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Due to successive deformation and recrystallization in the first phase coarse austenitic grain becomes finer, but after transformation it becomes a relatively coarse ferrite grain.
Ferrite grains are also formed on the austenite grain boundaries and on the internal flaws. 
With controlled additional water cooling the austenite is transformed into even smaller ferrite grains.
The main feature of controlled-rolled micro-alloyed steel is a fine grain ferrite structure with a grain size up to No13 by ASTM.
Arsić, Filler Metal Influence on Weld Metal Structure of Micro-Alloyed Steel, manuscript number: 201039, Supplement to the welding journal, Sponsored by the American Welding Society and the Welding Researc Council, vol.90, (2011), pp.55-62

The VT is extracted at 10 nA(W/L) and sample number is 80.
Generally, as the peak is narrow, grain size becomes large.
From this, it shows the grain size of poly-Si on oxide layer is larger than on nitride layer [4].
The reason why the grain size of poly-Si on oxide buffer layer is larger can be explained by the different grain growth due to the nucleation [5].
The narrow peak of poly-Si on oxide layer has high mobility due to the large grain size.

This is due to the Nb addition act as a stabilizer and grain refiner, the smaller grain size of annealed Ti+Nb strips compared to the grain size of annealed Ti only strips.
The microstructures of the both steels are shown in Fig. 5, which exhibit predominantly equiaxed ferrite grains.
The average grain sizes of the Ti+Nb additions and Ti only additions steels in transverse orientation are found to be 18.6 and 20.5 μm, respectively.
The finer grain size of Ti+Nb additions steel is due to the presence of the higher amount of Nb apart from its finer grain size.
It is believed that the improvement of hardness and strength to the spot welds by way of grain refinement will enhance its fatigue performance.

Experimental results and analysis 1.Influence of sputtering pressure on the composite film Fig. 1 shows the SEM images of the surface morphology and EDS spectrums of the composite films at diffrernt sputtering pressure.When the sputtering pressure is 0.5 Pa,there distribute a large number of 200 nm sized grains .When the pressure incresses to 0.8 Pa,on the film surface there are some distributed scattered grains , which are irregular in size,from 2 nm to 8 nm.
As the pressure continues to raise, the the grains formed on the film surface decrease.
When the power increases to 150 w, the composite film surface distributes of uniform and compact organizational ZnO grains.Thus grain micro-roughness and the contact angle increases.
Fig. 5 (c) shows a large number of granular tissue formed on the surface of film at the condition of the oxygen argon ratio is 15:30,the 200 nm grains uniformly disperses among the matrix .
There are a small number of 300 ~ 500 nm grains .

Introduction Severe plastic deformation (SPD) is an effective tool for producing bulk ultrafine-grained (UFG) metals.
The nonmonotonous deformation processes usually result in more effective grain-refinement.
Ductility of the workpieces continuously decreased with increasing number of ECAP passes as well as by applying the additional forming processes.
Subsequent deformation after 1 ECAP pass did not result in further grain refinement.
This feature may be the structure of grain boundaries, texture, and the interaction between dislocations and Mg2Si and Mg12Si7Al5 precipitates.

One of SPD techniques, ECAP processing is commonly used to produce fine-grained materials.
Addition of TiB2 particles would refine grains of as-cast structure and also would give benefit on accelerating grain refinement during ECAP processing, however it has adverse effect of increasing tendency of cracking.
However, the element of boron (B) could not be detected by XRF and EDS analysis due to its low atomic number.
Therefore pre-ECAP annealing specimen could be stronger than as-cast or annealed specimens because more grains in a material means that more grain boundaries exist.
The ECAP processing increases hardness and also refines grains of the annealed specimen.

It is well known that ceramic material is comprised of grains, pores and grain boundaries.
Because there are many lattice defects and lattice distortions along grain boundaries, the performances of ceramic materials are influenced greatly by grain boundaries.
Glass phase usually exists among ceramic grains.
NVT ensemble (fix the atom numbers, volume and temperature) is employed to model the sintering process.
Grain growth is mainly conducted by particle diffusion.

It is found that the in–situ formed SiC particles refine the MoSi2 grains and eliminate the brittle SiO2 glass phase.
Although numerous studies have been reported to introduce SiC phase into MoSi2 , these studies usually focus on the introduction of SiC phase, only a limited number of studies reported the introduction of SiC via in situ reaction.
%,and 40Vol.% SiC particles It was found in this study that SiO2 phase can’t be observed when the volume of SiC is more than 10%, the elimination of amorphous and brittle SiO2 phase is good for enhancing the mechanical properties of SiCP/MoSi2 composites.It also can be seen that the MoSi2 grains was refined when the SiC volume was increased, so the in-situ formed SiC particle is not only beneficial to reduce the harmful SiO2 amount but also effective to refine the MoSi2 grain size.
The mechanism of strengthening are the uniform distribution of the smaller in-situ formed SiC particles, the refined grain size of MoSi2, and the disappearance of brittle SiO2 phase.
The Improvewent in Mechanical Properties of MoSi2 through the Modification of Grain Boundary Phase .

The average grain size and the section structure of the undoped and doped BST samples were analyzed with SEM.
The grain of BST decreased slightly by small additions of CeO2, as illustrated in Fig. 3a-h.
Fig. 4 The variation of bulk density with amounts of CeO2 added into BST In an ideal cubic perovskites ABO3, the coordination numbers of the A-and B-sites are 12 and 6, respectively, t=0.77-1.1 [8].
The grain size was controlled efficiently and the sintering densification decreased by the doping of CeO2.
CeO2 additions suppressed the grain growth especially at 2mol%.

By adding Nano-Al2O3 powders and ultrasonic dispersion, which can refine grain and promote sintering, the grain size is uniform, the porosity is less and some grains were pulled out, the fracture mode changes from intergranular fracture to intergranular fracture and transgranular fracture.
Nano-Al2O3 particles have large surface area, high surface activity, small size effect and low sintering activity, at low temperature, it will react with large grain boundary to further reduce the sintering activation energy and sintering temperature[8.9].
Because the nano particles have the large surface area, high surface activity, and low sintering activity, it can effectively reduce the sintering activation energy and will react with large grain boundary at low temperature.
Fig. 7(b) displays the micrograph of sintered samples without Nano-Al2O3 powders, it can be seen that the grain is small and the pore is more, due to relatively low sintering temperature, the viscosity of cordierite liquid is high, and it almost has no effect on rearrangement and solubility of the matrix particle, besides, diffusion degree of grain boundary of the matrix particles is also weak, so relative density is low, there are only intergranular fracture.
The scanning electron photomicrograph added 15 wt% Nano-Al2O3 powders is demonstrated in Fig. 7(c), the pores in the sample are obviously reduced and the structure is compact, size of grain is more homogeneous, and transgranular fracture increases compare to the composite added 0 wt% Nano-Al2O3 powders and some grains are pulled out, which improve fracture toughness of the samples, there is the sign that the Al2O3 grains mutually bond, except for the high sintering activity of Nano-Al2O3 particles, adding Nano-Al2O3 particles to the matrix is also beneficial to improve the density of green body, it is clear that density of green body is higher and mass transfer path is shorter, which is more favorable to sintering process and densification of sintered body.