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By now a large number of studies were carried out on hot deformation behavior of 7075 aluminum alloy [3-6].
After heat treatment the distribution of precipitated phases changed markedly and their number reduced significantly.
Due to low aging temperature there existed a large number of dispersed small h¢ phase.
A small amount of precipitated equilibrium phase h on grain boundary should lead to a lower strength of alloy, but due to large number of h¢ phase and its significant strengthening effect, the strength reduction caused by precipitated h equilibrium phase was offset.
The reasons for fine grains are as follows: First, during recrystallization process a high nucleation rate and low grain growth rate could both lead to grain refinement.

But at 700°C the grain size and translucency were both increasing and grain boundaries cannot be clearly distinguished, which means the initial integration.
Therefore, it can be inferred that Vita Alpha powder contains a large number of ceramic components, rather than the glass-based composition.
From the microstructure of sintered ceramic as shown in Figure 3.2, we can see the grains have began to fuse.
The transparency and grain size were also gradually increased.
At 700°C, the Vita Alpha porcelain has showed initial integration and it's individual grains has unable to be distinguished.

The as-cast alloy consists of face-centered cubic (FCC) solid-solution with equiaxed matrix and network grain boundaries.
According to the Gibbs phase rule F=C-P+1 (F-degree of freedom, C-number of components, and P-number of phases) [6], the value of F equals to six for single phase or five for the two-phase region in the present six-component alloy system.
It means that the maximum equilibrium phase number of Al0.5CoCrCuFeNi alloy allowed by the Gibbs phase rule is much higher than the total number of phases.
As shown in Fig. 2 (a) and (c), typical equiaxed grain structure was observed.
The grain matrix and grain boundary denoted as “GM” and “GB” in Fig. 2 (b, d) is composed of only one simple FCC phase (see Fig. 1).

The intrinsic factor is ultrafine equiaxed grain structure, the average grain size is less than 10 μm, the smaller the better.
Sample number and process arrangements are shown in Table 2.
Grains do not see black and white area organizations.
Carbides and grain refinement.
The grain size of sample 6# is small.

These bars were cut into billets with lengths of ~65 mm and numbers of disks were sliced from the billets and polished to achieve uniform thicknesses of ~0.83 mm.
It should be noted that the error bar on each datum point represents the standard deviation of the numbers of measurements.
Valiev, Deformation behavior and plastic instabilities of ultrafine-grained titanium, Appl.
Mohamed, Mechanical properties of an ultrafine-grained Al-7.5 pct Mg alloy, Metall.
Valiev, Grain boundaries in ultrafine grained materials processed by severe plastic deformation and related phenomena, Mater.

Twins structure formed in the previous annealing treatment could be seen clearly located in some grains.
All the grains are separated by straight boundaries.
The grain boundaries changed their shape to curve.
Fig. 2a describes the change of crater number, i.e. area density.
The non-stationary stress fields lead to the severe deformation of grains in the modified surface.

With regard to nanotubes and other blocks it was proposed later [7] to extend the nanostructure type number up to 36.
It is clear from (2) that the effective grain growth retardation can be achieved by an increase of the number of inclusions and their radii decreasing.
The abnormal grain growth was studied experimentally for a number of copper, nickel and iron based alloys, as well as hard alloys and diamond (see references in survey [19]).
The number of pittings in the ultra-fine-grained samples was greater but their distribution was more uniform.
From the experimental data it was concluded that the number of pitting defects is decreasing with the increasing number of nano-twinned grains, and the passivating copper sub-oxide Cu2O layer with {111} texture (this layer slows down the corrosion) grows on the top points of the textured copper nanotwins.

Over time, this "competitive diffusion" results in an increase in the average size of the particle population, and in a concomitant decrease in the number density of particles.
In order to take into account the effects of non-zero volume fraction, a number of mean-field theories of coarsening have been developed over the past 40 years [4].
In the following, particle and grain can be interchangeable.
Where σgb is the energy of a planar grain boundary and σin is the interphase boundary energy, more detail about grain boundary energy σgb and interphase boundary energy σin are described in [9].
The number of orientation field variables is 30.

The reduction of the carbide grain average size was found as well (owing to nanoparticles blocking influence on re-crystallization).
Introduction Strength and tool life of hard metals correlated with their microstructural parameters: volume content of binder and carbides, carbide sizes, mean free path between carbide grains, intercarbide boundaries.
Conventional notions regarding the failure of hard metals composites indicate that the boundaries between carbide grains are very weak structural elements [3,4].
Introducing nanoparticles also inhibits the growth of carbide grains and recrystallization by mass transfer through the cobalt layer, while preventing the formation of intercarbide WC–WC boundaries.
(2) The probability of structural parameters l1 and l2 emergence was determined from: ; , (3) where: n0 – number of particles with volume; n2 – total number of nanoparticles.

Square boundaries of the grain were parallel to (100), (010) or (001).
Finally, the dislocation motion stopped at grain boundaries.
The stress of each model increased again at εx 5 106 − ×= because the mobile dislocation reached the edges of the model grain (i.e., grain boundaries) as shown in Fig.2.
Dependence of the critical stress on the number of network sheets is presented in Fig.5.
Fig.5 Relationship between the critical stress and the number of network sheets.