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The grain size of surface ultrafine grains was characterized by X-ray diffractometry.
The grain size of surface ultrafine grains on SMATed Fe3Al was characterized by X-ray diffractometry (XRD) on XPERT-PRO diffractometer.
Based on the broadening of (220), (400) and (422) diffraction peaks, calculation showed the grain size of surface grains was about 35 nm.
The above phenomena are all attributed to the lower diffusion activation energy and higher diffusion coefficient which induced by the non-equilibrium defects and grain boundary in nanocrystallines, especially a large number of triple junction boundaries. 4.
Width of deformed layer, grain size of surface grains, phase constituents and microstructure of transition zone in SMATed-Fe3Al/Al and Fe3Al/Al diffusion bonded joint were studied to reveal the influence of ultrafine grains on the weldability of Fe3Al and Al dissimilar materials.

The average grain sizes in all samples are less than 100nm.The average grain size changes with the sintering conditions.
So, it seems that the uniformity of grain sizes and orderliness of grain array are beneficial to the transparency and integrity of the ceramics.
The grain sizes of the ceramics are 50~80nm.
In addition, it is found that the uniform grain sizes, round-like grain shapes, ordered grain array and fewer pores are beneficial to the transparency of nano-ceramics.
Acknowledgements This work was supported by NSFC of China under grant number 50272040, Fok Ying Tong Education Foundation under grant number 91046, and Youth Foundation of Science and Technology of Sichuan Province under grant number 03ZQ026-039.

INTRODUCTION Grain refinement induced by severe plastic deformation (SPD) in metals is a well-known phenomenon.
In this study has been used ECAP method for synthesizing ultrafine grained materials, the mechanical strength of which is remarkably elevated.
ECAP is a very popular method for modifying microstructure in producing ultrafine grained (UFG) materials and nanomaterials.
The mechanism of grain size reducing based on SPD has been extensively investigated for those materials, such as Fe, Cu and Al, coarse grain structures are refined by various dislocation activities [1-6].
It was determined that for a number of two passes in an ECAP die with intersecting channels angle φ = 90° and a corner angle ψ = 20°, an increasing in ultimate tensile strength (σ UTS) up to approx. 100 and 200%.

The average grain size was controlled to 28 and 238 µm in order to understand the effect of grain size on mechanical property and flow behavior.
At room temperature and 943 K, 0.2% offset yield strength increased with decreasing grain size to exhibit grain size dependence.
At 943 K, a specimen with the average grain size of 28 µm showed higher yield strength than that obtained with a specimen having the average grain size of 238 µm.
Concerning the yield strength, the alloy with 28 µm is Journal Title and Volume Number (to be inserted by the publisher) 3 observed to have higher strength than that of 238 µm.
Journal Title and Volume Number (to be inserted by the publisher) 5 [2] M.

Ultimate tensile strength increased with decrease in grain size.
The software distinguished different grains using various color contrast, and then calculated equivalent diameter of each grain.
The base metal microstructure consisted of large elongated grains typical of a rolled structure, with an average grain size of 75μm (shown in Fig. 2a).
The grain size of the nugget zone is determined by two major factors.
The average grain size of the base metal was 75μm.

Hence it became a necessity to modify their structure and refine their grains.
ECAP autographic records, for ZA22 grain refined by Ti.
ECAP autographic records for ZA22 grain refined by Ti-B.
Hence reducing the number of stages required for forming them at high strain beyond the plastic instability and all its investigated micro alloys.
Packwood: The Grain Refinement of Zinc-Aluminum Alloys by Titanium Can.

Fig. 1 Elastic modulus, C11 - C12, and ideal shear strength, tmax, vs. valence electron number per atom, e/a, in bcc Ti-Nb binary alloys.
Fig. 2 Experimental elastic modulus, C11 - C12, by literature [11] and ideal shear strength, tmax, vs. valence electron number per atom, e/a, in Fe-Ni binary alloys.
The averaged grain size after HPT is 20 - 50 nm as previously reported [3].
How the elastic anisotropy affect the process of grain refinement during HPT?
Such localized transgranular shear seems to contribute to the significant grain refinement in the present case, and the inhomogeneous distribution of grain size shown in Fig. 4 would be attributed to this grain refinement process.

In addition, if the number of unique EFGs increases their respective fractions have to be smaller.
For coarse-grained materials with a grain size > 1 , the volume fraction of atoms in the grain boundaries is negligibly small, but for 100 nm grains one calculates already a volume fraction of 3%, which increases for 10 nm grains to 30% and might reach 50% for 5 nm grains [2].
Spikes are formed for a very short time in systems having a mean atomic number larger 20 [49].
The number of possible sites for probes increases.
Small numbers of probes can be deposited as a two-dimensional sub-monolayer.

In addition, a number of elastomers are available acting as a fuel.
These problems were more evident in slender grains.
There are at least two thin wires placed in specific sections of grain.
The grain is then ignited to be burnt one dimensionally.
Figure 2: Wiring pattern in a grain section.

The study has revealed three structure types in the alloy: (1) a smooth shagreen-type structure (an orange peel), which turns into a stripe-like structure (2) in some areas, and a grain structure (3) to appear as lengthy thin layers with the width of 50-80 µm and an average grain size of 12.5 µm, the most probable size of grains is detected to be in the range from 10 to 15 µm, a preferred number of such grains is 31%.
It is noteworthy that an increased number of micropores are detected on the boundary between these types of structure.
There is a grain structure in several areas in the form of lengthy thin layers with the thickness varying from 50 to 80 µm and average grain size of 12.5 µm (Fig. 1 d).
The grain size distribution demonstrates the most probable dimension of grain to range from 10 to 15 µm.
An average grain size in the identified structure was determined to be 12.5 µm, the most probable size of grains ranges from 10 to 15 µm; that is 31% of all grains.