Search results

Figure 1 shows the variation of grain size of different mc-Si ingots. [1-3] Since the grain boundaries (GBs) may act as the carrier recombination centers, the mc-Si ingots with large grains have been regarded as superior to those with small grains.
After h > 8mm, the number fractions have not changed so much.
Number fraction of GB characters with growth height.
Number fraction of GB annihilation according to the GB character.
Number fraction of GB genrtation according to the GB character.

Grain Boundary Structure and Boundary Migration Behaviour For a rough grain boundary, there are an unlimited number of sites on the two grain surfaces at which atoms can attach or detach.
Grain boundary migration takes place by diffusion across the grain boundary.
If the grain boundary is faceted, then the number of sites at which atoms can attach to the surface of the growing grain are limited.
If DGC « DGmax, then a large number of grains have DG > DGC, many grains can grow and pseudo-normal grain growth results.
A small number of grains will have DG > DGC; these grains will grow rapidly to form abnormal grains.

Both an increase in the number of low angle boundaries, and an increase in the number of low-index planes in boundaries was reported.
For numerical efficiency in grain growth simulations, which are effectively coarse domain structures, the number of field variables evaluated at any given point is restricted to the locally active set [30].
Plot of number of grains in the simulation (right axis) and the voxel difference signal (left axis) between the simulated microstructures and the measured microstructure [39].
The dotted horizontal line indicates the number of grains, 340, present in the measured microstructure.
The earlier time, (a), shows a large number of grains, whereas the later time, (b), shows that some large grains have grown into the measured volume that were not initially present; one such invading grain is labeled "I".

It can be said that CRSS is decided by the number of dislocation sources, existence of grain boundary and dislocation density.
While, in order to express activation of dislocations due to existence of the initial dislocation sources, mobile dislocations or grain boundaries, , and are modeled as , (3) , (4) , (5) where denotes the ideal shear strength, the initial CRSS, the minimum shear stress when dislocations are released from grain boundaries, the numerical parameter, the threshold value on the number of dislocation source and the threshold value of misorientation.
Furthermore, the number of dislocation sources , the number of mobile dislocation and the parameter on misorientation are given by , (6) , (7) , (8) where means the initial dislocation density, the representative volume, the random number between zero and 1, the norm of geometrical necessary (GN) dislocation density tensor [6] and the normal direction of slip plane.
Number of tetrahedral elements of FEM is 100694 and strain rate is 0.01s-1.
A few dislocation sources exist at the initial states and the number of dislocation sources increases due to accumulated dislocations.

Results show that alloying elements Nb and Al have a strong pining effect on the grain boundaries, Al/N ratio between 2.0-2.5 can promote the grain not to grow up for a long time, and refine grains significantly with furnace heating and after carburizing-quenching once, and can inhibit the abnormal growth of individual grains.
Table3 The level of grain size and the maximum grain size Heat number Code name Grain size/level Maximum grain/level Maximum grain size/ German material A1 B1 A2 B2 A3 B3 7 6 7.5 7 8 8 4 4 7 2 8 8 16 15 8 23 4 5 22180 A1 B1 A2 B2 A3 B3 8 8 8 7.5 9 8 6 5.5 7 7 9 8 9 10 8 8 3 5 13141 A1 B1 A2 B2 A3 B3 6 7 6 7 8 8 4 1 5 1 8 7 15 35 11 30 6 7 10105 A1 B1 A2 B2 A3 B3 8 7 7 7 8.5 8.5 5 6 4 6 8 8 13 9 17 9 4 4 Fig.1 The relationship between the overall grain size and the methods of heating and cooling Fig.2 The relationship between the maximum grain and the methods of heating and cooling Fig.3 The relationship between the maximum grain size and the methods of heating and cooling From Fig.1 to Fig.3 we know that the overall grain size in heat number 22180 is the best, and maximum grain size is the smallest.
The overall grain size in heat number 13141 is coarser than others’, individual grain grows seriously and austenite grain size is inconsistent(coarse grain is bigger 5-6 times than small ones).
The coarse grains will tend to eat up small grains and coarser at a high coarsening rate[5], the maximum grain is 3.5.
The level of grain size of German and heat number 10105 material is also good, but individual grain growth phenomenon happened, the reasons may be German material without Nb and lack of grain refining elements, and Al/N ration in both material is higher or lower.

