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Thus, there is no simple relationship between the number of passes and the extent of the uniform elongation.
By contrast, there is a tendency for the flow stress to decrease with increasing numbers of ECAP passes.
Figure 2 shows the evolution of the Vickers hardness as a function of the number of ECAP passes.
It is apparent that the flow stress depends on the number of passes of ECAP and this dependence is not continuous.
Fig. 2 Evolution of microhardness in ZK60 magnesium alloy processed by different numbers of passes of ECAP Fig. 3 True stress-strain curves for the ZK60 alloy processed by different numbers of passes of ECAP.

The grain size dispersion was 100 nm.
Thus, ρG increases when the grain size decreases, and the GND accumulates at the grain boundaries (GBs).
It should be emphasized that the numbers of the substructure units in Table 1 and Fig. 3 are the same.
An increase in numbers from 1 to 6 means a decrease in the size of the structural formation, within which there is an accumulation of dislocations (r, rS and rG).
The critical grain size is 250 nm.

The paper focused on analysis of local texture changes, particularly at the boundary between grains.
The shear grain is decomposed by lattice rotation in contrary directions.
(b) The pole figure magnification with marked element numbers and groups of rotation.
(c) Scheme showing finite element mesh with assigned element numbers and group of orientations.
In Fig. 6 the orientations of elements with shear orientation at grain boundary are presented.

Because of the increased number of grain boundaries the motion of dislocations is hindered.
During solidification ultrasound can cause a reduction in grain size, the columnar equiaxed transition and/ or a more homogeneous grain structure.
The grain sizes of samples have been determined.
Figure 2 shows measured grain sizes against the amplitudes.
b) The shorter the solidification times the smaller the grain size.

Grout can transport every grain of aggregate, which allows for the migration of grains in relation to other grains.
Series number 3, containing 40% of recycled cement obtained body density rate by 9% lower than series number 1 and 2.
The gross density of the selected series of the fine- grained samples was examined.
The results of the porosity of concrete maturing for 28 days under the laboratory conditions Series 1 8.07 The porosity of the fine - grained concrete [%] Series 2 9.05 Series 3 15.17 The lowest porosity of 8.07 % was obtained by series number 1, which did not contain any recycled cement. 20% addition of recycled cement resulted in a slight increase of porosity, while the highest porosity rate of 15.17% was obtained by series number 3 which contained 40 % of recycled cement.
The study variance was N = 12 , while the number of repetitions n = 3.

The effect of grain size on the crack behavior was well explained by the grain size dependence of stress concentration at grain boundaries due to dislocation pile-ups.
And, from the TEM image shown in Fig.1-c), the average grain size is 7μm(circle equivalent grain size).
X-axe shows the rating number of cracking, and Y-axe shows the absorbed energy in compressed to 100mm length.
where σapp: stress in the crystal, σ0: resistance force by the precipitate at the slip in the grain, φ: the stress concentration coefficient at grain boundary.
(2) It is effective to be fine grained for the crack prevention, and it makes the stress concentration reduce at the grain boundary, resulting in prevention of the grain boundary fracture.

Compared these inverse pole figures, we can see that the number of grains with <111> pole orientation was larger in the ND in samples warm-rolled at 700°C, which means that samples warm-rolled at 700°C had more grains with {111} planes oriented to the sheet surface than the samples warm-rolled at 800°C.
The {111}<112> oriented grains had high stored energy, when warm-rolled an 700°C, more stored energy leaded to get more grains with the {111}<112> orientation, at same time, those grains had a small subgrain size, based on the subgrain coarsening theory [5], {111}<112>grains had a high mobility and consumed other orientations during recrystallization annealing, then, the more population of{111}<112>grains orientation were appeared in the samples warm-rolled at 700°C.
Frequency (%) Low angle CSL High angle Grain boundary type Fig.3.
Population of grain boundary types in two samples warm-rolled at 800°C and 700°C, respectively Fig. 3 gave the population of grain boundary types in two samples.
Grain boundaries were general classed into three main types: low angle, high angle and coincidence site lattice (CSL), CSL was a special type of high angle grain boundary type and usually expressed by ∑ value.

Thirty Years of Superplastic Ultrafine-Grained Materials: Examining the Legacy of Oscar Kaibyshev Terence G.
Since this grain size was exceptionally small, and smaller than any grain sizes available in western scientific research at that time, the author communicated by mail with Oscar Kaibyshev and immediately received an invitation to visit Ufa.
Processing by SPD to produce exceptional grain refinement can lead to exceptionally high superplastic elongations even in materials where the numbers of slip systems are limited, as in Fig. 8 where there is an elongation of 3050% in an Mg alloy processed by ECAP [13].
Langdon, A unified approach to grain boundary sliding in creep and superplasticity, Acta Metall.
Langdon, Ultrafine-grained materials: a personal perspective, Int.

Precipitation strengthening and grain refinement strengthening are the main strengthening mechanism in HSLA steels, precipitation strengthening and grain refinement strengthening accounted for more than 70% in all strength contribution[4].
Fig.1,2 show that a large number of dispersed fine precipitates appeared on ferrite matrix, grain boundary and dislocations, precipitate size on ferrite matrix is10 ~ 20nm, vanadium carbonitride was identified as precipitates through TEM diffraction spot calibration.
The grains degree of ferrite in core is 11.0 grade and their average size is 7.06 um while the grains degree of ferrite in interlayer is 11.5 grade and their average size is 5.86 um, and the grains degree of ferrite in fringe is 12.0 grade and their average size is 5.0um.
As the deformation temperature decreased, Ar3 point dropped, and then the stability of austenite reduced, induction phase changing of ferrite occurred when Ar3 coincided with the deformation temperature which refined the ferrite grain size and increased the content of ferrite, there were a large number of small equiaxed ferrites not only improving strength of materials but also keeping good shaping of materials.
Through adding adequate VN alloys and nitrify intensifying agent, a large number of the dispersed V(CN) precipitates(sized 10~ 20nm) are precipitated in the grain boundary, dislocation line and the ferrite matrix, precipitates of V (CN) accounted for 67.54% of the total vanadium in steel, effects of precipitation strengthening is significant.

The grain size was found to be increasing with the rise in temperature.
The bandgap was found to be increasing with decrease in grain size.
The Fourier transform infrared (FTIR) analysis was carried out by using Perkin Elmer Spectrum 100 series FTIR spectrometer in the wave number range of 4000-400 cm-1.
The variation of grain size with temperature is shown in figure 2.
That is, smaller the grain size, larger would be the bandgap.