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The ECAP processed material after three passes exhibit superior LCF lives at low strains presumably due to higher strength and large refinement of grains.
The work pieces can be pressed a number of times using the same die because the cross-section remains constant.
Refinement of grain size occurs because of the increasing strain.
As a result, the structure and mechanical properties of materials processed by ECAP are affected by the number of passes and the processing route [2 - 4].
The superior performance of the material after three passes may be attributed to higher strength and large refinement of grains (see Fig. 3).

As the number of ECAP passes was increased, the applied strain was accumulated in the samples as calculated in Table 1.
A fine-grained material is harder and stronger than one that is coarse grained, since a fine-grained material has a greater total grain boundary area to impede dislocation motion [4].
Hardness and strain stored in the specimens as a function of number of ECAP pass.
No Number of ECAP pass Hardness (Hv) Strain 1. 0 44.9 0 2. 2 99.4 0.67 Referring from Fig.2, ageing heat treatment at 1 hour shows that ECAPed specimen has higher hardness than that of raw (cast) specimen, this is probably caused by the grains of ECAPed specimen are relatively smaller (Fig.4).
The accumulated strain leads to directional grain orientation and grain refinement. 2.

It is shown that combination of strain effects leads to possessing the ultra-fine grain structure in carbon wire.
Besides, products made of modern materials can be processed technologically in a number of different ways.
Ultrafine grain structure forming is one of the most promising methods of steel properties improvement [4-9 etc.].
Combination of operations reduces their total number while the number of semi-product transformations does not change.
Biswas, Ultra-fine Grain Materials by Severe Plastic Deformation: Application to Steels.

Traditional Cellular Automaton model can only predict the grain structure and grain size.
Free growth of equiaxed grains and the competitive growth of columnar grains were simulated.
Discretized step is ∆x=∆y=∆z=0.01mm, the generated grid number is 1000000.
From modeling results, it was indicated that a nucleated equiaxed grain grows continually to form a fully dendritic grain, which has six primary stems in 3D.
Calculation domain is 1mm×1mm×2mm, mesh is divided by ∆x=∆y=∆z=0.01mm, grid number is 2000000.

It is also presumed that hydrogen atoms inside grains are transported with the aid of mobile dislocations to the grain boundary depending on strain rate [3].
The average grain size after the heat treatment was 16.3 µm.
In the condition for the QMS2, the signals corresponding to the mass numbers from 1 to 4 were all detected.
It is obvious that the mass number 3 and 4, which represent HD+ and D2+, respectively, were detected only from D-charged specimen in the stage of deformation.
When we estimate the hydrogen concentration at grain boundary assuming that the first evolution peak represent hydrogen atoms segregated at grain boundary, the value becomes about 3.0×10-7 mol / m2.

To study the influence mechanism of the excavation stability of the debris accumulation body by the expansive fine grain, it has used by Particle Flow Code, based on indoor test, the fine-grain expansive effect has divided into fine-grain intensity attenuation and volume expansion, and it has linear decreased down from the surface on the accumulation body.
Table. 1 The properties of the unit classification of grains and bedrock interface properties fine grains gravel rolling stone bedrock interface number 2200 2500 30 5 density/[kg/m3] 2000 2600 2600 - radius/[m] 0.05～0.2 0.2～1 1～2 - normal stiffness /[pa] 5e8 1e9 1e9 1e8 shear stiffness /[pa] 1e8 2e8 2e8 1e8 coefficient of friction/[f] 0.5 0.9 0.9 1.0 normal cohesive strength/[pa] 1e5 - - - shear cohesive strength /[pa] 1e5 - - - Simulation of expansive effect.After analyzed by indoor SEM, X-ray diffraction and ESCA, it is found that the debris accumulation body contains lots of clay minerals of ledikite and turface.
First, strength degradation caused by expansive fine grains is consecrated.
Then, based on the reduction of intensity, the expansion of fine grain is considerate having volume expansion.
The Particle flow code method is used to simulate pressure balance method to measure the type expansion of fine grains, and the simulation model is shown in (Fig. 2b), and with the volume expansive corresponding control grain density and the module change thus is obtained that the grain radius increases by 1.000005 times each time the loop repeats, after repeating 2000 steps, the fine grain types expansibility reaches 75~80kPa, the free swelling rate reaches 60%~65%.

Thermal annealing below 600℃, the movement of grain boundaries mainly led a reduce of the number of microvoids, and vacancy defects began to recover due to the growth of MgO nanoparticles after annealing between 600 to 900℃.
Compared with traditional bulk materials, volume fraction of grain boundaries in nano-ceramics is meaningful and thus open volume defects in grain boundaries play an important role.
The movement of grain boundaries might lead to decrease the number of microvoids below 600℃; and above 600℃, the particle size begins to grow and intensity decreases to about 0.5%, which indicates that most of microvoids are recovered or some microvoids agglomerate into larger pores.
The agglomerations of a number of nanoparticles were found.
For MgO nanocrystal, the total defect density decreases with the increasing annealed temperature, below 600℃, the movement of grain boundaries might lead to change the number of microvoids; above 600℃, the particle size begins to grow, associated with recovery of vacancy defects in the grain boundary region.

Furthermore, studies on the templated growth of elongated grains showed that, the number of initial stable seed crystals is the dominant factor for microstructure control,regardless of shape and size of the crystals [13].
Dimensions of the grains were determined by using UTHSCSA Image Tool measuring over 200 grains in each system.
Although microstructure of unseeded α-SiAlON has also exhibited elongated grains according to the Sm 3+ existance, increase in the number of the elongated grais is obviously observed by microstructural characterisation in both seed and powder nuclei containing samples.
And in the last step according to the grain boundary phase amount, since the grain growth is somewhat diffusion controlled, α-SiAlON grains start to grow.
Indentation fracture toughness values of the samples Conclusions In this study, the substitution of powder nuclei with seeds is investigated and the results were compared: � Addition of both α-SiAlON seed and powdered Y-Sm/α-SiAlON as a nuclei resulted in the increase of the number of elongated grains and the aspect ratio

The erbium content was optimized by measurement of grain refining effects and tensile strength.
Previous study [3] suggests that the modification ability of an element may be the result of a certain combination of the valence electron charge number, the atom number, and the atomic radius of the modifier.
In addition, grain size tends to become bigger than the grain size with the solution temperature of 595°C in Fig. 5(d).
Table 5 The tensile property of two specimens Number σb (MPa) σs (MPa) δ (%) 3#-5 335.98 330.52 3.3 3#-7 367.20 350.44 5.0 Conclusions 1.
Grain refinement mechanism in an Al-Si-Mg alloy with scandium.

It is accepted that P segregation at grain boundaries causes the improvement in grain boundary cohesion, intergranular oxidation resistance, and grain boundary precipitation [2-4].
However, a large number of blocky or needle-like shape η phase precipitated along the grain boundaries, and few granular phosphide particles were observed at grain boundaries through EDS.
However, the η phase was distributed within the grain matrix and along grain boundaries.
The grain size was unchanged compared to the as-rolled grain structure (Fig. 1a).
For the unchanged grains microstructure, the phosphide particles stayed at the original place (Fig. 6d); for the grown grains microstructure, the phosphide particles appeared within the grain interior outlining the original grain shapes (Fig. 6e).