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The mechanical alloying process produces changes in the particle grain and the crystal size.
On the other hand, the particle collisions may also cause the decreasing of particle grains.
The SEM images show that PbTiO3 particles have secondary particles, which contain a number of crystals, due to agglomeration.
It shows that the higher sintering temperature causes faster grain growth that can be observed that the distribution of particles is not homogeneous due to the agglomeration.
As shown in Figure 4, the grain size becomes larger and the grain boundary decreases with increasing sintering temperature.

Although it is recognized that materials with the ultrafine grains always exhibit a variety of superior properties in comparison with those with coarse grained materials, producing the epigranular and stable cuprous chloride with high activity for the direct synthesis of triethoxysilane has been rarely reported.
The silicon grains and cuprous chloride catalyst grains (120-160 mesh: purity 99.9%) were mixed in a vial with vigorous vibration.
The average size of CuCl grains is about 72 nm, which is in accordance with the results observed by scanning electron microscope.
When 10 wt% CuCl is used, the SEM image shows that the CuCl grains remain uniform even after the pretreatment of the silicon-CuCl mixture at 533 K.
Acknowledgement Financial support from National Science Foundation of China (Grant number: 20776070) and Open Foundation of Chemical Engineering Subject are greatly appreciated.

Discussion It is well known that the addition of Ca can refine the equiaxed grain in many casting magnesium alloys.
The second phase which distributes along the grain boundaries, forming a continuous network with a thick grain boundary width to separate the grains.
It will decrease the tension between the grains and debase the deformation coordination.
Acknowledgement This work was financially supported by the National Key Research and Development Program of China (grant number. 2017YFB0103904).
Sun, High-temperature tensile properties and deformation mechanism of polycrystalline magnesium alloys with specifically oriented columnar grain structures, Mater.

The very slow cooling rate of 0.003 K/s resulted in several packets or colonies of similarly aligned O phase- lamellae (gray area) within the prior B2 grains and a nearly continuous α2 phase (black area) at the grain boundaries.
Although the final heat treatment was performed in the (B2 + O) two-phase region, the microstructure maintained the grain boundary α2 phase.
In addition, O phase-lamellae with a type of basket-weave morphology were present in the central area of the prior B2 grains.
At this cooling rate, most of the area in the prior B2 grains was occupied by the O phase-lamellae with a type of basket-weave morphology, and the colonies with limited growth of O phase-lamellae were only seen adjacent to the grain boundaries.
As shown in Fig.4, the fatigue ratio does not take the same values at each number of cycles: instead, it increases with increasing cooling rate.

Figure.3 describes SEM images of ZnO(Al,F) thin films deposited at the different substrate temperatures.The crystalline grain size is smaller at room temperature.
As substrate temperature increases, the grain size significantly increase and the grain boundaries become more clearly.
The decrease of films resistivity with the increase of substrate temperature is caused by the improved crystallinity, which makes grains bigger in size and defects fewer in number.
This is because the crystallinity of the films improved with the increase of substrate temperature and the weakening of scattering and absorption of light because of the increase of grain size.
But as further increase in substrate temperature, the band gap decreased to 3.33eV at 400 °C.This is because when the substrate temperature is too high, the crystallinity become poorly and the grain boundaries become more and more.

Although ultrasound induced grain refinement has been shown to be effective in many metallic alloy systems, almost all previous researches have interpreted the mechanism of grain refinement based on post-mortem microstructure characterisation of the solidified alloys and the empirical correlation between the measured grain size and the input ultrasonic power.
Real time imaging of solidifying microstructures have been conducted by many researchers using organic transparent compounds of melting temperature <70 °C to mimic metal alloys since the 1960s [3], but most of them were carried out at an image acquisition rate of a few hundreds of frames per second (fps) or less, unable to reveal in-situ, the highly dynamic interaction between ultrasonic cavitation and the growing grains [4].
A very recent high speed-imaging study of ultrasonic treatment of a solidifying organic transparent alloy revealed that the shock wave emitted from imploding bubbles can fracture the growing dendrites [5], increasing the grain multiplication effect that lead to the enhancement of grain refinement.
Modelling The ultrasonic pressure distribution in the liquid metal induced by the ultrasound sonotrode tip was simulated by solving the Helmholtz equation for acoustic pressure using a commercial finite-element software, COMSOL Multiphysics (COMSOL, Inc., Burlington, MA), (1) where Pa = cos(ωt) is the acoustic pressure, k = ω/c is the wave number, and ω = 2πf is the angular frequency.
Katgerman, Criteria of grain refinement induced by ultrasonic melt treatment of aluminum alloys containing Zr and Ti, Metall.

