Search results

At 20 % deformation a relatively large number of voids can be observed.
At 70 % cold work the number of voids is smaller than at 20 %, but their shape is again almost spherical.
They number is not different from that recorded at 70 % cold work.
Continuous deformation leads to new grain formation, and the number of the grains increases as the forming degree increases.
From figure 3, it is also observable that the number of the grains is not changing appreciably, only the shape of the grain become more elongated.

Zhu, Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility, PNAS 112(47) (2016) 14501-14505
Another issue when discussing pure metals is the fact of limited numbers of defects (vacancies, dislocations and grain boundaries) contributing to strain hardening.
Kaibyshev, On nature of grain boundary recovery, Phys.
The mechanical properties were examined at room temperature after HPT processing through different numbers of turns and at elevated temperature of 250 °C.
Microhardness of bulk titanium evolves typically for HPT-processed bulk pure metals increasing in 4-5 times with increasing numbers of total revolutions.

Accordingly, grain boundary energy should be used here.
(3) The experimental values [4, 5] of KH-P for a number of FCC metals are listed in Table 1.
After the S value is calculated, grain boundary energy density, WGB, defined as the amount of grain boundary energy per unit volume (J/m 3), can also be computed, written as, dSWGB /2γγ == , (5) where γ denoted the grain boundary surface energy, i.e. the energy per unit grain boundary area.
It is now hypothesized that an expression to demonstrate the energy-stress proportionality, similar to that shown by equation (2), should also hold for grain boundary component; as a consequence, the grain boundary stress component and grain boundary energy density must satisfy the following equation: 2 GB GBW σ∝
Furthermore, if assuming that equations (4), (5), (6) and hence also (7) are independent of grain sizes, the equation (8) obtained in the present work should hold over all grain sizes.

During homogenizing treatment, a large number of dispersive Mg2Si phase appeared inside grains, and large number of the phases containing Er were dissolved into the matrix.
Fig. 2(a) shows that the grain size is non-uniform.
In addition, the bright granular phases appeared inside grains.
The bright granular phases inside the grains and the bright strip-liked phase in the grain boundary were complex compounds rich in Al, Mg, Si, Fe and the rare earth elements of Er (called Er-rich phase).
Besides, Er-rich phases on the grain boundary became smaller or even disappeared, while in the grain boundary Er-containing phases became discontinuous and sparseness.

A number of studies on Inconel 690 have been carried out, of which most of them are focused on the evaluation of corrosion or tensile properties [6, 7], and the precipitation behavior and detailed observation of the intergranular carbides have not been dealt with so far.
The mean grain size was around 29.0µm±0.8µm.
Nucleation and growth of the Cr-rich carbides in the grain boundaries of the Inconel 690 require continuous Cr support through the grain boundaries because grain boundaries provide fast and easy diffusion paths.
There are two adjacent grains across a grain boundary and the two interfaces are facing together.
When we have different point of view on the grain boundary migration, wavy undulating grain boundary could be effective for an improvement of mechanical properties [8] due to increased grain boundary diffusion distance and retarded grain boundary rupture.

Several methods to obtain fine crystal grains have already been proposed.
The plates consist of fine crystal grains with a preferred orientation.
Compared with a sample formed under single axis compression, the sample formed by dynamic molding possessed a Vickers hardness number that was about 2.4 times larger (27 versus 66 Hv).
In addition, the Vickers hardness number of the molded sample was about 1.9 times larger (35 versus 66 Hv) than that of 1060-H18 aluminum, which is dissolved and treated by work hardening.
In addition, it became clear that each crystal grain is a single crystal.

The initial grain size distribution before vibration is shown in Fig. 3.
The main grain sizes of the crushed rock sample range from 25 to 45 mm.
Then, the water weight of each layer was measured via draining away the pore water of each layer in order of hole Number 1, 2, 3 and 4, as shown in Fig. 1.
Finally, the relevant porosity in each layer of the crushed rock sample from the sequence as a function of the cycle numbers was measured.
The grain sizes of the crushed rock sample are relatively smaller than the initial garin sizes due to fracturing edge angles of crushed rock grain during vibration.

For that reason, a reference element was considered in order to minimize the number of tests and to maximize the amount of information collected from the test campaign.
The tension parallel to the grain tests consisted in the application of a load parallel to the timber grain's main direction.
Tension parallel to the grain tests.
Table 3: Results of the tension parallel to the grain tests.
A reference element was considered in order to minimize the number of tests.

The 2D and 3D AFM micrograph of the PZT thinfilm annealed at 1000 °C illustrates fine grain growth, smooth and uniform surface pattern with large number of grain boundaries.
This may also be attributed to the increase in number of grain boundaries, which in turn increases the surface energy and reduces the dislocations and this fact is in agreement with other reported results.
Further the surface studies indicate the presence of fine grains with extremely least surface roughness and large grain boundaries with oriented crystallite growth.
The increase in hardness with the annealing temperature may be attributed to the increase in grain size and surface smoothness at higher elevated temperature (as evidenced by the AFM images) and increase in the number of grain boundaries, which in turn increases the surface energy and reduces the dislocations.
Further the surface studies indicate the presence of fine grains (average grain size 200 nm) with extremely least surface roughness.

The adjacent boundary between one grain and another is called grain boundary.
PTh is the ratio of those pixel number with gray level less than and equal to Th1 to S
In this figure, 0~7 stand for the numbers of eight directions, that are direction codes.
The total number of related pixels on these chains is PB (=1798 pixels).
Additionally, the direction code is just one of eight numbers from 0 to 7, and it can be encoded by 3 bits.