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Liquid copper could easily penetrate into the grain boundaries of solid iron due to lower free energy of the new interfaces between liquid copper and solid Iron than the free energy of the grain boundaries (decrease in the free energy of interfaces).
Copper mainly migrates in the inter particle channels and covers most of the grains.
The microstructure of the sample number 1 with 0% nickel and 0% molybdenum which is sintered at 1120˚ C for 30 min and etched in Nital 2%, (The ferrite regions with light color covered by copper rich grain boundaries.
The microstructure of the sample number 5 with 1% nickel and 0.5% molybdenum sintered at 1120˚ C for 30 min and etched in Nital 2% (The ferritic region with light color and bainitic region with dark color and some porosity).
The best result is obtained in sample number 7 with compositions of 3Ni, 0.5Mo, 0.8C, 2Cu, Fe (base) and 1 wt.% Zn-St which had the best density, hardness and microstructure. 5.

TG-DTA analysis of simple substance Mg, Ni and Ti to generated alloy phase. 2.2 Refinement of grains under sintering temperature range As shown Figure 2, the alloy phases generated when the temperature increased to above 600°C according to the result of TG-DTA, the expansion of the lattice space between the two phases produced at the temperature of 650°C and 850°C.
The results indicated that the grains of Mg2Ni coarsened with the heating temperature.
The grain size can effectively expand the surface area of the composite material and can improve the activity of hydrogen absorption and adsorption, which had ultimately avoided the negative effects on the hydrogen absorption and desorption.
For produced negative factors from absorbing and desorbing hydrogen, many researchers from domestic and foreign had a large number of experiments to improve kinetic and thermodynamic properties.
In the process, the amount of hydrogen absorption and desorption was obviously improved, in which the amount of hydrogen desorption reached 4% within 5min. 4 Conclusion The study synthesized advantages of the powder and the metal to optimize the structure of the crystal through adding trace element Ti; the composite effectively overcame inconvenient from the powder on storage aspect and avoided negative factors of small surface area due to an increasing of the grain boundary between the crystal grains and the channels of H entered into the material increased.

The methodology has been applied for optimisation of strength, grain structure and costs of 6xxx series aluminium extrusions.
The main output from Alsoft is the fraction recrystallized (Xrex) and the recrystallized grain size (Drex) NaMo.
(ii) Keep the grain structure non-recrystallised.
A high TH is however detrimental for the recrystallization resistance since the dispersoids become coarse with a low number density.
Vatne, In the First International Conference on Recrystallization and Grain Growth (Eds.

In all samples there is a duplex distribution of the grain sizes with the microstructure mainly composed of fine grains with few regions containing coarse grains.
The ZK60, Fig. 1 (a) contain coarse grained regions with a grain size of ~40 μm and regions of fine grains of approximately 1 μm due to oxide particles preventing grain growth.
With the addition of HA, the number of regions with coarse grains decrease and the fine grain regions become more prevalent and ZK60-20, Fig. 1 (d), contained mainly fine grained regions with grain size not resolvable using optical microscopy.
In the ZK60-20 alloy the coarse grained regions contained a grain size of ~15 μm.
The addition of HA decreased the grain size significantly thus providing surfaces where recrystallization can occur, possibly through particle stimulated nucleation or the HA particles prevent grain growth.

Samples which extrusion for one time is 1#, and the sample numbered 1#, 2#, 3#, 4# followed by analogy.
The number of short fiber gradually increases, and some short fibers form a "tadpole-like" structure.
Ag grain size distribution is between 100 ~ 500 nm, which has been refined to the ultra-fine grain size range.
At the same time, a large number of dislocations further accumulation, movement and annihilation in the sub-structure and the boundary, some sub-boundaries has already begun to change in large grain boundary [12].
In addition, when the grain was refined to the nanometer scale, the lattice distortion and internal stress will be further increased.

In this regime, the physical properties may be strongly influenced by the presence of a large number of interfaces in compact materials ,or the large surface to volume ratio in nanostructured particles of thin films.
As an example, the emission at room temperature of a sample with 50 nm grain size is shown in comparison with that of the coarse grained reference material in Fig. 3.
Fig. 2 Diffuse reflection spectra of nanocrystalline Y2O3 and coarse grained reference [7] Fig. 3 Emission spectrum of nanocrystalline (50 nm grain size) pure Y2O3 and the coarse grained (10 µm) reference at room temperature [8].
They do also find a reduction of quantum efficiency with decreasing grain size.
Fig. 7 Diffuse reflection spectra of nanocrystalline and coarse grained Y2O3:Eu [14].

The pure ZrTiO4 appeared to have a wide grain size of 5~20 µm interlinked fine- ZrTiO4 particles at the grain boundaries would accompany grain growth as shown in Fig.
On the other hand, the pure Al2TiO5 sintered at 1500ºC for 4h exhibited significant the grain boundary micro- cracks with grain sizes of about 5~7µm and also abnormal Al2TiO5 grain growth.
This grain boundary microcracks observed at the Al2TiO5 grains are expected to be highly thermal anisotropic Al2TiO5 crystal.
The average grain sizes of Al2TiO5 phase of ZAT5 are in the range of 3µm.
The microstructure of sintered ZAT7 phase at same conditions consists of discontinu- ous larger grain of Al2TiO5 and this grains showed abnormal grain growth to 5~20µm in microstruc- ture.

Fully-densed polycrystalline Ce:LSO ceramics with fine grains were fabricated on optimal sintering conditions of 1350℃ for 5 min under pressure of 50 MPa.
Due to combination of the high density and high effective atomic number, these materials were endowed with the excellent performances of radiation absorption ability, the good light yield, the fast decay time in nanosecond scale and the high energy resolution.
Further observation on polished surface in Fig.4(b) revealed that the grains of Ce:LSO ceramic is shown to be in equiaxial shape uniformly with average grain size of about 2-3 um.
No second phase or impurities is found to be segregated at grain boundary, which is quite beneficial to achieve good optical transmittance.
The prepared Ce:LSO ceramic had a uniform microstructure and the fine grain size with the relative density of 99.5％.

Morphological analysis carried out by optical microscope shows increase grain refinement with the increase of calcium content in Mg-Ca composites.
According to the micrographs, it can be clearly stated that the addition of calcium element caused a decrease in the grain structure of magnesium.
In another word, further grain refinement was observed with increasing calcium content in Mg-Ca composites.
The deviation in measured values was attributed to the slight variations in a large number of processing parameters involved in the fabrication of composites.
The increase of Ca content causes the precipitation of Mg2Ca phase on the grain boundaries.

The deformability of alloy B is better than that of alloy A and C at RT due to small grain size reduced by α2 phase appearance, lamellar microstructure and interfaces.
Fig.4d shows SEM image of tensile facture surface of alloy B at 1173K, the fracture mode of alloy B is ductile fracture with a large number of dimples.
The grain of either g phase or a2 phase in alloy B is finer than that of alloy A.
In general, the tensile ductility is inversely proportional to the grain size, grain refinement will help to improve the ductility.
Vol.12(4) (2002), p.625 [8] XIE Kun, WANG Jian-nong, TANG Jian-cheng, et al:Refining TiAl grains by cyclic heat treatment, Rare Metal Materials and Engineering.