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In the study, improvements in the dispersion of the reinforcement were observed with increasing number of FSP passes, and finer grain sizes were produced with the addition of reinforcement particles.
It was also observed that the final grain size for various FSP passes were similar, as grain size is dependent on welding temperature [9].
Table 2 Grain size measurements Material and Process 6061 [13] μ-6061 n-6061[8] Average Grain Size (μm) 5.0 3.9 2.5 Standard deviation (SD) 3.5 2.3 2.0 Significant reduction in grain sizes were observed after FSP was performed.
The addition of micro sized particles further reduced the grain sizes.
The size of the reinforcement particles affects the average grain sizes.

It was the intention of this work to investigate a number of open questions, which have been raised in state-of-the-art literature [2-6].
This analysis showed that within the RD-fibre grains the strain heterogeneities were mainly concentrated in the vicinity of the grain boundaries whereas the grain interiors were much more homogeneous (cf.
In the ND-fibre grains, on the other hand, the fragmentation was more distributed over the entire volume of the grain.
This produced a structure in which a limited number of excessively large grains gradually consumed the fine grains of the starting microstructure.
This mechanism involves the disappearance of low angle grain boundaries, which appear to be of key importance for the onset of local grain coalescence between grains that are only separated by low angle grain boundaries, cf.

n is a dimensionless number and defined as the number of grains which could be always founded in a volume wherever as large as n times the specific volume per grain, which means that the grains are uniformly distributed at the scale of n times the specific volume per grain, within that volume, however, n number of grains are randomly distributed.
However, the actual number of abrasive grains remaining on the working surface is much less because the over-exposed grains would pull out during conditioning operation.
One is the areal density of grains number Nm ( T > t ) with the protrusion height T larger than the specified t , as shown in Fig. 6, which represents the cutting edge distribution Nm ( T > t ) in depth-wise, and also is one of the most important factors influencing on grinding process.
Bt=i=0Nmπ(rgi2-(t-Zi)2)　　 (1) In this Eq. (1), Nm represents the number of the protruding grains at the specified height t , and rgi and Zi stand for the grain radius and the center position of abrasive grains in z-axis, respectively.
From the information of these results, the areal density of grains number Na ( T > t ) of protruding abrasive grains with the protrusion height T larger than the specified t can be counted.

A large amount of strengthening phases such as Mg3Zn6Y(I-Phase), Mg12ZnY(X-Phase) and MgZn2, which were massive, grainy and clavate, dispersedly precipitated from the matrix along grain boundary during ageing treatment at 225℃ after extrusion, and made the sliding of grain boundaries restrained, which resulted in an enhancement for mechanical properties to a great extent.
As can be seen, the average grain size of the as-cast is 50-60μm.
As can be seen from the graph, a large amount of strengthening phases which are block-like, grain-like and rod-like precipitate in the grain and along the boundary after being ageing treated.
While the grains grow obviously and the amount of precipitated strengthening phases decrease when the ageing time is as long as 28h.
Acknowledgements Thanks for “The General Program of Liaoning Province Committee of Education (program number: L2012035) and the 12th Five-Year” National Science and Technology Support Program (program number: 2011BAE22B01) for funding supporting the experiment.

For the sintered Ni, the 3D reconstructed volumes revealed the grain connectivity, necks formation and particle rearrangement in the densification process.
MgB2 is characterized by transparent grain boundaries being also a light, non toxic and relatively cheap compound composed of just two elements.
The synthesis of this material suffers from a number of drawbacks, related to the volatility and oxidation of Mg which hinder the precise control of the stoichiometry and impurification features.
By post-processing the reconstructed volume data one can derive valuable local and statistical information such as grain sizes, contact area, number of contacts between grains, density variation, etc.
This allows the determination, by visual navigation inside the reconstruction, the determination of the number of inter-filament contacts.

It is noteworthy that the number density of the dispersoids significantly increases with strain.
Figs. 2(a) through (d) represent transmission electron micrographs showing the evolution of recrystallized grain structure during SPD.
During the early stages of SPD, large, highly misoriented subgrains developed by local migration of boundaries [marked by arrows in Fig. 2(a)] and merger of suitably oriented subgrains leading to recrystallized grains [one such grain is labeled at the centre of Fig.2(b)].
Such processes, however, became increasingly restricted because of the formation of an increasing number density of dispersoids with strain.
With increasing strain, both the number density of the dispersoids and the percentage recrystallization increased.

The number of items is seen as a possibility [7, 8] as well as the difference in nature of the sintering defects, thus criteria for rupture.
This may provoke either increased densification and/or uncontrolled grain growth.
Micromechanical Modelling Porous ceramic may undergo a number of micromechanisms of crack extension [22, 23].
Instead does failure arise from the coalescence of a number of individual micro-cracks.
Energy criteria for grain boundary failure are considered in the elastic material.

Behavior of Basal Plane Dislocations and Low Angle Grain Boundary Formation in Hexagonal Silicon Carbide Yi Chen1,a, Govindhan Dhanaraj 1,b , William Vetter 1,c , Ronghui Ma2,d and Michael Dudley 1,e 1 Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY, USA 11794 2 Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA 21250 a yichen1@ic.sunysb.edu, bgdhanaraj@ms.cc.sunysb.edu, cwvetter@ms.cc.sunysb.edu, d roma@umbc.edu, emdudley@notes.cc.sunysb.edu Keywords: Low angle grain boundary, Basal plane dislocation, Dislocation dipole Abstract.
The three-dimensional (3D) distribution of BPDs can lead to aggregation of opposite sign edge segments leading to the creation of low angle grain boundaries (LAGBs) characterized by pure basal plane tilt of magnitude determined by the net difference in densities of the opposite sign dislocations.
It is also believed that the influence of low angle grain boundaries (LAGBs) on device performance is related to the presence of BPDs which in part comprise them.
The three-dimensional distribution of BPDs in the crystal caused by the thermal gradient will lead to the formation of low angle grain boundaries in SiC.
Colin Wood) and by Dow Corning Corporation under contract numbers N0001405C0324 and DAAD1701C0081.

And for stable Goss oriented grain, the orientation gradient increased slightly, but for meta-stable cube oriented grain, the orientation gradient increased dramatically.
And in spite of the same Taylor factor for both oriented grains, the dissipated averaged energy for cube oriented grain was higher than for Goss oriented grains, and the distribution width of dissipated work in cube oriented grain was also wider than that in Goss oriented grain.
With quaternion as orientation representing parameters [10, 12], the parameter mθ for describing intra-granular inhomogeneous deformation can be defined as following: ( )( ),i m i n θ θ =∑ q a (1) where ()iq is quaternion of the ith part in the grain, a is the quaternion of average orientation, n is total number of parts in the grain, ()( ),iθ q a is the misorientation between the ith part and average orientation. θm=0 means that the grain orientation is absolute uniform.
And even some parts of the grain rotated along two opposite directions, i.e., grain subdivision occur during plain strain compression.
The distribution width of PD in cube oriented grain is wider than that in Goss oriented grain.

An addition of BLT generally decreased grain size of the ceramics.
High purity PZT - BLT ceramics with systematic microstructural changes from equiaxed PZT-rich grains to plate-like BLT-rich grains were observed.
BLT ceramic contained plate-like grains while PZT had more equiaxed grains [3].
This was a reason the ceramic with smallest grain size (0.97PZT - 0.03BLT) showed the highest hardness value compared to those with larger grains.
Not only the number of grain boundary played an important role on hardness changes, but also the density of ceramics, i.e. 0.97PZT - 0.03BLT ceramic had the highest density.