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Only one or two slip systems seem to be active in almost each grain.
No special affects of the grain, sub grain or twin boundaries can be observed.
Most of the grains contain only bands with one particular orientation but in some grains, bands with two different orientations can be observed.
The width of these bands is larger than the width of those observed after experiments and their number is probably underestimated.
These bands are too large and their number is underestimated.

Most grains became much finer and coarse grains were broken into fine grains.
In addition, by increasing the number of PITS-ECAPT passes, micro-hardness of the sample was slightly increased and almost remained the same.
Most particles were contacted with each other, both the number and the size of pores were reduced, thus the compact density was slightly improved.
By increasing the number of ECAPT passes, as the powder compact was almost approached to the theoretical compacted density, the mechanical properties were increased slightly.
As the number of passes increased, larger accumulated strains were sufficient to reduce dislocations by annihilation and rearrangement within grains, so the dislocation density was nearly constant, i.e., a dynamic balance between working hardening and grain recovery was occurred.

Since superplasticity requires a very small grain size, typically <10 µm, it is feasible to process HEAs using severe plastic deformation in order to introduce significant grain refinement.
Furthermore, when the number of alloying elements increases beyond five, the contribution of the configurational entropy to the total free energy becomes sufficiently significant that it can overcome the enthalpies of compound formation and phase separation and thereby stabilize the solid solution state relative to any multi-phase microstructure [1-3].
It is reasonable to anticipate that there may be an opportunity to achieve a combination of high solid solution strengthening and good ductility if the solid solution phase possesses a simple crystal structure, such as a face-centred cubic (fcc) lattice, where there will be a large number of active slip systems [1-4].
Thermo-mechanical processing is generally employed in industry to achieve the requisite small grain sizes but this processing is capable only of producing grain sizes of the order of a few micrometers and it is not possible to achieve exceptional grain refinement into the submicrometer and nanometer range.
Experiments show that HPT has an advantage over ECAP because it produces both smaller grain sizes [12] and a higher fraction of grain boundaries having high angles of misorientation [13].

In the case of the Zr containing alloys, a very fine columnar grain structure was found over the entire surface, independent of the subsurface grain structure.
In this large Peclet number regime the front advances near the point of absolute stability, above which a planar solidification front is seen [5].
It is likely that the columnar grain growth is selective, with those 'seed' grains that have their fast <100> crystallographic direction well aligned to the maximum thermal gradient outgrowing less well aligned grains.
They mimick the grain size of the unmelted substrate, leading to fine columnar grains forming over FSW nugget regions and coarse grained layers over the parent plate, TMAZ and HAZ.
In Zr containing alloys (2096 and 7150), fine columnar grains were observed, irrespective of the substrate grain structure.

The 200 peer-reviewed articles in this “Nanomaterials by Severe Plastic Deformation” special collection are a convincing demonstration of the relevance of bulk ultrafine grained and nanostructured materials, produced by severe plastic deformation, to a wide range of researchers and engineers., The total number of articles in this edition, larger than that in the 2008 edition, shows that this community is, in fact, growing.
The coverage includes all aspects of NanoSPD: Principles of SPD Processing, Microstructural Evolution and Grain Refinement, Mechanical Properties of SPD Materials, Functional and other Properties of SPD Materials, Innovation and Applications.

Grain Boundary properties.
The total system energy at a given time (MonteCarlo time) is given by E = 1 2 γ(Si,Sj) 1−δSi S j( )+ F Sj( ) { } i n ∑j N ∑ (1) Where, E is the system energy, the first summation is over the total number of orientations, grains, in the microstructure, the second summation is over nearest neighbors, 26 in this case, γ(Si, Sj) is the interaction energy between different orientations (grain boundary energy) and F(Sj) is used to introduce stored energy as function of grain orientation in the system.
× exp −∆E kT       ∆E > 0        (2) Where, µ(Si,Sj) is the mobility of the grain boundary between grain i and grain j and γmax and µmax are the maximum grain boundary energy and mobility respectively.
As the value of T/Tc increases the level of anisotropy, in high angle grain boundaries as a function of grain boundary misorientation, decreases.
Acknowledgements The authors would like to acknowledge project support under contract number DE-FC07- 01ID14194 from the Office of Industrial Technology of the US Department of Energy (DOE) and from the MRSEC at Carnegie Mellon University under NSF grant number is DMR-0520425 for providing access to experimental facilities.

