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Ultrasonic waves exert time-dependence forces on crystal lattice defects resulting in a number of different phenomena such as self-organization of dislocation ensembles [7], dislocation reactions [8], multiplication of vacancies [9], etc.
One can see a minor grain growth after annealing at 130°C with the resulting mean grain size d » 0.24 μm.
Noticeable changes occur in the microstructure of nickel annealed at 150°C: there is a significant grain growth, some individual grains with size of d » 1.5 μm appear in the ultrafine-grained matrix with mean grain size of d » 0.3 μm (see Fig. 1, c).
The structure consists of dislocation-free equiaxed grains having mean grain size of d » 320 nm.
Reduction of the distortion and excess energy of grain boundaries supresses the grain growth.

Background Severe plastic deformation (SPD) has emerged as a promising technique for creating ultra fine grained (UFG) metals and alloys, with grain sizes of a micrometer or less.
There has been a tremendous interest in developing severe plastic deformation processes, as well as in the study of mechanisms that cause grain refinement during SPD, as evidenced by the large number of publications and topical symposia [1,2,3,4].
Figure 4 shows the change in hardness on the cross section of the billets of different sizes with increasing number of passes.
In addition to conventional forging stock and the ECAP material, this part was also made with a cast fine grain AA-6061 with a starting grain size of ~100 µm.
Ferguson, "Multi-axis Deformation Methods to Achieve Extremely Large Strain and Ultrafine Grains," in Ultrafine Grained Materials, Ed. by R.S.

Fig. 12. and 13. show the inverse pole figure maps (IPF) of the selected areas and optical microscopic images of numbered color etched microstructure.
Color etched image the area of interest (Original magnification: 500x, Klemm I-Beraha 10/3 reagent) [3] The individual grains are numbered on both the color etched image and on the IPF map.
Table 1 shows the orientations of grains in the area of interest.
Table 1 The orientations of individual grains in Fig. 12.
Grain No.

SEM study show that BaSiO3 doping can make grain grow uniformly and suppress the grain to grow up, and the structure of ceramics is compact with little pore.
This liquid phase can also purify the grain and grain boundary through adsorbing, promote uniform grain growing and restrain abnormal grain growing of (Ba,Sr)TiO3(BST) ceramics [4].
The formula of experiment Formula Number 1 2 3 4 BaSiO3 [mol%] 0 1 2 3 Results and discussion Effect of BaSiO3 doping on the dielectric constant and dielectric loss of BST ceramics.
The ΔC/C of BST ceramics Formula Number 1 2 3 4 ΔC/C[%](Positive temperature) 14.7 10.5 12.3 18.0 ΔC/C[%](Negative temperature) -19.9 -25.1 -24.2 -23.1 Effect of BaSiO3 doping on the material phase composition of BST ceramics.
From the Fig.6 a, b, c and d，it can be seen that there are many tiny particles on the grain surface and the grain size decreases with the increase of BaSiO3 content in BST ceramics, the tiny particles was finally disapeared.

Grain boundaries and interfaces are mesocrystalline characterized by lower density and presence of defects such as grain boundary dislocation, vacancies and interstitials.
In Table 2, we have listed results in a large number of polycrystalline materials.
After prolonged annealing, the interface between the Pb and Sn grains behave more or less like a high grain boundary as shown in Fig. 6(B).
SUMMARIZI#G REMARKS We have examined a large number of diverse materials to establish that the absolute interface/grain boundary free energy is the difference between the free energies for self- diffusion in the lattice and the interfaces.
McLean, Grain Boundaries in Metals, Oxford Uni.

We study the crystallization ratio, grain size of the silicon thin film specially.
The silicon thin film crystallization ratio and grain size changed sharply when PRF =70 W.
The physical properties such as crystallization ratio and grain size were tested by different instruments.
The grain sizes of the samples are estimated by relative formula and shown in the Fig.3.
This large number of high-energy H atom can cover the samples surface adequately and fully reorganize the irregular Si-Si structure.

Meanwhile, materials with ultra-fine grains manufactured through severe plastic deformation have different physical properties from general materials that have coarse grains[6].
During ECAP, the effects of strain hardening become effective until the critical pass number is reached.
However, the hardness tends to remain fixed after the critical number of passes[7].
TEM micrographs after different numbers of passes of ECAP.
However, after 8 passes of ECAP, ultra-fine grains were formed.

After heating, a sub-micron grain size is retained.
The equivalent deformation introduced after a number of passes N is eN = 0.906N [9].
The microstructure for N=3 consists in well defined grains of about 200nm in size.
The main effect is that the peaks are shifted to lower temperatures when the number of passes is increased.
A substantial grain refinement is obtained for N=3; the fine grains are randomly oriented.

The average grain size was about 2.8 µm.
It was found that the average grain size was about 12.0 µm.
The fine-grained TMAZ (B) microstructure within the outer region containing 50.2 % α2 phase and 49.8 % γ phase has an average grain size about 6.1 µm (Fig. 4c).
However, a large number of voids were formed at the interface and were uniformly aligned along the bond line (Fig. 5b).
The joints exhibited cracks on the γ-TAB side and large number of voids at the interface of the joints.

Ciphers in used marks of studied samples indicate numbers of ECAP passes (1T, 2M, 4B and so on).
Marking includes number of ECAP passes and region of section.
At that, in both cases this angle changes as number of ECAP passes increases.
In both Cu and Ti rods the substructure anisotropy decreases with the number of ECAP passes and in most grains some perfection of the crystalline lattice takes place (Fig. 4-6).
The fraction, characterized by ultrafine grains with the relatively low lattice distortion and dislocation density, grows gradually with number of ECAP passes.