Search results

The carburizing process involved heating at 10°C/minute, followed by a defined number of boost and diffusion steps.
The grain boundaries, as can be seen from the micrographs, can be attributed to the slow furnace cooling from the austenitic temperature of 750oC to room temperature.
The heat-treated samples have a ferritic matrix with an irregular grain size which could be due to the distribution of the austenite from a carbon-enriched zone of the ferrite from the dissolution of the pearlite grains.
However, it can be observed that a more defined austenite grain structure is obtained in Figure 5, especially in the sample with pCNT.
The layer closest to the surface has austenite leading to ferrite with a change in grain size, attributable to the size of the carbon powders.

These variables are the number of training data points (N), network size (number of hidden layer and neurons in each layer), and number of training iterations or epoch (C).
Also the ANNs can be judged by various parameters such as the Mean Square Error (MSE) ∑∑== − = Q m N n n n mymd QN MSE 1 1 2 0 0 )]()([/1 (3) Where N0 is the number of output, Q the number of training sets, d desired output, and y the network output.
The number of neurons used in the hidden layer is 4.
At constant temperature, increasing Austenitizing time conduces to austenite grains growth and the mechanical properties of martensite were decreased with an increase in the austenite grain size.
The results also show that increasing in austenitizing time at constant temperature tends to cause a growth in the austenite grain, and consequently leading to degradation in the mechanical properties.

Introduction The rotor blade is one of the key components of aero engine structure parts, because it is the moving parts with high-speed rotation, large number, thin shape, harsh loading conditions and complex working environment, so the failure rate of it is high.
Fig.3 Microstructure of the cladding layer 100× Fig.4 Crack in some cladding zones 100× Near the first combination surface is large dendrite grain.
Slightly away from the first combination surface is small dendrite grain relatively, and the direction of the dendrite is better (Fig 5).
And because the part that close to the first binding belt is in the inner layer, the cooling rate of it is relatively slower, so the grain size in the inner layer is bigger.
Cause analysis: there is large number of carbide hard phase at the combined location, resulting in the raise of the hard.

The grains within the layer have obvious recrystallization phenomenon with loose remelting microstructure.
The matrix located below has uniform structure and compact texture, but the texture of the loose layer has changed obviously after electrode micro-detonation machining with coarse grains and dense micro-cracks at grain boundary, which has the typical topography characteristics of recrystallization.
A large number of N elements and partial Si elements are reduced from Si3N4.
Fig.6 Ideal pressure-time curve in the air According to the step change equation of micro-detonation wave in the ideal gas, it can be obtained in Eq.2 [7]: 0 0 γR T U = M M (2) In Eq.2: M0－the mach number in front of the micro-detonation wave, M0 = dielectric velocity in front of the micro-detonation wave /340.
The grains within the layer have obvious recrystallization phenomenon with loose microstructure.

In the Au-Ti-Al system a number of different binary and ternary phases can be encountered depending on the temperature [13].
A DF image of such grains (marked by arrows) and the corresponding SADP are presented in Fig. 7a.
Nevertheless, one may distinguish two characteristic grain sizes in both samples - small ones, less than 50 nm, which are attributed to the Al3Ti grains, and bigger ones of the order of 200 nm and more, which are seen in a white contrast in Fig. 8 and belong to the Au2Ti phase.
It seems that the grain size of the dominant phases formed (i.e.
The sizes of the Au2Ti grain increase significantly with an increase of the temperature.

WAAM is characterised by a number of issues that are slowing its wider implementation.
The long, columnar grains in the microstructure of AM components leads to anisotropy [2].
When rolled at 50 kN the average grain size was 125 μm (Fig. 4b), and when rolled at 75 kN the grain size was 89 μm (Fig. 4c).
Note however that there was no grain refinement in the top 2 mm of the rolled specimens.
There is some debate over the precise mechanism: whether it is conventional recrystallisation or a consequence of the deformation and rotation of the β phase during rolling which increases the number of β grains when the material is reheated by the subsequent deposition process.

These new properties are linked to the high density of grain boundaries and interfaces that result from their nanoscaled structure.
During the sintering step, the elimination of the inter-agglomerate pores need high temperatures that also encourages grain growth, which is incompatible with the aim of keeping the sintered grain size in the nanometer regime [17].
During the milling needle-like particles breaking up and it is possible to see the increase of the number of small particles.
The changes in porosity, grain shapes and sizes caused by mechanical activation are clearly visible.
This work was funded by the project Grant number 142040 entitled "Advanced Metal Oxide Electroceramics and Thin Films", financed by the Ministry for Science and Environmental Protection of the Republic of Serbia.

Introduction Coiled tubing is widely used in oil field for well logging, well completion, drilling, work over and other operation in various fields to solve a number of conventional operating techniques problem which are difficult resolved, and it plays a more and more important part in exploration and production at oil field. [1] It will improve the efficiency of exploration and exploitation, studying, developing and using coiled tubing technology.
Each contour presents the same value of the power dissipation efficiency, and the number of the contour indicates the dimension of the efficiency of power dissipation in the same hot deformation conditions.
The instable map is separated to two parts by the number 0 of the contour, and the shade area is the region of flow instability as delineated using the criterion given in Eq.(3).
At lower temperature (850˚C- 950˚C) and lower strain rate, the conversion of the energy of deformation into activation energy is lower because of the lower strain rate, and the DRX do not occur at this region; at lower temperature (850˚C- 950˚C) and medium strain rate, part of DRX occurs because of strain rate, and the instability because the inhomogeneous original grain and the DRX grain; when temperature is about 1000˚C, the strain rate is higher, it is need more time for DRX to nucleate and grow, however the deformation time is shorter, and the effect of working hardening is higher than the softening by DRX, then, the instability exhibits.
At the higher temperature, after fast repeat-rolling, the austenite grains are refined by DRX; at the lower temperature, the DRX is not occurred for austenite grains, but the dislocation strengthening and phase-change strengthening are reinforced.

For such studies investigations of HPT deformation of single crystals make sense since the effect of certain initial lattice orientations can be studied separately, and the influence of grain boundaries can be derived from comparison with HPT deformation of polycrystals of the same material.
Single crystal texture results were calculated without any symmetrization, in order to avoid statistic errors at this type of coarse grain structure.
When comparing the results of this work with those recently reported by us for polycrystals of the same Mg purity [9], we can conclude that the absence/presence of grain boundaries do not affect the appearance of either the shear components or of those of recrystallization.
Comparing with results from Mg polycrystals, also the presence/absence of grain boundaries seems to play a role here
This difference is attributed to the smaller number and higher anisotropy of slip systems of hcp lattice compared with those of fcc lattice.

Since then a number of tests have been taken to obtain MgB2 both in the mono- and polycrystalline form.
Ex-situ MgB2 rods were prepared using commercial available MgB2 powder (Alfa Aesar) with 325 mesh grain sizes.
Figure 3.c,d discloses very dense grains packing with a grain mean size of several micrometers.
It was ascertained that the obtained MgB2 rods consist of different grain sizes and are free from any foreign phases such as Fe2B or MgCu2.