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It can improve the combining strength among the grains interface, and makes every grain effective during the drilling.
Within the end of drilling process, the drilling spindle direction force decreases along with an increase of the number of drilling holes. 47 36 64 496 485 502 0 100 200 300 400 500 600 Electroplated BrazedDrilling hole number 0 50 100 150 200 250 0 100 200 300 400 500 Drilling hole number Drilling force( N) Electroplated core drill Brazed core drill Fig.4 Tool life of thin-walled electroplated Fig.5 Comparison of the values of forces and brazed core drill 0 50 100 250 350 500 (Numbers mean the drilling hole number) Fig.6 Wear process of brazed diamond grains The observations on tool life and drilling spindle direction force can been better understood if one observes diamond grit fail process during drilling shown in Fig.6 and Fig.7.
For a smaller number and sharper blade of real working diamond grains on the commencement of drilling process, drilling spindle direction forces of thin-walled monolayer brazed diamond core drill and electroplated core drill are the same and smaller.
The thin-walled monolayer brazed diamond core drill has super-excellent machining performance only with a smaller number of diamond grains. 3.
No pulling out and smaller number for the brazed diamond grains are two key factors of longer life and higher machining efficiency of the thin-walled monolayer brazed diamond core drill.

One efficient approach is processing NC material that combine grains with bimodal distribution in which NC grains provide high strength, whereas coarse grains can enhance ductility.
As such the total density of dislocation can be described by , where and are the volume fraction of the coarse grains and NC grains, respectively, and are the density of stored dislocation in the coarse grains and NC grains[9], respectively.
The total back stress stemmed from all dislocations accumulated along the grain boundaries[10] is expressed by : (3) where is the number of dislocations stopped at the grain boundaries, and,is the density of nano/microcracks ,is the maximum number of dislocation that can be emitted from the nano/microcracks tip along one slip plane.
To calculate the maximum number of lattice dislocations that can be emitted along one slip pline , we use the following calculation procedure as introduced by Ovid’ko and Sheinerman[11].
Fig. 1 Dependence of the maximum number of edge dislocation that can be emitted from the crack tip along one slip plane on the grain size d in bimodal copper It has been proved that the number of nano/microcracks in BNC materials increases during plastic deformation, which leads to the density of nano/microcrack being sensitive to the applied load.

It was found that creep behaviour is strongly dependent on number of ECAP passes.
Fig.2 shows Vickers hardness HV as a function of the number of ECAP passes.
This difference consistently increases with increasing number of ECAP passes.
Increasing elongation together with increasing number of ECAP passes indicates that high-angle grain boundaries have a lower strengthening effect under creep than low-angle ones.
High-angle grain boundaries were formed with increasing number of ECAP passes and actively influence creep properties.

The EN AW-2017A alloy consists of a grains and the Al2Cu phase.
Between large elongated grains are also visible cluster very small equiaxed α phase grains in the system band.
At the same time, the number of load cycles N was recorded.
In many cases, they are generated at the grain boundary of the solid solution.
Fatigue crack length „a” versus number of cycles N (active side specimen).

However, a limited number of studies were dealt with examination of superplastic behavior of Al alloys subjected to ECAP and followed by rolling [5,6].
Most of grains contain no well-defined substructure.
However, former ribbons retain as chains of elongated grains.
In the alloy subjected to warm rolling the static annealing leads to grain coarsening with retaining grain aspect ratio (AR), defined as the ratio of the grain dimension in the longitudinal direction to that in the transverse direction (Fig.4(c)).
Acknowledgments The financial support received from the Ministry of Education and Science, Russia, under Grant No. 14.578.21.0097 (ID number RFMEFI57814X0097) is gratefully acknowledged.

