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By increase of the rotational speed; the number of impacts of the brushing tips into the surface in a certain time is increased while at the same time the impact energy due to the higher impact speed and the stiffness of the brush wires are also increased.
Ruano: Grain refinement of Mg-Al-Zn alloys via accumulative roll bonding, Scripta Materialia, 51 (2004), 1093-1097
Zhao: An Ultrafine-Grained AZ31 Magnesium Alloy Sheet With Enhanced Superplasticity Prepared by Accumulative Roll Bonding, Journal of Iron and Steel Research International, 14, 5 (2007), 167-172

This sharp peak decreases and shifts towards larger sizes in the grip portion of crept sample (fig. 3b) due to primary coarsening of M23C6 particles at the high-angle grain boundaries.
The number of particles with sizes less than 100 nm decreases and large particles with sizes more than 500 nm appear on high-angle boundaries in the gauge portion of crept specimen (fig. 3c).
However, during long-term aging and creep the M23C6 carbides and Laves phase most likely lose their coherency with ferritic matrix previously and these grain boundary particles coarsen up to nearly the same sizes in the both portions of specimen.

The grain and sub-grain boundaries, the dislocation pipe and the micro-crack of oxide film become the short diffusion channel of metal ion, and S element can enter the matrix through these channels.
Because of the high defect concentration in the sulfide, the metal ions further diffuse outwards producing a large number of sulfides (Fig.6), and then the alloy is subjected to catastrophic corrosion.

Comparison of different repair technologies takes into account time required for particular operations, number of subsequent steps and properties of materials as bond strength to the substrate and durability under expected loading.
For investigation the commercial repair materials were chosen: • low grain size (up to 8 mm) concrete, based on alumina cement (ACC), • polymer-cement mortar (grain size up to 2 mm) based on Portland cement (PCC) Bond strength were measured by pull-off and WST tests in relation to the surface roughness of the concrete base, measured after substrate pretreatment.

Furthermore, grain boundary diffusion and/or grain boundary rotation are probably invoked.
The change in the number of contour fringes indicates a change in the magnetization of the particles during heating.

Results and Discussion Figure 1a shows the densification behavior of the first series samples 1 to 10 sintered at temperatures 1300 and 1500 0C; figure 1b - of the samples I to VI of second series sintered over temperature range from 1100 0C. 0,50 1,00 1,50 2,00 2,50 3,00 1 3 4 5 6 10 Sample number B u lk d en sity, g /cm 3 1300 1500 0,5 1 1,5 2 2,5 3 1100 1200 1300 1400 Temperature, 0C B ulk d ensity, g/cm3 I II III IV V VI Fig. 1.
The mullite (grey phase) grain sizes are in the range of 5 - 10 µm.
It may be supposed that crystallization takes place from nuclei in the formed liquid phase as well as the crystals grow on the grain boundary of pores and liquid.

Meanwhile, computational modelling has been introduced to predict the hot tearing, and a number of criteria had been developed [4-8].
This suggests a force relaxation taking place during the solidification due to the rearrangement of the solid grains and the remaining liquid under the imposed solidification stress.
%Al alloy (Fig. 7 (a)), the surface of hot tear is very smooth and clean with some evidence of fractured grain bridges.

The process parameters are adjusted so that the deposit has a columnar grains structure perpendicular to the interface.
It has been suggested that the factors, which may influence the stabilisation, are size, valency, and concentration of solute cations and crystal structure of the solute oxides, where the valency and concentration determine the number of oxygen vacancies created by the formation of substitucional solid solutions[13].
Ta2O5 has been found to affect the phase stability and the electrical properties of ZrO2, and Nb2O5 has also been found to dramatically change the grain boundary electrical conductivity[18].

Typical Mechanical properties of Cast and PM TiAl alloys Rotating bending fatigue tests were conducted at both room temperature and at elevated temperature (650 oC), the number of fatigue test specimen is both 6 for two different near net shape processes (cast and powder metallurgy).
The microstructure of PM TiAl alloy is normally lamellar with uniform grains with no texture.
The grains of PM TiAl are much smaller than that of cast TiAl.

Wu Zhenyu et al. [17] investigated tool wear on wt.15%SiCp/Al composite in the milling speed range of 10-180m/min with ultra-fine-grain carbide tools.
Wu Zhenyu et al. [17] reported that the number of the crushed, and the detached SiC particles increased with the increasing of cutting speed, which resulted in the increase of cutting vibration, cutting forces, cutting temperature and the value of surface roughness.
Reinforcement volume fraction, cutting speed, reinforcement particle size, cooling condition, tool material grain size, heat treatment of the matrix and tool wear were these significant factors which influenced the machined surface quality.