Search results

The greatly reduced impurity embedded in grain boundaries and more uniform grain sizes do indicate the improvement of material strength and ductility.
The inferior formability of Mg alloy results from the limited number of slip systems of hexagonal close-packed microstructure, which suffocates their applications in the sheet metal forming operation.
A number of previous research showed that elevated temperature can increase the number of slip systems and change the slip direction, which can enhance material ductility and reduce material anisotropy.
Based on a rough calculation using Grain Counting Methods, ASTM E112, the grain size after heat treatment is much more uniform than the original condition.
The average grain size and the roughly calculated maximum grain difference at homogenization temperature of 400 °C with various periods of heating are illustrated in Fig. 3.

It is dependent on not only the number of grain-boundaries but also an intrinsic varistor-voltage (= Vgb) at a grain boundary.
Therefore, it is necessary for them to independency clarify effects of the number of grain-boundaries and Vgb.
By the way, in the functional layer at the lower limits, since the number of grains between inner electrodes is around 6 to 7 in the direction of the electric field, the varistor-property at a grain-boundary should be gradually dominated with decreasing in grain-boundaries.
It is suited for MLCV as it is consisted of fine grain (average grain size = 2.3 μm).
Fabricated MLCV was thickness of functional layer of 17μm and the number of about 7 grains between internal electrodes of Au.

A zone of fine grains is located next to the columnar ones, and at an interface with the bronze matrix much coarser grains are seen.
The Nb3Sn grains in continuous diffusion layers get larger by a factor of 1.5 and the grain size scattering broadens (Fig. 3, Table 1).
As seen from Table 1, Ti does not result in grain refinement of superconducting layers, which we already observed in a number of previous studies [8,11,16].
Parameters of Nb3Sn grain size distribution No.
There is a zone of columnar grains adjacent to the residual Nb, a zone of fine equiaxed grains and some amount of coarser grains at an interface with the bronze matrix, which is typical of bronze-processed wires.

The mechanical anisotropy was measured by tensile testing after different numbers of ARB cycles.
Introduction Bulk ultrafine-grained (UFG) materials produced by accumulative roll bonding (for processing details see [1,2]) have very interesting mechanical properties [3] mainly because of a significant grain refinement (grain sizes smaller than 1µm).
With increasing number of ARB cycles an ultrafine-grained structure develops in the B layers by continuous recrystallization [8], while discontinuous recrystallization occurs in the A layers.
The laminates are labelled as AB_#, with # being the number of ARB cycles.
The global texture and the mechanical anisotropy change with increasing number of ARB cycles.

Fatigue Behavior of Age-Hardening Cu-6Ni-1.5Si Alloys with Different Grain Sizes M.
Fig. 3 shows Vickers indentation pressed inside a grain (load = 0.49 N).
The number of cycles to initiate a grain-size crack (l ⁓ 0.04 mm) in the NR specimen is about 3 times larger in that in the CR specimen (l ⁓ 0.1 mm).
This is because that the grain size of CR specimen was larger than the NR specimen.
Cold-rolling before SHT brought a grain growth during a heating at SHT.

This could be attributed to different corrosive resistance properties of NC nickel and coarse-grained nickel coatings.
Based on the above results and analysis, the different tribological behavior of NC nickel and coarse-grained nickel coatings can be understood in varying lubricated condition by considering the effect of the grain size, the number of grain boundaries and tribochemical reactions.
Wang et al. [4] have proved that the hardness increased with decreasing the grain size and the friction coefficient decreased with decreasing the grain size under dry friction conditions.
It can be explained as following: the passivation first started on surface crystalline lattice defects and NC nickel materials have high density of grain boundaries and dislocations inside grains when lubricated using ionic liquid.
Therefore, it is believed that the high fractions of coarse-grained nickel coatings will provide an increased number of active sites to quickly form a continuous and protective passive film.

The grains, which formed at the old grain boundaries, possess a characteristic of 'necklace' and are of only one-tenth of the size of the original grains and 2-5 times of that of subgrains.
The result shows that there are a considerable number of fine grains possess high angle boundaries while some boundary misorientation is of medium value.
The grains may then become flattened and the size of boundary serration will become comparable with the grain thickness.
An equiaxed microstructure with a large number of high angle boundaries is therefore evolved by such a process of boundary impingement without the operation of any new recrystallization mechanism [9].
Very fine equiaxed grains possessing large-angle grain boundaries with their neighboring grains develop as a result.

The number of grains for D301 is consistently over all cycles.
The grain area ratio increases with increasing number of cycles.
In the bottom diagram the number of grains for D601 is constant.
Thereafter, the number of grains decreases.
At the end the number of grains decreases again.

Simultaneously, the effect of number of passes during ECAP was also discussed in terms of the microstructure change.
Special attention was paid on the effect of number of ECAP passes on the morphology of semi-solid.
The total number of passes was two, using a Molybdenum disulfide (MoS2) lubricant in a pressing speed of about 1 mm/s.
When the temperature reaches to above solidous, the high-energy grain boundaries of these new grains are penetrated by liquid, leading to the fragmentation of original grains to small equiaxed grains.
The presence of liquid causes grain growth and spheroidization of the newly grains.

Next, cool down to 800˚C by respectively taking the cooling rate of roller as 6˚C /min （water quenching，serial number A1）,600˚C（water quenching，serial number B1），and cool down to 400˚C by taking the stack cooling rate as 0.3˚C /min（water quenching，serial number C1）.
Wherein, stands for the volume fraction of precipitated particles; stands for the number of precipitated particle; stands for the average diameter of precipitated particle; stands for the measurement area.
As a result, the precipitated particles rapidly precipitates along austenite grain boundary (ferrite omentum), and thus destroys the strength of austenite grain boundary.
As shown in Figure 7, after the entry into furnace, the thermal stress received by austenite grain transforms into pulling stress, and produce grain boundary sliding under the action of thermal stress.
Following the solution of precipitated particles, the continuous holes form tiny cracks along austenite grain boundary.