ISSN 0412-1961
CN 21-1139/TG
Started in 1956

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    , Volume 34 Issue 7 Previous Issue    Next Issue
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    ELECTRONIC STRVCTURE ANALYSIS OF PRIMARY SLIP PLANES IN HEXAGONAL CLOSE-PACKED METALS
    SONG Yan; YANG Rui; LI Dong; HU Zhuangqi(Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)
    Acta Metall Sin, 1998, 34 (7): 673-677. 
    Abstract   PDF (476KB) ( 697 )
    Based on the electronic structure theory, the electronic structure and some parameters were calculated for hop metals by using the discrete variational Xa cluster method,and the intrinsic relationship between the interaction parameters and the properties of materials was discussed. A criterion of the choice of primary slip planes for hop metals was advanced by using the electronic structure theory. The primary slip planes are (0001) for Zr, Cd, Co, Be;{1010} for Ti, Zr, Mg, and both of (0001) and {1010} for Y and Sc at low temperattire. The conclusions are in agreement with experimental observations.
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    MICRO-/MACRO-SCOPIC MODELING OF SOLUTAL MASS TRANSPORT IN DENDRITE SOLIDIFICAfION WITH PARTIAL SOLID BACK DIFFUSION
    XU Daming ; ZHANG Chengjun ; SI Guangju (School of Materials Science and Engineering; Harbin Institute of Technology; Harbin 150001)(Engineering College; Jiamusi University; Jiamusi 154007)
    Acta Metall Sin, 1998, 34 (7): 678-688. 
    Abstract   PDF (1019KB) ( 576 )
    The continuum model proposed by the present authors for macroscopic solidification transport phenomena and macrosegregation formation was extended to account for the effect of any incomplete solid back diffusion through a microscopic dendrite solidification model. A generalized coefficient for the solid back diffusion was proposed by the present microscopic/macroscopic model, which includes the growing dendrite dimension, the parameters for the dendrite geometry, the solidification rate and partition coefficient etc besides the solid diffusivity.Numerical simulation of macrosegregations in a horizontal directionally soliditied A1-4.4Cu ingot with assumed different solid diffusivities of the copper solute was performed using the extended continuum model. The computation results show that the variation of the solid back diffusion can evidently influence the macrocomposition distribution in the soliditied ingot, and the greater the solid solute diffusivity, the lighter the macrosegregation seventy.
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    THE EFFECT OF APPLIED STRESS ORIENTATION ON THE HIGH TEMPERATURE CREEP BEHAIOUR OF DIRECTIONALLY SOLIDIFIED NICKEL BASE SUPERALLOY
    YUAN Chao ; GUO Jianting ; WANG Tieli ; YANG Hongcai ; WANG Shuhe ;ZHANG Hao (Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)(Materials and Metallurgy School; Northeastern University; Shenyang 110006)
    Acta Metall Sin, 1998, 34 (7): 689-695. 
    Abstract   PDF (2443KB) ( 622 )
    The effect of applied stress orientation on the creep and fracture behaviour of a directionally solidified nickel base superalloy at 980 ℃ in the stress range of 130 - 190 MPa has been studied. The results show that the creep curves of three orientation specimens, in which the grain boundaries are oriented longitudinally, transversely, and 45° to the applied stress axis, have the same shape. In terms of Dorn creep law, three orientation specimens have same creep mechanism, which is controlled by the dislocation climb process. The strain to fracture in longitudinal specimens is much higher than that in transverse and inclined specimens, the reason is the change of creep fracture mechanism from the transgranular to intergranular failure mode.
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    COMPARISON BETWEEN CYCLIC DEFORMATION BEHAVIORS OF NON-ISOAXIAL COPPER TRICRYSTAL AND BICRVSTAL
    JIA Weiping; LI Shouxin; WANG Zhongguang; LI Xiaowu; LI Guangyi(State Key Laboratory for Fatigue and Fracture of Materials; Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)
    Acta Metall Sin, 1998, 34 (7): 696-704. 
