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To develop superplastic materials, small grain (usually < 10 μm) [1] is an important prerequisite because the superplasticity occurs through sliding of mutual grains at grain boundaries [2].
Here, we adopted the HPT process for an Al 7075 alloy to produce fine grains and then to investigate the superplastic behavior.
Microhardness increases with increasing distance from the disk center for all numbers but the hardness saturates to a constant level.
This study clearly demonstrated that high strain rate and low temperature superplasticity was attained through grain refinement of an Al 7075 alloy when the grain size was refined by HPT processing.
Shin, Low-temperature superplastic behavior of a submicrometer-grained 5083 Al alloy fabricated by severe plastic deformation, Metall.

An ultrafine-grained (UFG) material with the submicrocrystalline (SMC) grain size between 0.1 and 1mm can be obtained by using a severe plastic deformation (SPD) technique.
The average grain size in Fig. 1(a) is determined to be 0.2 mm.
In addition, considerable numbers of equiaxed grains consisting of high angle boundary and subgrain formation consisting of low angle boundary with misorientation less than 15゜ in the martensite variant can be noted in Fig. 2(b).
Figure 4 shows (a) EBSD-grain boundary (GB) map and (b) distribution of area fraction of grain size in hot rolled sample.
The average grain size of a phase from Fig. 4(b) is determined to be 0.3 mm.

These stages are connected with relaxation of the defects, migration of nonequilibrium grain boundaries and grain growth.
A mean grain size in the sample was obtained by averaging of more than 100 grains.
A number of SAED patterns from the small neighbouring areas 0.09 µm2 indicate the formation of grain boundaries (GBs) mainly of a high angle type (Fig. 1c).
This observation is in agreement with a great number of spots uniformly arranged in circles on SAED patterns from the larger square area 0.5 µm 2 (Fig. 1a).
Grains of about 1.5 µm size are formed within ultrafine grained "matrix" (20 - 30% of observed areas).

Grain A, B and C share the grain boundaries each other.
dV wF n i i V nji ji ij jiij       −+         ∇∇− = ∑ ∫ ∑ =< 1 2 1 2 φλφφ ε φφ , (1) where i and j represent the orientations of grains; n is the number of distinguishable orientations and � is a Laglangian multiplier.
The number of distinguishable orientations is 1,000,000.
One iteration corresponds to 540 ™ 540 ™ 8 calculations, where 540 ™ 540 is the number of grids and 8 is the maximum kind of orientations which each grid has.
The grain boundary between the black grain and the two type I grains has the energy of 0.3 whereas the grain boundary between the two type I grains has the energy of 1.0.

Kirkendall Effect During Grain Boundary Interdiffusion in Polycrystalline Thin Films Leonid Klinger, Eugen Rabkin Department of Materials Engineering, Technion – Israel Institute of Technology, 32000 Haifa, Israel klinger@tx.technion.ac.il, erabkin@tx.technion.ac.il Keywords: thin films; grain boundaries; stress relaxation; Kirkendall effect; interdiffusion Abstract We consider the kinetics of chemical interdiffusion along the grain boundaries in stressed thin metal film attached to inert substrate.
Grain boundary (GB) self-diffusion of the film atoms is an important mechanism of stress relaxation in unpassivated films.
For simplicity, we will consider a quasi one-dimensional film, with the stripe-like grains of width L.
This is because for DBnumber of A-atoms leaving the film is larger than the number of B-atoms penetrating into the film, especially for the short annealing times for which the concentration gradients driving chemical interdiffusion are high.
Kaur I, Mishin Y, Gust W (1995) Fundamentals of grain and interphase boundary diffusion, Wiley, Chichester, UK

As equiaxed grains are observed at all the cycle numbers, it is believed that dynamic recrystallization occurs during CVCE.
Larger numbers of interior dislocations are present.
It clearly shows in Fig. 4(d) that UFG (ultra-fine grain) structures with grain sizes about 1μm were formed.
The grains are mostly equiaxed and the grain boundaries are sharp and mostly clear.
It is known that large grains in UFG materials contain dislocations while grains smaller than a certain size are dislocation free[12].

But they are strongly dependence on the number of ECAP passes and the pressing route.
Fig. 1 Dependence of the average microhardness on the number of ECAP passes.
Fig. 3 Dependence of static toughness on the number of ECAP passes for 1050 Al.
But they are strongly dependence on the number of ECAP passes and the pressing route
Producing bulk ultrafine-grained materials by severe plastic deformation.

The deformed ferritic material contains a large number of geometrically necessary boundaries with large misorientations, while the martensitic material does only contain original grain boundaries such as prior austenite grain boundaries, packet boundaries and block boundaries.
number of fine grains surrounded by geometrically necessary (GN) boundaries within the initial grains.
However, since there are few high angle boundaries within the blocks, the number of the high angle boundaries existing in the martensitic structure is much smaller than in the deformed ferritic structure.
The number of recrystallized grains is gradually increased and the size of them is enlarged as the softening proceeds (b), and then the deformed structures has been completely replaced by the recrystallized grains when the hardness reaches a stable minimum (c).
The results obtained are summarized as follows: (1) The ferritic material deformed by 80% reduction contains a large number of geometrically necessary boundaries with large misorientations, while the martensitic material does only original grain boundaries.

The number of crystal grains per the cross section of SAC305-6.0In-1.0Sb was stably several tens or more.
In particular, the number of crystal grains of SAC305-6.0In-1.0Sb was 200 or more in all specimens.
Fig. 4 Number of crystal grain in the cross sections shown in Fig. 3.
It means that the clear effect of the number of grains on the range of variance of elongation is not found
(1) The number of crystal grains in Sn-Ag-Cu-In-Sb solder was larger than that of SAC305

Before rolling, the material was annealed at 753 K for 8 hr. to produce a large grain size of 30~60 µm.
In both microstructures, it is evident that the original grains with the size of 30~60µm have been greatly refined.
Their grains are 2.2 and 1.4µm, respectively.
Number next to symbols indicates the pressing number by ECAP.
Significant grain refinement took place during both processes owing to introduction of large shear deformation.