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The polycrystal structure is presented by pearlite grains of lamellar morphology (eutectoid mixture of ferrite and cementite in which the both phases have the shape of extended plates) (fig. 2), ferrite grains in the volume of which one can observe the cementite particles of different shapes (subsequently referred to as grains of ferrite-carbide mixture) (fig. 2, c-e), and grains of structurally free ferrite (ferrite grains which do not contain the particles of carbide phase in the volume) (fig. 2, f).
Relative fraction of grains of ferrite-carbide mixture is slightly smaller (from 12% to 65% of steel structure).
In the ferrite of pearlite grains only the first two types of dislocations substructure (substructure of dislocation chaos and netlike dislocation substructure) are observed; the cellular and fragmentary dislocation substructures are revealed only grains of structurally free ferrite and grains of ferrite-carbide mixture. 0,5 μm a b d 250nm c 250nm 250nm f F 0,5 μm e Fig. 2.
TEM image of structure of lamellar pearlite grains (a, b), ferrite-carbide mixture (c, d, e) and structurally free ferrite (f, grain is designated by F); a, c–f – bright-field images, b – microelectron diffraction pattern to (a).
Designations: the first digit – regime number; the second digit – scalar dislocation density in ferrite components of pearlite grains (1); or grains of ferrite-carbide mixture (2) axis – analysis along the center axis; S – from semicircle.

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.

Metals of nano-grain sizes deform by grains sliding pass each other, with little distortion occurring in the grain cores.
Accommodation mechanisms such as grain boundary diffusion, grain sliding and grain rotation control the kinetics of the process.
Nano-grain metals of such small grain sizes deform mainly by neighboring grains sliding pass each other with insignificant distortion in the grain shape.
There are about 3N number pairs ( α αα Xx −= td/d α α θ= α θ td/d α α x= ω ),βα belonging to this set.
The cell contains 9 regular hexagon grains and is termed the 9-grain cluster model.

The sintering behavior of powder compacts was investigated by evaluating the densification, the lattice constant c for AlN, and the dihedral angle of the interface between the AlN grains and the grain boundary liquid-phase.
Furthermore, it changes the grain-boundary phase to Y4Al2O9→YAlO3→Y3Al5O12 while it traps oxygen inside the AlN grain, promoting purification of the AlN.
AlN Al VOAlOAl ⋅⋅⋅ +'+→ 3232 (1) These point defects generate a stacking fault with a coordination number of 6, with a smaller lattice constant than the AlN stacking with its coordination number of 4.
The wettability of AlN grains with a grain-boundary phase was improved by the presence of a solid solution of oxygen in the AlN lattice as discussed below.
Consistent with this trend, the wettability of the AlN grains by the liquid phase was worse with the elimination of oxygen from AlN grains.

In these the phenomenon of "ridging" or "roping" is often observed, leading to the discarding of a large number of parts and raising production costs.
For steel 434, Fig.2b, layers of large, heterogeneous grains near the central plane of the sheet sandwiched between regions of smaller grains can be seen.
Large {001}<110> oriented grains.
Table 2: Predicted R-values for the orientations in the grain colonies.
The coarseness of the pattern will depend on the colony width and grain size.

Tungstendisilicide (WSi2) was formed at the tungsten/silicon interface as well as grain boundaries of the silicon.
The size and the area of the silicon melting and the viscosity of the SiO2 layer were strongly influenced by The EB energy, which determined the size and the number of the voids in the capping layer.
The eutectic statistically distributed at the primary silicon grain boundaries.
In addition, the WSi2/Si eutectic became coarser at the primary silicon grain boundaries and spread more widely.
The strong tendency of formation of tungstendisilicide at the primary grain boundaries would reduce the efficiency of the solar absorber.

The typical nugget stirred zone and TMAZ are surrounded by a heat affected zone (HAZ) thus resulting in a very fine and equiaxed grain structure in the weld nugget causing good elongation [6].
Though large number of investigations has been carried out on friction stir processing of aluminum alloys, the study on friction stir processing of magnesium alloys is limited.
They investigated that FSP leads to finer and more homogenized grain structure.
These elongated grains are transformed into significant grain refinement in the nugget region and it has been reported that because of dynamic recrystallization due to frictional heat between the shoulder and the workpiece, initial elongated grain structure are transformed into fine equiaxed grains.
A significant equiaxed grain refinement is obtained in the nugget region, due to which the friction stir processed AZ31B material can exhibit superplasticity characteristics.

These results are described in the present investigation together with a summary of unpublished data on the thermal properties of a number of UHCSs.
The grain size in the coarse grained UHCS was reduced to 7 μm by a subsequent cold rolling and recrystallization process.
The average linear grain size is less than 5 μm.
Thermal expansion tests were pursued at the Lawrence Livermore National Laboratory on a number of UHCS-1.6Al materials containing different amounts of carbon.
A limited number of tests were done on the mechanical properties of UHCS-10Al materials at room temperature.

Coarse-grained heat-affected zones (CGHAZ-W) in weld metal were simulated using three different cooling times from 800 °C to 500 °C (t8/5).
In the CGHAZ-W simulation the number of Mn-bearing inclusions increased compared to the unaffected single-pass weld metal.
A number seven components can be combined into 127 unique combinations, i.e., NMI classes, therefore reducing of the classes was needed.
The number density of inclusions was similar in all CGHAZ-W samples regardless of the cooling time (Fig. 1a).
Gáspár was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences (Grant number: Bo/00643/22/6).

The irradiated pressure tube samples obtained from 13 locations were showing average alpha grain width, grain length and aspect ratio in the range of 0.17-0.27 micron, 1.7-2.3 micron and 7.1-8.5 respectively.
The off-cut from End-1 showed average alpha grain width, grain length and aspect ratio to be 0.18 mm, 1.65 mm, and 7.75 respectively.
The off-cut sample from End-2 showed average alpha grain width, grain length and aspect ratio of 0.2 mm, 1.7 mm and 8.0 respectively.
Hydride platelets were also absent in the irradiated Zr-2.5%Nb pressure tube unlike the irradiated Zircaloy-2 pressure tube samples, which showed significant number of hydride platelets.
The b phase had globulised in large number of regions but remained at the a/a interface.