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Therefore, there is a long term need for developing the heat treatment technology which can produce a dual grain structure disk part specifically with a fine grain in the bore and coarse grain in rim.
The grain size of the disk is ASTM 10.
As a result, the number of the mesh, as well as the calculation of numerical simulation, was be decreased greatly.
The number of mesh was 67137.
Mathey, Jupiter, Fla., “METHOD OF MAKING SUPERALLOY TURBINE DISKS HAVING GRADED COARSE AND FINE GRAINS”, U.

The grain size was reduced to an average size of 08 µm due to the effect of grain refiners.
These vacancies reduced the mass transport and diffusion at grain boundaries that result in reduction of grain growth and finally finer grain size [14-16].
The grain boundary area increased with grain refinement and a non-ferromagnetic layer exists within a certain width of grain boundaries [17-18].
The X-ray diffraction patterns were confirmed by JCPDS cards, the card numbers 79-2264, 35-0734, and 35-790 were in accordance with BaTiO3, SrTiO3, and CaZrO3 respectively.
Grain boundaries oxidized more as compared to grains internal area.

Using biased enhanced growth can reduce the grain size for fabrication of NDFs.
The diamond film surface was characterized with AFM and TEM to observe the grain size.
The film appears very dense with a fine-grained morphology.
This proves that the grain sizes of the diamond films are reduced to the nanometer scale.
Nanocrystalline diamond films are composed of fine diamond particles with grain sizes range from 7nm to 15nm, and contain a large amount of grain boundaries and sp 2 bonded components.

It can be seen from Fig. 5a that many pores are observed in the trijunctions of grain boundaries of the ceramic sample (sintered for 10h).
And the grain boundaries in this sample are very clear.
When the holding-time is increased, pores in the sintered samples decrease gradually (Fig. 5b and Fig. 5c) and the grains grow large.
For the sample prepared with a holding-time of 40h, few pores exist and the grains are well-grown.
Acknowledgement This work was supported by NSFC of P.R.China under grant number 50272040, Fok Ying Tong Education Foundation under grant number 91046, and Youth Foundation of Science and Technology of Sichuan Province under grant number 03ZQ026-03.

The equiaxed ferrite was observed and small amount of pearlite scattered in the grain boundary in Fig 1 (a) and (b).
The polygonal ferrite was observed and large number of precipitate distributed in ferrite grain and grain boundaries in Fig 1 (c).
The size of grain was measured by the method of the pulling line, 5.23in (a), 6.60 in (b) and 6.64in (c), the size of ferrite grain in 1# was the smallest in all.
Number, size and distribution of inclusions were significantly influenced by deoxidaton process.
In order to obtain larger number of inclusions, deoxidaton process should be reasonably developed.

Widmanstätten microstructure revealed several colonies (200 � 300 µm) in the prior � grains of about 600 µm in diameter.
The width of lamellar � was about 5 µm, and that of grain boundary � layer was 7 µm.
The contour numbers represent the percentage efficiency of power dissipation projected on a temperature-strain rate plane.
(a) (b) Fig. 3 Processing maps for (a) equiaxed and (b) Widmanstätten microstructure at a strain of 0.6: contour numbers represent a percentage efficiency of power dissipation.
Table 1 Comparison of measured and simulated grain size and volume fraction of � phase.

The markedly finer grain in samples taken from the tube walls and the chamber when compared to the other samples (Fig. 2b) is of course a positive feature.
Fig. 2 (a) Typical row arrangement of pearlite, (b) markedly finer grains in tube walls, magn. 200x Fig. 3 Tiny cavities in the parts with higher operating temperatures On a number of sites in the boiler components submitted there were large cracks (see, for example, Fig. 4).
Nevertheless, a number of samples were taken in such a way that the subsequent metallographic specimen included both the edge of the crack and sites that were ca 15-30 mm distant from the edge of the crack.
Irrespective of the crack site (i.e. its location in various parts of the boiler or its proximity to the weld) a structure of completely identical nature was found to exist near the crack (markedly elongated deformed grains, made more pronounced by bent rows of perlite), with equiaxial grains farther from the crack (Fig.5a, 5b).
Pictures of crack surfaces that were taken for a number of selected samples after the removal of the corrosion layer fully support the findings above.

The results show that the microstructures of S890 steel change from tempered martensite to bainite and a little ferrite , pearlitic when welding heat input changes from low to high, and accompany the austenite grains coarsening ,so the impact toughness and hardness of welding HAZ at lower peak temperatures and shorter are higher than that at higher peak temperature and long .
Table 3 Parameters of one thermal cycle simulation test Sample Numbers 01 02 03 04 05 06 07 08 peak temperature[℃ ] 1320 1320 1320 1320 1320 1320 1320 1320 [s] 6 6 10 10 20 20 40 40 Table 4 Parameters of two thermal cycle simulation test Sample Numbers 09 10 11 12 13 14 peak temperature[℃ ] 1150 1150 1100 1100 950 950 [s] 10 10 10 10 10 10 2 Test Results and Analysis 2.1 Impacting Toughness .The impacting Toughness Ak-20℃ of S890 steel obtained by the one thermal cycle simulating test are seen in table 5 , the impacting toughness Ak-20℃ of S890 steel obtained by the two thermal cycles simulating test is seen in table 6 .
For the welding of high-strength low alloy structural steel, heating peak temperature (and breadth) or t8/5 all reflect the thermal input of welding,and may become the main reason that cause coarse austenite grains at the nearest neighboring fusion line .
During multiple rolls welding, because of the overlap for HAZ and HAZ separately producing by once and two thermal cycle, so the partly and completely reheating zone appear, chiefs among which are sub-critical and intermediate-critical reheating grain coarsening HAZ, in the zone, primitive microstructure is again tempered or partly re-phase transformations and re-cooling.
The reason is that microstructure of steel changes from tempered martensite to ferrite and pearlitic, and austenite grains coarsen during welding heat input change from low to high

In spite of the processing advantages, however, thermal process of hydrogen reduction inevitably accompanies grain growth during the process at elevated temperatures.
To solve this problem, we have been finding a way to minimize grain growth by using a low temperature reduction process such as electrochemical reduction at room temperature.
Such high temperature process is limited to suppression of grain growth and too difficult to fabricate nano powder [3-6].
Power supply Thermometer + _ 20 30 40 50 60 70 80 90 Cu Cu2O CuO 2 h 1 h 0.5 h Intensity (a. u.) 2 ���� Journal Title and Volume Number (to be inserted by the publisher) Figure 3 shows SEM and TEM images of electrochemically reduced Cu powder (20 V, 2 h).
Ball-milled CuO powder (particle size ~100 nm and grain size ~40 nm) was completely reduced under optimal condition of 20V, 0.5 mol NaCl solution and 2 h reaction time, producing Cu nanopowder (particle size ~80 nm and crystallite size ~25 nm).

The bulk density, grain density and water absorption rate were tested according to standard methods (GB/T 17431.2-1998).
The number, such as 1050, 1100 and 1150, represented the sintering temperature were 1050, 1100, and 1150, respectively. 60μm LSC-1050 LSC-1100 LSC-1150 LFC-1050 LFC-1100 LFC-1150 Fig. 1.
When the samples were heated at 1100, there was a matrix containing a large number of isolated, approximately spherical pores in the framework of the ceramic pellets (images LSC-1100 and LFC-1100).
The bulk density, grain density water absorption and rate of expansion of LSC and LFC at different sintering temperature are shown in Fig. 3.
From Fig. 3, it can be seen that both the bulk density and grain density increased with the rise of the temperature at first and then decreased after 1125.