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Processing of Ultrafine-grained Cu-Fe-Cr Composite by Equal Channel Angular Pressing K.
All Cu-Fe-Cr specimens showed ultrafine-grained microstructures with the shape and distribution of Fe-Cr phase dependent on the processing routes.
Iwahashi et al. [17] studied the effect of processing parameters on the grain refinement in Al and found that the subgrain and grain size are in the range of 0.5-1.5 µm.
The size of second phase particles decreased with increasing number of passes.
Fig. 8 shows the variation of the hardness against the number of passes.

Another mechanism of new grains formation is continuous dynamic recrystallization.
Improvement of mechanical properties through grain refinement has contributed to the rapidly expanding field of materials engineering, in which ultrafine-grained materials with the grain size less than 0.5-1 mm are produced using severe plastic deformation (SPD).
Unlike cubic metals with their large number of slip systems (e.g., twelve for fcc metals), hexagonal metals have far fewer deformation modes with which arbitrary imposed strains can be accommodated within polycrystalline aggregates.
The limited number of slip systems in hcp metals may result in the formation of unstable walls of edge dislocations rather than stable dislocation boundaries [6] such as high-angle deformation-induced boundaries.
The microstructure of the rod was homogeneous with a mean grain size of 35 mm.

It was found that a single grain was easily removed from the material.
The number of abrasive grains on the surface of the wheel was determined through observations using a microscope.
Furthermore, the numbers were evaluated by a calculation using the wheel particle frequency and the degree of concentration.
As a result, the number of abrasive grains on the surface of the wheel was assumed to be approximately 12,800 particles per square mm.
Figure 3 shows the value of Ft (<0.18 mN) on a single abrasive grain.

According to Eq.3, the contact pressure of each effective abrasive Pi is related directly to the number of abrasives involved in machining.
Usually, there are a lot of effective abrasive grains in the working area, and the number of them may be thousands or even more.
Normally, the contact pressure of a single abrasive grain Pi is very small.
Once some abnormal larger grains are interfused in polishing process, the number of abrasive involved in machining will be decreased sharply.
Maybe only hundreds of abrasive grains or even less are still active.

Fatigue cracks in ultrafine-grained structure develop both in the regions of larger grains and also in the fine grained areas.
The average grain size in the fine grained areas is 3.3 ± 0.5 µm whereas in the large grain areas the grain size is 9.9 ± 4.5 µm.
The shift in number of cycles to failure is nearly two orders of magnitude.
Cracked grain boundaries in fine grained area. σa = 180 MPa, N = 1.5 x 103 cycles.
In the case of UFG alloy, the number of slip bands rapidly decreases with decreasing stress amplitude.

Grain size 0,5 µµµµm Fig. 3.
The alternation in temperature dependence of conductivity in different temperature ranges is well known and appears in a number of oxide materials, and is attributed to a change in the dominating charge transport mechanism.
As a comparison a number of results from previous research on polycrystalline alumina is shown.
Ref [11] undoped, average grain size 3 µm, relative density 99.5%.
Ref [16] MgO doped, average grain size 20 µm.

During cold rolling, the coarse-grained, random texture of the slab is transformed into the classical rolling texture of a fine-grained Al-alloy, with elongated Al-grains delimited by thin Sn-ribbons.
Grain growth within the original cold-rolled grains is fast, but once the recrystallised grain size reaches the length scale of the second-phase distribution, it slows down and both phases coarsen simultaneously, accompanied by a significant texture change.
Grains are often delimited on both sides by the Sn-ribbons, but often collections of smaller grains are present between two parallel ribbons.
In general, the appearance of “exotic” components such as M, b and c may be associated with local strain heterogeneities which are present in too small numbers to be observed in the recrystallised texture but, having originated at sites of higher stored energy may posses a size advantage when secondary recrystallisation is activated by the ongoing coarsening of the liquid Sn.
In: Recrystallisation and Grain Growth, Ed.

Its goal is to provide an ultrafine-grained (UFG) structure in metals and alloys (with grain sizes in the range of 10~1000nm)[4-6].
It can be seen the initial size of grains is coarse in the solid solution treated 7055 samples before ECAP (Fig.1a).
From the further observations (Fig.1d), it can be seen that the elongated micrometer-sized grains along the shearing bands form during ECAP, and most of the grain sizes are less than 1 μm after two passes of ECAP.
With the number of ECAP increasing, the scattering intensity of samples increases.
In case of 7055 alloys, the atomic numbers of aluminum and magnesium, zinc and copper are very close.

First, the finite element model of the SRM grain is established by using MSC.PATRAN.
The finite element model of the SRM grain According to symmetry of the loading and configuration, as shown in Figure 2, one-twelfth of an axisymmetric start of the motor grain is considered for the analysis.
Fig. 2 The radial and longitudinal section of SRM grain Fig.3 The regional 3-D finite element model of SRM grain and the debonded cracks in stress-release boot (b) Rear of the grain (a) Fore of the grain The SRM grain is a composite structure consisting of variety materials.
As shown in Fig. 5, 11 numbers of crack nodes are used over the crack foreside line.
Fig. 8 shows that one rear debonded crack with width 40mm and depth 16.5mm. 11 numbers of crack nodes are used over the crack foreside line, and crack 1, crack 2 and crack 3 correspond to the depth of 16.5mm, 27.0mm and 36.5mm to simulate the rear debonded crack growth.

By this the amplitude and frequency of which varies in a variable voltage wide range depending on the number of blades on the rotor stage and number of blades on the stator stage and depend on also from the rotor rotation frequency.
By Boyd-Lee is shown in work [7] that the fatigue cracks were formed via nanoporosity and this is the reason of fracture at very high cycle’s number.
During EUF the chemical condition of grain boundaries was changed.
The cycle’s number was increased from 2.107 to 4 x 2.107 cycles by step-by step (40 MPa) at increased load.
By (x) in Fig. 5, b is shown HPC blade fracture at HCF strength at corresponding cycle’s number.