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Concentration Profiles For Grain Boundary Diffusion in B-regime With Regard To The Formation Of Atomic Complexes In Grain Boundary Vladimir Esina, Boris Boksteinb, Alexey Rodinc National University of Science and Technology “MISIS” (MISIS), Department of Physical chemistry, Leninsky pr., 4, 119049, Moscow, Russia avladimir.esin@misis.ru, bbokst@misis.ru, crodin@misis.ru Keywords: grain boundary diffusion, grain boundary segregation, atomic complexes in grain boundary, nonlinear concentration profiles Abstract.
Thermodynamics of the atomic complexes formation in a grain boundary (GB) is discussed applying to AB complex.
Introduction Commonly accepted model of grain boundary diffusion (GBD) was given by Fisher [1].
A large number of experiments affirm this conclusion [4,5]. 1.
Equilibrium and nonequilibrium segregation The equilibrium between GB and grain leads to the adsorption (segregation) isotherms of different types.

The average grain size of the alloy was reduced from ~150 mm to a grain size in the range of ~500 nm through processing by HPT.
It is observed that an increase in the number of turns leads to a more pronounced refinement of the structure.
The results can be converted into hardness as a function of the equivalent strain by using the correlation between equivalent strain, , and distance to the disk center, r, the disk thickness, h, and the total number of turns of HPT, N: (1) Figure 4 shows the evolution of hardness as a function of the equivalent strain.
It is also observed that the distributions of grain sizes are similar in the materials processed by different numbers of turns and subjected to a similar annealing treatment of 5 min at 250° C despite the difference in initial grain size distribution.
The initial coarse grain structure, with a grain size of ~150 mm, was successfully refined to a grain size of ~0.5 mm after HPT.

The plasticity can be enhanced with the increase grain size, the elongation ratio is 80% with 35µm grain size, but the elongation ratio is 59% with 5µm grain size.
There are three different curves for different grain size.
One hand the frenquency of misorientation angle between 35 and 55 is different, that of grain size 5µm is higher than 0.01 while that of grain size 35µm is below 0.01, On the other hand the frenquency of misorientation angle between 55 and 60 is also different. that of grain size 5µm is only 0.5 while that of grain size 35µm is so high to 0.12.
As we see, the Grain is mainly high angle grain boundaries (> 15 degrees), the misorientation of grain is 60 DEG holds the very great proportion.
The twin formed in the annealing experiment is the twin, so the difference between the orientation of grains in 60 degrees, so obviously high frequencies appear 60 degrees near is the annealing twins[11], the number when grain size is 35µm reached 61%, while the number when grain size is 5µm is only 45%.

Grain growth proceeded preferentially in the higher temperature region and resulted in a large grain surrounded by small grains.
Two-dimensional microstructure model was adopted for the calculation based on the algorithm of Monte Carlo method [2-3]. 200 x 200 cells were used for the description of microstructure and each cell has its own number correlated to grain orientation.
Grain boundary migration is an important and fundamental process of grain growth.
Migration process is simulated by changing the site number to that of a site randomly selected from the surrounding sites.
The hatched grains are preferentially grown grains during spot heating calculation.

Grain boundary liquid grooving process takes place during the contact of solid phase with the melt.
Introduction The problem of interaction between solid and liquid metal phases was described in a number of theoretical and experimental works [1,2].
It is well known that liquid-metal grooves form on the liquid-solid interface at its intersections with grain boundaries (GBs).
The average grain size of copper samples was about 40 μm.
Straumal, Grain boundary phase transitions, Nauka publishers, Moscow, 2003

The increase in the number of passes could promote the growth of dynamic recrystallization grains under the same amount of deformation.
The DRV grains were continuously deformed, and the number of DRX grains was gradually increased.
A large number of fine DRX grains appeared in the grains, which much of them were existed along the grain boundaries.
The increase in the number of passes can increase the relative density at the same amount of deformation.
The increase in the number of passes can promote the growth of DRX grains under the same amount of deformation.

Journal Title and Volume Number (to be inserted by the publisher) 3 It is important to know the characteristics of the environment that surrounds the critical nuclei, in other words, the orientation of the matrix grain and, especially, the misorientations around the nuclei.
It is expected that deformed grains of low pattern quality consist of a larger number of smaller subgrains than that of high pattern quality grains.
Shear and transition bands generate considerable grain fragmentation leading to relatively abrupt changes of orientation in space, or steep short range Journal Title and Volume Number (to be inserted by the publisher) 5 orientation gradient besides high stored energy due to strain localization.
But its volume fraction in the deformed microstructure is extremely small inevitably leading to a small number of nuclei.
In addition, because the deformation behavior of a grain is also affected by the neighboring grains, the consideration on the orientation of neighboring grains may also be necessary.

While dressing the grain tips of the coarse grained grinding wheels are truncated by the diamond grains of the dressing cup wheel.
The results demonstrate that the new dressing method for single layered coarse grained diamond grinding wheels offers a number of advantages over the mechanical dressing technique [6].
Experimental results For the dressing experiments single-layered coarse grained diamond wheels with a grain size of dG = 181 and 301 µm, stochastic grain distribution and a grain concentration of C = 100% are investigated.
A number of experiments have been conducted to investigate the feasibility of the new dressing process to eliminate wheel waviness and obtain a sufficient run-out, as well as removing the highly protruding grain tips and obtain flattened grains with a uniform protrusion height.
Thus, the flattened grains´ topography and their average grain protrusion hk were derived.

Many previous studies were isothermal experiments performed using laboratory equipment for a limited number of temperature values.
The main assumption is that grain-growth arises via GB (grain-boundary) motion and that the driving force is represented by an inner pressure related to the GB curvature, therefore inverse proportional to the average grain-size G.
During continuous heating, a two-stage normal grain growth behaviour dominated by grain boundary diffusion was also evidenced for Agdoped specimens (Fig. 8).
The grain growth behaviour during isothermal annealing follows the grain-size dependent GB pinning model (Fig. 9).
Normal grain growth governed by grain boundary diffusion is observed during constant rate heating, while a lockup effect caused by grain-size dependent grain boundary pinning occurs during isothermal annealing at high temperatures.

Fig. 2 shows the distribution of rotating particles which marked black color under the condition of different that the number of rotating particles decreases with increases and the shear plane becomes misty.
(a) 0.5mm/min (b) 25mm/min (c) 75mm/min Fig. 4 Particle rotation velocity field under different shear rate Fig. 4 shows that with the increase of shearing rate, sample destruction is no longer along the shear plane, but a large number of failure areas appear in internal sample when the shearing rate is 75 mm/min based on particle rotation velocity field, and the number of rotating particles increases which resulted from large cracks generate in internal sample.
Micro-simulation of triaxial test of coarse grained material.
The influence of mesoscopic parameters in particle flow model on macro-reaction of coarse grained material.
The Shear Dilation and Shear Band of Coarse Grained Material Based on Discrete Element Method.