Search results

Shaping and flattening diamond grains.
Classification of fabricated diamond grains.
Figure 7 shows a typical feature of diamond grains observed after the truing test.
Thus, an experiment to elucidate the effective truing conditions for forming flat diamond grains was conducted by counting the number of grains categorized into the five types from the total of approximately 350 grains observed in four SEM views obtained by rotating the tool by intervals of 90 degrees.
It was confirmed that crushed grains became detached from the bond face and that the edge of diamond grains became sharp.

The morphology (SEM) of sintered sample showed a fine grained microstructure with equiaxed grains.
The Nd and La had lower atomic numbers in all of the 17 rare earth elements, thus the Nd2O3 and La2O3 could be seen as typical light rare-earth oxides which show higher basic.
Our previous (Table 2) study on melting behaviors of SiC and a series of RE2O3 (mole ratio,1:1) had shown that the melting temperatures raised with the increasing of the atomic number of rare earth elements (from La to Er and Y).
While the overall grain sizes remained very fine for all compositions investigated, it can be noted that the grain sizes decrease with the increase of additive cationic radius.
Apart from crack deflection, grain-bridging due to the weak grain-boundary may also play a significant role in the toughening of LPS-SiC ceramics (Fig. 3b).

However, applictions of Mg alloys have been significantly inhibited by low formability inherited from the hexagonally close-packed crystal structure and insufficient number of slip system.
Equiaxed grains were well developed with an average grain size of 19 mm after 2-hour annealing treatment at 430°C, as shown in Fig. 1 (b), which is larger than the typically required grain size of d < 10 mm for grain boundary sliding superplasticity.
The grains in the evenly deformed gauge region, as shown in Fig. 3 (e) and (f), was slightly elongated along the tensile direction and refined with an average grain size of 15 mm.
The grain refinement should be attributed to dynamic recrystallization (DC).
The grain elongation is generally related to dislocaiton creep other than grain boundary sliding (GBS), which is consistant to the relatively large grains in the gauge region, where grain elongation occurs by absorbing or releasing dislocationes.

Although the size the utra-fine equiaxed grain is quite different from one to another, an average grain size about 0.7�m has been obtained.
The dislocations are distributed both in the grain and in the grain boundary.
The grains have evolved into more regular equiaxed shape and the average grain size becomes a little bit larger to about 1�m.
The enhanced grain boundary diffusion is caused by the fact that ECAP-processed alloys possess non-equilibrium grain boundaries.
The results show that ECAP shows an excellent capability of grain refinement, with the pass number of pressing, the grain of pure Al can be refined to about 700nm.

The tensile deformation at 473 K led to the additional grain growth and formation of new grains.
In particular grain boundaries influence creep behaviour of ultrafine-grained materials because the increasing contribution of grain boundary sliding to the total creep deformation can be expected.
The high number of HAGBs in the microstructure in the connection with relatively small grain size probably lead to the higher activity of additional creep mechanisms like GBS, cavitation and more intensive diffusion processes.
Furthermore, grain boundaries can influence creep behaviour of ultrafine-grained materials due to synergetic effect of additional operating creep mechanisms like grain boundary sliding (GBS), intergranular cavitation or more intensive grain boundary diffusion [19].
Creep in ultrafine grained aluminium.

When the sintering temperature was 1000 ℃, the average grain size of the crystal particles was 100-200 nm and the thickness of the thin film was about 380 nm when the coating layer number up to 10.
While the sintering temperature was 1100 ℃, the average grain size of the crystal particles was 200-300 nm and the thickness of the thin film was about 320 nm also 10 layers.
Analysis with the coordination number of A-type LSO and B-type LSO from Table 1, the reason why the thin film became much more thinner under 1100 ℃ was that the coordination number of B-type LSO became lower and the reengineering of the organization structure[9].
The thin film was of average grain size of 100-200 nm at 1000 ℃, besides, the thickness was of about 380 nm when the coating layer number up to 10.
While the average grain size was of about 200-300 nm at 1100 ℃ and the thickness was of about 380 nm.

Electron backscatter diffraction (EBSD) was used for characterizing the preferred orientation, grain size distribution, and grain boundary character distribution.
Due to a number of data obtained from EBSD analysis, it is impossible to present all of results and therefore Fig.1 shows, for instance, the orientation image map, the inverse pole figure and the grain size distribution under the current density 0.5A/cm2 and the frequency 340Hz.
Using OIM analysis software, the average area grain size ν is determined by the following: ∑∑ == = � i i � i ii AA 1 1 νν (1) where iA is the area of grain i , and iν is the grain size of grain i .
If the average grain size and twin fraction are displayed in a plot in Fig. 2, it was observed that the grain size increases as the twin fraction increases.
In the case of the grain size > 1 µm, however, the twin fraction decreases, as the grain size increases.

I have returned a number of times since, each time to be greeted warmly by old and new friends, and to be continually impressed by the advances in Chinese science and engineering.
Large grains at surface of chill cast thin plate.
In isothermal coarsening of a simulated 5160 seconds, a number of pinching-off events were found in the sample with the slightly more open structure.
In any of the foregoing cases, a number of ways may be imagined as to how the dendrite structure evolves.
Spherical grains are seen.

The mechanisms of recrystallization nucleation in fcc bicrystals have been the subject of a number of previous studies [1-8], but usually without the advantages of modern EBSD techniques for detailed microtexture analysis.
The orientations of the grains composing the bicrystals are chosen to represent grains of unstable or stable deformation behaviour.
recrystallized grain and the deformed neighbourhood, taken globally for the regions around both grains is not very clear.
In Fig. 3a one of the recrystallized grains, R1, can be seen to grow into the deformed grains of both 'shear' and 'Goss' orientations.
As can be seen on the {111} pole figure (grain R2), this grain's inability to cross the grain boundary may result from the absence of a common {111} plane with a crystallite of 'Goss' orientation.

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.