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To date there have been many experimental investigations on the influence of route and number of passes on texture formation in ECAP [3-5].
The character of the crystallographic texture depends on the chosen pressing route and the number of passes.
The most wide spread theories, used for the analysis of texture formation processes in plastic deformation, are the Taylor model (identical deformation of grains) [7], Sachs model (identical stresses in grains) [8], and various versions of self-consistent viscous plastic (VPSC) models, which take into account the interaction of grains with each other [9,10].
At present, the conclusions on the role of the number of passes and the choice of the ECAP route are ambiguous.
Influence of Route and Number of Passes.

The effect of the reaction pressure on the grain size and crystalline morphology of CrN powders were characterized by transmission electron microscopy and X-ray diffraction.
The results indicate that high purity CrN powders with grain size of 40-60 nm can be obtained through the aminolysis at temperature of 650℃ and pressure of 0.6MPa for 2 hours.
This method produces high purity CrN nanopowders with grain sizes of 40-60 nanometers under only 650°C temperature, 0.6 MPa pressure, aminolysising for 2-4 hours.
Average grain size is 15 nanometer.
It appears that the higher the temperature the larger the grain size, and the increase of the grain size is faster with the increase of temperature.

Nearly all properties possessed by ceramic polycrystals are essentially dependent on the grain size.
This process is usually accompanied with tenfold or even higher grain growth.
It follows that the grain size is of utmost importance in the case of nanometric powders.
In other words, a number of grains surrounding a pore must be smaller than the so called critical coordination number, which is dependent on dihedral angle measured through the gaseous phase [6,7].
The number of such layers along the unit length depends on the crystallite size (~8 nm) and the packing density of the system (~40 %).

Diamond powders with the average grain size of 0.5 µm mixed with various concentrations of SiC powder of 175µm average grain size were employed.
However, the diamond grain size changed considerably with the concentrations of SiC powder in the seeding diamond suspensions.
The diamond grain size of substrates seeded without SiC powder is much smaller (1-3µm) and more uniform as compared to the diamond grain size of substrates seeded with mixtures of diamond and SiC powder with the range of 1-3µm (Figure 1a).
With the increasing number and much bigger size of SiC powder making diamond powder more difficult to seed reducing the diamond nucleation rate and also resulting in lower mechanical interlocking which reduced the adhesion strength.
With larger diamond grain size produced, it is very suitable for abrasive applications such as grinding.

When it was increased by varying current, tensile strength of the weld metal increased even if more primary ferrite and wider columnar grains were observed.
It shows that impact toughness of multipass weld metal shows the best relationship with the length of coarse grained region.
Relationship between heat input and length of coarse grained region is also shown in Fig. 5.
It shows no clear relationship because the length is strongly influenced by the number and sequence of deposition in multipass welding.
Variation of impact absorbed energy as a function of the length of (a) fine grained, (b) coarse grained region, and (c) relationship between heat input and the length of coarse grained region 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 Impact absorved energy at 0 o C (J) Length of fine grained region (mm) (a) 0 10 20 30 40 50 60 0 1 2 3 4 Length of coarse grained region (mm) Heat input (kJ/cm) (c) 0 1 2 3 4 0 50 100 150 200 Impact absorved energy at 0 o C (J) Length of coarse grained region (mm) (b)

(a), the samples were compressed in the axial direction of the crystal grains, lots of raw grains were elongated along a radial direction.
At the same time a large number of sub-grain boundaries are formed at the original grain, that is, dynamic recrystallization began to appear.
Deformation original elongated grains are surrounded by the dynamic recrystallization grains.
As the deformation temperature rises, the number of the original grain with large deformation decreased, while the dynamic fine equiaxed recrystallized grains became more and more, which indicates that the volume fraction of dynamic recrystallization is also constantly increasing with temperature increases.
A few of initial grain with large deformation can be seen from the Fig.

A number of ships are wholly constructed of composite sandwich consisting of foam cores and glass or carbon fiber reinforced skins.
Such improvement is related to the decreased mobility of dislocations in smaller grains, mainly due to dislocation pile-ups at grain boundaries acting as barriers, thus resulting in an increased yield stress.
The decrease in grain sizes incidentally raises the volume fraction of grain boundaries, which are overwhelmingly high angle, high energy with low coherence, and drastically decreases the overall material ductility [7].
In the following, we indicate the series number (1–10) with the letter “ A ” for steel-side impact samples and “ B” for composite-side impact samples.
In: Takaki S, Maki T, editors, International symposium on ultrafine grained steels.

The material was studied in coarse-grained (CG) and UFG states.
The number of passes was 4 or 8.
As a result of ECAP the elongated ultrafine-grained structure was formed (fig.2 a, b).
All TEM images show that the generated UFG structure includes a significant number of dislocations.
A greater number of small particles is located in the places of accumulation of dislocations.

The number of cells within a cell block and the cell block width decrease monotonically with increasing strain.
The number of the latter is significantly higher (about 2-5 in rolling) than the number of original grain boundaries, depending on the initial grain size [8].
For each grain on average a number of 3-5 domains have been observed [10]. and it is tentatively suggested that this macroscopic break up may contribute to later grain break-up into specific texture components [10].
To obtain a strain of this order and higher a number of alternative processes have been developed.
This phenomenon has been studied recently in aluminium and aluminium alloys of different initial grain sizes and a number of criteria has been suggested to decide whether continuous recrystallization takes place [38-40].

This is because the grains in NZ and TMAZ have realized recrystallization.
The smaller the grain size is, the smaller the grain boundary area is, and the lower the energy needs to overcome the grain boundary, the easier to merger the grains.
At the same time, the grains have been broken in FSW, and the grains stored too much distortion energy and gathered a large number of dislocation, energy has been saved within the grains, so the energy threshold of grain growth reduced, as a result, it is easy to merger the grains.
These aggregated particles reduce the number of θ phase in surrounding matrices, and weaken the intensity of HAZ.
After PWHT, there is no obvious evidence of θ phase changing in number.