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Grain size non-uniform, eutectic product along the grain boundaries or dendrite boundary discontinuous distribution with the crystal with black second phase particles precipitated by SEM and EDS spectrum scanning analysis shows ZK80 Mg alloy lamellar structures and granular middle mainly MgZn and MgZn2, as show in Fig. 3, the base body is relatively clean and coarse grains, about 70μm.
It can be seen from Fig.2 (b) that significant strip microstructure take place during extrusion process, and significantly elongated along the extrusion direction, at the same time, there are lots of needle shape twin organization and a small amount of secondary twin, part of the twinning occurred kink, coarse grains, the grain size of about 23μm；deformation at higher temperature, due to the low magnesium fault energy, sensitive to deformation temperature [7], the center of the extruded perform billets shows obvious dynamic re-crystallization(DRX) microstructure, and coarse dentrite is replaced by finer equiaxed grain with average size of 5.3 μm, part of the dynamic re-crystallization grain inclusions between serious deformation of grain.
According to Hall-Petch equation (), which is the yield stress, is of single crystal yield stress, K is a constant, d is grain size, strength of alloy increase with the decrease of the grain size, so the grain size larger influence on the strength of the magnesium and its alloys[8].
As can be seen from Fig.2(b) that there are lots of twins in extrusion ZK80 magnesium alloy, and extrusion preformed billets center for isometric obviously, the each grain internal possible slip band and twin belt and there are grain boundary and grain orientation to different between adjacent grain during die forging forming process，because of three to stress, the mechanical properties of ZK80 Mg alloy is improved obviously due to substructure change, twin microstructure disappear and obvious dynamic re-crystallization occurs, grain are refined greatly, the dislocation density increase under die-forging forming.
Grain-boundary sliding in AZ31 magnesium alloys at room temperature to 523 K[J].

Therefore, a large number of methods have been explored in recent years, in order to obtain higher strength and toughness of the magnesium alloy.
It can be seen that the microstructures are the equiaxed grains with the average grain size of 3.4μm, but the average grain size of AZ31 alloy prepared by the same process is 5.6μm [4].
When the dislocation pile up to a certain extent will rearrange and combine, producing dislocation cells and sub-boundaries, sub-boundaries further transforms into high angle grain boundary, and ultimately into the recrystallized grains with high angle grain boundaries.
Although the grains slightly grow up along the stretching direction, but still are equiaxed grains, which indicates that the grains growth and movements that along the grain boundaries are isotropic and GBS is the main deformation mechanism of AZ31+Sr+Y alloy during the superplastic deformation process.
When temperature increases to 400℃, the fracture morphology exhibits a large number of dimples and tear ridge which connecting dimples (as shown in Fig. 7d), proving that the fracture mode changes from microviod accumulation fracture to intergranular fracture.

Choose of transition metal as growth substrate is also very important because it could largely affect the number of graphene layers and produced defects [6].
Besides that, accurately controlling growth time is another key factor to determine the number of graphene layers[14].
The intensity of 2D band (~2663.9 cm−1) is found to lower than that of G band, which indicated a number of layers growth in most parts of the sample [17].
A, B and C region are corresponding to dark grain, light grain region and grain boundary of Cu.
It is also found that the growth of graphene is not related to different part of Cu including grain and grain boundary.

After forging at 1050℃ the grain growth is not obvious and original β grain as well as intragranular lamellar are fine.
The grain deformation is not uniform, there are still undeformed grains.
The grain growth is not obvious, the original β grains and the intragranular lamellar are fine after forging at 1050℃, thus the strength and plasticity at room temperature and high temperature are higher, as a result of the effect of fine grain strengthening.
Fig. 5(b) shows that the fracture mode is a mixture of cleavage fracture and ductile fracture, there are a large number of small and shallow dimples.
The dimple size increases, and the number of tearing ridges decreases, thus the plasticity increases.

Grain size refinement by using equal channel angular Extrusion (ECAE) is an effective way to improve workability and strength of the magnesium alloys.
The deformation mechanism of ECAE for grain refinement is obtained.
Especially, the relationship of material grain refinement and the deformation behavior needs to be studied further.
Five numbered nodes were marked onto the workpiece, these nodes a–e are placed on the cross-section, 1-1, in the die channel, respectively, as shown in Fig. 3, representing different zones in deformation.
Conclusions This paper presents interesting results concerning a dual analysis between finite element simulation and experiments for understanding and predicting grain refinement in ECAE.

The work indicates that the recrystallized grains, which migrate into the deformed grains, are mainly with the high misorientation angles.
The large percentage of the recrystallized grains, whose misorientation angles with deformed grains exceed 15°, are corresponding to the {111} transformation texture.
From picture, we can see that almost all the recrystallized grains and deformed grains were separated by high angle boundaries (>15°).
The {110} grains have the highest stored energy, but since this texture component is very weak, the number of nuclei produced is small.
(3) The migration of recrystallized grains into deformed grains is difficult to proceed if the misorientation angles are less than 15°.

The measured austenitic grain size is in the range 80~160 mµ .
Meanwhile, dislocation cells are elongated along deformation direction with the increase of cold deformation degree, the number of the dislocation cells rise and the sizes reduce.
Recrystallization will completely transform grains after cold transformation into a new equiaxed grain structure by nucleation and growth, and its mechanical properties will also change markedly.
The main reason of single austenite-grain obtaining ultrafine is that：due to the existence of deformation martensite, austenitic grains after severe cold deformation import austenitic-martensite(γ/M) phase boundaries.
Influence of Heat Treatment on the Grains of Cold Worked Austenitic Stainless Steel.

The test samples used in this study are ground by vitrified bond diamond grinding wheels with different grain sizes.
And the grinding wheels with grain sizes of 25μm and 7μm were both used.
It is found that the surface of the glass-ceramics ground by grain size of W25 with rough surface has large numbers of dense pits.
For the ultra-precision grinding process, the material removal mechanism can be considered as the cutting of a single abrasive grain and the interaction of large numbers of closely spaced abrasive grains [5].
Two vitrified bond diamond grinding wheels with the grain sizes of 25μm and 7μm were both used, in order to research the influence of the abrasive grain size on surface and subsurface integrity during ultra-precision grinding.

Crystal grain size and shape were evaluated by optical microscope.
The sheets were consists of equiaxial crystal grains.
Average grain size of 1, 2 and 3 ADB cycles was 20 mm, which is too large to induce a grain boundary sliding.
Tensile strength increased with increasing the ADB cycle number.
Vol. 210 (2010), p.751. ] due to fine crystal grain structure.

In this paper, the Mg-Zn alloys with different alloying ratios were prepared, which were Mg-3Zn, Mg-4Zn, Mg-5Zn (the number of Zinc in the front was the percentage of Zinc in the alloy), respectively.
The size of Mg-3Zn grain is small, the grain size of the matrix in the field of view is almost all about 500μm, has good uniformity, the size and distribution of Mg-Zn phase are not uniform, and some grain boundaries have obvious point , Indicating that Mg-Zn phase precipitates on the grain boundary.
Only a small part of the grain boundary can be observed.
The distribution of Mg-Zn phase in the grains is the same as that of Mg-4Zn.
It is also exhibits distribution of different points in the grain.