogen, such as grain boundaries, vacancies, voids, dislocations, etc.
Hydrogen frequently leads to the degradation of material characteristics, diffuses through the grain-boundary and locates itself in the lattices.
The hydrogen tries to diffuse into, via grain boundaries, for example, and cause it to fail.
The hydrogen concentration at the trap sites CT is: CT = θTNT (9) where ���� is the occupancy of the trap site and ���� is the number of trap sites per unit volume [32].

The effect of number of methylene, n, on the structure forming and the band gap magnitude has been studied.
The results demenstrate that the number of methylene has effect both on the forming of the layered structure and on the magnitude of the band gap.
When the number of the methylene, n is from Fig. 4 The images of the hybrids (C6H5CnH2nNH3)2PbI4, where (a) n=0,(b) n=1,(c) n=2. 0 to 1 and to 2, the crystal grains are from bar-shaped to blocks and to sheet-like.
So the difference of the interlayer distance should increase 2.415×2=4.830(Å) if the number of the methylene increase one.
The number of the methylene has obviously effect both on their layered structure forming and their values of the band gaps.

Shorter distance produces higher heat input and causes the material stringers to melted with the filler, while longer distance increases the number of porosity and prevents the formation of a complete fusion zone.
Torch distance porosity diameter n (number of porosity) weld area (mm2) porosity/ mm2 image measurement 18 0.063 147 60 3.35 0.124 41 0.231 13 Total 201 27 0.062 240 37 7.40 0.13 29 0.254 5 Total 274 36 0.049 260 39 7.69 0.126 37 0.273 3 Total 300 Duan, et al [15] reported several factors that may cause porosity defects during the welding process.
Also, a large number of porosity defects in the welded T-joint (Fig. 3) and small dimples on the fracture surfaces (Fig. 4) were observed.
This phenomenon is due to the partial melting of the grain boundaries, and the diffusion of alloying elements from solid phase to liquid phase during the welding process.

Thermo-temporal treatment of the melt leads to a favorable structure formation, decrease in its chemical and physical heterogeneity, reduction in size and number of shrinkage defects.
Structural ordering of the fluid is characterized by quantitative parameters: r1 – the most likely shortest distance and z1 – the number of nearest neighbors, as well as cluster sizes – by the correlation radii.
On this basis, a number of heats were poured into molds with reduced profitable extensions, which made it possible to increase the suitable alloy of steel at the first conversion by 2-3% [20-21].
For example, advanced high-carbon steel ingots are characterized by increased dispersibility of the carbide phase, the austenite grain size decrease and reduction of area of columnar crystals.

One of the factors is the number of loads, which is taken into account by introducing a separate multiplier as a function of the number of loads N.
The number of applications of repeated loads is 106 and more.
The limit number of loads n is usually n=100…200.
Ling et. al., Permanent Deformation Characteristics of Coarse Grained Subgrade Soils under Train-Induced Repeated Load.
Article Number 03010 [21] P.

Fe is mainly existed with impurities of FeAl3,T1,T2, and so on .When Fe content is slightly higher in the industrial pure aluminum and the content increases, the number, size of impurity phase will be also increased and aggregated distribution along the grain boundary.
They gathered at the grain boundaries and make condensate depression largen and refinement.
It also can change the form of Fe in aluminum alloys to reduce the needle-like grain, increase the spherical crystal[45].
Guan Ke-xiang et al.[46]have studied the rare earth industry to add aluminum and found that Ce with Fe and other impurities can product the high melting point intermetallic compounds in grain boundaries.
It can make rich-Fe impurity phase refinement and stabilize the grain boundary.

Furthermore, Finite Element (FE) analysis based on the experimental configuration was carried out to obtain the stress distribution on the contact surface, crack initiation location and number of cycles to the fretting fatigue failure were predicted based on the FE results.
In this paper, a circular arc dovetail attachment was designed and the tension fatigue experiment was also performed, the experiment results show a great fatigue performance and can satisfy the operating requirement for turbofan engine, furthermore, FE analysis of the experiment specimen was carried out, and the number of cycles to fretting fatigue was predicted based on the FE results as well.
TC4 alloy is a medium strength alloy which consists of α- and β-phase with a mean grain size of 10μm, the mechanical properties of this alloy are given in Table1.
For the convenience of analysing the variation of contact state at the edge of contact region under cyclic loads, the number of nodes is ordered regularly as shown in Fig. 2 (b).
The initial contact point on the tenon contact surface is node 8716, the node number increases from external to internal side of the contact region, a contact length of 128μm is concerned in this study based on the results of sliding distance from FE analysis.

The presence of boron nitride, BN, in the coating, which positively effected a reduction in the oxygen content in the molten alloys, resulted in an increase in the number of cases of impermissibly high nitrogen content (Table 1).
These precipitates appeared as clusters at the grain boundaries and small particles inside the grains (Fig. 5).
A visible effect of rolling was the refinement of the grains and precipitates present in the microstructure (Figs. 8b, 9b), and this effect was particularly large in the alloy deformed at a higher temperature (Fig. 9b).
Summary The results of the authors' own previous studies and those conducted in this work on evaluating the possibility of melting titanium alloys in vacuum induction furnaces equipped with metal and ceramic crucibles and coated ceramic crucibles have indicated that the material of the crucible, the material and means of applying the coating, and the number of melts carried out in the crucible dictate the purity of the alloys.
Despite their presence, these alloys can be plastically deformed under multipass hot-rolling processes that produce high overall deformation, which results in considerable refinement of the grains and precipitates present in the microstructure.

The desired final grain size in the product is 35mm.
The optimum ram velocity for achieving the above grain size is found to be 160mm/s when billet temperature is 1080oC.
The measured average grain size was 38mm, very close to the designed value.
This is a first of its kind dual purpose system in the country and has been applied for a number of applications.
Acknowledgements This paper is written based on the innovative ideas and consistent efforts of a large number of dedicated scientists at IGCAR, mostly from the Metallurgy and Materials Group.

A large number of small coherent Zn-Mg clusters are formed during natural aging in the Al-Mg-Zn alloys, which are transformed to the larger incoherent meta-stable precipitates during subsequent artificial aging.
The total number of counts in each spectrum was about 106.
The critical strain appears to be independent on the number density and the size of the T’-phase, while the type of precipitates seems to have a marked influence on the onset for serrated flow.
These changes in the mean positron lifetime illustrate that semi-coherent or incoherent precipitates are transformed from coherent solute clusters and the trapping site of positron changes from the vacancy in coherent cluster to the misfit dislocations or the grain boundary-type interface, as reported [11].
A large number of small coherent Zn-Mg clusters are formed during natural aging for the Al-Mg-Zn alloys, which are transformed to the larger incoherent meta-stable precipitates during subsequent artificial aging. 3.