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The Vickers number (HV) was calculated using the following formula (Eq.1) : HV = 1.854(F/D 2) (1) with F being the applied load (measured in kilograms-force) and D 2 the area of the indentation (measured in square millimeters).
The SEM micrographs for the fracture surfaces (see figs. 3 a and b) in the specimens obtained in both sintering temperatures indicate that depending on sintering condition and amount of cordierite, various kinds of microstructures (isolated glass particle, continuous glassy grain boundary phase) were formed.
The structure of the obtained composites observed using scanning electron microscopy of the fractured surfaces revealed predominant sub-micron size grains of Y-TZP accompanied by both isolated glass particles and continuous glassy grain boundary phase (Fig. 3).
It is concluded that cordierite consists mainly of glassy phase that was located in the grain boundaries.

A pseudo-perovskite layer (Am-1BmO3m+1) is sandwiched between the fluorite type sheets (Bi2O2) 2+, where m and m-1 are the numbers of oxygen octahedral and pseudo-perovskite units in a layer, respectively.
In addition, with the increase of the La content, the intensity of (040), (060), (0100) and (0140) diffraction peaks become strong, indicating that the orientation of crystalline grain along b axis becomes strong.
The grains size becomes fine with the increase of La in the Bi4-xLaxTi3O12(x=0, 0.75, 1.0).
The grains size becomes layered tablets in the Bi2La2Ti3O12.
In contrast, Bi2La2Ti3O12 sample seen to have the largest grain size, why and how behaved like this still needs further investigation.

Situ video recording the whole process of solidification of the alloy from melting to continuous video cut into a number of pictures, each picture display time and instantaneous temperature.
It begins to crystallize as high temperature ferrite (δ) at 1544 °C, 1538 °C solidified with decreasing temperature, the crystal grains grew up, the ferritic phase by the high temperature (δ) in 1385 °C its initial crystallization transition to the austenite phase (γ) .
CLSM in situ observed, δ → γ phase transition, the γ phase priority in the δ phase at the grain boundaries, trigeminal nucleation, the initial the γ crystals tend along the δ grain boundary expansion to form γ crystal sheet, as shown in Figure 4 shown; δ / γ morphology to thumb-like, low undercooling δ / γ interface along the δ grain boundary propulsion; undercooling is large, δ / γ interface can even advance to the δ phase matrix.

Rolling is an effective process to refine the grain size and enhance the mechanical properties for the cast strip.
It was found that , because of the higher cooling rate, the grain size of strip is 20-60µm and finer than that of ingot which is more than 100µm.
Fig. 3 is homogenized microstructure of the cast strip at 400 for 4h in which ℃ β-Mg17Al12 particle decreases in number and grain size almost doesn't change.
The distorted structure indicates that the dynamic recrystallization has occurred in rolling deformation and there are many equiaxed grains in the strip(Fig. 4(a)).

It improves the strength of the material by large number of dislocation piling up and intersection forming tangles when the dislocation gliding[1-4], therefore increasing the resistance of dislocation motion and the strength of the metal.
The reasons for the mechanical properties changes are the high dislocation density tangled into smaller sub-grains improving the strength of the metal at low-temperature tempering after pre-tension deformation, and the deformed metal take place recovery, recrystallization, and grain growth.
Sub-grains became large size grain and reduced grain boundary area at high-temperature tempering[10].
So the microstructure did not change significantly, and the shape and size of grains are almost the same as the microstructure without tempering.
The recrystallization nuclei and new small equiaxed grains would emerge at regions of grain boundary, slip bands or intense deformation zone.

High surface energy, higher surface roughness and grain size of 1μm to dozens of μms will seriously affect the application of diamond films in optics and electronics.
To overcome this shortcoming, it is necessary to reduce their grain size.
Gruen proposed the following four important elements: (1) The basic element: film grain size should be several to hundreds of nano; (2) Film thickness: at least 3um; (3) Non-diamond component: less than 5%; (4) Random orientation of crystal grains maximizes Π key bonding, which is the only way to ensure excellent mechanical properties of nano-crystalline diamond films.
Therefore, solution to nano-crystalline diamond reuniting and stable dispersion will be of important practical significance for exerting its excellent performance and promoting its application in a number of technologies.
Reducing the Grain Size for Fabrication of Nanocrystalline Diamond Films, Journal of Crystal Growth, 2001, 222：591-594

The bulk 2.7Y-TZP ceramic with an average grain size of 110 nm reached a hardness of 13.6 GPa and fracture toughness of 11.2 MPa·m1/2.
A nano-grained alumina/zirconia composite with an average grain size of 92 nm was obtained, and the hardness increased to 16.8 GPa.
Grain sizes were determined by a linear analysis of SEM micrographs of the polished and etched (1100 °C for 1 h) surfaces.
An average fracture toughness and standard deviation for each sample were computed from the total number of fracture toughness values per sample (12 values).
At this temperature, the grain size remained in the nano-scale range [3, 7].

Most of the graphite could be found at a grain boundary, so grain boundaries were the major sites of the nucleation of graphite [2,3].
A few graphites also existed in the grain because of boron segregation, boron rich precipitates or voids [9,10].
Another reason for the existence of graphite in the grain boundary is due to transfer from the grain boundary to the inter-grain by grain growth, even though the graphite nucleated at grain boundaries.
Comparison of Fig. 3 and Fig.2 revealed that the number of the spherical shape tracks abruptly decreased in the B2 specimen, whereas the size of boron segregation and boron-rich phase increased in all the specimens at 750℃ for 10 hrs.

The simultaneous measurement of strain rate, strain and temperature offers the possibility of exploring a number of phenomena such as dynamic recovery and recrystallization, and their role in microstructure refinement during the SPD.
The bulk Ti sample, in the form of a plate, had an initial grain size of ~60 µm and a Vickers hardness of 144 kg/mm2 (300 g load).
The resulting Ti chip foil consisted of ~ 100 nm subgrains with a Vickers hardness of 230 kg/mm2 [5, 6]; this grain size is somewhat finer than that in Ti deformed by ECAP at an elevated temperature of ~ 400°C [2].
The concurrent measurement of the strain and temperature fields should enable a quantitative study of dynamic recovery phenomena in the SPD, since this recovery is likely to play a crucial role in determining the level of grain refinement that is ultimately achieved.
Clearly, large T implies small Z and therefore a coarser final grain size.

The structure of the studied steels, the grain size and the crystallographic orientation were evaluated using EBSD.
The average grain size in the transverse direction was (1.5 ± 0.1) μm.
The structure further shows random grain orientation in the longitudinal and transverse directions.
The protruding grains in the longitudinal direction are preferably oriented in the direction [α1] forming the α-fiber.
Yvon, Structural Materials for Generation IV Nuclear Reactors, Woodhead Publishing Series in Energy: Number 106, Duxford, 2017, ISBN: 978-0-08-100912-3 (online)