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After these pioneering works the subject of superplastic UFG alloys became quite popular and the progress in this trend was successfully demonstrated in a number of recent reviews [8,9].
The fatigue tests of blades were performed on a special vibration testing machine VEDS – 400A at room temperature and symmetric loading cycle R= -1, the number of cycles 2x107, frequency f=500 Hz [15].
Smaller Zn grains with sizes between ~50 and ~150 nm were located at the triple junctions of the aluminum grains.
Although there is some grain growth during superplastic deformation, the grain size remained less than 100 nm (Fig. 4a).
Langdon, Twenty-five years of ultrafine-grained materials: Achieving exceptional properties through grain refinement, Acta Mater. 61 (2013) 7035-7059

Methodology of High-Carbon Wire Rod Perlite Grain Grade Identification I.G.
When viewing each view field, the 1st grade grains are counted and the grains of another dispersion are counted (2-10 grades).
Afterwards, the percentage of 1st grade grains is determined in relation to the total quantity of grains.
According to the scheme (Fig. 1), in the cross-sectional area of the samples, the pearlite dispersion was measured in each view field (Table 1), with the percentage of the 1st grade grains defined relatively to the total number of grains.
To the determination of the zones boundaries with the different 1st grain grade pearlite percent values (1 is the zone with a large pearlite percentage; 2 is the zone with a lower pearlite percentage) To improve the methodology for the perlite grain grade determination, it is necessary to define the number of the counted view fields.

Introduction Grain boundaries (GB) are planar defects where two grains of different orientation meet.
The interaction between solute and migrating GBs has been studied by a number of researchers since the 1950's [3, 8-37].
To begin, one simple microstructure is considered: a shrinking spherical grain embedded inside a cubic grain driven by curvature, to mimic grain growth in single-phase materials.
Fig. 1 Composition profile along a line across the center of a spherical grain embedded in a cubic grain.
Therefore, this study provides a solid base for performing 3D simulations of grain growth of a large-scale microstructure with a statistically meaningful number of grains that will be performed in the near future.

Grain Refinement on AZ31 Manesium Alloy by Highly Strained and Annealed Method A.
Grain sizes after the solution heat treatment were about 20 to 150 µm.
Small grains of about 1 µm have been achieved by these methods.
Number density of inclusions were larger in AZ31(Mn) alloy than that in AZ31 alloy.
Precipitates formed in the alloys suppress grain growth, especially those in the AZ31 alloy containing manganese seem to have a higher redissolution temperature and lead to fine grained structure.

Essentially, there are two basic methods which can be applied for promoting formation of a dominant equiaxed grain zone with finer grain size in solidification structure of steel castings: melt stirring during solidification or introduction of a larger number of solid particles to the melt prior to solidification.
The applied stirring induced multiple fluid flows of liquid metal inside the melt, breaking dendrites during the course of their growth and creating a larger number of heterogeneous nucleation sites – broken dendrites for enhancing formation of equiaxed grains, thus, leading to final more uniform solidification structure with an enlarged equiaxed grain zone.
As-cast structure of 42CrMo4 steel exhibited a large number of micro-pores evenly distributed over entire volume of the specimen which is dominated by a columnar zone consisting of columnar grains of larger sizes (Fig.3a).
The area fraction is a ratio of points falling into the zone of interest to the total number of grid points.
In the case of determining the area fraction of the occurred porosity, the 225-point test grid was placed randomly over 10 fields of dimension 4000×4000 µm in the solidification structure; and the area fraction of the occurred porosity is a ratio of the average number of points falling into the pores and the total number of the grid points.

A number of algorithms and strategies are now being used to solve complex optimization SRM grain design problems, which are used to be treated by classical or heuristic optimization methods[2-4].
On the other side, in the engineering practice, the designing of SRM grain is constrained by a number of performance and structure restrictions, which narrow down the optimizing space remarkably.
The grain regression based on PFCADM is achieved by embedding the regression parameter in the variable defining when modeling grain CAD model, i.e.,.
Thus, the objective and constraint functions from designing variables of sphere slot grain to grain performance parameters is established.
These restrict application on the grain optimization problem.

The experimental results show that the ferrite fine grain around 5μm supports the properties of both high strength and plasticity, while the ferrite with percentage more than 90% leads to high elongation, and the large number second precipitation phase NbC with uniform fine size around 10nm is helpful to fine ferrite grain and form strong(111)textile fiber.
The test micrograph displays that the large number fine second phase particles are founded, as shown in Figure 2 (a)～(b).
It is well known that the small large numbers of NbC particles are blocking (100) textile grain growth because it has weak deformation store energy during cold-rolling procedure.
(2) The optical micrograph shows that the uniform fine ferrite with grain size less than 5μm is gained, and the large numbers of ferrite with the percentage more than 90% is obtained for the experimental steel sheet, while the fine grain ferrite leads to high strength and the large percentage ferrite results in high plasticity
(3) The TEM analysis and X-ray diffraction measurement results show that there is large numbers of small precipitation particles, which leads to fine grain and form strong beneficial (111) textile in the experimental steel sheet.

Grain growth occurs as the result of grain boundary migration.
Grain Growth Activation Energy of Yttria.
Large number of nuclei and small grains may be obtained in the early stages of amorphous yttria converted to cubic yttria, in which the nuclei and small grains are closely interdependent.
In the second condition, once larger grain is form, the grain surface energy becomes relatively low and the interconnection between the larger grains become more difficult.
Thus, in the midanaphase stage of grain growth, the main mechanism of grain growth is the thermal diffusion of structural unit to grain suface and its oriented arrangement.

A number of attempts have been made to study the austenite grain growth in the presence of second-phase particles.
Grain growth modeling.
Therefore, the net driving force ΔP for grain growth is governed by the sum of all driving and retarding forces acting upon the grain boundary motion.
The driving force for grain growth is given as a pressure per unit area of grain boundary and it can be expressed according to Smith and Zener (1948) [5] as (3) where kd is the driving force parameter, γg the grain boundary energy, and D the grain size.
Non-isothermal grain growth in metals and alloys.

Introduction Within the last decade a number of x-ray diffraction methods have been presented for non-destructive 3D characterization of polycrystalline materials. 3DXRD [1] and Diffraction Contrast Tomography [2,3,4] are examples of such methods providing full spatial and crystallographic information of the individual grains.
Furthermore, spatial moments of the individual grains are obtained.
Note that each grain will give rise to as many matches as the number of times the grain diffracts within the ω-interval.
If there is agreement between the simulated grain candidates and measured data, the grain candidate is accepted as a grain.
Kinetics of individual grains during recrystallization.