Search results

It was observed that the grains were homogeneously developed with narrow grain boundaries and small number of pores.
Thus, the dielectric and piezoelectric properties of the sample can be enhanced by developing more grains through reducing the grain size with different processing.
The smaller grain size might produce more grain effect with 90 ° domain and thus, enhanced the polarization orientation.
Based on the capacitance measurement, the grain and grain boundary effect were observed.
The capacitance values lie within the range of grain effect domination (10-9 to 10-10) which is in a good agreement with the SEM microstructure images where the grains are homogenously developed.

By AF1100-type EDM machine, graphite rod as a tool electrode, misted deionized water mixed with fine-grained C powder as working medium, the strengthening coating was prepared on the surface of TC4 titanium.
While mist medium has low consumption, less waste liquid displacement, and can be mixed with fine-grained powder (C, B4C, etc.) to get a better strengthening effect.
The author chooses misted deionized water mixed with fine-grained C powder as working medium to discharge medium.
Table 2 The thickness of the strengthening layer of TC4 titanium (um) specimen number 1 2 3 4 5 6 7 8 9 thickness 12 13 5 15 6 18 18 16 17 The influence of discharge parameters on the surface hardness The hardness of the strengthening layer of TC4 titanium specimens (specimens 1-9 as shown in Table 1) are shown in Table 3.
Table 3 The surface hardness value of the strengthening layer of TC4 titanium (HV) specimen number 1 2 3 4 5 6 7 8 9 hardness 1039 1151 724 1209 846 1446 1432 1051 1172 Conclusions (1) Polarity Select strengthening effect on TC4 titanium alloy has an important influence, the use of negative for the tool electrode can get better strengthening effect than the use of positive

Introduction Materials with a mean grain size of hundreds of nanometers are called submicro-crystalline or ultra fine-grained materials.
These materials are attracting a growing interest due to a number of unusual physical properties.
It has been shown mainly by X-ray powder diffraction and by positron annihilation spectroscopy [1-3] that in addition to small crystallite size, such samples contain inhomogeneously distributed high number of dislocations and also microvoids.
The addition of a small amount of Al2O3 stabilizes the fine-grained highly defected structure to much higher temperatures.
Journal Title and Volume Number (to be inserted by the publisher) 5

Along with the increase of doped-boron concentration in the film, two-point resistance measurement indicates that film resistance presents exponential decrease; Raman spectrum test shows that, the characteristic peak value of diamond 1332cm-1 in the spectrum moves toward low frequency, the semi-height width of diamond peak, peak D and peak G, etc. in the spectrum is expanded, and the component of non-diamond bonds such as sp2, etc. in the film is increased; SEM and AFM observation shows that, increasing the doped-boron concentration could further subdivide the crystal grains in the film, and is beneficial for the growth of nano- or ultra-nano-crystalline diamond film; film annealing test shows that, micro-nanocrystalline diamond film with higher doped-boron concentration has better thermal stability than the micro-nanocrystalline diamond film without doped boron.
The number of boron atoms entering into sp3 diamond structure increases along with the raising of B/C ratio in reaction gas source, and the resistance of film decreases quickly along with the increase of boron content [2]. 0 20000 40000 60000 80000 100000 120000 0ppm 1500ppm 3000ppm B/C R es i st a nc e Fig.1 Resistance of NCDs with different boron concentrations Shape of Surface and Section.
Fig.2(a) shows the zero-doped microcrystalline diamond film(MDF) without doping, and according to it, diamond grains are of complete crystal form and big size, film layer is continuous, and grain orientation is mainly crystal face {111}; Fig.2(b) shows the NCD without doping and growing under relatively high carbon source concentration, and on the NCD, there are MDF grains of complete crystal form and big size, and grain orientation is mainly crystal face {100}; Fig. 2(c) and 2(d) are 1500ppm and 3000ppm boron-doped micro-NCD respectively, and along with the increase of boron concentration, the grain size decreases, the crystal form gradually becomes incomplete and changes to spherical crystal grains, crystal defects are obviously increased, secondary nucleation is noticeable, and film surface seems to be relatively smooth and flat; Fig. 2(e) is the sectional view of 3000ppm boron-doped micro-NCD, and under a relatively high doping concentration, the columnar structure
Obviously, along with the increase of B-doped concentration, the content of non-diamond phase in the film becomes higher and higher, while crystal grains become smaller and smaller.
SEM and AFM observation shows that, increasing the doped boron concentration could further subdivide the crystal grains in the film, and is beneficial for the formation of nano- or ultra-nano-crystalline diamond film. 4.

