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During the initial deformation stage, the dislocation density and the number of sub-grain structures increased gradually, and many dislocations formed tangles, resulting in work hardening.
The dislocations can be found both at grain boundaries and in grains.
At the same time, the number of sub-grain structures increases obviously, which enhances the effect of hindering on dislocation motion.
Comparing with the sheet of 80% reduction, the number of dislocations appeared at grain boundaries and in grains decrease greatly, besides, the tangle phenomenon of dislocations was significantly reduced.
With the increasing of cold rolling reduction, the dislocation density and the number of sub-grain structure in alloy sheets increase and a large number of dislocation tangles are formed, leading to work hardening.

Evaluation of texture and structure were carried out using the orientation distribution function (ODF) restored from the X-ray direct pole figures and the large number of individual orientations measured by the EBSD method.
The volume fractions of low angle grain boundaries (LAGBs) and high angle grain boundaries (HAGBs) were 30 and 70%, respectively.
The main reason for low ductility is associated with an insufficient number of deformation systems, activated at these temperatures due to the hexagonal crystal lattice type of the alloys with a high ratio c / a.
The distribution function of orientations (ODF) and the volume fractions of the main orientations were calculated using Gaussian approximation of a large number of normal distributions [7].
It should raise the average grain size to 10 μm by the subsequent annealing.

So is the case as between powder grains.
At the same time, with the increase of the coordination number, the surface curvature of free grains converts from convex to concave.
Coordination numbers in dense structures are found to be at 12.5-14.5 [5].
When this coordination number is achieved, the rearrangement of grains becomes impossible and the initial stage of the sintering process is over.
The relation between packing density and coordination number is shown in Fig. 5.

Austenite grain size conforms №6 and 7 in grain fineness scale compliance.
Austenite grain size conforms №6 and 7 in grain fineness scale compliance.
Austenite grain size conforms №6 and 7 in grain fineness scale compliance.
Austenite grain size conforms №6 and 7 in grain fineness scale compliance.
Former austenite grain size conforms №6 in grain fineness scale compliance.

As seen in Fig. 1b, when the annealing temperature increased to 300 ℃, the aluminum matrix were fully number of recrystallized grain increased and the size became larger compared to 1 h annealing at 250 ℃ (Fig. 1b).
According to Fig. b-d, it can be found that after 300℃, with the annealing temperature further ascending, the number and size of recrystallized grains hardly changed.
As the annealing time increased, there was no significant change in the grain size of recrystallized grains.
In the GOS maps, “blue” grains (misorientation angle less than 2°) denoted recrystallized grains.
The graphene was homogeneously dispersed at Al grain boundaries, and the presence of graphene would prevent grain boundary migration and restrict the growth of grains [4, 14, 18].

An adequate microstructure was defined as displaying a small number of grain boundaries and a high amount of γ’ in the joint.
To judge the results regarding the grain boundaries the following characteristic number was used: A grid of parallel lines perpendicular to the brazing seam was projected on the joint area and the intersections of these grid lines with grain boundaries were counted.
To gain a number independent of the evaluated length of the joint, the intersections were divided by the number of grid lines.
This means if the number equals zero, no grain boundary developed in the joint and the value one means one grain boundary or several grains are located in the joint.
Regarding the grain boundaries developed in the joint, all samples are similar except one in which developed on average three grains boundaries in the joint.

The results show that composite lead-free solder after constant 125˚C aging treatment for 24 hours, Al particles has two types of morphologies: one is small amount of solid solution，another type is a large number of aluminum particles structure.The existence of Al particles slowed down the coarsening rate of the Bi Phase grain, and obtained uniform refined the Bi Phase grain.
In figure 3, the black particles are Al particles which have both small amount of solid solution and a large number of aluminum particles structure exist at the Sn-58Bi solder.
Because the Al powder prevent the Bi phase grains from growing up and getting together.
It is composed by β-Sn grains and sheet Bi grains.
With 3.0N stress aging treatment, grains in the brazing joint still keep small.

The tensile strength of the alloys increased with increasing the number of ARB cycles.
In the Al-Si and Al-Ag alloys, the post-uniform elongation increased with increasing the number of the ARB cycles.
The mean grain size (thickness) was 750nm.
The main results can be summarized as follows: (1) The 4N-Al ARB processed by 7cycles showed an equiaxed grain structure having mean grain size of 750nm.
On the other hand, the strength of the solid solution alloys monotonously increased with increasing the number of the ARB cycles

The interior of these new grains is free of dislocations.
ation method refines structure across Al plate in dependence on the number of passes performed and/or on level of strain introduced.
TEM microstructure analysis results indicate that there is a very low fraction of submicron grains with high angle grain boundaries even in case the strain applied is the highest.
A distinction between the values for the initial state and the deformed plates subjected to CGP straining due to the different number of pressings evident.
In order to clarify the CGP effect on grain refinement, transformation of subgrain boundaries to high angle boundaries and appearance of a small fraction of dynamically recrystallized grains, all these structural changes may substantially contribute to modification of plastic deformation of strained Al specimens, as regards the number of pressings.

A small amount of CoO up to ~ 0.3 mol% was effective for the suppression of grain growth, but the addition of 1.0 mole % resulted in an enhanced grain growth.
A small amount of dopant suppressed the grain growth.
In fact, extra ordinary large grain was not observed.
A small amount of CoO up to ~ 0.3 mol % was effective for the suppression of grain growth, but the addition of 1.0 mol % resulted in an enhanced grain growth.
A small amount of CoO up to ~ 0.3 mol % was effective for the suppression of grain growth, but the addition of 1.0 mol % resulted in an enhanced grain growth.