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Equal channel angular extrusion (ECAE) is a processing method for introducing an ultrafine grain size into a material.
Equal channel angular extrusion was first used to refine the grain size of copper samples.
These specimens were annealed for 2 h at a temperature of 700 oC to give an initial grain size of 68-70 µm.
The dependence of the microhardness of the ECAE sample on the number of passes is furnished in Table 1.
In addition, the grains became less equiaxed (more elongated) in the cross section after cold rolling.

Equalchannel angular pressing (ECAP) is one of the methods of severe plastic deformation (SPD) that produces ultra fine-grained material.
Introduction ECAP is one of the most wide-spread techniques for producing ultra-fine grained materials.
On Fig. 6 the dependences of area reduction and elongation on number of passes for each route are shown.
On Fig. 7 the dependences of yield stress and ultimate tensile stress on number of passes for each route are shown.
Alexandrov, Ultrafine Grained Materials III conference (2004)

The best grain refinement effect of primary Fe2B is obtained when the amount of K/Na modificator is 0.3%.
To further improve the wear resistance of high-boron alloys, it is necessary for high-boron alloy to increase boron content forming a large number of primary borides.
The grain refinement rate of primary Fe2B after modification treatment is shown in Fig. 4.
So K/Na modification not only slows down the crystal growth speed to refine grain, but also enhances round state tendency of primary Fe2B.
The best grain refinement effect of primary Fe2B is obtained when the amount of K/Na modificator is 0.3%.

It shows that high pulse electrical parameters can promote the transformation from low angle grain boundary to high angle grain boundary.
In this process, a large number of dislocations were consumed, which promotes the transformation from elastic deformation to plastic deformation.
In the two groups of experiments, a large number of substructures appeared, suggesting the occurrence of dynamic recovery.
As shown in Fig. 7b, the orientation of all grains in the macrozones was almost the same, so the whole region can be regarded as a large grain.
In addition, compared with the "big grain", the grain around the macrozones has a larger orientation difference, which belongs to hard grain.

Over time, this mechanism results in an increase in the average size of the particle population, and in a concomitant decrease in the number density of particles.
In order to take into account the effects of non-zero volume fraction, a number of mean-fieldtheories of coarsening have been developed over the past 40 years [4].
In the following, particle and grain can be interchangeable.
The number of orientation field variables is 30.
Note that Wagner's 3D PSD is same as the Hillert's 3D grain size distribution, but Hillert's 2D grain size distribution is different from Wagner'PSD.

Usually grains are between the 100-300 nm [3,16,17,19-21,23,31-46].
Special attention is paid to grain refinement to nanometric dimensions.
The magnitude of the accumulated strain, calculated from the dual change of the section, during the extrusion of sample from one chamber of the die to the other, is: ϕ = 2n ln (do 2 /dm 2) = 4n ln (do/dm) where: n - number of deformation cycles, do - chamber's diameter, dm - constriction die diameter.
The largest grains appeared in pure Cu (d = 200 nm).
In alloys deformed by CEC, it was found that AlCu4Zr, with an average grain size of about 125 nm, contained about 26 % of grains below 100 nm, and AlMg5 alloy with the mean size of 150 nm, contained about 34 % of grains below 100 nm.

TEM examination revealed a nanostructure ceramic, in which 200~300 nm TaC grains are cemented by iron binder.
However, the number of tiny square particles has been highly decreased and sizes also increased a little from the surface to the matrix.
There are equiaxed grains with size about 200~300 nm in the TaC ceramic coating.
The SADP (inserted image in Fig. 3) of these equiaxed grains was indexed to TaC.
Toughening via crack deflection has been well established for ceramics with micrometer grain sizes [10].

The experiment process Table1 Experiment scheme of titanium alloy TC4 Group number grain type particle size [#] Abrasive belt speed [m/s] Grinding pressure [N] Feed speed / [m/min] 1 zirconia-alumina 36,60,80,120,240,360 16,19,22,25,28,32 20 0.4 2 zirconia-alumina Silicon carbide 120 24 20 0.4 3 zirconia-alumina 120 18,20,22,24,26,28 20 0.4 The experimental results and analysis The analysis of the titanium alloy surface roughness The influence of particle size on surface roughness The experiment shows that grain size has larger effect on the roughness, in the same conditions, with slim particle size, roughness become lower, because the scratch and uplift processes from fine grain correspondingly small.
The relationship between grain size and surface roughness in belt grinding of TC4 is showed in figure 6.[4] The influence of belt speed on surface roughness Abrasive belt speed is higher, the smaller the roughness, because when abrasive belt speed increase, the number of grain enter the grinding area increase in a certain period, single abrasive cutting depth become smaller, thus reduce roughness.
Fig. 8, 9 show the surface morphology produced by 120 # zircon corundum and silicon carbide in abrasive belt grinding of TC4. [6]From the diagram we can see: 1）As long as the grinding speed and grinding depth is appropriate, grinding trail is clear with zirconia-alumina abrasive, indicating that grain bear small plastic deformation during the grinding process.[7] 2）The grinding trial seems disorder and residual chip looks more with silicon carbide abrasive belt indicating that the cutting effect is not enough.[8] Figure 8 Surface morphology generated by zirconia-alumina abrasive Figure 9 Surface morphology generated by silicon carbide abrasive The influence of belt speed on residual stress The surface residual stress is diverse with different abrasive belt speed after grinding, as shown in fig. 10.When the belt speed rang from 18 to 24, the specimen surface residual stresses mainly appear as compressive stress, while it become complicate as the speed rang from26~28 meter per
The main reason is that belt speed increase means increasing the number of grain enter the grinding area in a certain period, which will lead to cutting depth decreases, chip become thin and grinding force decreases by single grain, thus reduce the grinding force.

However, it was found that abnormal failure of diamond grains hindered the cost-effective use of diamond tools which was due to the poor bonding force between the diamond grains and matrix.
The grains were only mechanically held by the bonding material.
The morphologies of diamond grains were observed by a digital and video microscope system (Hirox KH-1000).
Ni-Co alloy Journal Title and Volume Number (to be inserted by the publisher) 147 was used as the matrix material of the electroplated diamond tools.
The average number of diamond grains on each segment surface was about 34 for the three diamond segments.

The typical microstructure observed for the films deposited at RT consisted of columnar grains with dotted Ta-rich particles, reflecting a relatively inhomogeneous structure.
Annealing at 400 oC leaded to the individualization of grain boundaries and to a coalescence of the Ta-rich particles.
The typical microstructure of the films deposited at RT consisted of columnar grains with dotted Ta-rich particles, reflecting a relatively inhomogeneous structure.
Annealing at 400 oC lead to certain crystallization materialized through the formation of grains and to a coalescence of the Ta-rich particles.
Acknowledgements The support by a grant of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project number PN-II-ID-PCE-2011-3-0837 is acknowledged.