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Hence, plastic deformation processing can be a possible method for grain refinement of metallic materials.
In recent years, severe plastic deformation (SPD) process was developed by Russian scientists as a new method of manufacturing bulk specimens having ultrafine grained (UFG) microstructure [3-7].
It is known that grain refinement by SPD can improve the physical and mechanical properties of metals and alloys.
The numbers of initial volume elements are 3552 for workpiece and 82584 for die.
Due to the deformation induced heat release, the temperature rise during the ECAP with high ram speed can be as large as to raise the workpiece temperature above the recovery temperature or the grain growth temperature.

Compared with other forming process, the HIP method has high shape variability, high degree of densification to near theoretical density, simple technique and low cost, isotropic, but there is relatively coarse grain size, need other treatment process defects.
It can dissolve a lot of alloy elements, make the alloy has excellent solid solution strengthening, precipitation strengthening and grain boundary strengthening effect [9].
Table 1 Chemical composition of FGH97 P/M super alloy（wt%） C Cr Co Al Ti W Mo Nb Hf B Zr Mg Ce Ni 0.02~ 0.06 8.0~ 10.0 15.0~ 16.5 4.8~ 5.3 1.6~ 2.0 5.2~ 5.9 3.5~ 4.2 2.4~ 2.8 0.1~ 0.4 ≤0.015 ≤0.015 ≤0.02 ≤0.01 bal From the analysis of chemical composition and mechanical properties: alloy strengthening includes solution strengthening, precipitation strengthening and grain boundary strengthening.
Appropriate amount of Hf contribute to the elimination of the prior particle boundary (PPB), when the Hf content is over 0.6%, it will lead to the prior particle boundary appears again in the alloy; (5) Harmful element S in alloy can react with Hf to form a stable compound, which helps to reduce the alloy grain boundary brittleness.
In the process of rough machining, we can choose larger removal amount to reduce the tool path number.

While in MgAl2O4-Y3Al5O12 ceramic composites, the number of intergranular and intracrystalline pores obviously declined.
And a high-temperature continuum formed uniformly around the spinel grain boundary, forming an interlocking structure with the spinel grain.
This stabilized the grain boundary of spinel.
F. and Kagawa, Y., Effect of grain boundary microcracking on the light transmittance of sintered transparent MgAl2O4.
Bratton, Sintering and Grain-Growth Kinetics of MgAl2O4.

In most analysed cases, the microstructure of the solidified melt regions is dominated by amorphous and/or ultra-fine-grained phases.
The selected area diffraction patterns (SAED/TEM) show the dominance of ultra-fine-grained regions involving amorphous phases, both with chemical compositions close to Zr50Fe25Cr19Ni7.
This is confirmed by structural observations in the SEM and TEM scale, documenting the presence of amorphous and/or ultra-fine-grained phases with a strongly differentiated range of chemical compositions.
The nano-grained or amorphous volumes make a scattering in a small angle region (small angle scattering) giving rise to characteristic humps in the background.
Significant changes in the number of individual phases depending on the distance from the interface were also observed (measurements were made in steps of 0.1 mm, with a diameter of the beam on the sample of approx. 0.2 mm).

The first two of the dispersoids were in majority, followed by the middle two and a small number of the fifth.
Introduction It has been reported that submicron /hundreds of nanometer particles in Al-Mg alloy were important to the hot ductility of the alloy since these fine and stable particles can be used to pin grain or subgrain boundaries, increase the recrystallization temperature [1], and improve the strength and ductility [2-4].
Fig. 9(a) presented an image of another E-particle with three stripes (marked by white lines) visible inside the grain.
The particles are present either at the grain boundaries or in the grain interior.
As with the case of the conventional grain boundary, the formation of the twin must be energetically favored, i.e., the change of the boundary free energy due to the formation of the twin boundary must be minimum.

For most applications, the amount of information which is possible to extract depends on the nature of the sample microstructure (crystallinity, structure imperfections, c rystallite size, texture), the complexity of the crystal structure (number of atoms in the asymmetric unit cell, unit cell volume) and the quality of the experimental data (instrument performances, counting statistics). 2.
The analysis of macro-stress by powder diffraction analysis gives new impulses to understand the elastic and plastic grain interaction in massive specimens, in particular because new materials of specific grain morphologies can be prepared (e.g. thin films).
Analysis of gradients of stress near interfaces and grain boundaries will become possible.
Reviewing the seven editions of the EPDIC proceedings, the ratios of the numbers of papers on developments in the methods and techniques of powder diffraction and those on applications of powderdiffraction methods to specific classes of materials are found to be I, 0.7, 0.S, 1, 0.9, 0.S, and 0.7.
(Without this special chapter the ratio of the numbers of papers on methods and instruments and those on applications would have been 0.S.)

