材料期刊网

HIGH TEMPERATURE OXIDATION AND STRUCTURE OF SCALE AND WHISKERS FOR Fe-Ni-Cr SEALING ALLOYS

DONG Zhili , MA Jusheng , TANG Xiangyun , YOU Liang Tsinghua University , Beijing , China lecturer Department of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

The oxidation rate,the growth,morphology and structure of oxide scale and whiskers for Fe-Ni-Cr sealing alloys in H_2-H_2O atmosphere at high temperatures have been studied. The growth rate of scale is controlled by diffusion.The scale is composed of Cr_2O_3 and spinel(Fe,Mn)O·Cr_2O_3 and the oxide whisker,are spinel(Fe,Mn)O·Cr_2O_3.

关键词: oxidation , null , null , null

DESIGN AND PREPARATION OF SILICON NITRIDE COMPOSITE WITH HIGH FRACTURE TOUGHNESS AND NACRE STRUCTURE

Y Huang , H.N Hao , Y.L. Chen and B.L.Zhou (1)Department of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China 2)Institute of Metal Research , Chinese Academy of Sciences , Shenyang 110015 , China Manuscript received 26 August 1996)

金属学报(英文版)

A new way of designing and preparing silicon nitride ceramic composite with high fracture toughness and nacre structure has been proposed. To mimic the laminated structure of nacre, Si_3N_4 matrix ceramic layer can be obtained through compacting rolling method. To mimic the secondary toughening of nacre structure, SiC whisker is added into Si_3N_4 and acts as the secondary toughening phase. Boron nitride (BN)is selected to mimic the organic layer in nacre so as to form the weak interfaces between Si_3N_4 layers. Alumina is added into BN to adjust the bonding strength of the interface.The Si_3N_4 sheets are stacked into the die after coating with BN. After the removal of the organic matter in them, the green body is hot pressed at 1820℃for 1.5 hours under N_2 atmosphere. The fracture toughness of the so-made Si_3N_4 composite at room temperature is 20.36MPa m~(1/2), the three-point bending strength at room temperature is 651.47MPa. The crack spreads and deflects along the interface between BN and Si_3N_4 layer and extends through the BN layer into Si_3N_4 layer. The improvement of the fracture toughness may be due to the staircase-shape-like crack which provides the long crack path, the fracture and deformation of Si_3N_4 layer, and the pullout of SiC whiskers from the Si_3N_4 layer.

关键词: :secondary toughening , null , null , null

AGING PRECIPITATION OF Cu-Zr AND Cu-Zr-Si ALLOYS AND AFFECTED BY COLD WORKING

DONG Zhili TANG Xiangyun Tsinghua University , Beijing , ChinaHORI Sgigenori FUJITANI Wataru Faculty of Engineering , Osaka University , Japan DONG Zhili Dept.of Material Science and Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

The hardness and electrical conductivity of Cu-Zr and Cu-Zr-Si alloys varying with differ- ent aging regimes were measured and the factors influencing the electrical conductivity were analysed.It is believed that a little Si can refine the precipitates and improve the resistance to softening.The improvement of materials properties by aging and the effect of cold work were also discussed.

关键词: aging , null , null

PREPARATION OF B-N FILMS BY ION BEAM ASSISTED DEPOSITION

JIANG Hai TAO Kun LI Hengde Tsinghua University , Beijing , China lecturer , Department of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

BN films,synthesized by ion beam assisted deposition,were analysed by RBS,AES, IR spectra and TEM.Formatiom of c-BN phase was shown not only by IR spectra at absorption peak of 1100 cm~(-1),but also by electron diffraction pattern.The results of AES demonstrate an effect of N~+ implantation near the film surface.The deposited films consist of three layers,i.e.,ion implantation layer,film layer and mixed intermediatelayer, according to the difference of concentration.The micro-Knoop hardness of the film is 25—35 GPa.

关键词: ion beam assisted deposition , null

EXTRACTION KINETICS,SYNERGISTIC EFFECTS AND INTERFACIAL CHEMISTRY FOR D_2 EHPA MPA-Fe~(3+) MIXED EXTRACTION SYSTEM

YU Jingfen LIU Difei Tsinghua University , Beijing , China professor , Dept.of Chemical Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

The thermodynamics of micella formation,interfacial characteristics,synergistic effects and interfacial kinetics for synergistic extraction system D_2 EHPA-MPA-Fe~(3+) have been studied.It was found that D_2EHPA in the mixed system strongly exhibits the effect on the micella formation thermodynamics and interracial characteristics of MPA.Some ther- modynamic parameters for constants of micelles formation(K_m).free energies of micelles formation(ΔG_m)and critical micella concentrations(CMC)were obtained.The inter- facial adsorption behaviour of D_2EHPA is opposite to that of MPA.The emulsification for single MPA and the mixed system was discussed.The synergistic effects were found in this mixed extraction system.It is proved that the process of the Fe~(3+) extraction for non-mixed extraction system is controlled by chemical reaction and the controlling reaction occurs at the interface.

关键词: interfacial chemistry , null , null , null

APPLICATION OF MOLECULAR ORBITAL THEORY TO ANALYSIS OF PHASE STABILITY FOR ALLOYS

YIN Hong TAO Kun PAN Jinsheng LI Hengde Tsinghua University , Beijing , China professor.Department of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

The critical _d vahues ( _ ) of the γ/(γ+σ).γ/(γ+μ) and γ/(γ+γ') phase boundaries in some ternar alloy phase diagrams at various temperatures are calculated by averaging the _d values of sererai selected characteristic points at the phase boundaries.Approxmate equations for the temperature dependence of the critical _d of γ/(γ+σ).γ/(γ+μ) and γ/(γ+γ') phase boundaries are established.The accuracy of the analysis is discussed in detail. It is found for the first time that the average value of the bond order _ at the phase boundaries ts also approximatelr a constant and therefore a critical average bond order _ like - can be introduced for the analysts of phase stability

关键词: molecular orbital theory , null , null

CREEP FRACTURE OF INTERMETALLIC COMPOUND(Fe_(60)Ni_(40))_3(V_(98)Ti_2)

YAO Xuexing KANG Feiyu CHEN Nanping Tsinghua University , Beijing 100084 , China

金属学报(英文版)

The creep fracture behavior of intermetallic compound(Fe_(60)Ni_(40))_3(V_(98)Ti_2)has been studied. The variation of dislocation substructure was observed with TEM in the process of steady-state creep.It is found that there exists a large amount of stacking faults,dislocation pairs and also high density dislocation networks.SEM analysis of section near fracture sur- face points out that the intergranular crack due to coalescence of small cavities is the main creep fracture mechanism of(Fe_(60)Ni_(40))_3(V_(98)Ti_2).

关键词: intermetallic compound , 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）

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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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Towards the ultimate storage ring: The lattice design for Beijing Advanced Photon Source

中国物理C doi:10.1088/1674-1137/37/5/057003

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