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

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    , Volume 30 Issue 21 Previous Issue    Next Issue
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    NUMERICAL SIMULATION OF ALLOY SOLIDIFICATION BY A TWO-PHASE MODEL
    NI Jun; BECKERMANN Christoph(Department of Mechanical Engineering;TheUniversity of Iowa; USA)
    Acta Metall Sin, 1994, 30 (21): 385-392. 
    Abstract   PDF (618KB) ( 561 )
    A two-phase model of the transport phenomena during solidification of alloys is presented that describes The effect of solid transport and liquid convection on macro-segregation and grain structure evolution.The model considers nucleation, thermal and solutal undercooling, and the macro-movement of solid grains, thus combining macro-transport phenomena with the microstructure of the solid.The two-phase model was used in a numerical simulation of solidification of Al-4%Cu equiaxed alloy and representative results are presented.
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    SURFACE AND BULK DEFORMATION NEAR CRACK TIP FOR PURE COPPER UNDER APPLIED ANODIC CURRENT
    WEI Xuejun;LI Jin;ZHOU Xiangyang;KE Wei(Corrosion Scicnce Laboratory; Institute of Corrosion and Protection of Metals; Chinese Academy of Scicnces;Shenyang)
    Acta Metall Sin, 1994, 30 (21): 393-397. 
    Abstract   PDF (352KB) ( 545 )
    The SPI technique was used to investigate the bulk deformation at crack tip in CF process by comparing the crack tip opening displacement(CTOD)of pure copper speci mens in air and in 3.5%NaCl solution with an applied anodic current of 20 mA / cm2.In order to study the difference of anodic current influences on the bulk deformation from and the surface deformation of crack tip,comparative analysis has been carried out by measuring the variations of the surface strain distribution under the same conditions.The experimental results showed that, after applying anodic current,both the plastic zone size and the strain value on the surface near crack tip increased significantly, however, the crack tip opening displacement which reflects the bulk deformation of crack tip only increased a little. It has been shown that the anodic current has no direct influence on internal material at crack tip, but can relieve the surface strain hardening and enhances the crack tip surface deformation significantly.
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    Na_2SO_4 INDUCED HOT CORROSION OF Ni_3Al-Fe INTERMETALLIC COMPOUND AT INTERMEDIATE TEMPERATURES
    ZENG Chaoliu;ZHANG Jianqing;WU Weitao(Corrosion Science Laboratory; Institute of Corrosion and Protection of Metals; Chinese Academy of Sciences ;Shenyang)GUO Jianting (Institute of Metal Research; Chinese Academy of Sciences; Shenyang)
    Acta Metall Sin, 1994, 30 (21): 398-402. 
    Abstract   PDF (441KB) ( 527 )
    Ni_3Al-Fe suffers from catastrophic hot corrosion in the presence of Na_2SO_4 salt film at 700- 820 ℃,which may be ascribed to the formation of eutectic Na_2O-Na_2SO_4 melt produced by the reaction between Fe and Na_2SO_4 . Then, MoO_3, the oxidation product of Mo in the alloy, may also contribute to the electrochemical cathodic reduction, and induce rapid corrosion of Ni_3Al-Fe. The acidic conditions of molten salts established by the SO_3 produced by the reaction between Na_2SO_4 and MoO_3,and the internal sulphidation along substrate alloy may also accelerate the corrosion of Ni_3Al-Fe.
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    INHIBITORY ACTION OF Si ON GROWTH OF INTERFACIAL COMPOUND LAYER DURING HOT-DIP ALUMINIZING
    QIAN Weijiang;GU Wengui(Shanghai Iron and Steel Research Institute)
    Acta Metall Sin, 1994, 30 (21): 403-406. 
    Abstract   PDF (254KB) ( 808 )
    Investigation was made of the structure and composition of the interfacial compound layer of hot-dip aluminized 08F steel strip influenced by an addition of 2 at.-%Si to the hot-dipping bath.Results show that Si enriches the interfacial layer to form compound Fe_2(AlSi)_5.The inhibitory action of Si on the growth of interfacial compound layer may be to fill the vacant sites in Fe_2Al_5, to retard the diffusion of Al and then to reduce the thickness of the layer.
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    MORPHOLOGY OF ION-NITRIDED LAYER AND STRUCTURE OF γ'/ε INTERFACES
    LI Fengzhao;SUN Dongsheng; AO Qing(Shandong University of Technology; Jinan; Laboratory of Atomic Imaging of Solids;Institute of Metal Research;Chinese Academy of Sciences;Shenyang);DAI Jiyan;LI Douxing (Laboratory of Atomic Imaging of solids;Institute of Metal Research;Chinese Academy of Scicnces; Shenyang)
    Acta Metall Sin, 1994, 30 (21): 407-412. 
