材料期刊网

Multi-range Fractals in Materials

Qiwei LONG (C.W.Lung) International Centre for Materials Physics , Institute of Metal Research , Academia Sinica , Shenyang 110015 , China

材料科学技术（英）

A new model of multi-range fractals is proposed to explain the experimental results observed on the fractal dimensions of the fracture surfaces in materials.The relationship of multi-range fractals with multi-scaling fractals has been also discussed.

关键词: fractals , null , null , null

CURRENT STATUS OF HIGH-RESOLUTION ELECTRON-MICROSCOPY AND ITS APPLICATIONS TO MATERIALS SCIENCE AND CONDENSED MATTER PHYSICS

材料科学技术（英）

The present paper summarizes the current status of high resolution elect;on microscopy ( HREM) and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction, subnanometer level analysis, image simulation and image processing.

关键词: juxtaposed pentagonal antiprisms;two-dimensional quasicrystal;domain;boundary structures;close-packed phases;nanocrystalline materials;crystal-structure;copper oxidation;initial-stage;translational;symmetry;rotational symmetry

Current Status of High Resolution Electron Microscopy and Its Applications to Materials Science and Condensed Matter Physics

Douxing LI and Hengqiang YE (Laboratory of Atomic imaging of Solids , Institute of Metal Research , Chinese Academy of Sciences , Shenyang , 110015 , China)

材料科学技术（英）

The present paper summarizes the current status of high resolution electron microscopy (HREM)and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction,subnanometer level analysis, image simulation and image processing.

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Novel hard materials with controlled (W_0.5Al_0.5)C grain shapes: in-situ high pressure preparation and mechanical properties

Zhuhui QIAO

金属学报(英文版)

A novel hard material with various (W_0.5Al_0.5)C grain shapes was successfully prepared through mechanical alloying and in-situ high-pressure sintering process. X-ray diffraction apparatus and scanning electron microscopy were used to characterize the phase and the microstructures of the samples. The novel hard materials with ``fibrous", ``rounded" and ``plate-like" grains, which do not contain sharp edges, have the improved mechanical properties. The bulk boundless (W_0.5Al_0.5)C hard material with various (W_0.5Al_0.5)C grain shapes possesses good mechanical properties and light weight. The formation mechanism for the non-equilibrium (W_0.5Al_0.5)C grains during in-situ high-pressure sintering is also discussed.

关键词: Novel hard material

Microstructure characterization of long W core SiC fiber

材料科学技术（英）

Microstructure of SiC fiber manufactured by chemical vapor deposition (CVD) onto tungsten (W) wire core was investigated by analytical electron microscopy (AEM). The results reveal that the fiber consists of W core, SiC sheath and C-coating. SiC sheath could be subdivided into two parts according to whether containing C rich stripe, or not. An emphasis was put on W/SiC interfacial reaction products and the transition zone between sub-layers in SiC sheath. The W/SiC interface consists of three layers of reaction production, namely, W2C, W5Si3 and WC. And there are amounts of facet faults existing in (100) face of WC crystalline and two classes of stack faults in WC have been revealed. The formation essence of different sublayers in SiC sheath was also discussed.

关键词: siC fiber;chemical vapor deposition (CVD);analytical electron;microscopy (AEM);C-rich zone;reaction products;chemical vapor-deposition;silicon-carbide;model;dichlorodimethylsilane;interface;pyrolysis;hydrogen;strength

X-ray powder diffraction data for Al-Cu-W phases

Powder Diffraction

Ternary Al-Cu-W alloys were investigated. The previously reported Al(3)Ti-type phase (space group 14/mmm) with the average composition Al(67)Cu(11.5)W(21.5) was found to have a=3.7296(4) angstrom and c=8.3797(10) angstrom. The ternary phase forming around Al(67)Cu(21)W(12) has a hexagonal structure with a=8.6594(13) angstrom and c=15.2677(21) angstrom. (C) 2011 International Centre for Diffraction Data. [DOI: 10.1154/1.3549770]

关键词: Al-Cu-W;powder X-ray diffraction;system

Study on Design Techniques of a Long Life Hot Forging Die with Multi-Materials

X.J. Liu , H.C. Wang

金属学报(英文版)

A new design technique for the long life hot forging die has been proposed. By finite element analysis, the reason for the failure of hot forging die was analyzed and it was concluded that thermal stress is the main reason for the failure of hot forging die. Based on this conclusion, the whole hot forging die was divided into the substrate part and the heat-resistant part according to the thermal stress distribution. Moreover, the heat-resistant part was further subdivided into more zones and the material of each zone was reasonably selected to ensure that the hot forging die can work in an elastic state. When compared with the existing techniques, this design can greatly increase the service life because the use of multi-materials can alleviate the thermal stress in hot forging die.

关键词: hot forging die with multi-material , null

Long-term Durability of Cement-based Materials with Very Low w/b

武汉理工大学学报-材料科学版(英文版)

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Preparation and Arc Breakdown Behavior of Nanocrystalline W-Cu Electrical Contact Materials

Wenge CHEN

材料科学技术（英）

Nanostructured (NS) W-Cu composite powder was prepared by mechanical alloying (MA), and nanostructured bulk of W-Cu contact material was fabricated by hot pressed sintering in an electrical vacuum furnace. The microstructure, electric conductivity, hardness, breakdown voltage and arcing time of NS W-Cu alloys were measured and compared to conventional W-Cu alloys prepared by powder metallurgy. The results show that microstructural refinement and uniformity can improve the breakdown behavior, the electric arc stability and the arc extinction ability of nanostructured W-Cu contacts materials. Also, the nanostructured W-Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

关键词: Nanostructured materials , null , null , null

Mechanical alloying of Fe-Nb-C materials

Materials Letters

Mechanical alloying (MA) of elemental powder mixtures of Fe50Nb35C15, Fe60Nb30C10 and Fe50Nb40C10 was performed using a high energy ball mill. In the MA processing, ball milling first leads to a Fe-Nb-C amorphous phase and nanocrystalline NbC. Further milling results in the formation of a nanocrystalline solid solution of Fe(Nb, C) and nanocrystalline NbC in Fe50Nb35C15 and Fe60Nb30C10, while the final product for Fe50Nb40C10 is a mixture of amorphous Fe-Nb-C and nanocrystalline NbC.

关键词: mechanical alloying;Fe;Fe, Nb and C powders;amorphous;nanocrystalline;solid solution