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The atomic structure of the grain boundary was mainly examined by HRTEM (high resolution transmission electron microscopy).
Both microstructures did not show grain growth up to the very high temperature.
Al2O3–Al16Ti5O34 has a stable microstructure without amorphous phase and grain growth is formed at the interface between the Al2O3 and Al16Ti5O34 phases.
Kerans, Wright Laboratory, Wright Patterson Air Force Base, OH, Report number WL, TR,91,4061. (1992) [6] Y.

Possible parameters, which control their mechanical properties, are prior austenite grain size, block size, colony size, inter-lamellar spacing and carbide thickness [1,2,3].
The number of studies on mechanical properties of cementite is quite limited since it is difficult to produce single-phase cementite that is large enough in dimension for having experiments.
Thompson, Effects of the prior austenite grain size on the ductility of fully pearlitic eutectoid steel, Metall.
Sugirbekov, Effect of grain size and pearlite morphology on the components of the fracture energy in steel 45 in the region of the ductile-brittle transition, Met.

The coating protects the tool against abrasion, adhesion, diffusion, formation of comb cracks and other wear due to the high strength of their covalent inter-atomic bond, small bond distance, high coordination number and its Vickers hardness HV of 40-60 and >70 GPa [1-2].
However, the three most important nano-structures are deposited today: • nanogradients (with continuous changing of the composition from the substrate to the top of a cutting tool), • nanolayers (with typical sublayer's thicknesses of 3-10 nm) and non-linear relation of hardness depending on precisely specified periods of coating), • nanocomposites - nanocrystalline grains nc-AlTiN are embedded into an amorphous matrix aSi3N4 due to the spinodal segregation (silicon is not in the metallic phase); the strong interface hinders grain boundary sliding at crystallite size less than 10 nm.
(4) However, a lot of technological variables can affect the final result such as preparation of the substrate, its chemical composition, grain size, phase distribution, thermal stability, hardness/toughness, etc.

There have been a large number of works performed on producing composite materials from powders by nonconventional powder consolidation methods in which densification is enhanced by the application of a pulsed electric current combined with resistance heating and pressure: plasma pressure compaction (P2C), spark plasma sintering (SPS), plasma activated sintering (PAS) [3].
The interest in these methods was motivated by their ability to consolidate a large variety of powder materials to high densities within short periods of time and without having to increase grain sizes.
Fig. 2 Typical pulse current traces from registration system (Rogowski coil) (Peak currents: 1 - 50 kA, 2 - 80 kA, 3 - 110 kA) The following commercial WC-Co-diamond powder was used as starting material for electrodischarge compaction: WC - ~80 wt.%, Co - 20 wt.%, free carbon 0.101 wt.%, total oxygen 0.13 wt.%, grain size WC < 5µm, grain size of diamond < 40µm.

In Table 1 the optimal PLD conditions (substrate temperature T, laser pulse duration τ, energy density ε, number of pulses N, target-substrate distance d) are collected, which allows us to obtain high quality layers.
The observed grains are of uniform shape with the average diameter of 50 nm indicating nanoscopic type of the layer.
The rings in the first picture are continuous and sharp, which results from finely crystalline structure of the grains in Fig.2.
The last set indicates the presence of the grains with [100] preferable growth direction.

Experimental Details The SnSe thin films studied in this work were deposited a glass substrate at room temperature by using fine – grained pulverized SnSePb0.1 powder (99.99%) prepared in stoichiometric proportion by vapour phase reaction in a sealed envelope.
The fine grained SnSePb0.1 powder was used to deposit thin films by flash evaporation technique onto ultrasonically cleaned glass substrates under pressure of 4 × 10-6 torr using Hind Hivac BC300 coating unit.
(1) (a) (b) Fig. 2The small angle X-ray diffraction pattern of SnSePb0.1 (a) 100nm and (b) 500nm thin films Where l the wavelength of the X-ray used n is the order number and q is Bragg’s angle.
(3) The values of inter planner spacing (d) Grain size (D), and Dislocation density (r) are calculated from equation1, 2, 3 are given in table 1.

Experimental SiC powder with particle mesh number of #90 (222 µm of median diameter) and #120 (157 µm of median diameter), VBM powder (KM-0036) with 10 µm of median diameter and LiAlSiO4 powder with 17 µm of median diameter which prepared the solid-state methods [4] were used for raw materials.
The empirical Young's moduli are plotted by different symbols and draws a maximum peak for each SiC grain size.
The VBM amount for highest empirical Young's modulus sifts large amount as the SiC grain size increases.
The minimum amount of VBM depends on the surface area of SiC i. e., SiC grain size.

Introduction Silicon carbide (SiC) is focused to be most attractive, offering significant advantages in high power, high frequency and low loss device applications.[1] It is well known that there are large numbers of polytypes for SiC material.[2] The control of the polytypes during crystal growth is quite important, because the band gap energy and electrical properties for polytypes are different.[3] It has been extensively studied that the SiC powder with impurities and the Si/C ratio of SiC powder give an effect on the defect generation and the polytype formation, respectively.[4] However, the generation of poly-crystal and different polytypes has not been reported from the view point of SiC powder phases (α- and β-SiC). α-SiC powder includes 6H, 4H, and 15R etc, and it is prepared by Acheson process at above high temperature of 2000oC.
It has been reported that the Si/C ratio in sublimated vapor depends on the grain size of the powder [5].
First of all, it was investigated that the occurrence of poly-crystals and polytypes depends on the grain size of α-SiC powder (SiCP1, SiCP2, and SiCP3).
The Si/C ratio in sublimated vapor depends on the grain size of the powder as stated by Lilov et al.[5] Consequently, to evaluate the formation of polycrystals and polytypes as the effect of powder size and to compare with the effect of powder size (150 µm) for β-SiC source, 6H-SiC crystals were grown by using various size of green (α-SiC) powder.

For example, electrical current pulse could refine the grain size in eutectic Pb-Sn casting structure [1], enhance the recrystallization process of pure copper [2], prevent the embrittlement of Fe-based amorphous alloy[3], improve the mechanical properties of metals[4], prepare nano-structured materials[5] et al.
It has been proved that the high current density electrical pulse can not only control the nucleation rate of metals, but also retard the growth of grains.
A number of precipitates resembling coffee beans with contrasts were observed in the specimen aged by electrical pulse at electrical pulse duration time 120μs for 60s as can be seen in Fig.1.
Fig.2 Electrical conductivity and Vickers hardness vs. pulse duration time. them have the average grain size about 20nm.

From large number of trail runs, the optimized parameters for obtaining defect free joint are rotational speed, welding speed and tool pin offset distance of 1000 rpm, 40 mm/min and 3 mm towards copper side respectively.
Since the tool offset was given on the copper side, it undergone significant plastic deformation under higher temperature by the axial movement of the tool and due to the friction between the rotating tool shoulder and the workpiece respectively, which leads to generation of recrystallized fine grains in the stir zone as shown in Fig (Region c).
Since it is a dissimilar combination, there is a large fluctuations in the grain size at TMAZ is observed, due to different thermo-mechanical properties of the copper and stainless steel.
There is an increase in the hardness near the weld and this can be attributed to the grain refinement that has occurred.