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As shown in Fig. 3(a), the grains of GH4037 samples heated at 1310℃ for 30min differed from one another in size and shape, and there existed a large number of lamellar twins.
In Fig. 3(b), the grains became larger and more round than that at 1310℃, and the number of lamellar twins decreased.
Besides, a large number of lamella-like straight annealing twins appeared in the microstructure of semi-solid billets with such high solid fraction.
With the increasing of soaking time, the number of intragranular liquid droplets decreased and the solid grains became larger and more globular.
Therefore, the large solid grains were divided into some tiny grains.

%Ni alloy with the average grain size of about 30 nm.
For cubic grains 
 = 2�/d.
However, the number of relevant experimental points is too small to extract reliably the inter-agglomerate boundary diffusivity.
The GB diffusion measurements in a coarse-grained material in the C regime are accompanied with serious experimental limitations and high requirements to the sensitivity of the radionuclide detection equipment, since the fast tracer flux proceeds only in a relatively small number of GBs.
The counting statistics is decisively improved since the small atomic fluxes occur in a huge number of short-circuit diffusion paths.

The grains had a large protrusion height and kept good integrity after ultrasonic dressing.
For 35kHz ultrasonic vibration assisted dressing processes, the grit protrusion was large, and number of static effective grains great.
The surface of bond is smoother than that of CBN grains so that the frequency of micro salient of bond surface is much higher than that of CBN grains on the dressed grinding wheel surface[9-11].
The acoustic parameters have great role on the counts of static effective grains.
Furthermore, for ultrasonic dressing, the uniformity of protrusion height of grains is better, and the top area of grains is bigger, which demonstrated that the grains keep integrity well after ultrasonic dressing process.

In the specimen under consideration the diffusion layers mostly demonstrate areas of fine equiaxed grains, with minor grain size scattering (Fig. 3a).
The layers also mostly consist of fine equiaxed grains with minor grain size scattering.
Only in some electron diffraction patterns, the relative number of which is not big, there are additional super-structural reflections forming weaker Debye rings along with the main rings of this phase (see, for example, Fig. 4c, in which these super-structural reflections are indicated by arrows).
Parameters of the grain size distribution of the Nb3Sn grains Wire diameter, mm 0.8 0.5 Minimal grain size, nm 30 30 Maximal grain size, nm 160 130 Average grain size, nm 70 60 RMS deviation, nm 17 15 Conclusion Nanocrystalline structure of the Nb3Sn layers forming in multifilamentary Nb/Cu-Sn composites, the external diameters of 0.8 and 0.5 mm, after the two-staged diffusion annealing of 575°С, 150 h + 650°С, 200 h has been studied by SEM and TEM.
In the wire of smaller diameter the structure of the diffusion layers is more perfect, namely, both the average grain size and the grain size scattering are smaller.

Due to the Hall-Petch effect, ultrafine grained (UFG) metals possess a number of improved properties such as 3-4 times higher yield strength and 2-3 times higher ultimate tensile strength (compared to an annealed material) [4]; the high cycle fatigue is also improved [5].
Other applications just take advantage of the small grain size and the increased amount of grain boundaries.
It has been mainly utilised in its isothermal forging form to refine grain structure in Ti-6Al-4V [25].
The first conference publication of the idea took place in 2007 [38] and since then there have been a number of publications describing further development of the method and experimental results [39-48].
TEM observations revealed elongated grains (due to route A), with the average grain/subgrain size after 8 passes of about 450 nm (Fig.15). 500 nm Fig. 15: TEM image of Al 1070 plate subjected to 8 passes of I-ECAP (route A).

Introduction It has been observed in a number of experiments that grain size exerts a dominant influence on the mechanical behaviour of polycrystalline metals and alloys at the micron and sub-micron scales.
Having updated the lattice spin, we can obtain the reorientation of crystal grain represented by matrix crys T .
The average size of the lattice grain is represented by the dimension of the element, so that the coarse mesh (1455 elements) in Figs.1-2 stands for grains of larger size and the fine mesh(4203 elements) in Figs.3-4 for grains of smaller size.
The comparison of the simulation results of different mesh size, hence grain size, reveals the strong grain size effect in the microforming process and demonstrates the availability of the code developed.
J., Grain-size effect in viscoplastic polycrystals at moderate strains, Journal of the Mechanics and Physics of Solids,48(10),2213-2230,2000

The result shows the difference of electrochemical behavior between X plane and Y plane is still exist, and even in the unodd number passes for “route C” of ECAP process.
It provides extremely large imposed strains repeatedly in bulk without fracture to realize grain refinement and significant hardening through extremely line-grained structure formed by simple shear.
Several studies have showed that the extrusion direction can affect the microstructure of UFG materials especially in odd number passes for ECAP process, but the effect on the even number passes is weaken.
The aim of this experiment is investigated the effect of the even number passes.
The grain size in X plane is more uniform than that in Y plane.

The grain orientation is randomly assigned to grains, and zero-thickness cohesive elements are embedded on grain boundaries and inside grains.
The total mesh number is 9383.
Picking three numbers n1, n2, n3 randomly between 0 and 1, and then computing the three Euler angles ( in degrees) as: (2) The code can accomplish the orientation assignment to each grain quickly.
The number of grains in each microstructure is 50, 100, 150 and 200, respectively, and the corresponding average diameter d is 0.2 μm, 0.1 μm, 0.067 μm and 0.05 μm, respectively.
Zero-thickness cohesive elements are embedded inside grains and on grain boundaries, and the grain orientation are randomly produced and specified to every grain.

An UFG microstructure with a mean size of secondary grains of about 0.3 μm was processed by a rotary swaging.
In the cross section, grains of primary phase were curved and took an oval shape with a mean size of about 2 μm.
TEM studies showed the formation of subgrains and increased dislocation density inside primary α-grains.
Acknowledgements The reported study was funded by RFBR, project number 20-38-70105\20.
Zhu, Producing bulk ultrafine-grained materials by severe plastic deformation: ten years later.

EMF measurements were conducted under fuel cell conditions to evaluate the ionic transport number of the composites.
As a result, the conductivity at the grain boundary was improved.
The ionic transport number was calculated from the ratio of the measured EMF to theoretical value [15].
The ion transport number is more than 0.9 at 750 °C, slightly increasing with lowering temperature.
High ion transport numbers indicate that this material is a good ion conductor over the temperature range of interest.