    Abstract   PDF (3545KB) ( 621 )
    The cyclic hardening and saturation behaviors of copper tricrystal and bicrystal were investigated by using successively increasing amplitude method. The results show that, to the inclined grain boundary bicrystal with single slip components, the cyclic stress strain curve (CSSC) ealsts a plateau or quasi-plateau region, while the CSSC of tricrystal shows no plateau.Observation of surface morphologies indicated that owing to the strain incompatibility of three grains, at lower strain amplitude the triple junction retards obviously the primary slip in grains and makes deformation near it smaller than that near bicrystal junction. The eastness of crack initiation at the same triple junction is closely related to loading direction.
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    THE RELATIONSHIP BETWEEN PLASTIC DISSIPATED ENERGY, FRACTAL DIMENSION AND FATIGUE- LIFETIME OF ZIRCONIUM AND ZIRCALOY-4
    XIAO Lin; GU Haicheng(State Key Laboratory for Mechanical Behaviour of Materials; Xi'an Jiaotong Universityl Xi'an 710049)
    Acta Metall Sin, 1998, 34 (7): 705-712. 
    Abstract   PDF (698KB) ( 618 )
    Low cycle fatigue lifetime curves of zirconium and zircaloy-4 at room temperature and 400 ℃ were measured, respectively. Cyclic plastic dissipated energy and fractal dimension of fracture surfaces are selected as damage variable to evaluate the fatigue lifetime. The accumulated formula of plastic dissipated energy is established on the basis of considering cyclic deformation character of zirconium and zircaloy-4. The test results indicate that the relationship between cyclic plastic dissipated energy and fatigue lifetime fits power law. Fractal analysis of fracture surface shows that the relationship between fractal dimension and fatigue lifetime can be also expressed as power law. An empirical formula describing the relationship between dissipated energy, fractal dimension and fatigue lifetime, D ≈ 0.027 lnN f + 1.099 ≈0.120 lnWpf- 0.025, is obtained, and their physical mechanism is discussed thermodynamically.
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    MICROYIELD BEHAVIOURS OF SiCp/2024A1 COMPOSITE AND 2024A1 ALLOY
    ZHANG Fan; LI Xiaocui; JIN Cheng; QIU Jiming; HU Zhengjun(The State Key Laboratory of Metal Matrix Composites; Shanghai Jiaotong University; Shanghai 200030)
    Acta Metall Sin, 1998, 34 (7): 713-718. 
    Abstract   PDF (1285KB) ( 702 )
    microyield behaviours of SiCp/2024A1 composite and its matrix alloy were investigated in this work. The results indicated that the composite showed quite different strain relaxation before" general" microyielding and its microyield mechanism was not same as that of the matrix alloy. It was also showed that during aging treatment, the microyield strengths of both composite and matrix alloy were dependent to precipitation of the strengthening phase,S', and exhibited a peak aging trend. Thermal cycling treatment could improve the microyield strength of the matrix alloy, but lower the microyield strength of the composite.
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    MECHANICAL PROPERTIES OF QUASI-SOLID Al-Cu ALLOY AND INFLUENCE OF TRACE ELEMENTS DUING SOLIDIFICAfION
    WEI Xiaowei; ZENG Ming; WU Xueting(Department of Materials Science and Engineering; Sichuan Institute of Industry; Chengdu 611744)
    Acta Metall Sin, 1998, 34 (7): 719-724. 
    Abstract   PDF (1575KB) ( 845 )
    The increase rate of strength, range of quasi-solid and failure strain of quasi-solid A1-5%Cu alloy during soliamcation are investigated with special apparatus. The influence of B,Ti, salt-refiner and mischmetal on the mechanical properties is also studied. Results obtained show that the range of quasi-solid is equivalent to the range of hot brittleness, and B, Ti as well as mischmetal all lower the quasi-solidus and enhance the strength around solidus and the increase rate of strength of the alloy. The effect of mischmetal is greater than that of B, Ti.Salt-refiner decreases the strength of quasi-solid and the failure strain of the alloy.
