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When the solution temperature was close to the phase transition point (830 ℃, 820 ℃, 810 ℃), many sub-grains appeared inside the grain, which greatly reduced the average grain size but the uniformity of grain size was not at a good stage.
When the solution temperature dropped to 780 ℃, the average grain size was about 10 μm, the grains were small and evenly distributed.
This was mainly due to the large amount of deformation in the forging process and the large number of dislocation generated inside the alloy, which provides the locations for the secondary α phase nucleation.
The grains are small and evenly distribute. 2.
A large number of fine and dispersive secondary α phase precipitate in the grain after solution at 780 ℃ and aging at 500 ℃, 520 ℃, 540 ℃, 560 ℃, respectively.

The peak intensity was also increased after adding the dopant due to the increasing of the number of oriented crystallite.
This observation was made by Law et al. which were found that the increase of the peak intensities on XRD pattern showed the number of domains oriented also higher [4].
The grain size is decreased with addition of dopants in PZT system.
Kalem et al. [7] also reported the reduction in the grain size has been attributed to the solid solution impurity drag mechanism in which the La concentration gradient present at grain boundaries was claimed to cause blocking of grain mobility leading to slower grain growth rate.
The addition of dopants remarkably decreased the grain size of the PZT sample because this effect influences the grain growth which may depends on the suitable device application.

However, low ductility resulting from the limited number of independent slip systems in hexagonal close-packed (HCP) structure limits the use of the magnesium alloys.
However, the as-rolled AZ31 plate had an average grain size of 15.1 µm with many fine grains.
The grain size controlling factor and DRX mechanism need to be elucidated to understand the relationship of process parameter and grain size.
In this case, FSP produced a fine-grained supersaturated solution.
FSP fine-grained magnesium alloys exhibited good superplasticity.

Introduction Severe plastic deformation (SPD) methods are an effective means of obtaining nano- and ultrafine-grained structures for various metals and alloys. [1-5] A large number of works is devoted to the study of processing features of metallic materials by such methods, including the processes of structural-phase transformations.
As a result of heat treatment, a coarse-grained structural state was formed in both materials.
The studied samples of commercially pure M1 copper and Cu-1.1Cr alloy in the initial state had a coarse-grained structure (Fig. 2) with an average grain size of 60 ± 6 and 120 ± 9 μm, respectively.
Mechanical properties and energy dissipation in ultrafine-grained AMts and V95 aluminum alloys during dynamic compression.
High-strain-rate response of ultra-fine-grained copper.

Fine spherical grain in the semi-solid 9Cr18 slurry can be obtained at α=45°and L=600mm, the major grain equivalent diameters are less than 55μm and more than 40% of the grain shape factor is in 0.75, exhibiting better grain fine degree and roundness.
Compared to forging operations, however, SSM would reduce the number of processing steps to one single forming operation, a reduction in energy input, and an increase of component complexity.
Here, A expresses the area of measured crystal grain; L expresses the average length of measured crystal grain.
D expresses the size of the grain; the smaller the value of D is, the smaller the grain is.
Fine spherical grain in the semi-solid 9Cr18 slurry can be obtained at α=45°and L=600mm

The alloys had a coarse-grained structure composed mainly of near-quasi-equiaxed grains of size 10–70 μm.
The numerals indicate the number of complete reduction cycles along three orthogonal directions (a, b, c) and single reduction along the axis a.
Optical metallography reveals both grains with clearly defined deformation traces and grains which are almost free from them.
In the specimens rolled at е = 0.07, coarsening of grains compared to grains in the initial specimens was detected.
At е > 2.0, intense quasiperiodic microcracking began and the number of cracks increased rapidly with an increase in e.

But they are strongly dependence on the number of GP passes and the pressing modes.
However, nearly all of the investigations were focused on the microstructures evolution and grain refinement of the materials.
The results are plotted in Fig. 1 against the total number of passes in GP.
In addition, the decrease in the dimple size should be associated with the grain refinement of samples processed by GP [21-22].
But they are strongly dependence on the number of GP passes and the pressing modes

This type of technology is based on the effect of adhesive friction between the rotating tool and the workpiece material, which has been well studied in a number of papers.
In the process of embedding into the surface of the tool blanks and conducting the process of friction stir welding a number of processes of plastic deformation, fragmentation and material flow along the tool contour take place [6].
In the stirring zone the material is mainly represented by submicrocrystalline equiaxial recrystallized grains.
In the channel, the zones of fine-grained structure and deformed structure alternate in layers and are rather heterogeneous.
The distribution of areas with different grain sizes in the structure is less heterogeneous.

The deformed grains either contain homogeneously distributed subgrains of similar size, or heterogeneously distributed small subgrains at grain boundaries (mantle subgrains) and relatively large subgrains in the core of grains (core subgrains).
Substructured and Subgrain Free Grain Fraction.
To avoid confusion, we will use the terms subgrain free and substructured grains rather than recrystallised and deformed grains.
Still, the AMG of a subgrain free grain will be typically smaller than ~1° and therefore the cut off AMG to distinguish a subgrain free grain from a substructured grain is chosen to be 1°.
The number of domains on which the average is based is given between brackets. (*) size without distinction between core and mantle.

The Fig.1(a) shows that a number of point-like matter are dispersed on the Al substrate,grains were elongated and extend along the rolling direction and show distribution of fibrous or streamline.
Discussion The main reasons of the grain was elongated and extended that endured the tensile stress in the rolling process.
So these grains in form of fibrous or streamline distribute;Besides,the grain shown a prolate state under the influence of compressive stress,while its in form of needle-like or rod-like shape[3]in Fig.1(a)(b).
Fig.3 shows the SEM and EDS of fracture of RE-7075 Al alloy′s hot rolled sheet.The fracture surface mainly appeared candy-like pattern and crystalline,which presented brittle fracture.Due to impurity atoms segregated or melted off and the second phase separated out in the grain boundary which came into being smooth grain surface.The grains started the slip system starting-up when the microstructure bore external force which lead to smooth grain surface,too.
Discussion (1) There are needle-like or rod-like grains in the SL direction and the fibrous or streamlined grains in the LT direction of hot rolled sheet′s microstructure