Search results

Pressed powders sintered at 1250°C were analyzed by X-ray diffraction and X-ray fluorescence; their surfaces were observed by scanning probe microscopy (SPM) for topographical analysis of grains and grain boundaries.
CaTiO3 (CTO), which has a distorted perovskite structure with orthorhombic symmetry at room temperature, shows also the ability of forming solid solutions with a large number of oxides and, therefore, many compounds have been synthesized for different applications [12-18].
The specimens prepared with powders synthesized by the chemical route are highly homogeneous, dense and composed of well defined grains, such that each grain is itself composed of a large number of tightly packed sub-grains.
Sintered pellets prepared with these powders present homogeneous grains and sub-grains.

As a commonly used tool materials, high-speed steel, fine grain and ultra-fine grain carbide, single crystal diamond material is an ideal tool material for micro cutting.
In contrast, fine grain carbide is better than high speed steel in the mechanical properties.
Eq.1 is the relationship of helix angle with the pitch diameter and the parameter of module of the micro gear (mn) and the number of the chip slot
（1） As a standard round blank of fine grain carbide, the outside diameter is 25mm, and the hole diameter is 8mm.
The number of the chip slot (z0) is usually taken to be even for the reason of convenience in manufacture.

In the case of pure Mo, uniform morphology of fine “grained” structure is observed.
Revealed grains have morphology of mounds with similar height.
In the core of the laser path the coating has a grained microstructure with crack network located mainly on the grain boundaries.
A basic difference in morphology of remelted zone is related to grain size.
This effect was due to high number of imperfections on top surface of TZM alloy and in consequence high number of potential points of nucleation and growth of new remelted grains. here was no significant effect of laser remelting process on the phase composition of the coatings.

The simplified structure of the tube rotary dryer is shown in figure 1. 1－Feed inlet 2－Condensed water outlet 3－Discharging port 4－Steam entrance 5－Exhaust outlet Fig 1 The simplified structure figure of tube rotary dryer Particle Transfer Model In a completely mixed conditions, if the particles are spherical, the heat coefficient between the wall and particles hs is determined by the following equations [3]: (1) (2) (3) Where hp is the heat transfer coefficient between the heating surface and the first grain layer; h2p is the heat transfer coefficient between the heating surface and the second grain layer; hs is the heat transfer coefficient between the heating surface and the grain; dp is grain diameter; is the thermal conductivity of gas clearance; Cg is the specific heat of gas clearance; R is universal gas constant
On the basis of experiments, we have experience formula: (4) The average thermal conductivity in the packed bed can be calculated by the following formula: (5) Where cp is the specific heat of grain; is material density; τR is contact time; is the thermal conductivity of grain.
The overall coefficient of heat transfer h can be calculated by the following formula: (6) In order to calculate the changes of humidity and temperature of the materials in the drying process, the instantaneous drying front position ζ is introduced with the following equations: (7) (8) (9) △X (10) Where T0 is the temperature of heat surface; Tb is the temperature of material surface; △X is the humidity difference of materials in one dryer segment; △T is the temperature difference of materials in one dryer segment; AR is the heating surface area; Sdry is the flow rate of dry materials; rev is the latent heat of vaporization; X is the humidity of materials; cp is the specific heat of grain; cpL is the specific
The simple definition of tube rotary dryer class is given as follows: class CRotaryTube_Dryer : public CConductive_Dryer {protected: double m_average_heat_transfer_coefficient;// average heat transfer coefficient double m_tube_number；//tube number }; Example Analysis We develop the simulation software for the indirect dryer by using the object-oriented method and particle transfer model based on MFC.

So, the function ( ) ( ) ( ) , , , x t N x t V x t Ω = , (12) where N − grains density [nuclei/m 3 ], V − a single grain volume is introduced.
Denoting u = ∂R /∂t (u is a crystallization rate, R is a grain radius) we have ( ) ( ) ( ) 3 0 4 , πν , , τ dτ 3 t x t N x t u x   Ω =    ∫ , (13) at the same time for spherical grains ν =1, for other types of crystallization ν <1.
In this place the following assumptions can be introduced - a constant number of nuclei N(∆Vi, t f ) =const.
Constant number of nuclei Figure 4.
Grains families As an example the solidification of aluminum plate (L = 0.02[m]) is considered.