The domain size is 3mm wide by 4mm high, giving a total number of 600×800 cells.
A thin layer of fine grains grew from prefixed seeds and only a few long columnar grains succeed in growing due to the competitive nature of the growth.
Equiaxed grains are formed immediately from a thin layer of fine columnar grains near the surface.
Density of nuclei in bulk liquid changes from 6.5×1010 (number of nuclei/m3) (Fig. 3 (a)) to 6.5×1014(number of nuclei/m3) (Fig. 3 (e)).
-4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 -4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 -4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 -4 -3.5 -3 -2.5 -2 2 2.5 3 3.5 4 4.5 Log (G) [K/m] Log (V) [m/s] Log (V) [m/s] Log (V) [m/s] Log (V) [m/s] Log (G) [K/m] Log (G) [K/m] Log (G) [K/m] 1wt%Cu1wt%Cu 3wt%Cu 7wt%Cu 5wt%Cu 1wt%Cu Equiaxed Grains Equiaxed Grains Equiaxed Grains Equiaxed Grains Columnar Grains Columnar Grains Columnar Grains Columnar Grains Figure 4 Progress maps showing the effect of alloy solidification range on the CET: (a) open and filled diamonds indicate equiaxed and columnar grains for Al-1wt%Cu; (b)open and filled circles indicate equiaxed and columnar grains for Al-3wt%Cu; (c) open and filled triangles indicate equiaxed and columnar grains for Al-5wt%Cu; (d) open and filled squares indicate equiaxed and columnar grains for Al-7wt%Cu.

However, hot rolling is a very complex process, which requires a strict control over a number of different parameters.
C)Recrystallized grain size.
As the pass number is increased, the critical strain increases.
In Fig.7b, large grains characteristic of the deformed, unrecrystallized austenite are apparent with a few smaller recrystallized grains often located at three grain intersections on prior austenite grain boundaries.
In this figure, the evolution of average austenite grain size during rolling is graphically represented against pass number.

The crack on the nozzle’s vanes was studied and a kind of grain refiner was used to solve crack issues by improving shell strength.
Moreover, the number of the turbine nozzle’s vanes is 31 with only 0.7mm thickness, so the cracks usually grow in the vane trailing edge.
Repeated experiments were made to determine the shape and size of the part A and the No.1’ sprue with no changing of the number of the elder sprues.
The cobalt particle generated through the casting process refined the grain of the vane’s surface.
During the crystallization nucleus increases, the grain size of the vanes refined [9].

It should be note that under conditions of conducted creep tests, material deformation caused by volume diffusion (Nabarro-Herring model) and diffusion along the grain boundaries (Coble model) may occur concurrently, and contribution of each of these processes to the deformation depends on temperature, stress, grain size, and structure of grain boundaries.
HT means heat treatment procedure Designation of heat and specimen Evaluation of the structure of superalloy Carbide content in surface area AA Morphological parameters of macrostructure 1 AA = 2.12% N = 45 - number of grains A = 0.57 mm2 - mean surface area of the grain 2 AA = 1.45% N = 7 - number of grains A = 3.55 mm2 - mean surface area of the grain 1 after HT AA = 1.97% N = 24 - number of grains A = 1.1 mm2 - mean surface area of the grain 2 after HT AA = 1.90% N = 10 - number of grains A = 2.7 mm2 - mean surface area of the grain Examination of nickel superalloy macro-structure demonstrated that the use of only bulk modification in casting experiment (blue filter - heat 2) result in a coarse-grained structure.
Analysis of creep tests results concerning the casts in their initial state (specimen no. 1 and 2) shows that coarse-grain superalloy is 27% than the fine-grain superalloy.
This influence is well described by the implemented parameter AA/N, (ratio of carbide content in surface area and the number of grains in a specimen, Table 2).
Creep resistance vs. selected morphological parameters of structure MAR-247 nickel superalloy Heat and specimen designation Creep resistance tz [h] Rate of steady-state creep Vu [s-1] Carbide content in surface area AA [%] Number of grains on specimen section N Ratio of carbide content in surface area and number of grains AA/N [%] 1 250.3 2.5 x 10-8 2.12 45 0.047 2 317.4 2.2 x 10-8 1.45 7 0.21 1 after HT 292.9 1.66 x 10-8 1.97 24 0.08 2 after HT 352.4 1.06 x 10-8 1.91 10 0.19 Conclusions Analysis of characteristic curves of creep for MAR-247 superalloy indicates that diffusion creep process on the grain boundaries determinates their resistance in the conducted creep tests.