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After this grain growth occurs resulting in large grains that meet up at the centre line.
(ii) Nucleation and growth of few grains ahead of the first set of recrystallised grains which grow into the grains with low deformation.
The two above events are illustrated in Figure 2 where grain area of selected grains 1-7’ undergoing growth is plotted against time.
Plot of grain area with time of selected grains in the compressed and tensile regions.
All the initial nuclei labelled 1-4, in Figure 3a were highly deformed and had a number of zero solutions, the arrowed location 4 in Figure 3a had no solution where a near (111) <110> oriented grain labelled as 4’ in Figure 3d nucleated and grew.

The effect of the loading conditions on the number of cycles to crack initiation is evidenced using a ∆εt-Ni plot.
The majority of the cracks are smaller the average grain size.
In "small SCV slip systems", the effective grain size is much smaller than the actual grain size.
Since the number of PSB remained exactly the same in all the simulated cases, this means that slip irreversibility increase takes place at the scale of individual PSBs.
CONCLUSIONS The number of cycle to initiation of large cracks (50-150µm) in thermal fatigue is 4-5 times faster than in conventional fatigue, for a fixed ∆εt,eq.

The reference numbers used are as follow: forsterite (00-034-0189), periclase (00-043-1022) and enstatite (00-011-0273).
L is the average interception length, C is the total length of the test line, M is the magnification of SEM and N is the number of intercepts [10].
Smaller grain size was known to produce better mechanical properties for ceramic as more grain boundaries in unit of volume will serve as barrier for crack propagation.
Acknowledgements This study was supported under UMRG grant number RP024B-13AET, UMRG grant number RP011B-13AET, PPP grant number PG129-2014A and Esciencefund grant number SF010-2014.
Mendelson, Average grain size in polycrystalline ceramics, J.

For site-saturated reactions and random distribution of the grains, the microstructural path is described by: ( ) 3 2 1 1 ln1             − −= V V V V VBS (2a) 3/1 3 4 3       π = VN B (2b) where SV is the interface area between the recrystallized grains and the matrix and NV is the number of grains per unit of volume.
The interfacial area density per unit of volume separating recrystallized grains and the recovered matrix (Sv) was measured by optical microscopy superimposing a grid of straight lines on a planar section and counting the number of intercepts between the straight lines and the interfaces [7].
In consequence, the substructure developed within grains and the corresponding amount of stored energy varies significantly from one grain to another.
The nucleation of these grains is far from to be regarded random.
Therefore, a relatively small number of grains were measured that unavoidably led to the high scatter observed.

The reduction of the carbide grain average size was found as well (owing to nanoparticles blocking influence on re-crystallization).
Introduction Strength and tool life of hard metals correlated with their microstructural parameters: volume content of binder and carbides, carbide sizes, mean free path between carbide grains, intercarbide boundaries.
Conventional notions regarding the failure of hard metals composites indicate that the boundaries between carbide grains are very weak structural elements [3,4].
Introducing nanoparticles also inhibits the growth of carbide grains and recrystallization by mass transfer through the cobalt layer, while preventing the formation of intercarbide WC–WC boundaries.
(2) The probability of structural parameters l1 and l2 emergence was determined from: ; , (3) where: n0 – number of particles with volume; n2 – total number of nanoparticles.

As shown in Fig. 2, dynamically-recrystallized grains were observed near initial high angle grain boundaries before peak strain.
After hot compression up to 0.05 of true strain, recrystallized small grains seem to be formed first at triple junctions or at the point where slip band meets high angle grain boundary.
Journal Title and Volume Number (to be inserted by the publisher) 3 Fig. 2.
It implies that the controlling factor for DRX nucleation is not the matrix precipitate (�”) or grain boundary phase (�), but the strain rate, i.e. the dislocation accumulation rate on grain boundaries.
Variation of critical strain with Zener-Hollomon parameter at different initial grain size

By contrast, it was shown that after solution treatment, the eutectic phase at the grain boundaries decreased, a little secondary twin grains and some petal-shape phases were founded inner the grains.
It reveals that the grain refinement by dynamic recrystallization was effective and the average grain size was about 2~3μm.
The Mg-RE phases dispersed along the grain boundaries or inner the grains.
The increase of dislocations number and the phenomena of dislocations interacted and twisted near the grain boundaries were observed.
For Mg-2.7Nd-1.2Gd-0.4Zn-0.3Zr alloy, the alloying RE content was low, and the precipitate phase volume fraction or number density was not high even after aging treatment (Fig.10(a)), so the strength increase after extrusion and aging is not obvious.

The influence of the grain material, grain volume VG, grain size according to FEPA, axial feed faA, number of starts z0A and cutting speed vcA can be seen in Fig. 4.
The number of starts has the third biggest impact with approximately 15%, followed by grain material and grain volume with 10% and 7%.
The effect size of the number of starts and the grain material is clearly influenced by interactions with other parameters.
In the analogy trial each grain machines the same volume, but the number of cuts and the undeformed chip geometry are different.
The transferability of the influence of the number of starts to generating gear grinding is therefore not directly possible, because depending on the number of starts z0 during generating gear grinding the number of grains which are used for grinding a tooth gap varies.

The interior of these new grains is free of dislocations; grain boundaries are straight and they have a similar morphology to the already polygonized subgrains.
These can then be the nuclei of new grains with high angle boundaries, Fig. 4.
TEM microstructure analysis results indicate that there is a very low fraction of submicron grains with high angle grain boundaries even in case the strain applied is the highest.
A distinction between the values for the initial state and the deformed plates subjected to CGP straining due to the different number of pressings evident.
In order to clarify the CGP effect on grain refinement, transformation of subgrain boundaries to high angle boundaries and appearance of a small fraction of dynamically recrystallized grains, all these structural changes may substantially contribute to modification of plastic deformation of strained Al specimens, as regards the number of pressings.

An increased performance is expected with increasing grain size because the number of efficient recombination centers, present at grain boundaries, decreases.
Due to preferential diffusion of phosphorus along grain boundaries when diffused emitters are used, EBIC measurements at grain boundaries are greatly influenced.
A possible explanation for a grain size dependent value of Sgb would be a changing local impurity concentration at the grain boundaries, arising from impurity segregation at the grain boundaries in combination with a changing grain size.
Other limitations may arise for example from the presence of small grains and a broad grain size distribution.
Acknowledgments This work was partly funded by the European Commission under contract number 019670-FP6IST-IP ("ATHLET").