One important parameter in both thermomechanical treatment and temperature cycling is the prior-austenite grain size (PAGS).
Prior austenite-grain size was measured by using SIT SIMAGIS software [7].
Then we can obtain the information of Homology such as the Betti numbers b0 and b1 (cf. [8] and [9]).
The samples quenched thrice showed a finer martensitic structure caused by refinement of the prior-austenite grain size.
This work was supported by JSPS KAKENHI Grant Number 24654025. 7.

The results indicate that increasing the BPR leads to decreases in particle size and grain size of powders.
For a given milling time of 18 h and rotational speed of 250 rpm, ball milling with BPR of 20:1 produces an ultrafine powder with a mean particle size of about 2 μm and a grain size of about 20 nm.
At a higher BPR, due to an increase in weight proportion of the WC balls, the number of collision per unit time increases and consequently more energy is transferred to the particles, which resulting a finer, homogeneous powder.
The accumulation of defects and dislocations leads to a dislocation cell structure that creates low-angle grain boundaries and ultimately refines the grain size [15].
The particle size as well as grain size of powders decreases with the BPR increases.

Nano-Al2O3 particles enhanced the inhomogeneous nucleation of Fe-based alloy, refined the crystal grains and strengthened the mechanical properties of cladding layer.
There were a lot of nano-Al2O3 particles dispersing in the austenitic crystal grains.
There were a lot of nano-Al2O3 particles dispersing in the austenitic crystal grains.
Acknowledgements This paper was supported by the science and technology project of Zhejiang Machinery and Electrical Group Limited Company (project number, 2014JD001).
Besides, the author would like to appreciate the financial support from the scientific research sustentation fund from Zhejiang Provincial Education Department (project number, Y201328309) and Sliding Bearing Engineering Technology Research Center of Zhejiang Province (project number, 2012E10028).

The study of the reasons for decreasing KCU during heat treatment shows that in addition to the precipitation of phases causing brittleness at cooling, chromium zones at heating, and formation of chemical and structure inhomogeneity in the two-phase region, the main reason is the remelting method with the parameters which predetermine the variation in grain size in the structure, a small number of interstitial elements (IE), retained austenite in the structure, and lower level of KCU of the steel prepared by VAR both after quenching and after TST.
However, their use in products with a cross-section more than 60 mm leads to the increase of the liability to brittle fracture due to a number of reasons of metallurgical character; therefore, the search of ways for improving resistance to brittle fracture is still urgent.
The study of the reasons for decreasing KCU during heat treatment shows that in addition to the precipitation of phases causing brittleness at cooling [4, 5], chromium zones at heating [6] and formation of chemical and structure inhomogeneity in the two-phase region [7], the main reason is the remelting method with the parameters which predetermine the variation in grain size in the structure (Fig.1), a small number of interstitial elements (IE) (Fig.2), retained austenite in the structure, and lower level of KCU of the steel prepared by VAR both after quenching (Fig.3) and after TST (Fig.4).
Fig.1.Variation in grain size in steel 08Cr15Ni5Cu2Ti VAR (´100).
For making the ESR-steel functional, it is necessary that in the steel structure, the presence of retained austenite makes ~20% and the ratio of titanium and carbon is equal to or less than 1, which in combination with the small size number (9÷10) provides rather high content of retained austenite in the structure (20÷24)% [5].

Mechanical alloying (MA) is one of the most appropriate severe plastic deformation processes applied to powders in order to obtain good mixing, new different systems or alloys and / or to reduce particles grain size from the starting powders.
MA is then a severe plastic deformation process capable to alloy quasi homogeneous equilibrium or non-equilibrium atomic solutions as well as to decrease raw particle grain size until nanometric scale.
According to these results, experiments were conducted at two rotational speeds, 160 and 300 rpm for different number of cycles.
Fig 2 and Fig. 3 show milled powder at the two rotational speed conditions and for different number of cycles.
After 32h, grain size resulted as 18 nm and microstrain 0.1 10 -3.