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The amorphous precursor is crystallized to the epitaxial α-Fe2O3 grains in three steps with annealing temperature; i) the growth of the well aligned α-Fe2O3 interfacial crystallites to approximately 200-Å-thick, together with the transformation of the Fe3O4 crystallites to the α-Fe2O3 crystallites (< 400℃), ii) the growth of the less aligned α-Fe2O3 grains on top of the well aligned grains (> 400℃), and iii) the nucleation of the different less aligned α-Fe2O3 grains directly on the α-Al2O3 substrate (> 600℃).
The importance of iron oxide films led to an increasing number of surface science and film growth studies [5-7].
The inset of Fig. 3(a) shows the rocking curve of the crystallized α-Fe2O3(0006) grains at 600℃.
From these results, we suggest that the less aligned α-Fe2O3 grains, having the nucleation temperature of ~400 ℃, are homogeneously nucleated on top of the well aligned grains, as a preferred nucleation site.
The second step is the growth of the homogeneously less aligned (3.08 o FWHM) α-Fe2O3 grains, having the nucleation temperature of ~400℃, on top of the well aligned grains keeping grow to the CDS of 200 Å in the film normal direction.

The original grains are generally visible but the density of LAGB and HAGBs inside the grains is much lower: the strong influence of temperature on reducing grain fragmentation in Al-Mg alloys is clearly seen.
In the 3D grain texture simulations involving 14-sided grains, this grain coalescence by lattice rotations to 3 texture components leads to long, interpenetrating "orientation chains".
Fig. 4 illustrates a 2-D section of the evolution of grain structure and texture components during a grain interaction texture simulation.
It is important to note that at the end of each cycle (n x 3 x 0.2 where n denotes the number of cycles), the RCSQ is close to zero, which means that on each one of the 12 slip systems, the slip quantity produced by one increment ends up being annihilated during a future increment.
Since the texture components are fewer in number as compared to the grain neighbors on average, this leads to significant grain coalescence and eventually the formation of "orientation chains".

As reported in Ti-6Al-4V [12,13], α′ martensite has a considerable number of dislocations, interfaces of martensite variants and twins, which act as nucleation site for recrystallized grains.
The silicides at the recrystallized grains are more frequently observed in MS specimen than in LS specimen, whereas silicides in the recrystallized grain interior is less frequently in MS specimen because grain size is small in MS specimen.
It is reported that the reduction of recrystallized grain size results from the pinning of recrystallized grain boundary by precipitates or from nucleation of recrystallized grain at precipitate [14-17].
In the mechanism of pinning of recrystallized grains by silicides, silicides pinning recrystallized grain boundary exists at the recrystallized grain boundary.
On the other hand, in the mechanism of the nucleation of recrystallized grain at silicides, silicide acting as nucleation site for recrystallized grain exists in the interior of the recrystallized grain.

This means that the fraction of high-angle boundaries in the subgrain structure of given size, which can well be estimated as fhab = w/d [30], may be varied by varying the number of passes.
The minimum ε& min of creep rate increases by orders of magnitude as the number of passes goes up from 2 to 8.
Fig. 4.Modeled steady state deformation resistance of Cu in dependence of grain size d; d = 50 µm: conventional grain size; d ≤ 1 µm: "small" grains.
Fig. 4 illustrates the grain size dependence of the steady state deformation resistance of Cu with "small" grains in comparison to conventional grains.
"Small" means that the dislocations are stored at the grain boundaries only, not within the grains.

BaFe12O19 substituted sample shows a single semicircle at lower temperature and two overlapped arcs at 120 and 160 oC due to grain and grain boundary.
The electrical resistivity contribution by the bulk material (grain), grain boundaries or electrode can be identified from the arcs [3].
BaTiO3 phase was indexed based on the standard JCPDS data number 05-0626 for tetragonal structure.
R1 is much higher compared to R2 due to difficulty of the charges to move in the grain boundary compared to in the grain.
From 25 to 80 oC, the grain boundary relaxation peak frequency decreases with temperature but the Z“ value increases showing an increment in the grain boundary capacitance.

At a low value of Z abnormally large grains formed during annealing.
Although a number of studies have been undertaken on the static recrystallization of cold rolled interstitial free steel [e.g. 2-5], there is only minor reference in the literature to the recrystallization behaviour following warm working.
The average linear intercept ferrite grain size thus achieved was 25µm [10].
After 30 s a few new strain free grains can be observed.
In Figure 4c a number of the large apparently recrystallized grains contain, in their interior, a few low angle boundaries.

In order to avoid the grain-size effect, the ECAP-processed alloy was annealed to coarsen the grains.
The ECAP implementation results in the formation of ultra-fine grained structure of the alloy with an average grain size of 2.0-2.4 µm.
However, at lower deformation temperatures, the plasticity of the alloy noticeably decreases because of a limited number of the effective systems of deformation.
The averaged grain size of the MA2-1 alloy for the different regimes.
The different routes of ECAP of the alloy result in the formation of ultrafine grained structure with an average grain size of 2.0-2.4 µm.

The average grain size (d) was determined by the linear intercept method [15].
The addition of Gd2O3 increased the number of grains and here it acts as a grain inhibitor (Fig 2).
Conclusion In the Gd2O3 substituting of the ceramics, there is an increasing number of secondary phase that inhibited the grain growth and reduced the porosity, thus improving the sample microstructure.
Halim, Grain growth in sintered ZnO–1 mol% V2O5 ceramics, Mater.
Nelson, Lineal intercept technique for measuring grain size in two-phase polycrystalline ceramics.

Introduction Rotary kiln has been widely used in chemical engineering and mechanical engineering to process materials such as mixing of solids, drying grain, and coating of materials, clacination of cement, pyrolysis of oil shale, hazardous waste and oil sand.
Number of contacts between large and small particles in axial direction.
From Figure 4 we can see that number of contacts in the central region is lager.
The change of time-averaged number of contacts in axial direction From Figure 5 we can obtain that number contacts gradually decrease from the central region to both sides.
Taberlet, “Recent advances in DEM simulations of grains in a rotating drum,” Soft Matter, vol. 4, 2008, pp. 1345-1348, doi:10.1039/b71729c

However, the concentration value of Al at grain boundaries was smaller than that in grain interior since the trough valley values of spectra lines for Al were represented in grain boundaries.
In conventional solidification (without UST) grains grow up abreast, so the solute atoms are prone to pile up in grooves between grain boundaries which are parallel to the grain growth direction (shown in Fig.5).
Fig.5 Schematic diagram of grain boundary segregation formation With the application of UST to aluminum alloy melt, in liquid phase, firstly, ultrasonic cavitation effect can increase the melt undercooling and nucleation ratio in liquid phase [9, 13-17], therefore along the growth direction, the number of grains per unit area multiplies and grains combine tighter.
In this way, grooves between grain boundaries decrease greatly, thus weakening grain boundary segregation.
But when melt solidifies under ultrasonic field, grain size reduces significantly because the dendrites change into equiaxed grains.