Search results

Therefore the above equation can be solved by the simple iterations method: (15) Setting the initial value , we find after iterations: (16) The qualitative view of the obtained approximate solution  at various values of iterations number at is presented in Fig. 3.
Polycrystalline ceramics consist of grains with different orientation of their axes.
Modeling of Hysteresis Loops of Textured or Grain-oriented Ceramics.
The XRD data indicates that most of matrix grains were well-oriented and there were almost negligible residual randomly-oriented matrix grains.
Compared to fine equiaxed grains in PMN-PT-0BT random ceramics, the textured ceramic exhibited large brick-layer-like grains which aligned parallel to the tape-casting plane.

Recently, a rapid and economical processing, i.e. combustion synthesis in high-gravity field has been taken to prepare high-hardness bulk solidified TiC-TiB2 composites, and high-performance of TiC-TiB2 composites are presented due to the achievement in fine-grained and ultrafine-grained microstructure [3,4].
After the crucibles were cooled to ambient temperature, the samples were taken out of the crucibles and the oxide slag at the top of the sample was remov Fig. 1 The XRD pattern of the TiC-TiB2 ceramic Fig, 2 FESEM microstructure of the TiC-TiB2 ceramic Results and discussion XRD, FESEM and EDS showed the ceramic was composed of a number of fine TiB2 platelets as the primary phases, irregular TiC grains as the secondary phases and a few Cr metallic binder as intercrystalline phases, as shown in Fig. 1 and Fig. 2.
Moreover, ultrafine-grained microstructures characterized by the TiB2 platelets in thickness smaller than 1 μm, were clearly observed in either the intermediate or the nearby ceramic, as shown in Fig. 5.
For TiC secondary phases, because of a combination of their isotropic growth and high diffusion rate of C relative to B in metallic liquid, they grow very rapidly once they begin to nucleate, and ceaselessly compete for growth space and free Ti atoms against TiB2 primary phases, in this case, some of fine TiB2 platelets are surrounded by TiC irregular grains and stop to grow, thereby presenting the unique solidified microstructure that a number of fine TiB2 platelets are embedded in irregular TiC grains, as showed in Fig. 2 and Fig. 5(b).
XRD, FESEM and EDS result showed the ceramic was composed of a number of fine TiB2 platelets, irregular TiC grains and a few of Cr metallic binder, and physical and mechanical properties showed relative density, hardness and fracture toughness of the ceramic were 99.5%, 24.6 GPa and 15.6 ± 1.8 MPa·m0.5, respectively.

Fine dispersoids are well observed for all the alloys, and the number of the dispersoids tends to increase with increasing Si content.
It was also revealed that the number of coarser (>1 µm) dispersoids increases with increasing Si content, as shown in Fig. 4.
In contrast, the core alloys with the Si content of/cold rolled to 0.41%/10%, 0.64%/10-20% and 1.04%/10-45% contained a fine grain (below 200 µm in mean grain size) after brazing treatment (Fig. 8 and Fig. 9b).
In contrast, if the clad sheets are fabricated by non-optimum conditions, a fine grain structure is developed in the core during brazing.
The increased grain boundary area in the core could promote filler penetration into the core along the grain boundaries.

Crack sensitivity in the fine grain areas is quite lower than it in the coarse grain areas.
The fusion organization of weld seam in the fine grain materials is smaller than it in coarse grain.
Figure 2 shows the sensitivity of cracking for the coarse grain and fine grain materials.
In addition they are selected 20 mm on the position of the welding seam in under different grain degrees, and are observed for the number of welding seams surface crack in stereomicroscope.
Crack sensitivity in the fine grain areas is quite lower than the coarse grain areas.

The grain sizes of Al3Hf and (Al+12.5 at.
Average grain sizes of Al3Hf and (Al+12.5 at.
The smaller grain size of (Al+12.5 at.
Average grain sizes of Al3Hf and (Al+12.5 at.
However, average grain sizes of both specimens were maintained below Journal Title and Volume Number (to be inserted by the publisher) 5 100nm even after annealing up to 1300 � for 1hr.

The results show that the grain-growing process in the new ODS alloys is significantly affected by the thermomechanical treatment, leading to the maximum grain size within 20-h annealing at 1200 °C.
These grains start a very fast growth owing to the presence of ultra-fine surrounding grains with a high stored energy; such a mechanism was identified as static recrystallization.
Cracks between the grains are marked by arrows in Fig. 6f.
The room temperature strength and ductility with prevalent trans-granular ductile fracture morphology are satisfactory, but can be still improved by decreasing the impurities content that would lead to lowering the number of voids and preventing the low energy ductile decohesion along the grain boundaries.
The causes of grain boundaries weakening at high temperatures (over ~700 °C) are now under intensive investigation (e.g. possible Al segregation on grain boundaries).

The number of implanted ions was about 20.10 15 atoms by cm² and the affected depth of alloy was about 200nm .
This treatment made it possible to obtain a polished sample with a number of surface defects higher than simply-polished coupons.
What must be underlined is that the number of Cr2O3 nodules was greater for the sample which had been implanted.
On one hand, the oxide structure highlighted a higher density of grains or sub-grains for the oxide formed on the implanted alloy.
These two results well agree with a growth mechanisms controlled by a diffusion step at the oxide grain boundaries.

This technique could reduce change of cutting depth owing to difference of grain size and protrusion height of surface abrasive of grinding plate, and near equal-cutting-depth processing is realized.
The results showed that the abrasive grains cutting depth changed obviously with multi-unit-lapping plate.
The Analysis of the Abrasive Grain Cutting Depth Model For the cutting edge of single abrasive grain , its cutting force is distributed of the contacts arc.
The addition of the large grains is controlled by the motor on the beam.
The equipment used to test roughness is Mahr Perthometer S2 (vertical resolution: 0.8 nm, sampling numbers: 11,200).

For each datum point, ten structure images were used and at least 70 grains measured.
The alloy has a structure with a grain size of about 160 nm.
After HPT at 5 turns the structure becomes homogeneous with a grain size of 70 nm and mainly high angle grain boundaries (Fig. 2b).
However, the number of these particles was insignificant and Cu and Mg in the Al matrix were in a supersaturated solid solution state after SPD.
The reason is the contribution of hardening by the small grain size, the nonequilibrium state of grain boundaries and the presence of nano particles with an homogeneous distribution throughout the sample [6,8].

When the electron beam current is 12mA, a part of the weld dendrites structure are replaced with finely equiaxed grain, the dendrites structure are reduced and the contents of equiaxed grain are increased.
With the decreasing of electron beam current, the grain sizes are decreased gradually in weld metal.
So that the grains of the weld zone without more energy for growth and during welding thermal cycle is weakened, which leads to the grain sizes of the weld zone decreased with the decrease of electron beam current.
Since a large number of small θ(CuAl2) and S(A12CuMg) strengthening phase are dispersed in the matrix, and the fine grain size is uniform, which makes the base material possessing high micro-hardness(150Hv).
Grain refinement can improve the strength, the plasticity and toughness of materials.