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    THE SECOND PHASE STRENGTHENING AND TOUGHENING EFFECT IN HIGH HARDNESS STEEL WELDS
    REN Dengyi; DONG Jian; ZHANG Yuanbin(Colledge of Materials Science and Engineering; Shandong University of Technology; Jinan 250061)
    Acta Metall Sin, 1998, 34 (7): 725-730. 
    Abstract   PDF (2053KB) ( 666 )
    The feature of carbide and microstructure of matrix and their effect on toughness are studied in high carbon welds where Nb, Ti, V, Zr, RE coedest. Test results indicated that the synthetic effect of the multiple strong carbide elements and RE element leads to precipitate fine carbides before solidification of welds. The main mechanism of precipitating carbides from liquid phase is multiple direction precipitating at the same core. The contents of strong carbide elements and carbon element accorded with the fixed-ratio theorem, that made the matrix " carbon poor", and formed low carbon martensite. A weld with high hardness and good thoughness was achieved.
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    APPLICATION OF CALCIA CRUCIBLE TO MELT HIGH PURITY ALLOYS
    SUN Changjie(Technical Center of Tangshan Iron & Steel Group Co. Ltd; Tangshan 063016)xING Jiping(Department of Chemical Engineering; Tangshan University; Tangshan 063001)
    Acta Metall Sin, 1998, 34 (7): 731-734. 
    Abstract   PDF (366KB) ( 715 )
    A new process melting the high purity alloys by using calcia crucible has been developed. The calcia crucible with excellent refining and keeping temperature properties is made successfully in 10 kg vacutun induction furnace. The purified experiment of pure iron and GH169 alloys was carried out in vacuum induction furnace and adding Al, La and Ca as cleaner. In 10 kg vacuum induction furnace and tinder condition of 1.5 - 2.5 Pa vacuum and 1400 ℃,the contents of N, O and S in alloy GH169 are reduced to less than 20×10-4%, 20×10-4% and ×10-4% from 70×10-4%, 33×10-4% and 35× 10-4%, respectively. The refilling mechanism of calcia crucible was discussed.
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    CHARACTERIZATION OF A MULTIFILAMENTARY Nb3Al WIRE FABRICATED BY RAPIDLY HEATING AND RAPIDLY QUENCHING METHOD
    MAO Dali(The Public Laboratory of State Education Commission for High Temperature Materials and High Temperature Tests; Department of Materials Science; Shanghai Jiaotong University; Shanghai 200030)ITOH Kihao;WADA Hitoshi(National Research Institute for Metals; Tsukuba; Ibaraki 305; Japan)
    Acta Metall Sin, 1998, 34 (7): 735-741. 
    Abstract   PDF (1346KB) ( 530 )
    A rapidly heating and rapidly quenching method for the manufacturing of multifilamentary Nb3Al wire was introduced, which can obtained Nb3Al with the near stoichiometric composition. After annealing at 800 ℃ for 2, 12 and 96 h, critical temperature Tc of the samples measured by four probe method is 17 K. Critical curreds Ic was measured in the function of temperature and applied field in a split pair magnet. The relationship of normalized pinning force vs applied field follows simple Kramer equation. Grain boundaries were most probable pinning source for the magnetic line of force. The obtained upper critical field Bc2 existed a linear relation with the temperature. A critical surface of Ic - T - B was also plotted from the measurement of critical current.
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    CONSISTENCY(OR SIMILARITY) OF THERMODYNAMIC PROPERTIES OF METALLURGICAL MELTS WITH THEIR PHASE DIAGRAMS
    ZHANG Jian(Metallurgical Engineering School; University of Science and Technology Beijing; Beijing 100083)
    Acta Metall Sin, 1998, 34 (7): 742-752. 
    Abstract   PDF (952KB) ( 762 )
    After combining investigation of thermodynamic properties of binary metallic melts, molten slags, molten salts and mattes with their phase diagrams, it has been found that in case of identical or similar phase diagrams, the calculating models of mass action concentrations of different metallurgical melts are identical (consistency) in the major cases, and similar (similarity)in the minor cases.
