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Fig. 3 illustrates microstructure of the slurry Si-modified aluminide coating (hereinafter called Al-Si coating) dividing into three zones: P-zone where a large number of fine particles precipitate, A-zone where a few precipitates are present and I-zone where the substrate and coating constituents diffuse to each other.
(a) -3 -2 -1 0 1 2 3 4 5 0 20 40 60 80 100 aluminide grain boundaries.
After initiation, in case of Al coating small cracks have a lot of preferred paths (i.e. nickel aluminide grain boundaries) to growth through this granular structure.
The number of cracks after 10, 16 and 35 cycles of oxidation was determined 2, 4 and 9, respectively.

As seen from the temperature profile in Fig. 8 (b), the whole melt within the sump keeps the large undercooling state, which must increase the nucleation rate and number.
Therefore, it is observed that the microstructure of the billet cast during the LFEC process is very fine and uniform equiaxed grain, as reported in the literatures [5,6], which is difficultly observed during the conventional DC casting process.
The uniform temperature field, the low temperature gradient and the vigorous forced convection produced by electromagnetic stirring are the main causes for the formation of the equiaxed grain in the billet cast during the LFEC process. 6.
Acknowledgements This study was supported by the national "863" foundation of china (grant number: 2001AA332030).

This study shows, also, that the average of grain sizes is 5, 3 µm.
Results are presented in a bi-logarithmic graph of stress versus number of cycles to failure (Fig.7) and initiation (Fig. 8).
This agrees with the results of the recent extensive research into failure mechanisms according to which the accumulation of fatigue damage with a size of several grains and the fatigue strength of structures depend not only on the peak stress but also on the stress field intensity in the damaged zone.
Table 5: Value of the Notch Intensity Factor for different maximum load applied on roman tile F(max) [N] Ni (in air) Ni (under hydrogen) [MPa] [mm] [MPa.m1/2] 7000 125040 77829 661 0.999 52,38 8000 119820 70000 673,1 1,090 55,71 8600 113440 45000 682,9 1,120 57,29 We note that maximum load is the same for tests with and without hydrogen absorption, then the Notch Stress Intensity Factor is the same but the number of cycles to initiation is strongly reduced with hydrogen absorption.

Based on a large number of experiments, the abrasive belt grinding process parameters of Zr-4 alloy tube has been determined or refined.
By a large number of abrasive belt grinding experiment, the author get Zr-4 alloy tube grinding process parameters as shown in Table 2.
The process parameters range of Zr-4 alloy’s abrasive belt grinding Abrasive belt model Abrasive belt grain size Abrasive belt material Abrasive belt line speed (m / s) Workpiece feed speed （mm/min） The wheelhead cylinder pressure （Mpa） 461F P80 silicon carbide 12—25 500—3000 0.08—0.15 Table 2.
The reasonable process parameters of Zr-4 alloy’s abrasive belt grinding Abrasive belt model Abrasive belt grain size Abrasive belt material Abrasive belt line speed (m / s) Workpiece feed speed （mm/min） The wheelhead cylinder pressure （Mpa） 461F P80 silicon carbide 18 1000 0.12 2.3.1 The influence between workpiece feed speed Vw and the grinding amount ΔR As shown in Fig. 5, the workpiece’s feed rate has a greater impact on the amount of single-stroke grinding.1) A single stroke grinding amount is reduced with the increase of workpiece speed.

Testing Results of Silica Fume Compositions SiO2 Fe2O3 AL2O3 CaO MgO K2O Na2O SiC SO3 Ignition loss Content (%) 92.22 1.81 0.97 0.36 1.31 0.84 0.16 0.92 0.27 1.45 Aggregate: Take medium and coarse grained river sand as fine aggregate.
Therefore, take medium and coarse grained river sand as fine aggregate, and particle size range of coarse aggregate shall be controlled within 10-25mm
For meanings of serial number, take 48-F1 as an example: 48 - Total amount of cementation materials is 480kg/m3, 52 - Total amount of cementation materials is 520kg/m3, F - Mineral admixture is fly ash, S - Mineral admixture is silica fume, FS - Mineral admixtures are fly ash and silica fume.
Comparing the strengths after 12h steam curing and 3d standard curing, the former is higher than the latter mostly, and only a small number of 3d strengths are a little higher than 12h strengths, indicating that steam curing can obviously improve early strength of concrete.

Three kinds of hydrogen storage materials were prepared by mall milling for 3 h, denoted by Mg0.65C0.35, Mg0.65C0.3Mo0.05, Mg0.65C0.3Ni0.05, respectively, where the numbers mean the proportion of each raw material.
It was found that the crystallitic carbon from anthracite had a good scattered ability and a proper lubricity for the decrease of the magnesium grain size[14].
Along with the decrease of the magnesium grain size, the magnesium is hydrogenated to forming magnesium hydride as shown in Fig. 2.
While at 350 oC that is around the peak dehydrogenation temperature, the hydrogen desorption rate of MgH2 is so fast that a number of hydrogen atoms combine into hydrogen molecules and deviate from the material surface so as to lose the reactivity to react with CS2.

/min.] 420 Carrier gas (N2) flow rate [lit/min.] 20 Powder feed rate [g/min.] 40 Coating distance[mm] 280 Gun traveler speed [mm/sec] 10 Specimen rotating linear speed [mm/sec] 600 Number of passes 28 Vickers indentation fracture toughness measurements were conducted on the cross section of the coatings using a range of loads from 3kgf to 20kgf applied for 1 to 10 minutes.
These powders also have fine WC grains, which are in micron range.
In this schematic, each phase is represented by a different pictogram in which A is WC, N is Nano-crystalline matrix, B is WC-W2C crystallites, D is cobalt dendrites surrounding WC grains, and C is Splat boundaries.
The analysis of the microstructure confirmed that the number of retained WC particles was high with small quantities of W2C particles.

Several observations can be made: • Introduction of Ti in the steel increased oxidation kinetics, leading to thicker scales after 150 and 300 cycles compared to the reference alloy, due to Ti4+ doping effect in chromia as already proposed [7], • Decreasing adhesion with number of cycles was clearly evidenced on the Ti-containing material, • Internal precipitation of TiO2 along steel grain boundaries was detected as already observed in the case of isothermal oxidation [7] and was probably responsible for enhanced adhesion, blocking the propagation of the interfacial crack.
Grain boundary precipitation of Nb-rich phases was detected in the ferritic steel, as also observed in isothermal oxidation tests.
Comparison between values obtained with these tests were, except in a minor number of cases, in the same range, although the tests do not work in the same mechanical conditions and the derivation of adhesion values are not based on the same assumptions.

It is known that backscattered electrons (BSE) image of SEM is able to distinguish areas with different atomic, since the brightness of the BSE image tends to increase with a higher atomic number [9,10].
Therefore the brighter areas in the BSE image represent the existence of silver atoms beacause the atomic number of silver is much higher than other elements existed in dentin and resin.
In contrast to BSE, the power of electron beam for secondary electron image is lower, resulting in a less bright in areas containing silver atoms or grains.
Taking example for Clearfil SE Bond, Suppa et al [12] and Reis et al [13] observed silver grains dis- continuously distributed within hybrid layer, whereas Duarte et al [14] presented clusters of silver aggregated in zone within hybrid layer, the difference was significant.

In the process of cooling after rolling, secondary cementite can be easily precipitated preferentially at austenite grain boundaries in SWRH82B wire rods, and in severe cases, closed cementite network can be formed.
In process of drawing, cementite network will greatly weaken binding force between grains, and continuity of matrix is wrecked.
Table 2 Frequency of occurrence of cementite network in the experimental steel (wt. %) Samples / Numbers Cementite network / % 100 94 Table 3 Frequency of martensite appearance in the experimental steel (wt. %) Samples / Numbers 0.5-1(level)[%] 1.5-2(level)[%] 2.5-3(level)[%] 3.5-4(level)[%] 0.5-4(level)[%] 100 19.4 26.4 17.2 14.3 77.3 3 2 1 Fig. 1 Cementite network and martensite structure in central of the sample.