The Microstructure was mainly composed of granular bainite(GB) and a small number of lath bainite ferrite (LBF) as shown in Fig. 1.
The microstructure of CGHAZ (Tp1 is 1320 ˚C) is dominated by coarse lath bainite and granular bainite, and the grain boundary of original austenite is clear; in the austenite grain, the original grain is divided into different regions by lath bundles with different directions.
After the peak temperature of the second thermal cycle in 650 ˚C, the structure of the coarse grain zone experiences the tempering process associated with carbon precipitation, M-A decomposition, the number of granular bainite increasing and bainite bundles roughening.
A large number of blocky M-A is mainly distributed at the grain boundary (Fig. 3(c)).
Acknowledgements This work was financially supported by the National Natural Science Foundation of China Youth Found (grant number 51401112) References

Grain-oriented Bi4Ti2.92Nb0.08O12 (BITN) ceramics were prepared by hot-forging (HF) method.
In this study, grain-oriented Bi4Ti2.92Nb0.08O12 (BITN) ceramics were selected to confirm our concept as the first trial, because of its high Tc and ease of preparation of grain-oriented ceramics by hot-forging (HF) method.
Grain-oriented samples were prepared by the hot-forging (HF) method [5].
The grain-oriented factor, F, was calculated using the Lotgering method [10].
X-ray diffraction pattern for OF-BITN ceramic shows a single phase of bismuth layer-structured compounds with the layer number, m=3.

The results showed that grain size and domain size were small before HT,there was  high-density dialocation in the alloy.After HT,grain size  increased, the internal stress, dislocation and other defects were reduced,magnetic domains became wider,the number of the domain decreased and the exchange energy between the magnetic domain reduced,leading to the decrease of the coercivity and increase of permeability.It was also found that the curie temperature was not changed after heat treatment.
As to the grain size, the large grain size is preferred due to the decrease of the coercivity [10,11].The grain size increased and the area of the grain boundary reduced after heat treatment, reducing moving resistance of the domain wall and increasing movable distances of the domain wall in grain.
The grain size increased after heat treatment, making the coercivity(Hc) lower.
(2) The number of domains  reduced with the domain becoming larger,the exchange energy between magnetic domains and the energy of magnetocrystalline anisotropy reduce, which reduced the coercivity and increased the magnetic permeability
Interactive Effect of Grain Orientation and Grain Size on Magnetic Properties of Fe–78 wt% Ni Ribbons.

This study investigates the superplastic deformation mechanism of coarse-grain materials .Superplasticity deformation behavior of Ti-22Al-25Nb alloy with 200~410μm coarse grain has been investigated through tensile test at 940~990℃ and 3.3× (10-2~10-4) s-1 strain rate.
Results prove coarse-grain Ti-22Al-25Nb alloy primary depends on slipping of crystal planes between two phases to achieve superplasticity.
Good plasticity can be preserved because O phase can flow as solid particle in semisolid slurry in B2 grain.
Obviously, it is very difficult to achieve great elongation by grain boundary rotation and sliding [5, 6], when the grain size of the material for this experiment is within 200-410μm microns（Fig.1）.
However the larger elongation was obtained not by grain boundary sliding and rotation, it relied on a large number of atoms slipping on the crystal-plane slip instead

Peculiarity of Grain Boundary Diffusion of FE and CO in CU Khairullin Ainur1,a, Nikulkina Valeriya1,b, Zhevnenko Sergei1,c, Rodin Alexey1,d 1Department of Physical Chemistry, NUST MISiS, 4, Leninsky pr-t, Moscow, 119049, Russia aaika-88@inbox.ru, bfeba-3@ya.ru, czhevnenko@misis.ru, drodin@misis.ru Keywords: grain boundary diffusion, grain boundary segregation.
In this article new experimental evidences of anomalous grain boundary diffusion (GBD) of Fe and Co in Cu were describe.
Introduction Copper is a metal where bulk and grain boundary diffusion were studied carefully by many authors [1] and may be for the largest number of different elements.
Concentration profiles were measured by X-ray microprobe along the GB and in the grain bulk far from GB.
Kozma: Handbook of Grain and Interphase Boundary Diffusion Data, Ziegler Press, Stuttgart (1989) [2] L.