材料期刊网

HIGH STRAIN RATE SUPERPLASTICITY OF DISCONTINUOUS CERAMIC FIBER REINFORCED ALUMINUM COMPOSITES

T. Imai , L. Geng , J. F. Mao and I. Tochigi 1) National Industrial Research Institute of Nagoya , 1-1 Hirate-cho , Kita-ku , Nagoya , 462-8510 , Japan 2) School of Materials Science & Engineering , Harbin Institute of Technology , Harbin 15001 , China 3) Kanagawa High-Technology Foundation , Kanagawa Science Park , 3-2-1 , Sakado , Takatsu-ku , Kawasaki , Kanagawa 213 , Japan

金属学报(英文版)

β-Si3N4 whisker reinforced aluminum composites was fabricated by squeeze casting before extrusion and an effect of content of Mg on the High Strain Rate Superplastic- ity (HSRS) were investigated, The optimum temperature of the composites at which maximum total elongation is obtained decreases according to magnesium content and the β-Si_3N_4w/Al-3Mg exhibits the total elongation of about 200% at the strain rate of 10~(-1) s~(-1) and at 853-858 K, although the β-Si_3N_4w/Al-0Mg composite shows about 100% elongation at the strain rate of about 1×10~(-1) s~(-1) at 903-913 K. Optimum strain rate of the composites fabricated by squeeze casting was about 1×10~(-1) s~(-1) but TEM observation indicates that the β-Si_3N_4w/Al-Mg has a fine grain of about 2- 3μm and that the whisker might no react with Mg at the interfaces, although the β-Si_3N_4 whisker react with aluminum matrix.

关键词: high strain rate superplasticity , null , null

Recent Advances of Laser Coating Technology in China

LIANG Yong LI Ruiguo Institute of Metal Research , Academia Sinica , Shenyang 110015 , ChinaInstitute of Corrosion and Protection of Metals , Aademia Sinica , Shenyang , 110015 , China

材料科学技术（英文）

Recent advances in laser coating technology including laser cladding,laser surface alloying and laser vapour deposition in China are reviewed in this paper.

关键词: laser , null , null , null , null

A novel technology for preparation of high performance fiber by radio frequency heating CVD

材料科学技术（英文）

In this paper, radio frequency (r.f.) heating CVD technology for preparation of high performance fiber has been introduced. SiC, B fibers have been produced by this technology.

关键词:

A novel technology for preparation of high performance fiber by radio frequency heating CVD

Nanlin SHI , Kun LUO , Yapei ZU , Yading DUAN

材料科学技术（英文）

In this paper, radio frequency (r.f.) heating CVD technology for preparation of high performance fiber has been introduced. SiC, B fibers have been produced by this technology.

关键词:

Key R&D activities for development of new types of wrought magnesium alloys in China

Transactions of Nonferrous Metals Society of China

Many researchers in China are actively engaged in the development of new types of wrought magnesium alloys with low cost or with high-performances and novel plastic processing technologies. The research activities are funded primarily through four government-supported programs: the Key Technologies R&D Program of China, the National Basic Research Program of China, the National High-tech R&D Program of China, and the National Natural Science Foundation of China. The key R&D activities for the development of new wrought magnesium alloys in China are reviewed, and typical properties of some new alloys are summarized. More attentions are paid to high-strength wrought magnesium alloys and high-plasticity wrought magnesium alloys. Some novel plastic processing technologies, emerging in recent years, which aim to control deformation texture and to improve plasticity and formability especially at room temperature, are also introduced.

关键词: wrought magnesium alloy;microstructure;properties;alloy designing;plastic deformation;research projects;y-zr alloys;mechanical-properties;mg-4y-4sm-0.5zr alloy;grain-refinement;rare-earth;microstructure;gd;phase;temperature;evolution

Recent developments in high temperature intermetallics research in China

Intermetallics

A comprehensive survey was made of various advances of intermetallics research in China. The investigation focussed on the fundamental research and materials development. Charge density distribution and site occupancy of alloying elements, environmental embrittlement and chemical reaction, interface structures and phase transformation at the atomic scale, nanocrystalline intermetallics and its thermal stability, superplastic behavior and anomalous yield strength peak are reviewed. Several Ti-Al and Ni-Al based alloys have been manufactured, and show good mechanical properties. Diverse components have been fabricated successfully. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词: aluminides, miscellaneous;hydrogen embrittlement;mechanical properties;at high temperatures;superplastic behavior;phase interfaces;grain-boundary fracture;in-situ composites;environmental;embrittlement;hydrogen embrittlement;ni3al;compression;alloys;co3ti;boron;feal

CORRELATION BETWEEN STRESS COMPONENTS AND STRESS CORROSION CRACKS IN BRASS Lecturer,Department of Materials Physics,University of Science and Technology Beijing,Beijing 100083,China

QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing , Beijing , China

金属学报(英文版)

The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.

关键词: stress corrosion cracking , null , null , null

Influence of Preparation Technology on the Structure and Phase Composition of MoSi₂-Mo₅Si₃/SiC Multi-coating for Carbon/Carbon Composites

Xin Yang

材料科学技术（英文）

Oxidation protective MoSi₂-Mo₅Si₃/SiC multi-coatings for carbon/carbon composites were prepared by chemical vapor reaction and slurry-sintering method. The influence of preparation technology on the structure and phase composition of the coating was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, and then their relationship was discussed. The results indicate that the Si/Mo ratio of the slurry and sintering processing were two main factors that significantly affected the structure and phase composition of the multi-coating. Appropriate sintering process and relatively high Si/Mo ratio were essential for preparing the multi-coating with dense structure and favorable phase composition. After being sintered at 1723 K for 2 h and with the Si/Mo ratio of the slurry being 4.5 (weight ratio), a dense structure accompanied by favorable phase composition of the coating can be obtained. When heat treated at 2373 K for 1 h, this coating became more compact and continuous. Oxidation tests (performed at 1623 and 1823 K) demonstrated that both of these two obtained multi-coatings exhibited better anti-oxidation property than single layer SiC coating.

关键词: Carbon/carbon composites , null , null

Theoretical Foundation of Carbonation Pellet Process for Ferrous Sludge Recycling

HU Chang-qing , HAN Tao , ZHANG Yu-zhu , ZHANG Zhi-xia

钢铁研究学报(英文版)

For the recycling of ferrous sludge from steel industry, the carbonation pellet process should be considered as a “green” process, since no impurities are added as well as CO2 can be sequestrated and consumed. Through the thermodynamic calculation, the carbonation reaction can occur spontaneously and is an exothermic reaction. Based on the kinetic analysis through unreacted core model, the interfacial chemical reaction was the rate controlling step in the initial fast stage of carbonation, and the CO2 diffusion through the CaCO3 product layer was the rate controlling step in the following extremely slow stage. For the carbonation bonded mechanism, the pellet strength was gained by the formation and growing of CaCO3 product layer. Since the interfacial chemical reaction was the critical stage of the entire carbonation process, the emphasizes should be focused on the improvement of sorbent activity and the optimization of process parameters, such as pore structure, pore surface area, and total pressure, CO2 partial pressure, reaction temperature, etc to accelerate the reaction rate and to improve the quality of carbonation pellets.

关键词: CO2 sequestration , ferrous sludge , carbonation pellet , thermodynamics , kinetics , unreacted core model

Bibliography of Science and Technology of Rare EarthsPublished in China (2001)

稀土学报(英文版)

关键词: