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Fig. 1 - TEM micrograph PM 1000 alloy in the as-received condition showing a large number of particles (bright field).
It allowed verifying the presence of tiny elongated grains within a [100]-oriented grain after annealing (Fig. 5a).
Conventional SEM cannot resolve these tiny grains.
Fig. 3 - Details of recrystallized grains in grain boundaries in a sample 44% deformed and further annealed at 1200 o C for 2 h (SEM, BSE).
Conclusions The recrystallization of the PM 1000 alloy occurs by nucleation and growth of large grains with size varying of 10 to 20 mm at prior grain boundaries and also by nucleation of tiny elongated grains located within most of the grains.

But they are strongly dependence on the number of CGP passes and the pressing modes.
However, nearly all of the investigations were focused on the microstructures evolution and grain refinement of the materials.
As can be seen in Fig. 1, the grains have been refined to submicron-meter level after four passes.
The difference in variation trend may be attributed to the difference in the rate of grain refinement [15].
In addition, the decrease in the dimple size should be associated with the grain refinement of samples processed by CGP [16,18-19].

The correlation of carrier density images with etch pit density and grain boundary maps allows an assessment of the recombination activity of dislocations and grain boundaries.
The number of single etch pits composing a cluster was estimated by evaluating the average single etch pit area and dividing the cluster area by this number.
Fig. 7: Grain boundary image obtained by EBSD measurement.
The positions of the indentations correlate with just some grain boundaries, indicating different recombination activies for different grain boundaries.
True high angle grain boundaries are found in regions of low carrier density, however the number of these boundaries is very small.

However, most of the material surface of laser melting treatment is still integrity, but yet severe shedding only occurs in partial grain boundary.
So that grain refinement improves the fatigue strength of 17-4PH steel surface and prevents plastic fracture along the lateral propagation.
Due to stress concentration of the grain boundary, which has been suffered repeated impact, so it is easy for crack formation to be occurred at the grain boundary, leading to plastic deformation.
It is due to using laser treatment make the modified layer rapidly solidify to obtain ultra-fine grain microstructure and improve the surface strength.
Due to the lager number of defects in pits, the formation of new cracks and the superposition of new and original cracks are apt to happen.

In backscattered mode the different orientations of the grains and sub grains appear in different shades of gray.
While some grains had already reached their final size and shape many areas remained deformed and new grains were appearing.
Grains.
The result is that in most cases the grain boundaries of the recrystallised grains coincide with those of an old deformed grain [14].
Acknowledgements This research was carried out under the research program of the Netherlands Institute for Metals Research in the Netherlands (www.nimr.nl) project number MP97009-2.

The structure of the superconducting Nb3Sn layer depends on a number of various factors, such as diffusion annealing temperatures and duration, composite geometry (the number, shape and composition of Nb filaments and Sn sources), doping, etc.
There are areas of various morphology, i.e. with relatively fine grains and small grain size scattering (Fig. 4a), with coarser grains (Fig 4b) and with anomalously coarse grains (Fig 4c).
An average grain size in this specimen is about 106 nm.
It is interesting to note that these particles are mainly located in coarser grains, thus, they do not retard the grain growth, but on the contrary cause grain coarsening.
Diffusion layers mainly possess fine-grained and uniform structure, though there are areas with coarser grains and wider grain size scattering as well as anomalously coarse grains, especially in the wire diameter of 0.7 mm.

number of donated electrons is proportional to the valence of the ion.
This means that the ions studied behave as donors and that number of donated electrons is proportional to the valence of the ion.
enhances the conduction of the grain bulk breakdown voltage seen in Fig. 2 grain boundaries leads to the assumption that the barrier the defect gradient in the grain.
O both Ti and Ba ions reside mainly in the grain interior decreases towards the grain boundaries.
The singular behavior of Ti ion within the grain interior.

The SiO2 additives have significant effect on grain sizes.
The nonferroelectric phase of twinned ZrO2 and PbSiO3 also tend to segregate on the grain boundary, which enhances the bond energy of grain boundary.
In general, the great improvement of fracture strength with SiO2 dopant added to PMS-PZT ceramics should be attributed to two reasons: (1) the segregatation of the second phase on grain boundary inhibites the growth of grain sizes and reinforces the bond energy of grain boundary, which leads to the fracture mode change from the mixture of transgranular and intergranular to predominantly transgranular; and (2) the reduction of the number and distribution of pores in the specimens enhance the bond energy of grain boundary.
The great improvement of fracture strength with SiO2 dopant added to PMS-PZT ceramics mainly due to the secondary phase segregating on grain boundary inhibites the growth of grain size and reinforces the bond energy of grain boundary.
Acknowledgements The authors gratefully thank the support of National High Technology Research and Development Program of China (grant number: 2001AA325030) and Jiangxi Nature Science Foundation.

a Stuart.Hampshire@ul.ie, b Michael.Pomeroy@ul.ie Keywords: Oxynitride glass, Silicon nitride, SiAlON glass, viscosity, grain boundary, creep Abstract.
As Y:Al ratio increases, fracture toughness also increases which is indicative of easier debonding at the grain interfaces [8].
A number of studies [1, 5-8, 11-14] have shown that oxynitride glasses have higher glass transition temperatures, elastic moduli, viscosities and microhardness values than the equivalent silicate glasses due to extra cross-linking within the glass network as a result of substitution of oxygen by nitrogen.
Overall, these effects can be assumed to be related to changes in the density of the glass network and the numbers of non-bridging oxygens as Al changes from a network ion in 4-fold co-ordination (AlO4) to a modifying role in 6-fold co-ordination (AlO6).
Those cations with ionic radius smaller than Y exhibit higher viscosities and should provide grain boundary glasses with higher creep resistance.

Scandium addition to the alloy enables reducing the solidification processes and degree of segregation along the grain boundaries, as well as localizing partial melting of the grains without formation of coarse eutectic interlayers.
At present scandium influence on the properties of many aluminium alloys has been studied, and a number of promising scandium-containing alloys have been developed [7].
Heating above solidus temperature leads to partial melting of low-melting structural components along the grain boundaries, grain coarsening and formation of brittle interlayers and microdefects along the grain boundaries.
Grain structure remains unrecrystallized.
Compared to excess phases, number of phases of eutectic origin in the base metal increases 2-3 times.