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Mechanical Properties of Aluminium Wires Produced by Plastic Consolidation of Fine Grained Powders.
The standard mechanical properties of extrusion products have been determined and grain structure has been inspected.
Rapid solidification of pure aluminium can provide material with refined grain structure in form of powder or flakes.
In addition, the numbers of micro inclusion of aluminium oxides are present in both coagulated and thin layers form placed along the boundary of fibres.
Pre-compaction of powder does not change the structure of extruded wires, although the number of inclusion of oxides seems to be greater for non-compacted state.

The equivalent strain produced by HPT, e, is estimated as [3] (1) where r is the distance from the center of disc (or ring), N is the number of revolutions and t is the thickness of disc (or ring).
Fig. 4 Grain size at steady state plotted against shear modulus.
Figure 4 shows that the grain size tends to decrease with an increase in the shear modulus.
HVS: steady-state hardness, G: shear modulus, dS: steady-state grain size, b: Burgers vector.
The hardness and grain size reach steady-state levels at large strains where the hardness and grain size remains unchanged with further straining.

Figure 5 distinctly reveal the grain boundaries of AM60 alloy in T4 condition.
With the addition of Mg-Ca master alloy, the number of nuclei and the nucleation rate likely increase.
Average grain sizes of AM60 alloy grain structure of AM60 alloy in T4 condition.
The basic principles of the heterogeneous nucleation theory indicate that the grain size of a cast alloy is directly proportional to the number of nuclei available in the melt which are capable of acting effectively during the solidification process.
The Al2Ca phase segregated around the growing primary magnesium crystals acts as diffusion barriers to the growth of the primary a-Mg grains, which minimizes the size of grains.

Thus, the total number of microscopic slips is estimated as the total number of dislocations piled up at the grain boundaries as described by 　
First, as the hot rolling and annealing, grains with a small total number of microscopic slips might obtain a preferred orientation.
We suppose that the crystal orientation of the statically recrystallized grains would be the same as that of the grains with a small total number of microscopic slips.
The total number of microscopic slips is estimated as the total number of dislocations piled up at grain boundary.
The preferential recrystallization orientation that is the same as that of the grains with a small total number of microscopic slips indicates bulging at a high-angle grain boundary.

Consequently, the detector is removed as the temperature limiting factor in elevated temperature SEM grain observations.
The Problem Grain growth studies by SEM have particular requirements, specifically the ability to image grain boundaries by SEM.
Unfortunately, this detector is optimised for secondary electron imaging and is therefore unable to give grain orientation contrast.
Grain Orientation Contrast Grain orientation contrast is generated by electron channelling effects and is a naturally weak contrast mechanism.
This proportion, η is the backscattering coefficient and is determined primarily by incoming electron energy and the atomic number of the material (hence atomic number contrast).

processed by HPT as a function of the number of turns.
It is seen that the Hv at the center increases sharply with the number of turns sharply for a small number of turns, less rapidly after 20 turns and reach a saturation value after 40 turns.
The evolution of the microstructure with the number of HPT turns was investigated by TEM.
Fig. 3 (a)-(c) shows the bright field images of disks with different number of turns.
For a large number of turns the estimated values of Hv are higher than the measured values.

