材料期刊网

State-of-the-Art and Perspectives in the Field of Particulate Nanostructured Materials

R.A.Andrevski(Institute of New Chemical Problems , Russian Academy of Sciences , Chernogolovka , Moscow Region , 142432 Russia)

材料科学技术（英文）

A great attention has been paid to the research and development of nanostructured materials.The main preparation methods of ultrafine particles and nanostructured materials have been summarized. The applications of zone typical nanostructured materials have also been reviewed.The peculiar characteristics and properties. such as density, grain size, hardness, superplasticity,magnetic and catalytic properties have been discussed

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Flow of Steel in Mold Region During Continuous Casting

ZHANG Xingguo , ZHANG Wenxiao , JIN Junze , J. W. Evans

钢铁研究学报(英文版)

The particle image velocimetry (PIV) technique was used to study the fluid flow phenomena that occurred during continuous casting, using a water model with dimensions of 1 840 mm×280 mm. Two types of solidified shells, ie, the smooth type and the coarse type, were used to characterize the dendrite in order to simulate different liquidsolid interfacial conditions. The influence of the nozzle angle and the immersion depth of nozzle, as well as the casting speed on the flow behavior was investigated quantitatively. The results were as follows: (1) There are two large recirculations above and below the fluid jet in the mold, respectively, under the smooth interface condition. However, in the case of the dendrite solidified shell, it was found that the flow velocity of the fluid decreased and more smaller vortices appeared in the upper region of the mold. (2) The angle and the immersion depth of nozzle are two important factors affecting the flow pattern, and they are also capable of bringing about the change in the flow direction. (3) The higher the casting speed, the higher are the jet stream and the impacting point on the narrow face. However, the high casting speed causes serious fluctuation of the meniscus, and correspondingly leads to various defects.

关键词: particle image velocimetry;continuous casting;steel;fluid flow

A NEW METHOD FOR MEASURING LONG-TERM CREEP DEFORMATION IN A SMALL REGION

J.M. Gong , S.T. Tu , J. Xia and X. Ling (School of Mechanical Engineering , Nanjing University of Chemical Technology , Nanjing 210009 , China)

金属学报(英文版)

Creep deformation localization is generally found in structures at high temperamture,typically in weldments. As the heat affected zone (HAZ) in a weldment is very narrow, deformation in HAZ region can hardly be measured by conventional displacement gauge. A new method for measuring long-term local creep deformation was developed by quartz optical fiber and technique of digital image analysis. The creep deformations of base metal, weld metal and HAZ in weldments are thereby determined with crossweld specimens.

关键词: creep deformation , null , null , null

Interdiffusion in the beta phase region of the Ni-Al-Cr system

Scripta Materialia

This paper describes an investigation of the interdiffusion behavior in the beta single-phase region of the Ni-Al-Cr system by the modified Boltzmann-Matano method. The interdiffusion coefficient matrix is estimated and the cross-interdiffusion coefficients found to be smaller than the main interdiffusion coefficients at the examined composition ranges. Combining the thermodynamic calculation of the isochemical potential lines reveals that the thermodynamic interaction between Al and Cr in Al-rich beta-Nl(AI,Cr) is possibly negligible. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词: diffusion;intermetallic compound;beta-Ni(Al,Cr);zero-flux planes;ternary-systems;diffusion;profiles

Spectrum features of commercial derv fuel oils in the terahertz region

Science China-Physics Mechanics & Astronomy

Characteristic spectra in the 0.5-2.5 terahertz (THz) range of three commercial derv fuel oils have been obtained using THz time-domain spectroscopy and calculated using density functional theory. The simulated results and experimental absorption curves suggest that the skeleton vibration is predominant in the THz region, and the absorption bumps of diesels are a superposition of various components. The investigation demonstrates that different diesels can be distinguished using THz time-domain spectroscopy and THz technology is a promising method to detect the composition and properties of diesels via chemical analysis.

关键词: optical constants;derv fuel oil;time-domain analysis;terahertz;radiation;time-domain spectroscopy;thz;explosives;range

Molecular dynamics study of the microstructure of the near grain boundary distortion region in small grain nano-NiAl alloy

Chinese Physics Letters

Using the molecular dynamics simulation method, the microstructure of the distortion region near the curved amorphous-like grain boundary in nano-NiAl alloy is studied. The results show that due to the internal elastic force of the high-energy grain boundary, a distortion layer exists between the grain and grain boundary. The lattice expansion and the decreasing structure factor are observed in this region. The stacking fault in samples with a grain size of 3.8 mn is clearly observed across the distortion region at the site very close to the grain. The influences of different grain sizes on average distortion degree and volume fractions of the distortion region, grain and grain boundary are also discussed.