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    THERMODYNAMIC DESCRIPTION OF MULTICOMPONENT SYSTEMS BY INTERACTION MRAMETERS
    MA Zhongting; J. OHSER; D. JANKE(The Institute of Iron and Steel Technology; Freiberg University of Mining and Technology; Freiberg; Germany)
    Acta Metall Sin, 1998, 34 (7): 753-762. 
    Abstract   PDF (773KB) ( 761 )
    Novel analytical expressions for calculating activity coefficients of solvent and solutes are given in the present study which is based on the MacLaurin infinite series. These new expressions have thermodynamic consistency and more accurancy in comparison with traditional used Wagner's ε formalism. The another advantage of this treatment is found in a rather small influence of the higher order interaction parameters upon the properties of the studied systems.
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    REACTION MECHANISM AND DISTRIBUTION RULE OF SILICON IN MELTING GASIFIER
    LU Qing(Department of Metallurgy; Hebei Institute of Technology; Tangshan 063009)
    Acta Metall Sin, 1998, 34 (7): 763-768. 
    Abstract   PDF (1260KB) ( 421 )
    Smelting process of melting gasifier is simulated. According to chemical thermodynamics, source of [Si] in furnace, the reaction mechanism, the rule of distribution and factors related to [Si] content were discussed.
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    THE PREPARATION OF IRON CARBIDE BY GAS REDUCTION
    WANG Guanghui; JIANG Maofa; WANG Wenzhong(Department of Ferrous Metallurgy; Northeastern Universityt Shenyang 110006)
    Acta Metall Sin, 1998, 34 (7): 769-773. 
    Abstract   PDF (406KB) ( 552 )
    Influences of temperature and composition of CO-CO2-H2 gas mixtures on the formation rate of iron carbide during iron ore reduction are discussed through thermodynamic calculation and corresponding experiments. Based on the examination of the composition of reduction products, the feasibility is confirmed for the preparation of iron carbide by CO-CO2-H2gases reducing iron ore.
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    COPRECIPITATION PROCESS OF DOPED ZINC OXIDE POWDERS AND VOLTAGE SENSITIVE CHARACTERISTICS OF THE VARISTOR
    HUANG Kelong; PENG Bin; PAN Chunyue(Department of Chemistery;Central South University of Technology; Changsha 410083)
    Acta Metall Sin, 1998, 34 (7): 774-778. 
    Abstract   PDF (1021KB) ( 667 )
    ZnO voltage-sensitive ceramics doped with some metal chides were prepared by coprecipitation. The optimal preparing condition was determined as follows: reaction pH value of 6.90 ± 0.05, calcining temperature of 500 ℃, sintering temperature of 1100 ℃. Varistor ceramics made from coprecipitating powders showed improved electrical properties and stability to temperature. The powders were also examined by SEM, IR and XRD etc. The mechanism of zinc oxide ceramics showing the voltage sensitive characteristic has been discussed to some extent.
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    STUDY ON THE INTERMCIAL MORPHOLOGY AND STRUCTURE OF DIAMOND THIN FILM-CEMENTED CARBIDE SUBSTRATE
    KUANG Tongchun; LIU Zhengyi(Department of Mechanical and Electric Engineering; South China University of Technology; Guangzhou 510641)DAI Mingjiang; ZHOU Kesong; WANG Dezheng(Guangzhou Research Institute of Non-Ferrous Metals; Guangzhou 510651)
    Acta Metall Sin, 1998, 34 (7): 779-784. 
    Abstract   PDF (3427KB) ( 630 )
    The cross-sectional morphologies and microstructures of CVD diamond thin films synthesized onto the cobalt cemented tungsten carbide (YGS) substrate have been observed by means of SEM and TEM. The results show that after chemically cobalt-removed and plasma-etching decarbonized treatments the sequence of cross-sectional structure is as follows:diamond thin film, graphite carbon thin film, small WC grains layer; retained decarbonized layer (W and η phases), residual porous layer, YG8 cemented carbide substrate. Methane concentrations have obvious influences on the formation and thickness of above-mentioned layers.
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