Search results

The minor X-ray peaks matched the JCPDS file numbers: 05-0378, 03-3174, 21-1272 and 06-0395, respectively [7-10].
This correlates with JCPDS file numbers 05-0378, 06-0395, 05-0626 and 03-0675 [7,10-12].
These photographs show a well-developed grain size and dense microstructure.
Grain size of the samples range from 1.24 to 34.65 µm.
The particle size and grain size were increased with increasing calcination and sintering temperatures.

Feasible macrostructure of ingots: а –columnar grains; b – small equiaxed and columnar grains; c - small equiaxed, columnar grains nonequiaxed grains in the centre ; d – equiaxed grains [8] It is known [1] that the mechanical properties of solids are directly dependent on the properties of the structure, which is determined both by the nature of the interatomic interaction, crystal structure, grain size distribution, their relative position, quality of connections between them, the availability of defects, porosity, etc., and the thermodynamic state of the system as a whole. 
Mechanism of structure formation hardened compositions and factors, determining the strength, depend on the number of contacts accretion between the grains and the type of physical or chemical bonds between them. 
Fig. 1, a shows the columnar structure; the ingot comprises grains of a columnar shape, which in these conditions have started to grow on the wall of the mold and spread to a depth of the ingot center. 
Fig. 1, b shows the mechanism  of the ingot solidification provided that a large number of grains have arisen near the wall of the mold, but only a small fraction has increased towards the center forming a columnar structure. 
Under these conditions, the outer layer of the metal being in contact with the walls of the mold and primarily cooled, is formed from a large number of small grains. 

The composites produced by FSP have a uniform distribution of SiC particles between the grains of the base metal.
Despite the large number of studies that are being conducted to advance the FSP technology [25], the effects of FSP on various mechanical and micro structural properties still need further investigations.
Figure 4b shows that the SiC particle led the grain to be refined by the FSP through a recrystallization process.
Representative grain structures of (a) as-received 316L, (b) FSPed 316L with the SiC particles.
The microstructure and microhardness were evaluated by observing the grain size and the dispersion of the SiC.

The method is an extension of 3DXRD principles for studies of grain dynamics in connection with recrystallisation.
In favourable conditions 3DXRD can be used to study the volume, crystallographic orientations, positions, strain state and grain boundary morphology of hundreds of grains simultaneously.
The furnace was mounted on a goniometer comprising an (x,y,z) translation stage and an ω rotation Journal Title and Volume Number (to be inserted by the publisher) 3 stage.
Similar to the case of analyzing grain growth [9], the proportionality constant was found by calibration with a sample of known thickness and random orientations of grains.
For 8 of the sub-grains, no rotation was found within the experimental Journal Title and Volume Number (to be inserted by the publisher) 5 accuracy, which is about 0.3° in η and 0.2°-1° in ω.

The wear of diamond grains is a gradual change process.
When the tightening force of the diamond wire reaches 2100N or so, the damages of diamond grain will be fracture and broken, and the number of the broken grain on the diamond beads will increase obviously.
If too much part of diamond grain bare in adhesive, the whole grain will fall off from the diamond bead because the grain is no longer be fixed in its original position by adhesive, which can make the consumption of the diamond increase and the life of diamond beads decrease rapidly.
When going beyond this value, diamond grain will easily fall off.
The wear forms of diamond grains are mainly abrasion wear and partial fragment.

Thin alternate light and dark bands are found in some grains.
Sometimes they cross entire grains, and in some grains two or three sets are found.
Some grains contain no bands but exhibit equiaxed subgrains.
This has been called geometric DRX because it produces short grains with substructure, but could better be called grain refining DRV [9,10].
Conclusions The reverse straining confirmed the theory already derived from rising strain tests that the fraction of facets with angle >15 o changes as the number of subgrains touching the grain boundaries changes.

A bimodal structure consisting of a large fraction of deformed grains and a small fraction of newly formed grains are found in as-deformed alloys.
Equiaxed and fine-grained microstructures occur in as-annealed samples.
Al-Mn and Al-Ca compounds result in grain and Al-Mg intermetallic refinement.
Amount of fine recrystallized grains distribute in the shear bands.
A kind of distinct bimodal structure consisting of a large fraction of the original and deformed grains and a small fraction of newly formed grains is observed in deformed samples.

In Fig.4, the orientation relationships of each grain are illustrated.
With significant numbers of additional analysis, it is found that most orientation relationships are classified into these three groups related to types of rotational axis.
Each orientation relationship of the grains G1, G2 and G3 to the grain G0 is illustrated in the {011} pole figure, the {211} and the {111}, respectively.
Journal Title and Volume Number (to be inserted by the publisher) 5 Fig.5 {001} pole figure for the artifical recrystallization texture from the α-fiber of {100}<011>-{211}<011> Fig.6 The orientation relationships between the recrystallization grains G0, G4 and G5.
One is the rotation axis D between the grains G0 and G4, and the other the axis E between the grains G4 and G5, which are indicated as the circles in Fig.6.

The processing at high temperature is proved to be a necessary means for increasing thermal conductivity of the ceramics, which is generally attributed to the grain growth of the β-Si3N4 columnar grains [3, 4].
After the heat-treatment at 1873K, β-Si3N4 columnar grains are formed and grow up.
Similarly, β-Si3N4 columnar grains of the sample with higher heating rate are larger.
The small grain size usually accompanies with a high mechanical property.
Acknowledgement This research is partly supported by the National Foundation under a 973 grand program, the program Number is 2002CB613300.

Shevchenko, Cherkasy, 18017, Ukraine tvz@phys.cdu.edu.ua Keywords: electromigration, electron wind, failure, surface void, grain boundary, Monte Carlo simulation Abstract.
Since GBs seem to play important role in void movement, we provide our model with several grains.
We distinguish the following sets of lattice sites (formally including empty sites inside void and vacancies), Fig. 3: set {0} - dielectric; set {1} - atoms in the bulk of the first grain; set {2} - atoms in the bulk of the second grain; set {3} - atoms of the first grain, neighboring with set {-1}; set {4} - atoms of the second grain, neighboring with set {-1}; set {-1} - empty sites (void and vacancies). 6.
Regions 1, 2 correspond to the bulk of two different grains, 3, 4 - to the surface atoms of these grains, neighboring with void (-1) During realization of standard MC algorithm with displacements only to nearest empty sites we encountered a serious problem: influence of current remained practically unnoticeable for very long computation times.
After optimization of shape due to surface tension each surface atom has an optimal number of nearest neighbors.