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The damaged area and the number of deformed grains, which could be identified as dark reflection in optical microscope images was evaluated at certain numbers of loading cycles semi-automatically by using an image analysis software.
Grain size (D), average number of grains per cross section (ζ), ultimate tensile strength and Young's modulus (E).
The small number of deformed grains in the type A copper can be partially attributed to strengthening effect as described by the Hall-Petch effect where due to a higher density of grain boundaries in the films with a smaller grain size, the dislocation movement is hindered.
This effect is mainly due to a larger increase in the number of deformed grains with the type B copper.
This is especially pronounced with the thin 5 µm films where the deformation density with the type B copper is twice as high at 150◦C compared to room temperature while there is only very little increase in the number of deformed grains in the type C copper.

Considering the accuracy and efficiency of simulation, the total number of elements, nodes and sample surface polygons were 100500, 14117 and 19330, respectively.
The average grain size is about 43 μm.
After three CGP cycles, grains become finer and the average grain size is about 10 μm.
The grains of 5052 Al alloy can be refined significantly by CGP or UGP, but the processing conditions affect obviously the rate of grain refinement and the final grain size.
The CGP has higher rate of grain refinement and finer grains than that of UGP

In addition, with more nano-carbides adding, the number of white core grains increases and that of black core grains decreases.
Furthermore, the number of white core grains increaseswith more nano-carbides adding, In cermet D there are many white core hard grains.
Apparently, crazy grain growth occurs in cermet C, or D with nano-micro carbides, where big grains ,up to 5 µm, and small grains less than 0.5 µm coexist, and the heterogeneous microstructure results in poor material performances.
Judging from the forming process of the three hard grains, it is apparent that the microstructure of white core grain is superior to black core grain in improving material performances, wing to much more homogeneous composition transition of different phases .
Furthermore, with the addition level of nano carbides increasing, the number of white core grains increases and that of black core grains decreases.

Ultrafine-grained (UFG) commercially pure (CP) Ti with a grain size of about 200 nm was produced by ECAP up to 8 passes using route BC at room temperature.
The applied strain rate is always indicated by numbers, e.g. ‘‘-3’’ stands for a strain rate of 10-3 s-1.
This indicates that the deformation in UFG CP-Ti is controlled by the grain boundaries, such as grain boundary sliding, grain boundary diffusion and Coble creep.
The average grain size was measured to be about 200 nm.
The deformation in UFG CP-Ti, besides the classical deformation by dislocation slip and deformation twin, is controlled by the grain boundaries, such as grain boundary sliding, grain boundary diffusion and Coble creep.

A number of issues, such as high strength, high stiffness and deformation mechanisms [1-3], have been intensively studied in the last twenty years.
On the other hand, due to the increasing volume percent of grain boundaries (GB) and triple junctions, the GB induced mechanisms, such as mass diffusion through grain boundary, grain boundary sliding, grain rotation, etc., would dominate the deformation of nano-grained metals.
Based on the Ashby-Verrall model [1] of grain insertion, Yang and Wang [3] proposed a 9 grain cluster model that also accommodate a grain rotation stage in the deformation scheme.
The second term on the left hand side represents grain boundary sliding, with Bη being the grain boundary viscosity, and slideD the amount of grain boundary sliding along the grain boundary.
These equations provide the formulation to solve for the grain center coordinates X , the grain rotation Θ , and the mass flow along the grain I.

Numerical Study of Grain Boundary Diffusion in Nanocrystalline Materials D.
This allows us to analyze diffusion profiles for different geometrical situations such as a single boundary, square grains with the grain size of 80 nm and 25 nm and geometries comprising differently oriented boundaries of the average length of 30 nm .
The numbers indicate the x and y coordinate respectively.
In most experiments on nanocrystalline materials the GB diffusion length Lgb is larger than the average grain size d.
Gust: Fundamentals of Grain and Interphase Boundary Diffusion (Wiley, Chichester, 1995) [3] L.

The morphology is characterized as the columnar grains at the periphery and equiaxed grains at the core.
The discharge voltage, U and pulse frequency, ω (the number of repetitions per unit time of a complete sinusoidal current waveform) are adjustable in the experiment.
The constitution of the morphology is equiaxed grains in the center and thin columnar grains in the edge.
The microstructures of pure Mg under 5Hz, 200V pulsed magnetic field (a) peripheral columnar grains transiting to exquiaxed grains, (b) centeral equiaxed grains.
It shows that the smaller average grain size in center, the shorter columnar grain size was formed in edge.

Introduction Magnesium has a HCP crystal structure with limited number of slip systems operable at low temperature.
It was also very important to note that the microstructure of this alloy was a mixture of fine and coarse grains, fine grains were mainly distributed among the coarse grains, lenticular grains with 5 ~ 6 µm in length and 2~3 µm in width were found in the coarse grain area.
Thus, the long-range stresses associated with the non-equilibrium grain boundaries can affect grain boundary sliding dramatically, resulting in difficulties in accommodation for grain boundary sliding [8].
For ZK40-1P alloy, grain boundary sliding was not effectively accommodated, because many dislocation slips for accommodation of grain boundary sliding were hampered by the long-range stress of non-equilibrium grain boundaries existing within the coarse grains (Fig.4b).
Although the dislocation density in the grains of this alloy was very high, grain boundary sliding occurred readily, because the influence of dislocation movement within the grains can hardly take effect when the dominant deformation mechanism is grain boundary sliding (GBS) [9].

HIPIB irradiation experiment is carried out at a specific ion current density of 1.1 J/cm2 with shot number from one to ten in order to explore the effect of shot number on electrochemical corrosion behavior of magnesium alloy.
The improved corrosion resistance is mainly attributed to the grain refinement and surface purification induced by HIPIB irradiation.
With increasing shot number, numbers of crater reduced, but size of crater increased owing to the repetitive melting and evaporation/ablation under HIPIB irradiation.
Fig. 4 shows the potentiodynamic polarization curves of the original and irradiated samples with shot number from one to ten.
More importantly, grain refinement took place on the outer surface of irradiated sample, which have been identified by TEM observation.

The sample comprised at least 200 grains.
The contribution of grain boundary sliding (GBS) to the total deformation was calculated from the formula [10]: , (1) where h is the average step height, n is the number of boundaries per unit length on which steps were observed, and k = 1.5 is constant.
A lamellar structure is observed in the bulk of some grains.
The electron diffraction patterns of the structure obtained for an area of 1.4 μm2 show an appreciable number of reflections uniformly distributed over a circle (Fig. 1, a).
This is indicative of the presence of a large number of structural elements in unit volume and of their substantial misorientation.