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Keywords: grain growth, triple grain junctions, grain boundaries, kinetics, nanocrystals, interfaces.
Triple Lines and Triple Line Tension in Polycrystals The grain boundaries (GB) in a polycrystal are high energy regions, in the sense that the energy of a (large) number of atoms at the boundary is larger by 1E∆ relative to the energy of N atoms in the bulk of the grains.
'N atoms at the TJ have energy larger by 2E∆ relative to the same number of atoms at the GB's.
The total excess energy E∆ of the polycrystal, relative to a perfect crystal with the same number of atoms is Fig. 1-Section of a symmetrical triple line, showing the grain boundaries (GB) and the triple junction (TJ).
The distribution, shown in Fig. 3, was truncated at 8.1/ =>< aa ; the initial number of grains was 10000 and the initial average diameter was = 1.

A number of ultra fined grained (UFG) alloys produced by SPD exhibits favorable mechanical properties consisting in a combination of very high strength and significant ductility [2].
L and (l/L) values are plotted as function of number of deformation cycles are shown in Fig.2a.
Fig.2: Evolution of (a) grain size parameters (length and aspect ratio) as function of number of CARB and ARB [5] cycles and (b) grain boundary character distribution as function of number of CARB cycles of Fe-36%Ni (wt.%) alloy.
During ARB processing, the intensity of S and Copper components tends to increase with the cycle number.
· The estimated deformed volume fraction increased with increasing number of CARB cycles.

The austnite grain size also increased.
The distribution of inclusion size and numbers were measured and counted, and the semi-quantity distribution chart was shown in Fig.7.
Size of most inclusions in experimental steel is below 3μm, and the size of less than 1μm account for the majority of total number of inclusions.
At this point, the inclusions (particle size below 1μm) have a larger size and smaller relative number compare to the austenite grain, its effect on retard the grain boundary movement is extremely limited.
However, as the number of these mini type inclusions is still small and the dissolution of some MnS in a higher temperature, the austenite grain growth of experimental steel is still faster with the temperature increasing.

Introduction Reactive Ion Etching(RIE), is a kind of dry etching process which is assisted by plasma which is an ionized gas with equal number of positive and negative charges.
Table 1 : Maximum and minimum value for parameters Parameters -1 1 Oxygen 20 sccm 50 sccm Argon 30 sccm 80 sccm ICP power 500 W 1 kW BIAS power 100 W 300 W Next, the wafer is prepared whereby it is diced to get the number of samples needed for the DOE.
Fig. 2: Mean Grain Size Analysis before RIE Fig. 3 shows the statistic of the mean grain size for 16 experiments after RIE.
Fig. 3 : Mean Grain Size Analysis after RIE Consequently, this preliminary study presents that the RIE treatment results in increment of the grain size.
Overall comparison between grain size prior RIE treatment and after RIE treatment shows that grain size of aluminum increases after RIE treatment.

The Ms temperature is increased with increasing the AGS and can be represented as follows: G0.303.542)C(M os ×−= (1) where G is the number of ASTM grain size. 50 100 150 200 250 300 350 400 450 : Ms Strain Temperature ( o C) 850 o C-10min 900 o C-10min 950 o C-10min 950 o C-120min Fig. 1 Dilatational curves measured during quenching from different austenitization Fig. 3 Relation between the austenite grain size and the Ms temperature 6.75 7.00 7.25 7.50 7.75 8.00 8.25 8.50 8.75 280 290 300 310 320 330 340 350 Ms temperature ( o C) ASTM grain size number Fig. 2 Optical microstructures of the specimens quenched from different austenitization conditions: (a) 850℃-10min, (b) 950℃-10min, and (c) 950℃-120min The reason why the Ms temperature increases with increasing the
Thus, the fine austenite grains have more grain boundaries which play a role as obstacles to the growth of the martensite, finally reducing the Ms temperature.
At stage I, where the martensite volume is less 30 percent, the specimens with fine austenite grain sizes (ASTM grain size number: 8.44 and 8.68) reveal faster transformation kinetics probably because the fine grains provide more nucleation sites for the martensite transformation at the grain boundaries.
The transformation rates of the coarse grained (ASTM grain size number: 7.01 and 7.69) specimens at stage II, where the martensite volume is 30 to 80 percent, are faster than those of the fine grained specimens, because the grain boundaries obstacle the growth of martensite once nucleation is almost done.
(2) where VM is the martensite volume fraction, T is cooling temperature, G is the number of ASTM grain size, a0, a1, b0, b1, α, and β are the optimized parameters determined base on experimental kinetic data.

The process of strain-induced grain formation can be categorized into the three stages irrespective of deformation mode and temperature: i.e. i) an incubation period for new grain evolution in low strain; ii) a grain fragmentation by frequent development of MSBs and subsequently new grains in medium strain, and iii) a full development of fine grains in large strain.
Fig. 2 Effect of MDF at 763 K on (a) the average grain size, dUFG and the minimal spacing of deformation and microshear bands in remained initial grains, (b) the average misorientation of (sub)grain boundaries, Qave , in the fine- grained regions and (c) the fraction of fine grains evolved, VUFG.
Fig. 2 shows changes in some microstructural parameters in the AA7475 with repeated MDF at 763 K, i.e. the strain dependence of (a) the ultrafine grain (UFG) size, dUFG, (b) the average misorientation of (sub)grain boundaries, Qave, in the fine grained regions and (c) the volume fraction of the new grains evolved, VUFG. [8].
In stage 2, the number and misorientation of the boundaries of MSBs rapidly grow with strain in e > ec , leading to fragmentation of original grains into different misoriented small regions, where UFGs are preferentially evolved.
As the results, the number of grains having MSBs can be gradually decreased at elevated temperatures [9,11,14,15] and then UFGs with HABs are hardly developed in original grain interiors.

Conductivity of Grains and Grain Boundaries in Polycrystalline Heteropoly Acid Salts B.
The contribution to conductivity by grain boundaries is higher than that by grains.
Salts of small-weak cations crystallized with a large number of water molecules (25-17) and those of big-strong cations form precipitates with lower hydration degree [11].
These RC circuits correspond to grains and grain boundaries.
The conductivity of grains is higher than that of the grain boundaries.

Retardation Effect of Grain Boundary Segregation on Grain Boundary Diffusion B.
The effect of grain boundary segregation (GBS) on grain boundary diffusion (GBD) is analyzed in frame of the new model.
Their composition is close to that of the nearest phase in grain in equilibrium with solid solution in grain.
In a number of systems with strong interaction (e.g, Ni-S, Fe-S, Ni-P) [12-14], it was shown that such associates are formed.
[2] Grain Boundary Diffusion and Grain Boundary Segregation / Ed.

Copious nucleation applies a high undercooling during pouring and generates a large number of solid nuclei.
Fig.2. also demonstrates that the number of crystals poured at lower temperature is much more than that of high temperature.
So when the crystal nucleus produced during the pouring process move to the crucible, the crystal nucleus will be remelted because of higher liquid temperature, which results in the number of nucleus decreasing.
A large number of retained crystal particles exist in the liquid and prohibit the dendritic growth and thus promote the formation of the desired microstructure, so the grains obtained from slurry preparation are small and round at low pouring temperature.
Effect of grain refiner (0.06% Ti) on the average grain size at different pouring temperature 4.

Grain Boundary Relaxation in a Fe-Cr-Al Alloy Z.
Grain boundary relaxation strength remarkably decreases with increasing grain size.
When grain size reaches 520μm, the grain boundary relaxation peak almost disappears.
Large numbers of observations of grain boundary damping in internal friction experiments have been reported since the identification of Kê phenomenon [1-4].
Besides, the dependence of grain boundary relaxation on grain size has little been reported in Fe-Cr-X alloys.