Search results

The varistor voltage increases with increasing number of ZnO grain boundaries between the electrodes.
Therefore, in order to fabricate varistors with low breakdown voltages, it is necessary to reduce the number of ZnO grain boundaries between the electrodes.
The varistor voltage is determined by the number of ZnO grain and/or the barrier height formed at the boundaries of the ZnO grains.
Figure 4 shows the ratio of the number of ZnO grain boundaries with spot- and sheet-like deposits to the total number of grain boundaries on the fractured surfaces for samples with added 0.10 mol% Si.
Before annealing, the ratio of the number of ZnO grain boundaries with sheet-like deposits was significantly more than those with spot-like deposits.

The mechanism of grain boundary diffusion of Co in Mo and temperature dependences of segregation factor and grain boundary diffusivity have been determined.
At the same time a number of experimental studies by the emission Mössbauer spectroscopy showed that their results cannot be interpreted in the framework of this model [4-6].
Numbers 1 and 2 indicate spectrum components The temperature below which the volume diffusion is suppressed can be estimated based on temperature dependence of volume diffusivity.
We made such estimation based on the grain-boundary diffusion studies of Co in W and obtained quite reasonable value of grain-boundary diffusion width [13-14].
In particular, one can quite accurately determine all parameters of grain-boundary diffusion, such as the grain boundary diffusivity, segregation factor, grain boundary diffusion width, and make certain conclusions on possible mechanism of grain boundary diffusion.

Thus the results conclude that the mechanical properties of Al-Si alloys in general are controlled by a number of principal microstructural features.
A fine grain size is desirable, leading to improvement of mechanical properties. 1.
With the inoculation of the grain refiners and the modifier into the Al-Si alloy melt, heterogeneous nucleation sites are created for solid α-Al resulting in finer grain size.
The microstructure is fully equiaxed and no columnar grain is observed.
It is observed that the grain structure has become finer after inoculating the LM6 base alloy with grain refiner 0.2%wt Al-5Ti-1B.

Reaction temperature and grain size.
In addition, the process of crystal nucleation is an exothermic process, the increasing of temperature will not helpful to the direction of nucleation reaction and make the rate of nucleation decreased, in this way the number of nuclei decreased in the reaction system, forming large grains easily (Fig. 2(b)).
Holding time and grain size.
Concentration of precursor and grain size.
With the increasing of the precursor concentration, the grain size gradually decreases, because there exists sufficient source of Al and Si during the nucleation and growth process, and the number of nuclei increases in the solution and the nucleation rate would be accelerated, resulting in the grain size smaller(Fig. 4(c)).

According to the phase field model for grain growth [5], a large number of phase field variables η1(r,t), η2(r,t), …., ηQ(r,t), is used to distinguish the different orientations of the recrystallization grains.
In the following discussion, length and volume are expressed in number of grid points (g.p.) and time in the dimensionless time (t.s.).
Particles appear as black spots, grains are bright and grain boundaries grey.
The radius of a grain is calculated as /R A π= , with A the number of grid points within the grain.
They reduce the mobility of the grain boundaries and, when a critical grain size is reached, arrest grain growth eventually.

Gorlenkoc Magnitogorsk State Technical University, Magnitogorsk, Russia avdovin@magtu.ru; bfna87@mail.ru: cgorldima@mail.ru Keywords: high-manganese steel, wearability, hardness, microhardness, grain number, proeutectoid constituent.
The ability of the alloy to wear resistance depends on the parameters of the cast structure, namely, austenite grain size, the number and morphology of the carbide phase, its location relative to the austenite grain boundaries.
Increased cooling rate in the crystallization range results in increased number of grains from 3 to 5.
Summary table of the parameters of the microstructure containing high-manganese steel formed under different cooling conditions № VCryst, [°С/sec] Vpc, [°С/min] Grain number Number of carbides, [%] The temperature of the start of carbide precipitation, [°С] The temperature of the end of carbide precipitation, [°С] The temperature range of carbide precipitation, [°С] The thickness of grain boundary carbides, micrometers 1 1.1 14.4 3 14.80 788 693 150 ~ 30 2 1.9 21 3 6.70 782 632 149 <30 3 3.7 24 4 4.88 771 624 147 <30 4 4.5 60 4 4.26 763 617 146 ~ 1 5 8.9 108 4 2.83 757 613 144 ~ 1 6 13.6 196 4 2.63 731 591 140 ~ 1 7 17.6 255 5 2.37 711 575 136 ~ 1 8 25 327.6 5 2.10 694 563 131 ~ 0.3 The most uniform grain size structure of austenite is formed at the cooling rate of the alloy in the temperature range of crystallization of 4.5° C/sec.
Conclusion The cooling rate of the alloy affects the parameters of the cast primary structure of Hadfield steel: grain size, the number and morphology of the carbide phase.

In condition of ensuring single grain sampling, fixed the structure parameters of sampling rollers for South grains and North-east grains.
So to improve the mechanization level of grains drying is an important guarantee for grains harvest[1,2].
Grains size Varieties Southern grains Northeast grains Sample number 300 300 Average of lenghth [mm] 10.17 7.07 Standard deviation of length [mm] 0.08 0.02 Coefficient of variation for Length [%] 1.88 0.71 Average of width [mm] 2.1 3.41 Standard deviation of width [mm] 0.03 0.03 Coefficient of variation for width [%] 3.38 2.07 Average of height [mm] 1.78 2.34 Standard deviation of height [mm] 0.03 0.03 Coefficient of variation for height [%] 5.2 3.04 Learn from Table 1: (1) The geometrical size of different grains are different.
(3) Sampling single grain rate is between 92%～100%, which is a well single grain rate.
South grains is more tiny and prolate, meanwhile North-east grain is more round and full

Rebar rolling presents differences relative to flat rolling that can affect the role of Nb, such as the application of higher number of rolling passes, higher strain rates, lower interpass times, and, consequently, enhanced adiabatic heating.
Increasing the number of passes can contribute to austenite grain refinement.
For instance, the larger number of passes and the lower interpass times can help to refine the austenite microstructure, leading in some cases to the activation of dynamic recrystallization and to the development of very fine equiaxed austenite microstructures after deformation [[] B.
(a) 0.029Nb steel, average grain size (b) 0.015Nb steel, average grain size (c) 0.029Nb steel, Dc20 (d) 0.015Nb steel, Dc20 Fig. 3.
Regarding the 0.015Nb steel, at 1150ºC reheating condition, the precipitation behavior was very heterogeneous: large areas of the replicas were free of precipitates while a significant number of them were found in others.

Atomic Mechanisms of Grain Boundary Motion A.
asuzuki@gmu.edu, ymishin@gmu.edu Keywords: grain boundary migration; grain boundary dislocations; molecular dynamics simulation Abstract.
Introduction Grain boundary (GB) migration in materials plays an important role in many processes such as grain growth and recrystallization.
(b) Displacements of the grains and of the GB plane as functions of time. relative velocity of the grains parallel to the GB plane.
Suppose the GB moves up by a distance L, so that the lower grain 1 grows at the expense of the upper grain 2.

The grain boundary slipping is understood as the displacement of one grain relatively the other grain over the whole surface of the boundary.
The shear is developed in one grain, reaches the boundary, and causes the slipping in the other grain.
The paper [3] shows that a grain boundary slipping is realized due to the movement of grain boundary dislocations.
G1 and G2 - grains, CC - calculation cell, GB - grain boundary, θ r - vector of grain disorientations, n r - unit vector of a GB normal.
The number of atoms in three-dimensional calculated blocks ranged from 20000 to 50000.