    Abstract   PDF (442KB) ( 640 )
    The morphologies and the interface structures of ion-nitrided layers, which were obtained by ion nitriding of 35CrMo steel at 550 ℃ for 6 h, were studied with JEM-H800 TEM and JEM 2000 EX II HRTEM. The results show that the structures of theouter layer of ion-nitriding are s (Fe_2-3N)-phase and γ′(Fe_4N)-phase, which are arranged in alternating, ribbon-like strips. There are many various crystal defects, such as vacancies, dislocations,stacking faults,and twins in the internal layer compound——the γ′- phase. The interfaces between ε-phase and γ′ -phase are smooth and straight. Ledges of monoatom layers and multiatom layers were found. The existance of a number of crystal defects is the main reason why ion bombing accelerates the nitriding process.
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    MICROSTRUCTURES OF CRYSTALLITES IN NANOCRYSTALLINE Ni-P ALLOYS
    SUI Manling (Northeastern University;Internattonal Centre for Materials Physics.Chinese Academy of Sciences; Shenyang);LU Ke (National Laboratoryfor RSA Insti tute of Metal Research; Chinese Academy of Sciences;Shenyang)
    Acta Metall Sin, 1994, 30 (21): 413-419. 
    Abstract   PDF (483KB) ( 616 )
    Different grain-sized nanocrystalline Ni-P alloy samples with two crystalline phases of a Ni solid solution and a Ni_3P compound have been synthesized by the crystallization method. By means of the X-ray diffraction technique, variations of the lattice parameters of these two nanophases with the grain size were determined. It was found that the values of the lattice parameters for the two nanophases obviously deviated from the equilibrium data for the corresponding perfect crystals. Analysis of the experimental results indicated that the P concentration in the Ni(P) solution nanophase was much enhanced, being about 10-1 5 times as much as the equilibrium solubility, and a highly supersaturated Ni(P)solid solution formed in the nanophase samples. For the Ni_3P nanophase, an evident lattice distortion was detected, and the lattice distortion of the Ni_3P nanophase increases with a reduction in grain size, which might be oringinated from an enhancement of the vacancies in the nanometer-sized crystallites.
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    PREPARATION OF WHISKER REINFORCED Al-8.5Fe--1.3V-1.7Si COMPOSITES AND APPRAISAL OF REINFORCING BEHAVIOUR FOR VARIOUS WHISKERS
    MA Zongyi;NING Xiaoguang (Laboratory of Atomic Imaging of Solide; Institute of Metal Research;Chinese Academy of Scicnces.Shenyang); PAN fin (Changsha Institute of Technology);LI Jihong;LU Yuxiong;BI Jing(Laboratory of Alomic Imaging of Solids; Institute of Metal Research; Chinese Academy of Sciences; Shenyang)
    Acta Metall Sin, 1994, 30 (21): 420-426. 
    Abstract   PDF (613KB) ( 554 )
    Various whiskers, SiC, Si_3N_4 and Al_(18)B_4O_(33),reinforced Al-8.SFe1 .3V-1 .7Si alloy composites have been prepared by the P / M technique at elevated temperature. The interfacial reaction at the Al_(18)B_4O_(33) interfaces and interfacial reaction product at the SiC or Si_3N_4 interfaces were avoided by employing the alloy matrix without Mg. The strength and modulus of the composites may be obviously improved by incorporating the whiskers in effective sequence:SiC, Si_3N_4 and Al_(18)B_4O_(33). The strength of thess compositeswill linearly drop with increasing temperature, yet their service temperature seems to be 50-100 ℃ higher than that of SiCw / 2024Al composite.
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    INTERFACIAL REACTION IN K_2O·8TiO_(2(w))/ ZL109 COMPOSITE UNDER THERMAL EXPOSURE OR THERMAL CYCLING
    SHEN Baoluo;LI Wei;ZHONG Yumao(Chengdu University of Science and Technology);NING Xiaoguang;LI Jihong;YE Hengqiang(Laboratory of Atomic Imaging of Solids;Institute of Metal Research; Chinese Academy of Sciences;Shenyang)
    Acta Metall Sin, 1994, 30 (21): 427-431. 
    Abstract   PDF (347KB) ( 610 )
    A new phase, Ti_7Al_5Si_12.was found along interfaces between K_2O ·8TiO_2 whisker and ZL109 matrix of the composite under thermal exposure over 500 ℃for 100 h,and it might increase with prolonging the exposure time or thermal cycles.The tharmalexposure is more remarkable to accelerate the interfacial reaction than cycling.A transitionallayer between whiskers and matrix is observed under all conditions.
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    RELATION BETWEEN THERMAL EXPANSION COEFFICIENTS OF C_F / Cu COMPOSITES AND DISTRIBUTION OF FIBRES
    FENG Yi;YING Meifang;WEI Guangxia;ZHANG Xiaojun;WANG Chengfu (Hefei Universily of Technology)
    Acta Metall Sin, 1994, 30 (21): 432-434. 
    Abstract   PDF (150KB) ( 633 )
    Thermal expansion coefficients of the carbon fibre/Cu (C_F/Cu) composites with different modes of C_F orientation and distribution,prepared by hotpressing,wereexamined to be in order:unidirectional longitudinal References | Related Articles | Metrics