The microstructure is analyzed with optics microstructure analyzer and the crystal grain characteristic is studied.
The microstructures of region are planar crystal of the substrate growth, columnar crystal of the cladding layer boundary growth and fine grain zone in cladding layer from the left to right.
There’s no time for grain growth when the temperature gradient or compositional undercooling increases, which form the very fine equiaxed dendrite crystal, as shown in Fig.5.
Fig. 9 Coarse grain zone between laser cladding layer (sample 1-1) Fig. 8 The transitional zone between the microstructure of regional zone (sample1-2) As a result of multi-layer cladding used in this text, some coarse grain sometimes appears among the fine grains in the cladding layer, as shown in Fig. 9.
The surface is all fine grain, not the columnar or dendritic crystal, which owing to the good heat dissipation conditions and the large temperature gradient, as shown in Fig. 10.

The cooling rate decreases and the grain size increases with the increase of particle diameter during the rapid solidification, while the grain boundary of same particle diameter with larger cooling rate in argon gas is smaller, while the grain boundary of particles with smaller cooling rate in helium gas is larger.
Meanwhile, we analyzed the effects of particle diameter on the cooling rate of single particles based on the Newton’s cooling law, and then the effect of particle size on the solidification grain boundary and grain size.
The grain boundary of same particle diameter with larger cooling rate in argon gas is smaller, while the solidification grain boundary of particles with smaller cooling rate in helium gas is larger.
Therefore, particle diameter has an important influence on the grain size of particles.
As a result, the grain boundary of same particle diameter with larger cooling rate in argon gas is smaller, while the solidification grain boundary of particles with smaller cooling rate in helium gas is larger.

However, as many crystal grains and chemical elements of alloy are the factors to slip, it is considered that there was no peak since the dislocation movement was limited.
It is found that the inner friction (logarithmic decrement) reaches the peak at almost same atmospheric temperature for a crystal grains diameter.
Although many preceding researches were focusing on relatively pure materials to study, the authors use a material with a number of alloy elements with nickel as its main composition for Inconel 718 for this study.
It should also be noted that, as data obtained through the test was not sufficient in number or type, it is desirable to collect more data to design a viscoelastic dynamics model.
[3] Kê,T.S., “Experimental Evidence of the Viscous Behavior of Grain Boundaries in Metals”,　Physical Review, Vol.71, No8(1947), 533-546

The middle region is the area of recrystallisation and grain growth in the TMS82+ substrate, bounded on its inner edge by a grain boundary reaction front.
Dark γ grains marked x and y in SEM image (A), have varying contrast in FIB image (B), due to different grain orientations.
FIB image (B) shows the extent of grain growth Fig. 5.
The Ni-12Al alloy had a smaller number of larger irregular shaped voids that appeared to lengthen along the grain boundary at the interface to the parent alloy.
It may be that impurities and defects from electroplating were effectively pinning the outer region grain boundaries, inhibiting grain growth.

With the decrease of the final rolling temperature, the number of short-like pearlite in small grain increased gradually.
It is generally believed that grain refinement can improve the strength and hardness of materials, but the fine grain can be harmless to toughness.
Therefore, deformation-induced ferrite appears at the preferred nucleation sites, such as grain boundary and sub-grain boundary during deformation.
The ferrite grains are sufficiently refined.
Conclusion (1) With the decrease of final rolling temperature, the number of small-grain short-like pearlites and the proportion of ferrite increase, while the grain size and the hardness of steel decrease

SEM analysis of the microstructure was performed to obtain grain size and size distribution.
The line intercept method is selected to measure the grain size.
SEM analysis of TM-grade samples (fig 1) indicates finer microstructure having submicron grains.
The grains in all the investigated ceramics were fairly equiaxed.
Although sufficient number of grains is not measured in TZ-8Y sample, the cubic grains in TZ8Y are found be in the range of 2- 5 µm.