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The Ni-P coatings are space filling, and its non-crystal lacking the sensitive grains boundary for corrosion reaction, so it has very good corrosion resistant.
The nickel is face-centre cubic structure and coordination number 12, the lattice parameter A= 0.1352 nm.
If it had non-intact face-centred cubic structure, it would be the same as liquid-like structure-non-crystal, because the grains size of Ni-P is very small.
The low phosphor alloys (P≤3%) is crystal structure, which is a super-saturation solid solution; on the contrary, the high phosphor alloys (P≥8%) is non-crystal; when the phosphor alloys between 3%-8% are mixture with two grains.
(3) The mechanism of corrosion resistant had come from blocking off the circuit for the electrochemical reaction in galvanic couples, and the amorphous structure crystal of Ni-P coatings had not sensitive grains boundary for corrosion reaction.

However, this requires a strong probabilistic method for the determination of grain orientations in the absence of crystallographic texture synonymous with random crystallographic orientation of the grains.
On the contrary, when the width of the strut is decreased the reduction in constraint is promoted by the low number of grains of harder orientation and the apparition of softer zones, characterised by a stress raiser area, is privileged.
Thus, the material behaviour of one or two grains may have a significant impact on the global behaviour of the entire strut.
Fig.15: Number of cycles to failure versus the stent expansion diameter for both geometries.
It should be noted that the proposed approach does not consider the mechanical size effect on grain plastic deformation and fatigue life duration.

By reducing the grain size of Mg to nanocrystalline dimensions, the H-sorption kinetics are accelerated substantially [6-8].
The estimated average coherent grain size obtained from the CMWP method is 10 nm for the BM nanocrystalline MgH2, while it is 9 nm for the alloy milled with the catalyst, indicating that Nb2O5 has only a slight effect on the final grain size value.
Now let us consider a powder agglomerate containing large number of grains following a log-normal size distribution: [ ]( )22 2/)m/Rln(exp R 1 2 1 )R(f σ − πσ = where the microstructure is characterized by the variance (σ) and median (m) of the distribution.
Introducing the variation of grain size, the sorption curves show significant differences.
The grain and particle size reduction decrease the Hdesorption temperature.

The volume fraction of intermetallics increases with the increase of strontium addition and a grain boundary interphase network was observed in alloys AJ42 and AJ43, as shown in Fig. 1a.
It is apparent that a band structure of interphases with dark contrast instead of grain boundary network shown in as cast microstructure is arranged approximately parallel to the extrusion direction.
In the specimens of non Al containing alloys studied after creep test under the same condition, (e) Ordered arrangement Dislocation wall (d) (c) 011 -0 (b) (a) (b) (a) numbers of tiny plate-shaped particles parallel to basal and pinning of dislocations by the particles were observed, as shown in Fig. 4c, TEM micrographs taken from alloy N2 after creep test with the incident beam direction [0001].
Pile-ups of dislocations against grain boundaries and the formation of dislocation walls are shown in Fig. 4d and 4e, respectively. 4.
With the increase of Sr addition, a continuous network of intermetallics at grain boundaries forms and the creep properties is significantly improved.

The measured grain diameter (STM and XRD) confirms that the grain size is less than 12 nm, and the (220) preferred orientation was disturbed but not destructed.
Higher hardness is the result of small grain size because the volume of grain boundary is significant if TiN is deposited as thin film on the substrate.
A number of PVD processing techniques (evaporation or sputtering) are currently available to prepare TiN thin films as NsM deposited on different substrates [3].
The lateral grain diameter of about 10 nm was observed from STM results.
The grain size estimated from XRD (220) peak (Scherrer equation -vertical dimension of grains [12]) for all samples was less than 12 nm, i.e. the crystals are nanometer sized.

Here, Zr was added as a grain refiner.
The microstructures all consist of approximately equiaxed α-Mg dendrites and abundant intermetallic compounds distribute along the grain boundaries or inside the grains.
An apparent refinement of the microstructure can be observed with the increasing pressure, including the grains, grain boundaries and intermetallic compounds.
From Fig. 2, it can be seen that a small number of granular I-phases (circled in yellow) appear in the α-Mg matrix when the pressure is not applied (Fig. 2 a).
Generally, the YS of alloys is mainly influenced by the grain size.

The main advantage of the use of energy dispersive neutron diffraction is that it allows the study of many crystal families, phases, and sample directions using a single experimental setup and the strains in a large number of crystallites are measured simultaneously.
In this approximation the influence of interphase or intergranular stresses on the mean strain mean RD<  is neglected, because mean RD<  is calculated over the volume containing large number of grains belonging to both phases and having different orientations.
The most important result concerns the region of deformation, where the relaxation of elastic strains in some groups of ferritic grains (corresponding to reflections 211, 310 and 200) was observed, while the lattice stress for the grains corresponding to 110 reflection is stable until sample fracture.
This phenomenon can be connected with initiation of damage process in the ferritic grains having specific orientations.
It was found, that close to sample fracture, the elastic stresses do not relax and even arise for all groups of austenitic grains.

The substitution of Cu for Ni leads to a significant refinement of the grains of the as-cast alloys without changing the major phase Mg2Ni.
The substitution of Cu for Ni gives rise to a significant refinement of the grains without changing the morphology of the alloys.
The crystal defects in the as-spun alloy, stacking faults (denoted as A), twin-grain boundaries (denoted as B), and dislocations (denoted as C) as well as sub-grain boundaries (denoted as D) created by the melt spinning, can clearly be seen in Fig. 6.
The large number of interfaces and grain boundaries available in the nanocrystalline materials provide easy pathways for hydrogen diffusion and accelerate the hydrogen absorbing/desorbing process [8].
Orimo and Fujii [9] found that the maximum hydrogen Fig. 6 The crystal defects in the as-spun Cu2 alloy taken by HRTEM: (a) Stacking faults, (b) Twin-grain boundary, (c) Dislocations, sub-grain boundary and twin-grain boundary concentrations existed in grain boundary region and amorphous region.

A similar behavior is noticed when Péclet number is increased to 25 and then to 50.
We clearly see that the cumulative number of desorbed particles increases with Péclet number.
Figure 8 - Cumulative mobilized particle density as a function of Péclet number.
Johnson, “Role of grain-to-grain contacts on profiles of retained colloids in porous media in the presence of an energy barrier to deposition,” Environ.
Johnson, “Role of grain-to-grain contacts on profiles of retained colloids in porous media in the presence of an energy barrier to deposition,” Environ.

Lower heat input caused smaller grains and narrower welds.
Orientation mapping of the base material and the three weldments The BM microstructure exhibits equiaxed grains with an average grain size of 11.65 µm ± 6.1 µm.
With a welding speed of 3 m/min the microstructure exhibits also equiaxed grains but with a larger average grain size up to 28.67 µm ± 11.3 µm.
The dendritic grains are adjacent to the BM while the equiaxed grains are in the center of the fusion zone.
At higher welding speed the cooling rate increases causing a decrease in the grain size.