关键词: nanocrystalline

Cross-sectional electron microscopy observation on the amorphized indentation region in 001 single-crystal silicon

Acta Materialia

The amorphized region of single-crystal silicon (c-Si) induced by Vickers indentation has been studied cross-sectionally by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). A comparison between the V-shaped profile of the amorphous region and the stress isobars under the indenter shows that the deviatoric stress plays a significant role in the formation of amorphous silicon (a-Si). A number of defects near the crystalline/amorphous (cla) interface, and the refinement and rotation of grains at local regions, are observed by HREM. The distortion of lattice fringes in the c-Si region and the domains characterized by distorted lattice in the a-Si region near the interface as well as continuous transition from the crystalline to the amorphous region at the interface are also observed. A possible mechanism of defect-induced or heavy-deformation-induced amorphization of silicon under indentation is suggested. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.

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The improvement of the corrosion resistance of 309 stainless steel in the transpassive region by nano-crystallization

Electrochimica Acta

The effect of nano-crystallization on the corrosion behavior of 309 stainless steel in the transpassive region was investigated in 0.5 M Na(2)SO(4) (pH 2) solution. Three parts defined as transpassive dissolution, secondary passivity and oxygen evolution can be observed in the transpassive potential region of the anodic polarization Curves. In the whole transpassive region the nano-crystalline coating has a smaller corrosion current density than the bulk steel, which indicates the transpassive dissolution rate is decreased by nanocrystallization. In addition. there is an obvious difference in the surface micrographs of the two materials at transpassive potentials, as scanning electron microscopy (SEM) shows. The electron probe microanalysis (EPMA) reveals that nano-crystallization improves the homogeneity of Cr on the surface. Mott-Schottky plots displays that the carrier density of the oxide film in the transpassive region is decreased by nanocrystallization. Thus, the interfacial reactions are decelerated and the corrosion resistance of the stainless steel in the transpassive region has been greatly improved by nano-crystallization. (C) 2008 Elsevier Ltd. All rights reserved.

关键词: 309 stainless steel;Nano-crystalline coating;Transpassive;Oxide film;EPMA;iron-chromium alloys;dissolution mechanism;sulfate-solutions;passive;films;metals;ni;cr;molybdenum;impedance;stability

Damping behavior of Ti50.1Ni49.9 alloy in reverse martensitic transformation region

Science China-Technological Sciences

Damping behavior of Ti50.1Ni49.9 shape memory alloy during reverse martensitic transformation has been investigated by dynamic mechanical analyzer in a dual-cantilever mode. With the increase of strain amplitude, internal friction (IF) of the alloy increases in martensite and austenite states while decreases in transformation region. Based on the regularity of IF attenuation in isothermal condition, IFTr and (IFPT+ IFI) are decomposed from the strain amplitude dependent IF in transformation region. For practical application of shape memory alloys as a damping material, it is significant to evaluate the damping capacity by eliminating the influence of IFTr and consider its time independent real IF (IFPT+ IFI).

关键词: internal friction;attenuation;strain amplitude;martensitic;transformation;shape memory alloys;shape-memory alloys;capacity;cu;ti

Cu-based bulk amorphous alloy with larger glass-forming ability and supercooled liquid region

Journal of Alloys and Compounds

The glassy rod with a maximum sample thickness of I I mm and larger supercooled liquid region of 108 K was successfully fabricated when substituting Cu with minor amount of Ag in the Cu-Zr-Al-Gd alloy system. The value of gamma reaches a maximum of 0.418 for the Cu45.5Zr45Al7Gd2Ag0.5 bulk metallic glass (BMG) alloy. The high glass-forming ability (GFA) and larger supercooled liquid region are discussed from atomic size, negative mixing heat among constituent elements and thermodynamics. (c) 2007 Elsevier B.V. All rights reserved.

关键词: glass-forming ability;bulk metallic glass;supercooled liquid region;mechanical-properties;metallic glasses;system