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Introduction Ultrafine-grained (UFG) materials processed by severe plastic deformation (SPD) methods exhibit a number of improved properties such as high strength at room temperature, ability to deform superplastically at lower temperatures and/or higher strain rates than fine grained materials, high fatigue resistance etc. [1, 2].
Most probably, during deformation dynamic recrystallization occurs in the grains of the primary a-phase.
[12] ASTM E112-10, Standard Test Methods for Determining Average Grain Size, ASTM International, West Conshohocken, PA, 2010
Froes, Characterization of submicron-grained Ti-6Al-4V sheets with enhanced superplastic properties, Mater.
Valiev, Service properties of ultrafine-grained Ti-6Al-4V alloy at elevated temperature, J.

However, magnesium and its alloys show poor ductility due to the limited number of slip systems associated with the HCP crystal structure [1].
In order to understand the texture evolution in pure magnesium and magnesium alloys during deformation, a number of experimental and simulation studies have been conducted [2-4].
The specimens are annealed for 1h at 723K to produce a uniform grain structure.
attributed to the growth of the grains with (0001) orientation.
Thus the preferential growth of (001) oriented grains occurs, resulting in the development of (001) texture.

There are crack deflection and grain bridging toughening mechanisms owing to the rodlike grains of TiB2 in the products, which makes their fracture toughness is as high as 7.3MPa·m1/2.
The less the pores are, the less the 'head-water' of crack growth and numbers of crack are, thus fracture toughness of the materials is higher.
Effectiveness of grain bridge toughening is due to grain size, and the big the size of grain is, the more obvious the toughening effectiveness is.
Conditions of Grain b and c are different.
When the crack encounters grain TiB2 (b and c shown in Fig.4), it keeps away from the grains and grows along phase boundary of the grains, which is intercrystalline crack deflection.

A large number of subsequent efforts on ceramics as well as single-crystal samples were made to explain the universal dielectric properties of CCTO based on respective experimental results, and revealed additional features, such as dipolar relaxation, relaxor behavior and strong non-linearity [2-5].
And we found an obvious bimodal grain size distribution in CCTO-ST composite ceramics, in which large grains correspond to CCTO and small grains represent ST.
Each grain contains a cube-shape “core” at the centre of the grain and a uniform insulating “shell” on the outside.
ST is insulators whereas CCTO grain is conducting.
The average grain size decreases with the increase of x value, which means that the grain boundary content increases[14].

Because the plasticity of ferrite phase is better than that of cementite phase, a large number of dislocation lines (DLs) and dislocation tangles (DTs) are formed in the ferrite phases.
The boundary of the big grain becomes illegibility.
The grain size for this layer is about 5~65 nm with an average value of 16nm.
The SAED pattern shows approximatively random misorientations among these grains.
Along with grain refined and cementite decomposed, the size of grain tends to uniformity.

When the proportion of tungsten powder rose to 10%, there was reticular secondary carbide precipitating along the grain boundary.
The dendritic crystal grain was composed of higher melting point metal, such as W and Cr.
The crystal grain in transition zone was much bigger because it had longer growing time.
Acknowledgements This paper was supported by the science and technology project of Zhejiang Machinery and Electrical Group Limited Company (project number, 2014JD001).
Besides, the author would like to appreciate the financial support from the scientific research sustentation fund from Zhejiang Provincial Education Department (project number, Y201328309) and Sliding Bearing Engineering Technology Research Center of Zhejiang Province (project number, 2012E10028).

The results show that the corrosion rate of the ultrafine-grained alloy increases, in comparison with the coarse-grained alloy.
The number of ECAP passes is 4.
For the as-cast alloy, the average grain size is about 100 mm.
With multipass ECAP, remarkable grain refinement occurs by repeated shear deformation, and the grains were refined to submicron level after four passes.
(1) The corrosion rate of the ultrafine-grained alloy increases in 3.5% NaCl solution, in comparison with the coarse-grained alloy.

The ratio of the traversing rate to the rotation rate, i.e., tool advance per revolution (Table 1; the designators are only serial numbers), is essentially the same for these two samples; accordingly the SZ microstructures are similar and have been discussed in previous reports [19, 20].
Convergent-beam electron diffraction (CBED) patterns were taken from each α phase grain in a region of contiguous grains and the patterns were then analyzed to determine unambiguous lattice orientations of the grains.
The grain-to-grain lattice disorientation accuracy was then ~0.4º.
The boundaries in this image are shown in the tracing of the boundaries in Fig. 3(b) in which the line width corresponds to the grain-to-grain disorientation angles from TOCA analysis.
At this temperature 1 - 10 µm κiv particles will persist in α grains.

The instron machine is used to find out the number of cycles to failure of the material.
When the number of cycles is more, S-N curve is used for the fatigue analysis.
The media consists of semisolid carrier and abrasive grains.
Table 1 shows the number of cycles before the failure of the specimen and their averages.
Design of experiments A statistically design of experiments (DOE) technique, two-levels three variable full factorial design of experiments is used here [14].The three design factors considered in the design of the experiments are extrusion pressure (A), grain size(B) (or mesh number) and abrasive concentration (C).

Compared to Al-containing ODS steel, the finer grains of Al-free ODS steel are due to the formation of smaller coherent oxide particles which suppress the steel's grain growth.
Alloying element Ti was added in the ODS steels to decrease the size of dispersed oxide particles and increase their number density in the steel matrix.
This is consistent with smaller grain size of Al-free ODS steel [9].
As for the effect of grain refinement, the ion diffusion along grain boundaries is considered to be critical in the present ODS steels because the oxide scales of the previous ODS steels have been shown to grow exclusively by oxygen grain boundary transport [13, 18].
Compared to Al-containing ODS steel, the finer grains of Al-free ODS steel are due to the formation of smaller coherent oxide particles which suppress the steel's grain growth.