In the superplastic condition, superalloys are characterized by a fine grained (generally 10 µm or less), two-phase microstructure.
Fig.2 Assembling schematic drawing for SPF/DB of the four-layer sheet structure 1 -die; 2 -face sheet (GH4169 alloy); 3 - rib; 4 -core sheet (GH4141 alloy) Results and discussion Microstructure of the materials In the SPF/DB condition, superalloy is characterized by a fine-grained structure.
Preliminary material testing shows the sheets used for forming have fine-grained homogenous microstructure as shown in Fig.1.
The microstructure undergoes dynamic grain growth during superplastic deformation and static grain growth during diffusion bonding, the grain size of post-SPF/DB materials is larger than that of the as-received materials, as shown in Fig.3.
Acknowledgements This work was supported by the Postdoctoral Foundation of Heilongjiang Province under grant number AUGA41000551.

In FSP, a rotating non-consumable tool produces severe thermomechanical deformation that creates a fully recrystallized, porosity-free, fine-grained microstructure.
The linear raster (Fig. 2a) has uplifted grains with columnar morphology as compared to the fine grain or Widmanstätten in the bulk of the process zone between every other pass, which is due to the switching between advancing and retreating sides of the tool.
The observed differences in percent elongation are probably due to higher strain localization at the uplifted grains in the linear raster.
Linear rasters have a through thickness microstructural features (uplifted columnar grains), that probably cause strain localization and specimen failure.
Monotonic tensile properties of NiAl bronze as a function of FSP laboratory Rectangular Spiral Raster FSP Laboratory Number of Samples Yield Strength MPa (ksi) Tensile Strength MPa (ksi) % Elongation RSC 6 507 (73.6) 761 (110) 25.8 NSWCCD 5 479 (69.4) 758 (110) 28.0 SDSMT 5 466 (67.8) 724 (105) 19.0 Fatigue Properties.

The double pulse welding technology can also be introduced in the welding of 5083 aluminum alloy for its more beautiful scaly bead, which inhibit the occurrence of weld defects, decrease grain sizes and reduce crack sensitivity[1].
Among the three types of welding, the tensile fracture dimple bottom Inclusion number of forceArc welding is relatively small, In volume terms from the dimple, foreceArc welding is greater than double pulse than single pulse. from the perspective of size, the foreceArc is the minimum.
As different parts of the weld have different cooling rates, the weld central cooling slowly turns into equiaxed grains and near the base metal on both sides of the weld fusion line perpendicular become to the elongated grains.
Observing at 200 × under double-pulse weld precipitation is uniform, the double-pulse weld grain is smaller than single-crystal pulse and FORCEARC weld.
Weld metal is mainly reflected in the difference in grain size, the double-pulse weld grains are relatively small.

The alignments of the grains are orientated with low-angle grain boundaries.
Nevertheless the micrograph of sample that was exposed to neutron irradiation shows more random grain orientation and less textured.
Hence, higher porosity and subsequently less contact existed between adjacent Bi-2212 superconducting grains.
Thus the introduction of neutron irradiation created defects along the grain boundaries and act as flux pinning centers for the Bi-2212 phase vortices.
Acknowledgements This project is supported by FRGS research grant number FRGS/1/2017/STG02/UNITEN/02/5 from the Ministry of Higher Education (MOHE), Malaysia.