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And nucleation and growth mechanisms of iron crystal grain in gas-based reduction were investigated by optical microscope (Leica DMRXP).
Thermal charging can promote the migration and accumulation of iron crystal grain effectively.
Introduction With the increase of world steel production, large number of direct reduced iron (DRI) are needed for the electric arc furnace (EAF) steelmaking [1].
Nucleation and Growth Mechanism of Iron Crystal Grain.
And iron grain bonded with other in each iron phase sheet only a few fine pores remained.

The single holes were marked with ordinal numbers from 1 to 12.
A large number of small cracks were also especially on the disk projection.
The cracks spread along the boundaries of the original austenitic grains.
The corrosion products on the grain boundaries are mostly formed of oxides of iron.
High oxidation of the boundaries of the original austenitic grains could be caused by oxygen attack of previously attacked grain boundaries in the humid environment during shut downs (most probably this does not occur on the other disks).

Finally, the bulk ceramics were examined by SEM to investigate the grains of the ceramics.
The grains of the BT-S ceramics clearly appeared.
As reported by [20], the larger the crystallite size causes a larger crystal domain which further rises the number of dipole moments so that the polarization upsurges resulting in a higher dielectric.
Acknowledgements The authors would like to thank Kementrian Riset Teknologi dan Pendidikan Tinggi for financial support through Penelitian Dasar with a contract number of No. 112/UN27.21/HK/2020.
Takeda, Grain size effect on piezoelectric properties of BaTiO3 ceramics, Jpn.

The chemical composition was calculated applying the ZAF (Z- atomic number, A-adsorption, F- fluorescence) correction procedure and using pure Ag and In standards at resulting relative error about 4 %.
TEM image of the Ag/In/Ag joint diffusion-soldered at 193 °C for 90 min: (a) Overall view of the Ag/Ag2In/AgIn2 interfaces (underlined by dotted line) together with the positions of EDX microanalysis marked by numbers and (b) electron diffraction pattern of the selected AgIn2 grain.
Fig. 2b present the selected area diffraction patterns (SAED) made in the area of selected grains AgIn2 that confirmed the presence of tetragonal AgIn2 phase.
Fig. 3a and b show the AgIn2 phase formed different shape and size grains from about 100 nm up to 200 nm with linear or oval shape boundaries.
The selected area diffraction pattern (SAED) (Fig. 3c) made in the area of selected grains confirmed the presence of cubic Ag2In.

The results showed that a longer deposition time tended to produce a larger grain and a looser, rougher layer.
Introduction Siliconizing shows a wide application in the field of engineering because the siliconized layer has a considerable number of practical applications and fundamentally interesting properties.
The hot rolled grain oriented silicon steel (3.52 wt%Si, thickness 2mm) was used as substrate.
From Fig. 5a, b, c, d and e, we could see that the deposition time affected the grain size, a longer deposition time tended to produce a larger grain and a looser, rougher layer.
The results showed that a longer deposition time tended to produce a larger grain and a looser, rougher layer.

WU et al [10] showed that the dispersion phase of Al3(Er, Zr) of L12 structure with smaller grain size and higher volume fraction could be obtained after two-stage homogenization process.
These non-equilibrium eutectic phases are distributed in a continuous network along grain boundaries in the form of short bars, strips and lamellar.
After homogenization at 400℃ for 8 h followed by 470 ℃ for 24 h, dispersion phase Al3(Er,Zr) with smaller grain size and higher volume fraction appeared.
Since higher Er and Zr supersaturation at low temperature can promote nucleation of a large number of dispersions, the first step at 400℃is conducive to the precipitation of Al3(Er,Zr) dispersion phase.
Therefore, a large number of Al3(Er,Zr) dispersion phases with smaller grain size and more uniform distribution can be obtained by two-stage homogenization treatment at 400℃ for 8 h followed by 470℃ for 24 h.

This is because, as aging process continues, the precipitated β phase impedes dislocation movement which leads to accumulation of large number of dislocations.
In its as-cast structure, ZK60 magnesium alloy contains large number of eutectic structure, which consists of α-Mg and irregular-shaped MgZn [12].
There are a variety of eutectic structures: they may occur along crystal-grain boundary, they may also occur inside crystal grain; they may be of petal-shaped pattern, they may also be of strip-shaped pattern, and etc.
As aging temperature rises, there occurs a second-phase grain-distribution precipitation which grows gradually and forms networks at 170.
As new phases precipitate along crystal-grain boundary, these phases are in uniform distribution, making the toughness of the alloy increase.

The microstructure of samples SS 316L for austempering (Fig. 3 (b)) and martempering (Fig. 3 (c)) process shows the different size of grain structure which the grain of martempered sample is smaller than austempered sample.
Martempered sample (Fig. 4 (c)) has higher size and number of pitting than austempered sample (Fig. 4 (b)).
As discussed earlier, in Fig. 3 (c), martempered sample have finer grain and its lead to high pitting corrosion.
The smallest the grain structure size of the samples, the higher the hardness value will be formed.
In addition, hardness increased as the grain size decreased.

Ca incorporation caused a decrease of the grain size and Curie temperature.
At higher temperature and dwell time, grain growth is caused by the grain boundary migration, while grain boundary diffusion can still be activated causing enhanced density.
It is shown that clear grain boundary and uniformly distributed grain size could enhance the density of the x = 0.02 ceramics and may be advantageous to the electric properties.
This is due to the reduction in grain size.
Acknowledgements This research is financially supported by Prince of Songkla University under contract number SCI580905S.

Addition of BA has influenced on the average grain size of NKLNT ceramics.
The grain size decreased significantly with increasing BA content.
Moreover, many distinct pores in the grain boundary of the ceramics and the grain shape become irregular as 0.01 ≤ x ≤ 0.015.
This revealed that a small amount of BA doped in NKLNT ceramics, as a grain growth inhibitor, had an effect on grain size reduction.
Acknowledgements This research is financially supported by Faculty of Science, Prince of Songkla University under contract number 154003.