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The coarsest grain was obtained in steel 3(plain carbon steel, 15μm), while the finest grain size was obtained in steel2(10μm).
But compression temperature had an important effect on the ferrite grain size too.
Fig.5 Optical micrographs of steel 2 It can be seen from Fig.5 that the ferrite grains nucleated within the austenite grains besides austenite grain boundary which results to grain refinement in V-N steel.
Low temperature increased the nucleation driving force and activated a number of difficult nucleation sites such as crystal face, consequently refined microstructure.
Had V-N steel plus controlled cooling same grain size or smaller grain size than Nb-bearing steel？

Biphasic Calcium Phosphate: preferential ionic substitutions and crystallographic relationships at grain boundaries T.
Biphasic Calcium Phosphate, Grain boundary, solid solution Abstract.
Numbers in ( ) correspond to estimated standard deviations.
Imaging at high magnification showed that the lattice lines are stopped at the interface (boundary line) between the grains without direct continuity (Fig. 3).
This study was supported by 7eme PCRD GAMBA grant number NMP3-SL-2010-24599 and 7th PCRD REBORNE grant number GA-241879/HEALTH-2009-1-4-2.

The sheets are subjected to total number of three passes of CGP and further processing could not be continued due to initiation of cracks.
The ambiguity in grain size measurement arising from the non-equiaxed nature of deformed grains is minimized by measuring the number of intercepted grains from superimposition of grids on the image in different orientations (00,450,900).
Table 1 Estimated average grain sizes and tensile properties of CGP processed nickel sheets CGP Pass number Average grain size (mm) Yield strength (MPa) Tensile strength (MPa) Tensile elongation (%) Annealed 37±8 58 349 46.2 1 21±4 558 571 7.4 2 16±5 618 641 4.6 3 12±4 394 594 16 Microhardness evolution.
The variation of microhardness profile with increasing number of CGP passes is summarized in Fig.3b.
Grain sizes decreased continuously with increasing number of passes.

The (sub)grain size decreases both with decreasing temperature and with increasing number of passes.
This table also clearly shows that the “processing stress” (σProc=Fmax/S, being S the ECAP section equal to 1 cm2) increases with both decreasing temperature and increasing number of passes.
It is shown that at a processing temperature of 300°C (sub)grains decrease in size with number of passes similarly to other severe plastic deformation methods operating at low-intermediate temperature.
Applied force (Fmax, kN), (sub)grain size (d, nm) and hardness Vickers (HV) for samples ECAPed at various temperatures (T, ºC) and number of passes (N).
A proof of this relation is given in Fig. 4a for ECAP processing where the processing stress rationalizes the obtained (sub)grain data into a single line, irrespective of the number of passes and processing temperature.

In this paper, by reviewing the grain size prediction models, the important influence of solute diffusion layer in front of the grain growth front on the final grain size has been addressed.
This makes the evaluation of the grain refinement efficiency of grain refiners with different size distributions possible.
It was shown that there is a zone close to the growing grain within the solute diffusion zone, where the nucleation of new grains is suppressed.
The initial radius of grains is 4 mm.
StJohn, An analysis of the relationship between grain size, solute content, and the potency and number density of nucleant particles, Metall Mater Trans A 36 (2005) 1911-1920

The initial material has a uniform coarse-grained microstructure with a mean grain size of ~42 μm.
Moreover, cracks were developed for numbers of turns larger than three.
The initial material exhibits a coarse-grained γ-austenite with a mean grain size of ~42 μm.
Table 1 lists the grain size values obtained by TEM at the disk periphery for different numbers of turns.
A further reduction in grain size was observed with increasing numbers of HPT revolutions and after 20 turns the mean grain size was refined to ~48 nm.

An ultrafine-grained (UFG) pure Ti with an average grain size of ~96 nm was obtained.
A large number of tangled dislocations are visible near the grain boundaries and the grain boundaries are unclear and curved, indicating that the grain boundary is still in a non-equilibrium state.
The proportion of the DTZs within the grains remains high, but the density of dislocations is significantly reduced both inside the grains and near grain boundaries, indicating that a recovery process has occurred.There are no obvious changes in grain size with the average grain sizes of ~169 nm.
As can be seen from Fig.5 d), the grain boundary of grain marked as A is straight and clear, and there is a subgrain inside grain A.There is a dislocation tangle zone inside grain marked as B, and the grain boundary is wavy and unclear.The density of dislocations at the grain boundary is much higher than that in grain.
Compared with HPT 5 turns disks, the grains have grown significantly with an average grain size of ~914nm.

Packing density and coordination numbers of the grains in the sintered powder are analysed with application of computer simulation.
The parameters, most widely used in the description of the packing types, are: i. packing density defined as the ratio of volume of solids to the total volume of solid grains and voids; ii. the coordination number distribution which defines the coordination numbers appearing with various probabilities.
The program allows simulating the grain packing and related coordination-number distribution as well as a dependence between the both.
To eliminate the border effects the students make a series of calculations of the packing density (ρ) for various grain radii (R) and then draw the results in the ρ vs. �-1/3 scale (where N is a number of the grains in the given volume).
The screen of the results contains information about total number of the spheres in a given volume, packing density and the coordination number distribution (Fig. 3).

For the bilayer films containing larger Al grains, the nucleation rate of fractal patterns (Ge clusters) is faster and the number of patterns is larger.
Top left numbers represent the annealing times.
From Fig. 5, it is apparent that the number of the patterns increases when the grain size becomes larger.
However, we cannot see any essential difference between Fig. 6 and Fig. 8: that is, the similar influence of the grain size of polycrystalline Al layer can be seen and the number of the patterns increases when the grain size becomes larger.
(a) 19.0ks 22.4ks 24.2ks (b) 7.4ks 9.0ks 10.8ks 10µµµµm 103 104 5x104 103 104 105 Annealing time, t/s Number density, N/mm -2 � � � � 0 1.5x104 3.0x104 0 3 6 Mean radius, r/µµµµm Annealing time, t/s � � large�grain small�grain large�grain small�grain 2x103 10 4 3x104 103 104 2x104 Annealing time, t/s Number density, N/mm -2 � � 0 1.5x104 3.0x104 0 4 8 Annealing time, t/s Mean radius, r/µµµµm � � large�grain small�grain large�grain small�grain (a) (b) (a) (b) Fig. 9 Superimposed SEM images showing the evolutions of the same patterns in the course of in-situ annealing at 423K: (a) Al(50nm)/Ge(50nm)/SiO2 and (b) Al(50nm)/Ge(25nm)/SiO2 bilayer films.

It is demonstrated that under the DCAP processing the material is strengthened faster, by lesser number of passes, and microstructure’s thermal stability is somewhat lower after ECAP compared to that after DCAP, although after equal number of passes ECAP results in a more homogeneous microstructure.
Along with these fine grains there are much coarser and anisotropic grains.
Local areas with fine submicron grains surrounded by high-angle grain boundaries are also observed.
Under the higher number of ECAP the structure gets more homogeneous, but after 8 passes the percolation porosity appears [4,5].
With the increasing number of passes the pronounced deformation bands are formed, and inside them there are subgrains of submicron sizes decreasing with the increase of the number of passes.