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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.

The Influence of Grain Size and Grain Size Distribution on Sliding Frictional Contact in Laterally Graded Materials Romik Khajehtourian1, a*, Saeed Adibnazari 2, b, Samaneh Tashi 3, c 1, 2, 3 Department of Aerospace Engineering, Sharif University of Technology, Tehran 14646, Iran ar.khajehtourian@gmail.com, badib@sharif.ir, csamaneh.tashi@gmail.com Keywords: Graded Materials, Micro Scale, Grain Size, Grain Size Distribution, Contact Mechanic.
Also, increasing the grains aspect ratio and using optimum distribution of grains decrease stress distribution roughness on the surface.
In the micro FE model, grains arranged with appropriate volume fractions, randomly. wg, hg and wg/hg, respectively, denote the width of grains, the height of grains and grain’s aspect ratio.
Fig. 6 presents the normalized contact stress σyy(x,0)/(P/(b-a)) as a function of the grain’s aspect ratio with constant grain size distribution.
Thus once again, beginning of surface cracking at much lower number grain’s aspect ratio which causes less endurable surfaces in contact problems and effect of grain size distribution has demonstrated.

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.

In most cases, coarse crystal grains are included in aluminum casting alloy.
The two problems arise because of the existence of the coarse crystal grains.
For an accurate estimation of the stress measurement by neutron diffraction, a sufficient number of crystal grains must exist in the gage volume.
However the casting materials usually include coarse crystal grains.
The diffraction profiles frequently disappear due to the existence of coarse crystal grains.

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.

Grain Boundary Segregation and Grain Boundary Wetting Arkady Vilenkin The Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem, 91904, Israel Keywords: grain boundary segregation, grain boundary dynamics, grain boundary wetting Abstract.
Different hatching represents different grains.
LA Diffusion along Grain Boundary.
Grain Boundary Shape Function and Velocity.
In order to obtain simple algebra, we have made several numbers of assumptions.

The maximal absorption rate got 99.81%.The modified brewer's grains of amine surfactant modified is a promising treatment of chromium wastewater biological materials.
Brewer's grains is the main by-product of beer industry.
It have good hydrophilicity and easily adsorbed porous structure, containing a large number of hydroxyl groups.
The metal ion adsorption ability was increased by chemical modification of active groups[3].In the paper, the modified adsorbent was modified by amine reaction with brewer's grains that using epichlorohydrin(ECH) as etherfying agent,N,N-Dimethyl formamide (DMF) as dissolvent, triethylenete tramine(TETA) as cross-linking agent and introduce amino group,so as to utilize the brewer's grains as the low cost material for Cr(VI) wastewater purification, then the results would be the theoretical basis for the comprehensive utilization of the brewer's grains.
Material and Methods Material Preparation of modified brewer's grains biosorbent:The brewer's grains was from the bee laboratory in our school, washed with tap water, and dried at 50 °C to constant weight.

Metal with very fine grain size has higher hardness and ductile than metal with coarse grain structure (Hall-Petch theory) [5].
These standard arrays stipulate the way of conducting the minimal number of experiments, which could give the full information of all the factors that affect the performance parameters.
Grain size on speciment doesn’t homogen.
Figure 2: Grain Size Distribution on aluminium after ECAP process Grain size homogienity index calculate from grain size along cross section with equation (1).
Ci is represent of homogneity, lower Ci indicated more homogen grain and higher Ci indicated less homogen grain.

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.

Grain Refinement of Magnesium Alloys by CONFORM: A Continuous Severe Plastic Deformation Route?
The average grain size was measured as ~150 µm.
Near the rod surface (Fig. 4d), the texture is significantly weakened by a number of peak orientations with the basal poles aligned 43°, 53°, 67° and 90° to the ED.
This grain size non-uniformity impeded the development of conventional superplasticity through grain boundary sliding, resulting in the early failure of the specimens [7].
Compared to ECAP, the CONFORM process has the following advantages: 1) the process is operated in a continuous manner, so very long products can be readily produced and the production rate is very high; 2) cast rods can be directly used as the feedstock, no prior extrusion is needed; 3) the grain refinement effect is higher than ECAP, so less number of processing passes may be needed to achieve the same grain size; 4) the CONFORM machine is commercially available in the market and can be readily used for industrial production.