Introduction Reasonable simulation and visualization of microstructure evolution during hot deformation can show the distribution and evolution of grains intuitively．It has important theory significance and practical utility prospect for studying microstructure evolution and determining reasonable hot forming process．Because of the complexity of the deformation mechanism，nucleation behavior，interaction between grains and the large number of factors influencing the grain boundary mobility，the simulation on microstructure evolution during hot deformation is very difficult[1, 2] ．
Generation of initial microstructure An initial grain structure is obtained by simulating normal grain growth with modified Monte Carlo method according to the mechanism of grain boundary migration．In the modified Monte Carlo stochastic simulation technique which models grain growth，the complexity of the grain structure is approximated by discretizing the continuum microstructure on a two dimensional，square mesh（site） with periodic boundary conditions．Each site is assigned a random integer between 1 and Q，where Q is the total number of grain orientations introduced in the simulation，representing the orientation of the grain to which it belongs．Neighboring sites with different orientations form grain boundary sites．For each site on the grain boundary，its orientation is changed to one of the nearest neighbor orientations randomly．If the grain boundary energy decreases or maintains unchanged，the new orientation will be accepted．Grain growth occurs as a result of the change in the orientations
The energy can be expressed by the formula： （1） where J is the contribution from each elementary boundary between the analyzed site and its neighbors．In the case of isotropic material，J=1．Si ，Sj are the orientations of the analyzed site i and its neighboring site j，respectively，is the Kronecker delta function （2） The total number of orientations not only ensures the grains with same orientation impinge infrequently，but also ensures the computation time acceptable．The site size needs to ensure the computational efficiency as well as the accuracy．In the present simulation，the initial mean grain size is about 600mm．A 200´300 grid system with a grid spacing of 40mm is used to discrete the region．And the total number of grain orientations Q was taken to be 432．The initial microstructure of Ti-15-3 alloy is shown in Fig. 1．
At the beginning of the simulation，a constant number of nuclei is provided．Thereafter，only the growth of nuclei is admitted during the recrystallization simulation process．Assuming that there is no grain boundary motion between deformed matrix grains，a two dimensional grid system with a grid spacing of 10mm is used to discretize the region．Each site of the grid is considered as a potential nucleus．Firstly，we select sites situated at the boundaries of any deformed grains randomly．If nucleation at the site does not take place and the distance between the site with already recrystallized embryos accords with the recrystallized grain size，the nucleation attempt is considered to be successful．The embryo is given a new orientation randomly，such that no two nuclei have the same orientation．Repeat above procedure till the number of nuclei accords with the recrystallized grain density in the simulating region．
When the nucleation sites situated at the grain boundaries have been covered up with nuclei，the same procedure is performed for nucleation within the deformed grains．In order to make the simulation more time efficient，we select sites within the deformed grains randomly，where the number of nuclei does not satisfy the demand，to carry out the nucleation experiment．

A great number of investigations were carried on for ultrafine-grained titanium alloys produced by different methods; however, these mostly deal with the structure and mechanical properties of studied materials, while the physical properties of materials are studied insufficiently.
An area of ~1.8 μm2 cut from the pattern with a selector diaphragm shows a great number of micro-diffraction rings (Fig. 1), which is suggestive of the formation of grain-subgrain structure with grain sizes of less than a micron.
The strength properties of alloys having ultrafine-grained structure are enhanced by 1.5-2 times relative to the respective coarse grain counterparts (Table).
The effect of hydrogen concentration on the construction strength of the Ti-6Al-4V alloy: 1 – coarse grained state, 2 – ultrafine-grained state.
Hence the increase in the ultrasound rate might be attributed to the ultrafine-grained structure having lower density relative to the coarse grained structure.

The permeability of coarse-grained soil is influenced by many factors.
In practical projects, the number of engineering accidents caused by seepage at home and abroad is also very large.
There are many factors that can decide the seepage properties of coarse-grained soil.
Coarse-grained soil that got in a hydropower station dam is artificially burdened into 12 samples to study on the permeability coefficient of coarse-grained soil.
The particle size of soil sample is 0.0~60mm and the sample is numbered 1-1~4-4.

The bulk ultrafine-grained (UFG) materials usually show superior mechanical properties.
First, the exponent of the inverse grain size is given by p = 2.
In practice, the hardness decreases constantly with increasing numbers of HPT turns.
Fig. 4 Variation of the values of m for the Zn-Al alloy before and after HPT for different numbers of turns.
Over this wide temperature range, the submicrometer grains accelerate the level of grain boundary sliding leading to high ductility and plasticity in the Zn-Al alloy.