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There are many studies on the formation of sub grain and fine grain size to less than 1 µm (ultra fine grain) which explain the formation of fine grain.
The shear band are clearer and most dense at higher number of ECAP passed, see in Figure 1 (d) and (e).
According to reference [1, 2] this phenomenon is due to which dislocations which is increased with increasing number of pass (Fig. 2 (b) and (e)).
Heat up temperature take the same visible difference in the growth of the grain size after ECAP with different number of pass.
For a larger number of pass, the deformation energy received by metal increase so the heat energy will produce more recrystallization [1, 2].

The strain is calculated as εeq = 2π·r·n/(t·√3), where r, n and t are the distance from the torsion axes, the number of applied revolutions and the mean thickness of the sample, respectively.
Fig. 3a and 3b show that the fine-grained microstructure after HPT was completely transformed into substructurefree, fully recrystallized grains with polygonal grain shape having an average grain size of 10µm and 2 µm, respectively.
By analyzing the grain size distribution a significant bimodality is observed with a first maximum at 75 nm (fine grains) and a maximum at 500 nm (large grains).
GC is known as a process in which smaller grains are eliminated, large grains grow and the grain boundaries assume a lower energy configuration.
In the fine-grained region the number of favorable nucleation sites and the driving force (reduction in grain boundary energy) is very high.

The continuity requirements of strain components across the grain boundary plane between grain 1 and 2 is given by the following relationship [1]: (1) (2) yy yyε ε= , (1) (2) zz zzε ε= , (1) (2) yz yzε ε= , ( 11 ) here, (1) yyε for example, denotes the sum of elastic and plastic strain components and the number in superscript denotes the grain.
The continuity requirements of strain components across the other grain boundary planes, which are lying parallel to z-x plane, are represented by the following relationship: ( ) ( ) n m xx xxε ε= , ( ) ( ) n m zz zzε ε= , ( ) ( ) n m zx zxε ε= , ( 12 ) Fig. 1 Geometry and boundary condition for the models employed in this study here, n and m denote number of neighboring crystal grains.
The combination of crystal orientations for grains 1, 2 and 3 are chosen so that the angle(α) between loading direction and slip direction of the primally slip system are (1) α = (2) α =44° and (3) α =46°, here, the number in superscript denotes the crystal grain number.
Table 1 Grain number, Euler angles�κ,θ,φ�, Value of components of slip direction vector ( )9th b and slip plane normal vector ( )9th v of primary slip systems Grain Num.
�κ�θ�φ�[deg] (9 )th xb (9 )th yb (9 )th zb ( )9th xv ( )9th yv ()9th zv 1 (74.983, 24.535, 79.469) -0.6947 0.7193 0 0.7193 0.6947 0 2 (74.983, 24.535,259.469) 0.6947 0.7193 0 -0.7193 0.6947 0 3, 5 (79.645, 24.973, 75.236) -0.7193 0.6947 0 0.6947 0.7193 0 4, 6 (79.645, 24.973,255.236) 0.7193 0.6947 0 -0.6947 0.7193 0 Table 2 Grain number and values of Schmid tensor (9 )th ijP Grain Num

The crack growth rates in UFG copper are substantially faster than in coarse-grained (CG) copper.
Nevertheless, one can imagine initial small niche markets with relatively low number of products to appear before emerging to medium volume markets, targeting performance of the final products rather than their cost.
Even though a certain number of studies have been carried out for investigating static and fatigue properties of UFG metals, very few data on fatigue crack growth resistance are available[2, 3].
Results and Discussion Fatigue crack propagation tests were conducted on ECAPed specimens and a conventional grain-sized copper with an average grain size of ~ 50 μm.
The overall appearance of grain sizes and grain structure is rather homogenous after fifth pass in ECAP within the range of ultrafine grains (< 1 μm).

Misorientation and spacing of high-angle boundaries decrease with the number of passes.
This is interpreted as a result of the tendency to form equiaxed grains in a textured grain structure.
This has to do with the strong shearing of the grains transforming equiaxed grains into elongated ones.
F increases by 1/N (N: number of measurements) whenever φ equals a measured value φi.
It is seen from Figure 3 that the misorientation distributions F(φ) of (even-numbered) passes 2n are generally quite similar to those of the preceding (odd) passes 2n−1.

Formation of fairly large grains (crystallographic domains) of graphene exhibiting sharp 1x1 patterns in m-LEED was revealed and that different grains showed different azimuthal orientations.
A grain size of up to a few mm was obtained on some samples.
appear in the LEEM image the reflectivity curves show that most have the same number of graphene layers.
They were collected at two different locations outside the area shown in Fig. 1a) but where the number of graphene layers was also six.
ordered grains.

., lattice constant, c/a ratio, mean grain size, number of reflections per unit area, lattice strain, dislocation density, texture coefficient and standard deviation have been calculated from the experimentally observed XRD data and the effect of deposition temperature on these parameters have been elaborately discussed.
The grain size estimated from the SEM analysis lies between 100 nm and 350 nm. 1.
The mean grain size evaluated from the XRD data lie between 250 nm and 650 nm.
The grain size estimated from the SEM analysis lies between 100 nm and 350 nm.
The mean grain size evaluated from the XRD data lie between 250 nm and 650 nm.

There are undissolved second phase particles in grains and at grain boundaries.
Second phase particles can be found in grains and at grain boundaries.
The second phase particles appeared at grain boundaries and in grains.
There were some fine dispersion η' precipitates, about a few nanometers size, needle-like shape, and a small number of spherical GP zone precipitation in grain.
After aging treatment, alloy microstructure separated out a large number of dispersed strengthening phases, so the hardness must be improved.

Lattice sites having the identical Q number are considered as a grain, and a grain boundary segment is defined to lie between sites of different Q number.
NA and NB are the sites number of phase A and B, NC is the smaller sites number of that of phase A or B. δQiQj is Kronecker delta function, Qi and Qj denote the grain orientation state of the neighboring sites i and j.
Some grains significantly shrink, at the same time, some grains grow.
It can also be obviously seen that the number of nano-particles inside the matrix grains decreases with an increase in the size of nano-particles, this result is consistent with experimental observations that larger-sized nano-particles prefer to locate on the grain boundaries and smaller nano-particles often lie within matrix grains.
It can be found from Fig. 4 that the grain growth exponent decreases with increase of mean grain size for a given curve and to nearly zero when grain growth is pinned.

Implantation of aluminum into titanium has resulted in formation of the whole number of phases having various crystal lattices, like b-Ti, TiAl3, Ti3Al, TiC and TiO2.
The number of press moldings was equal to three.
Along with the α-Ti grains in the structure of alloy there are b-Ti grains. b-Ti grains also have the form of lamellar precipitates, located along the longitudinal boundaries of α-Ti grains.
Conducted studies demonstrated that aluminum ion implantation into titanium resulted in formation of the number of phases: Ti3Al, TiAl3, TiO2, TiC.
Implantation has lead to the formation of a number of secondary phases.