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It must be pointed out that the number fraction of in the under-aged sample increased during the thermal exposure procession.
The number of the precipitation also got the most when exposed for 20 h.
With further prolonging the exposure time, the precipitations coarsened to a small extent and the number decreased slightly.
With further increasing the exposure temperature to 300, the grain boundaries was deformed to some extent (Fig. 7(d)).
It might be due to the pinning effect of the massive phases during the migration of the grain boundaries.

Coarse grains in the HAZ enhanced ductility, while the fine-grained structure and increased precipitate formation in the WZ improved strength but reduced ductility.
Finer grains led to an increase in strength, while coarser grains offered the highest ductility [32,33].
Furthermore, the WZ displays fine grain boundaries when compared to the HAZ.
The presence of precipitates, evident in Figure 3, contributed to the observed increases in both UTS and hardness due to their greater number at the elevated temperature.
Additionally, the coarse grain structure observed in the HAZ was effectively counterbalanced by the formation of a large number of precipitates.

Since a polycrystal contains a large number of randomly oriented crystalline grains, all possible diffraction peaks should be observed.
The LMO fine particles consist of crystalline grains and amorphous-like grain boundaries.
Polycrystal LMO consists of crystalline grains and amorphous-like grain boundaries.
Since amorphous-like grain boundaries have a large number of dangling bonds per unit volume, a larger quantity of excess oxygen atoms are able to exist in those regions than the crystalline grain ones.
Thus, we consider that stronger hole self-doping occurs in amorphous-like grain boundaries than in the crystalline grain ones.

Cross-sectional TEM images of the coatings, Fig. 1-3, showed that all the coatings had columnar grain structures and that the average diameter of the columnar grains was greater in the monolithic coatings than it was in the multilayered coatings.
The column boundaries are also decorated by voids, their number and size increasing with distance from the substrate, particularly in the case of CrN.
This change in void size and number would appear to be linked to an increase in column size through the coating and are also visible in the multilayers, Fig 3, although their density appears to be lower.
Fig. 5: Cross-section of CrN monolith with a 300 mN indent with the columnar grains clearly visible and a number of cracks directly below the indent indicated by the arrows.
The multilayer with a 58 nm thick bilayer did not show cracking at the surface propagating between the columnar grains but in some cases shearing of a block of material vertically downward and along the columnar grain boundary was seen, Fig. 3.

It can be seen that the as-cast alloy consists α-Mg matrix and dendritic crystal that distributes on grain boundary.
In addition, the grain boundaries of as-cast alloy are covered partly by precipitated phases and have not been distinguished easily.
After solution and aging treatment, thick dendritic crystal disappears and the grain boundary is observed clearly in the aged alloy.
Moreover, there are some precipitated phases that distribute in the grain dispersively in the alloy.
The fracture surface of the alloy takes on a large number of cleavage facets and has few dimples at room temperature.

Polizu, Bucharest, Romania, RO-011061 Keywords: Sol-Gel Hydrolysis; Hydrothermal Treatment; Aluminum Titanate; Nanosize Grains Abstract.
The aluminum titanate precursor powders obtained by hydrothermal method presented good homogeneity and very small grain size.
The correlation between the grain size and microcracking is proved, a grain size distribution and a small size of particles being desirable for a good sintering behavior and a limited development of the microcracks [5].
Wave Number [cm-1] 1 2 3 4 From the resulted powder pellets were uniaxially pressed then were thermally treated in the temperature range between 1250-1400 0C.
A homogeneous and amorphous structure with aggregation tendency and nanosize grains (~5 nm) of the Sample 2 is presented in the Figure 3, a.

The flexural strength could be increase due to high rate of atomic diffusion in the grain boundaries.
When Al2O3 and MgO particles are compact during pressing process, the grain boundary number per unit length increases, in result higher temperatures and longer times for Al2O3 and MgO sintering lead to a greater shrinkage for the Al2O3 and overall for the ceramic material.
Porosity located among small grains.
For 1600°C sintering temperature, strong decrease in thermal conductivity has been shown in small grain ceramic (Z3) compared to larger grain material (Z1).
SEM analysis of 1600°C sintered samples showed that grain size has clean grain boundaries and absolutely no large porosity noticed.

Thus, grain boundary maps, which include many subgrain and grain boundaries with a misorientation larger than e.g. 5°, can be made.
However, since a significant number of boundaries are missing, both average boundary misorientation data and average subgrain size data will be incorrect in such a map.
During indexing of the EBSD scan, the software gives a CI-value for each indexed pattern as a ratio between the numbers of suggested similar crystal orientations over all suggested crystal orientations.
If the CI is less than a certain number, the software will simply disregard the information related to pixels in the scan where the criterion is fulfilled.
Driver, Sub-grain boundary mobilities during recovery of binary Al-Mn alloys, Int.

Further test with the deposited billet show that the grain size of the spray formed 7055-Al alloy is mainly ranging 10~30μm, which is about one third of that of as-cast billet.
The property benefits of the spray formed products arise from rapid solidification, which promotes grain refinement, structural densification and macro-segregation eliminates [3, 4].
The spray formed 7055Al alloy has the characteristic of uniform fine equiaxed grain, no dendrites and no macro-segregation.
There are a small number of porosities in the deposited billet and the brightness in the interior is higher than that of the grain boundary.
The grain size of the spray formed 7055Al alloy is mainly ranging 10~30μm, while for casting technology the number is 40~50μm.

Nanocrystalline materials generally have grain sizes lower than 100 nm and the improved physical and mechanical properties of the materials are due to the nanometer scale grain size as well as high volume fraction of grain and interface boundaries [5].
Some micropores of the grain boundary were also observed.
The number and size of small pores were decreased with increasing sintering temperature, but the relative full density of HP condition could be attained only by the lower sintering temperature of SPS process (800oC and 900oC).
Thus the hardness-grain size relation can be obtained.
In the SPS processed sample, the smaller grain size resulted in a higher Vickers microhardness.