Comparing the life cycles (N) of large grains to small grains at 172 MPa (25 ksi) up to 241 MPa (35 ksi), a dominant behavior of larger number of cycles to failure of small grains can be seen.
Comparing the two highest stresses (Table 5), a dominance in terms of the number of cycles for the large grains life cycles is noted.
The number of cycles to crack initiation (Ni) are lower than number of cycles to propagation (Np) at high stresses.
However, the high number of grain boundaries in the small grain sample appeared to slow the nucleation rate.
The fatigue crack growth rate started slowing as a result of the effect of higher number of grain boundaries of small grains.

Misch metal (Mm) addition to TM Mg-Al-Ca alloys makes precipitates within α-Mg matrix and their number density and size depend on heat-treatment conditions.
The number density and the size of precipitates are possible to control by heat-treatments.
The Cgb is calculated by the following equation; (1) where L is total length of grain boundary measured by TEM photos, N is total number of intermetallic compounds on grain boundaries, and di is the length of each intermetallic compound along the trace of grain boundary.
The number density of the precipitates in Mm added alloys increased after the heat-treatments.
The low temperature heat-treatment is useful to increase the number density of intragranular precipitates; however, the grain boundary strengthening by the network-like compounds decreases significantly.

In literature, there is a great number of fatigue life data of copper with conventional grain size (i.e. tens of microns, denoted here as CG copper).
The differences increase with the increasing number of cycles to failure.
This is generally true for the ultrasonically cycled specimens exhibiting very high numbers of cycles to failure.
Here the halfwidth of the hysteresis loop is plotted in dependence on the relative number of cycles to fracture.
N/Nf , where Nf is number of cycles to failure.

In order to quantify the plastic anisotropy of the ultrafine grained aluminium alloy AA6016 produced by accumulative roll-bonding (ARB) the Lankford parameter is measured by tensile testing as a function of the number of ARB cycles.
During ARB the coarse globular grain structure in the starting material changes to an ultrafine grained lamellar structure (Fig. 1).
increases steadily with increasing number of ARB cycles.
During deformation the coarse globular grain structure in the starting material changes to an ultrafine grained lamellar grain structure.
The key figure shows the position of the main texture components. 0 2 4 6 8 0 1 2 3 4 r number of cycles rRD r45° rTD Experiment 0 2 4 6 8 0 1 2 3 4 FC - Simulation r number of cycles rRD r45° rTD 0 2 4 6 8 0 1 2 3 4 r number of cycles rRD r45° rTD RC - Simulation 0 2 4 6 8 0 1 2 3 number of cycles 0 2 4 6 8 -4 -3 -2 -1 0 1 ∆∆∆∆r number of cycles ∆rFC ∆rRC ∆rexp Fig. 3: Lankford parameter r calculated for tensile deformation in different directions as a function of the number of ARB cycles, a) experiment, b) FC and c) RC Taylor model Fig. 4: Measured and simulated normal anisotropy (a) and planar anisotropy ∆r (b) as a function of the number of ARB cycles a) b) c) a) b) Conclusions Measurements of the Lankford parameter show that the plastic anisotropy of the ultrafine grained Al alloy AA6016 increases with the number of

The partially transformed microstructures were characterized by measuring the transformed ferrite volume fraction fvα, the mean ferrite grain size, dα, and the number of grains per unit area, NA.
The higher the number of active nuclei the smaller the ferrite grain size will be.
After saturation of the initial grain boundaries, the prior grain interiors stay almost free of ferrite grains.
It could be argued that the occurrence of some recovery in the austenite before transformation can lead to a reduction in the number of available nucleation sites through the decrease of the dislocation density.
There is experimental evidence showing that a part of the boundaries disappear, leading to a net decrease in the number of ferrite grains during transformation.