材料期刊网

INTERFACIAL STRUCTURE AND PHASE REACTION IN SiC/NiCr ALLOY JOINT

J. C. Feng , M. Naka , J. C. Schuster(School of Materials Science and Engineering , Harbin Institute of Technology , Harbin , 150001 , China , Joining and Welding Research Institute , Osaka University , Mihogaoka 11 - 1 , Ibaraki , Osaka 567 , Japan , Institute of Physical Chemistry , University of Vienna , Austria )

金属学报(英文版)

Bonding of SiC to SiC using Ni and Ni - 25at%Cr foils was performed at high temperature.Interface structures and reaction phases were investigated by EPMA analyses and XRD diffraction method, re- spectively. At a bonding temperature of 1273K Ni reacts with SiC and forms various Ni silicides con- taining graphite baside SiC. Ni3Si without graphite was formed at Ni side.The interface structure of SiC/Ni joint was SiC/Ni2Si + C/Ni31 Si12 + G/Ni3 Si/Ni. At the interface between SiC and Ni- 25at%Cr alloy the Ni silicide was only Ni2Si at the same bonding temperature,and further(Cr, Ni)7 (Si, C)3 carbide was formed between Ni silicide + graphite zone and Ni - 25at%Cr alloy.The interface structure of SiC/Ni - 25at%Cr alloy was SiC/Ni2Si + C/(Cr, Ni)7 (Si, C)3+Ni(ss. Cr, Si)/Ni - 25at%Cr.

关键词: interfacial structure , null , null , null

Effect of Austenite Pre-deformation on Isothermal Martensite Transformation in an Fe-20.5Ni-4.8Mn Alloy

Fuxing YIN , Jianxin ZHANG and Nanju GU(Hebei Institute of Technology , Tianjin , 300132 , China)Tsukio Tadaki(Institute of Science and Industrial Research , Osaka University , Japan)Ken , ichi Shimizu(Kanazawa Institute of Technology , Ishigawa 921 , Japan)

材料科学技术（英文）

With electron microscopy the investigation on isothermal martensite transformation in an Fe20.5Ni-4.8Mn alloy has been carried out to clarify the effect of austenite state on the transformation, by applying pre-deformation to austenite before isothermal holding. Under the condition without pre-deformation, the isothermal martensite products are lath martensite with {111}fhabit planes. Dislocations in austenite seem to contribute to nucleation of martensite, and in this nascent Stage austenite substructure has no obvious effect on martensite growth. The consequent thickening of martensite laths is apparently influenced by local austenite states, resulting in the changes in orientation, morphology as well as substructure of martensite lath. The kinetics of isothermal martensite transformation is controlled by intedece dislocation determined nucleation of martensite in primary stage, but to a larger extent, by the austenite accommodation for the shape strain of martensite in the thickening Stage

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Origin of Ordering Coupled Tweed Microstructures in Alloys with Large Atomic Size Factors

Xiaobing REN and Xiaotian WANG (College of Materials Science and Engineering , Xi'an Jiaotong University Xi'an 710049 , China)K.Shimizu and T.Tadaki (Institute of Scientific and Industrial Research , Osaka University , 8-1 , Mihoga-oka , Ibaraki , Osaka , 567 , Ja

材料科学技术（英文）

A theoretical study is developed on the evolution and mechanism of an ordering coupled phase separation, and on the origin of a resultant tweed microstructure. It is found that long-range elastic interaction among atoms with different atomic sizes plays a key role in the phase sep aration, and that the evolution of the phase separation is very similar to that Of conventional spinodal decomposition except that the separation is dependent on an elastic interaction order ing (EIO). This "EIO coupled spinodal decomposition" is shown to exhibit a periodical or tweed microstructure being accompanied by an EIO. It is also found that a large atomic size factor yields a large positive contribution of EIO to spinodal decomposition. Generally it is thermodynamically and kinetically favorable for the EIO to precede the onset of spinodal decomposition,though the former is not separable from the latter as a whole. We suggest that an initially disordered solid solution undergoes an EIO first, and then the partially ordered solid solution starts to decompose via a spinodal mechanism. Solute-enriched regions increase their degree of order along with an increase in solute content, and solute-depleted regions decrease their degree of order together with a decrease of solute content. The final microstructure is characterized by a periodical array of highly ordered solute-enriched regions and nearly disordered solute-depleted regions. The notion of EIO coupled spinodal decomposition is in general agreement with the transformation behaviour of a large number of alloy systems.

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DEFORMATION AND FRACTURE OF TiAl PST CRYSTALS UNDER MONOTONIC AND CYCLIC LOADING

Y.Umakoshi , T. Nakano and H .Y. Yasuda (Department of Materials Science and Engineering , Faculty of Engineering , Osaka University , 2-1 , Yamada-Oka , Suita , Osaka 565 Japan)

金属学报(英文版)

Plastic behaviour of TiAl polysynthetically twinned (PST) crystals is reviewed to show our knowledge and understanding for receiving a good combination of strength and ductility of two phase TiAl alloys under monotonic and cyclic loading conditions. Anisotropy and mechanism of strength, ductility, toughness. cyclic hardening and fatigue life are described focusing on the effect of lamellar structure.

关键词: :Fatigue. Deformation , null , null

EFFECT OF Ti CONTENT ON THE MICROSTRUCTURE AND PROPERTIES OF Si_3n_4/Si_3N_4 JOINT BRAZED USING Cu-Zn-Ti ALLOY

M. Naka , J. Zhang , H. Y. Fang (1.Joining and Welding Research Institute , Osaka University , Japan 2)School of Materials Science and Engingeering , Harbin institute of Technology , Harbin 150001 , China)

金属学报(英文版)

St3N4 ceramic was brazed using a filler of Cu - Zn - Ti alloy under the brazing condition of 1223K and 1.8ks. When the Ti content in the alloy is 20% at., the average shear strength of the joint is 265MPa. By using EPMA and XRD analysis, the metallurgical behavior of the interface between the filler alloy and Si3N4 matrix was studied,which affected the joint strength.It was found that with in- creasing Ti content from 5% to 20%at., the thickness of the brazing seam decreases and the amount of the reactant(Ti5Si3, TiN and Ti2N etc. ) increases,resulting in an obvious increase of the shear strength of the joint.

关键词: Si_3N_4 ceramic , null , null , null , null

University of Science and Technology Beijing

JIA Shizhen University of Science and Technology Beijing , China.

材料科学技术（英文）

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Department of Metallurgy and Materials Engineering of Chongqing University

YAN Guangting Chongqing University , Sichuan , China.

材料科学技术（英文）

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Institute of Materials Science at Jilin University——A Brief Overview

WANG Yuming Institute of Materials Science , Jilin University , Changchun , 130023 , China

材料科学技术（英文）

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Abstracts of papers from Journal of University of Science and Technology Beijing

稀有金属（英文版）

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RF deflecting cavity design for bunch length measurement of photoinjector at Tsinghua University

中国物理C

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