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For example, Si3N4 has good fracture strength and fracture toughness at room temperature but its high-temperature strength is sometimes inferior to SiC due to the softening of grain boundary glassy phases and consequent grain boundary sliding and cavity formation [5, 6].
Experimental Starting materials: SiC fine powders (74μm, purity 97%; 43μm, purity 99%; 0.5μm, purity 99%) with different grain diameter and Si3N4 fine powder (0.5μm, purity 99.99%).
Table1 The ratios of starting materials in the samples Sample number SiC Y2O3 Si3N4 PEG 74μm 43μm 0.5μm —— 0.5μm —— A1 5% 10% 35% 5% 42% 3% A2 0 50% 0 5% 42% 3% Result and Discussion Fig. 1(a) shows XRD patterns of samples A1 sintered at different temperatures for 3h under nitrogen atmosphere.
The phase transformation and grain coarsening lead to the generation of small pore and its density decrease.
However, the grain size of columnar crystal β- Si3N4 increased and grew to thick, β crystal have play a toughening role, so the strength is larger with the sintering temperature rising.

First of all, in the original phase gradually form new non-distorted small grains, with the rising temperature, the atoms of the small grains are activated by heat, and constantly swallowed around the deformed grains and grew up.
When the temperature reached 1000℃, the integrity of the triple grain boundary has emerged, in the crystal is naturally straight needle bundles of the secondary phase, that belongs to the typical Widmanstatten structure.
The cleavage crack propagation process, the number of steps of mutual confluence, they formed river pattern, the river flow and the crack extension direction is consistent, is a typical brittle fracture.
Under the tensile load, it is possible to initiate a crack beginning at the triple junction when the macroscopic strain is low, and then the crack develops along the grain boundary, resulting in the intergranular brittle fracture.
Under the impact, once the grain boundary resistance is broken, there will be a fracture and basically no stage of plastic deformation, with poor plasticity and low impact toughness [9].

In order to provide a new equipment for selective disintegrating, which will not damage the synthetic diamond single crystal quality, be used before the operation of ball mill for selective disintegrating of synthetic diamonds materials, especially for disintegrating and refining of synthetic diamond electrolysis residue with coarse slag and a great difference in grain size, the kneading mixer of synthetic diamond electrolysis residue is researched and developed.
Figure 1 Structure of kneading mixer The picture numbers stand for: (1) motor drive variable-speed system (speed control system), (2)framework, (3)hollow neck of shaft, (4)U-tank, (5)tank cover, (6)main shaft, (7)helical mixing blade, (8)tank overturn handle, (9)kneading bar, (10)tank positioning device, (11)electric cabinet, (12)timer.
Before starting, you could adjust the variable-speed system (speed control system) according to the number and nature of materials, and regulate the timer in the electric cabinet to regulate the running cycle time.
And then after the screen separation by supporting double mechanical shakers, you could get three materials of coarse-grained, medium-grained and fine-grained.
Fine-grained materials contain a lot of diamonds and can be directly gravidy separated with a shaking table, to remove most graphite and some pyrophyllite, and get synthetic diamonds with only a small amount of graphite for continuing the purification in the next process; medium-grained materials could be disintegrated by selective medium-sized ball mill to the qualified particle level for gravidy separation with a shaking table; coarse-grained materials are mainly electrolytic alloy pieces of incompletely dissociation, and will be returned for electrolysis.

Moreover, the dielectric characteristics of BaTiO3 ceramic depend on the microstructure, especially the grain size [13, 14].
The grain morphology and size were directly imaged using scanning electron microscopy (SEM).
The cell parameters of the ceramic are also calculated and given a = 4.027 Å, c = 4.000 Å and the tetragonality (c/a) is 1.007, which could be matched with JCPDS file number 76-0744.
It was achieved irregular shape grains with grain sized between 574 nm to 3.74 μm and the average grain size is 1.20 μm.
Discontinuous grain growth was found, leading to the reduction of density and the increase in intragrain porosity [12].

Subsequently, there is a large atom migration probability across the potential barrier by the energy fluctuation, and the formation of a large number of voids, thus favoring for the diffusion of atoms.
Depleted carbon exists in some local regions, and there is a small amount of porosity along grain boundary in CuNiMnFe end.
With increase of temperature, the diffusion is strengthed, the number of bonding atoms is increased, and the bonding area is enlarged.
As seen from Fig.3 (b), the grains at the transition layer are relative uniform, and no apparent porosity is observed.
A small amount of tiny particles exist along grain boundary.

It is observed from the figure that the grain boundaries are visible with a typical dendritic microstructure and an equiaxed grain size.
After exposure to hot forging, the grains in the hybrid composite were refined, and equiaxed grains were observed.
Multiple iterations were taken for accuracy, and the hardness number (HV) was determined.
The hot forging refines the grain boundaries and size of the grains, leading to increased hardness of the hybrid composite.
SEM micrographs revealed uniformly refined grain structures with evenly distributed reinforcements along the refined grain structure.

These treatments result in lower aging response in the successive artificial aging treatment which would affect the size and number density of the precipitates.
Another reason could be that the grain boundaries are stronger in this sample, which is governed by the precipitates along the grain boundary and precipitate free zone (PFZ), and this is still under investigation.
For the sample quenched at 70 oC, due to much lower number density and larger size of the precipitates, there was a decrease of UTS (130MPa) at peak aged condition.
These phases also have negative effect on the mechanical properties, because they can weaken the intrinsic toughness of the grain interiors [9].
Vacancies promote the formation of GPП and η' so that the number density of the precipitate after artificial aging increased with the increasing cooling rate.

The Correlation of Movements in the Technological System during Grinding Precise Holes Sergey Bratan1,a*, Stanislav Roshchupkin1,b and Anastasia Chasovitina1,c 1Sevastopol State University, Universitetskaya str. 33, Sevastopol, Russia aserg.bratan@gmail.com, bst.roshchupkin@yandex.ru, cnastya.chasovitina@mail.ru Keywords: internal grinding, technological system, grains, wheel, abrasive tool, precise hole, finish grinding, contact zone, quality parameters.
Introduction The high level of requirements for modern machines and devices has led to a number of problems associated with the creation of high-performance technological processes that ensure the production of parts with specified quality parameters.
During the tool and the workpiece approach, the center distance becomes greater than the difference between their radius vectors, and a contact zone appears, which is the area of mutual penetration of the grain vertices into the processed material and the protrusions of the resulting roughness in the gaps between the grains.
During approach of the tool and the workpiece the center distance becomes greater than the difference between their radius vectors by distance and a contact zone appears which is the area of interpenetration of the grain vertices into the processed material to a depth .
Number of contact , μm , μm , μm , μm , μm 1 2 3 4 5 10 15 14,95 9,04 4,12 1,83 0,8 0 -2,68 14,95 23,99 28,11 29,94 30,74 30,74 5,7 0 1,49 2,4 2,81 2,99 3,07 0,84 0 7,45 13,26 15,97 17,18 17,71 3,43 0,045 0,012 0,013 0,014 0 0 0,053 The processing cycle of a single hole contains a scheme for changing the increments and (fig. 2).

Meanwhile, Crystal is easier to grow in the liquid in the form of cell and dendrite, the velocity of grain growth greater than forming-core, which makes the grain coarse, and promote directly inverse segregation of Sn.
With the cooling speed increase gradual (Fig.1b), temperature gradient on the front edge of crystallization and the number of dendrite enhances that is benefit to restrict the Sn inverse segregation of ingots.
When the cooling speed further increase, the higher the degree of over cooling will be, the velocity of forming-core is greater than grain growth, therefore, grains will trend to fined to prevent Sn segregation (Fig.1c), which is effective function to reduce the Sn inverse segregation.
A lot of small and discontinuous particles assemble on the grain boundaries, which contains Cu, Ni and Sn.
Lepisto: Precipitation at faceting grain boundaries of Cu-Ni-Sn alloys, Materials Science Engineering A. 25 (1998),p 269-275

High-oxygen thermal annealing significantly affected the varistor, particularly in enhancing the growth of the grain even at a low annealing temperature (400 °C).
Meanwhile, a number of studies have focused on determining the effect of thermal or oxygen partial pressures on the stress and structure of ZnO [11].
The ZnO grains grew bigger to approximately 10.3, 12.2, 16.4 and 19.7 μm as the annealing temperature increased to 400, 600 and 800 °C, respectively (Table 1).
A decrease in the UV emission peak was observed at higher annealing temperatures as the compressive stress increased because of the increase in the grain size.
Increasing the annealing temperature from 400 °C to 800 °C resulted in a larger grain size and improved grain crystallinity, as indicated by the decreased intrinsic compressive stress deduced from the XRD lattice constant and FWHM data.