Sample Number Liquid Carrier Stabilizing layers Density, g.cm3 (20o C) Saturation magnetization (M at Hmax) [G] 1 MF/C6H13OH, Fe3O4 Oleic acid (double) 0.061 261 2 MF/H2O, Fe3O4 Lauric acid (double) 0.024 100 3 MF/TR-30, Fe3O4 Oleic acid (double) 0.057 244 4 MF/H2O, Fe3O4 Dodecylbenzenesulphonic acid (double) 1.268 248 Once the nanoparticles are deposited on the first PVC foil, a second foil is stacked on the top, to create a bilayer "sandwich" containing films of Fe3O4 nanoparticles at the interfaces of the matrix foils.
A probable reason is that in these samples it was succeeded to keep the dimensions of the grains to approximately 7 nm.
The grain size of the nanoparticles did not increase; one can see this from the microscopic analysis carried out.
Table 3 Mechanical properties Sample Number Young Modulus (GPa) Dynamic Mechanical Analyzer Universal Mechanical Testing PVC USW 1.59 1.56 1a 1.46 1.37 1b 1.29 1.29 1c 1.25 1.1 1d 1.32 1.43 1e 1.25 1.27 Summary This research is aimed at introducing a new method for manufacturing polymer nanocomposites with magnetic properties.
Wagner, Influence of grain size and oxidation on the magnetic properties of nanostructured Fe and Ni, NanoStructured Materials 9 (1997) 523-526.

Of course, as the possibility to obtain diamond and DLC materials with average grain size in the nanoscopic range, going from 102 to 10 nm and even smaller [7-8], a series of experiments are currently dedicated to the body response to the size decreasing.
PLD technique with high energy pulsed lasers is known to produce a number of different carbon forms, going from DLC to fullerene and nanotubes, generating carbon structures as the result of the high energy transferring process occurring to C-atoms and C-clusters both as neutrals and as ionic species.
Using the dimension of the diamond unit cell (a = 0.3567 nm), in which each atom is tetrahedrally bonded with four neighboring atoms, the number of unit cells composing the average volume of the observed structures reported in Fig. 2b is 1.4x10 9 and the corresponding number of contained Catoms is 1.6x10 10 .
The structures reported in Fig. 2a have volumes about three-order magnitude smaller. 100 200 300 400 500 600 700 800 0 5 10 15 20 25 30 35 (b) d=14 cm Crystals per 100µm 2 Grain size (nm) 20 40 60 80 100 0 500 1000 1500 2000 2500 3000 (a) d=8 cm Crystals per 100 µm2 Grain size (nm) Fig. 3: Histograms of the crystal edge size for the two samples of Fig 2.

From the XRD patterns in Fig. 1b, it is also observed that the diffraction peaks slightly shift to a lower angle with the increase of x value, which implies that the unit cell volume gradually increases due to a larger effective radius of (Sr0.2Ca0.8)2+ (1.148Å) than that of (Li0.5Nd0.5)2+ (1.014Å) at the same coordination number.
Because the slight difference of effective average ionic radius between (Sr0.2Ca0.8)2+ (1.148Å) and (Li0.5Nd0.5)2+ (1.014Å) ions at the same coordination number, this leads to the decrease of the lattice parameters of b and c axes, while the lattice parameter of a-axis remains nearly the constant.
From SEM images of Fig. 2a–d, the grain size of CSN ceramics decrease from approximately 8μm to approximately 4μm with increasing Ca0.8Sr0.2TiO3 content.
Thus, the doping Ca0.8Sr0.2TiO3 in CSN ceramics can lead to the reducing grain size of CSN ceramics at the same sintering temperature.
From the SEM images of CSN20 sample sintered in the temperature range of 1250–1350˚C, as shown in Fig. 2e–g, it is found that the average grain size and the number of large pores increase with the sintering temperatures.

It is a special form of microstructural influenced corrosion, whereby the grain boundary “region” of the alloy is electrochemically different to the bulk or adjacent alloy microstructure [7].
This phenomenon had involve localized corrosion at grain boundaries due to unstable carbide by which it can result in rapid through-wall corrosion and severe compromise of the material’s integrity [8].
The presence of carbides on the grain boundaries has resultant to low level of chromium at which it become a barrier to the formation of passive layer in the process of reducing corrosion [9].
The total acid number in the region of heavy vacuum gas oil (HVGO) was higher than the value of reduced crude oil (1.2mgKOH/g).
The values of total acid number (TAN) of liquid residue in the transfer line and of NAC rapid above 200°C to form an oil soluble iron napthenate and severe corrosion occurs [4].