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With the increase of the distance from the bottom of the starter block, the number of grains is gradually reduced, and the size of the grains gradually becomes larger.
With the increase of section height, the number of grain with an included angles that less than 15° between the <001> direction and the heat flux direction is increased.
The height of the starter block should be designed in the 13-36mm, which can ensure a certain number of grains to enter into the spiral part.
The number of grains in the spiral block is drastically reduced by the initial selection at (f) to (g) segments.
With the increase of the distance from the start block bottom, the number of grain decreases and the size of the grains become larger.

Introduction Although the first research on intercrystalline diffusion in nanocrystalline metals was carried out more than 20 years ago [1], up to the present time there is not a full understanding of specific features of the diffusion processes in such materials, and the number of studies dealing with the experimental investigation of diffusion in them is relatively small [2].
At the annealing the Mössbauer isotope atoms diffuse along grain boundaries.
As shown in [17-20] grains between agglomerates are the fastest diffusion paths in such materials while the diffusion properties of boundaries between nano-grains are the same as in coarse-grained materials.
As demonstrated by TEM in [28], grain sizes after such treatment are about 100 nm, and grain boundaries are wide and non-equilibrium, a complex diffraction contrast and moiré inside grains testifying high internal stresses.
At heating up to 873K grain sizes remain unchanged but recovery occurs, grain boundaries becoming thinner and straighter and grains clearing of dislocations, and at higher temperatures recrystallization starts with intensive grain growth.

Some elements, especially microalloying elements, segregate at grain boundaries, and this significantly retards grain growth.
The concentration profile across a grain boundary during grain growth can be calculated by coupling Eq. 1 and Eq. 2
During grain growth with velocity, v, it is natural that grain size increases gradually.
The total number of grid points for a calculation was 601.
Using this model, the concentration profiles across grain boundaries and grain size evolution were calculated.

The first one is transformational grain refinement [1-3], wherein the austenite ferrite transformation is explored to obtain refined ferrite grains from a prior austenite grain structure.
There have been only a limited number of investigations to show that nanostructured materials, especially at room temperature, have high strain-rate sensitivity.
Even though a number of different approaches have been tried out to achieve both high strength and ductility in a sample, no investigations have been reported to see if it is possible to combine the different approaches to increase the strength and ductility further and also to check if some of the effects have a synergistic effect.
These newly formed ultrafine ferrite grains are surrounded by clear grain boundaries as evidenced by clear etching and are indistinguishable from the original ferrite grains judged from the intensity of etching.
The effects of precipitation strengthening were investigated by adding carbon to increase the numbers of cementite particles.

Some authors have pointed out that Voroni tessellations underestimate the distribution of grain size and overestimate the number of faces per grain [5].
Given a volume bounded by an external surface and containing grains, two kinds of grains can be distinguished: the boundary grains, intersecting the external boundary, and the internal grains, completely surrounded by other grains.
The effective properties are obtained by taking the ensemble average of the apparent properties over a certain number of microstructure realizations with the same number of grains, see e.g. [13].
For a given number of grains, 100 different realizations have been generated and simulated.
It is worth noting how the scatter is reduced, and how the computed mean values get closer to the third order bounds, when an higher number of grains is considered.

The attenuation of sound wave can be expressed by Eq.3, in the case of plane wave [12]: (3) Where is the sound energy after propagation into the medium in x direction, is the sound energy before entering medium, is the propagation distance of the sound wave, , is the angular frequency, is the time and is the wave number.
Experimental result and discussion Material grain size The microstructures and grain size of all materials were found out by microscope model Leica DM 2500M.
Relation between grain size and sound velocity of material type SS 400.
SS400 Grain Size Echo Figure 5.
Relation between grain size and ultrasound echo height of material type SS 400.

Sandglass extrusion is an ultrafine grain size method.
Due to the repetitive and multiple extrusions, large strain can be accumulated and ultrafine grain size can be obtained.
Introduction Severe plastic deformation (SPD) is a kind of method for producing ultrafine grain size material.
This method can produce ultrafine grain size by SPD.
By using of this method, the ultrafine grain size material can be obtained.

Influence the number of passes through CONFORM machine on thermal stability was study by horizontal dilatometer and heat-flux calorimeter.
They are used for achieving grain refinement to the nano-scale, with the resulting grain size between 100 and 400 nm.
The grain size in this specimen was 1.4 µm.
The resulting grains are equiaxed.
Grain coarsening kinetics In the course of the isothermal annealing experiment, normal grain growth took place.

The position of metal mesh and the mesh number of metal mesh make significant effects on the MOE; the type of metal mesh and the angle of metal mesh-wood grain do not have any obvious effects on the MOE.
The type of metal mesh and the position of metal mesh make significant effects on the MOR; the mesh number of metal mesh and the angle of metal mesh-wood grain do not have any obvious effects on the MOR.
All of them had three different mesh numbers (mesh number is defined as the number of meshes in 1 inch by 1 inch area), including 20, 30 and 40.
Consequently, the position of metal mesh makes significant effects on the MOE of LVL, and then the mesh number of metal mesh, the type of metal mesh and the angle of metal mesh-wood grain in order.
Consequently, the type of metal mesh makes significant effects on the MOR of LVL, and then the position of metal mesh, the angle of metal mesh-wood grain and the mesh number of metal mesh in order.

Introduction In the recent years a number of studies have been done in grain refinement of metals through severe plastic deformation processing (for example, see Ref. 1).
When the temperature increases to above 275°C, the duplex grain structure converts to a uniform coarser grain structure with average grain size above 4µm (Figure 1c).
Further increase of temperature results in normal grain growth until abnormal grain growth starts at 500°C.
The grain size increases slowly with the increasing temperature and approaches 10µm at 560°C without abnormal grain growth (Figure 12a).
A duplex grain structure enhances the tensile elongation in both fine grained AA5754 and AA5182.