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

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    , Volume 26 Issue 4 Previous Issue    Next Issue
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    CHARACTER OF CARBON DEPLETED REGIONS IN UNDERCOOLED AUSTENITE AND THERMODYNAMICS OF BAINITIC TRANSFORMATION
    YANG Quanmin;KANG Mokuang Northwestern Polytechnical University; Xi'an Department of Material Science;Zhejiang Uniyersity;Hangzhou 310027
    Acta Metall Sin, 1990, 26 (4): 5-11. 
    Abstract   PDF (548KB) ( 534 )
    The chemical driving forces for the phase transformation from auste-nite in three different carbon depleted regions into ferrite with identical composi-tion have been derived respectively. The starting temperature of bainitic transform-ation, B_s, has been also calculated according to the shearing mechanism of baini-tic transformation in the carbon depleted regions of austenite. The maximum driv-ing forces for the phase transformation in both 3%Cr containing and CrMo steelsmay be obtained at temperature B_s. It was shown that the proposal of the shearingmechanism of the bainitic transformation is thermodynamically possible.
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    PULSED MAGNETIC FIELD-INDUCED MARTENSITIC TRANSFORMATION IN AN Fe-21Ni-4Mn ALLOY
    SUN Enxi;YANG Dazhi;XU Zuyao;YANG Fumiug;ZHAO Ruwen Dalian Institute of Railway Dalian University of Technology Shanghai Jiaotong University Institute of Physics; Academia Sinica; Beijing professor
    Acta Metall Sin, 1990, 26 (4): 12-17. 
    Abstract   PDF (896KB) ( 451 )
    Magnetic field-induced martensitic transformation in an Fe-2lNi-4Mn(wt-%) alloy with isothermal and athermal martensite transformation kinetics hasbeen studied by magnetization measurement and optical microscopy, applying apulsed ultrahigh magnetic field. The following results were found: a magnetic fieldhigher than a critical one is needed to induce the martensitic transformation aboveM_s. The critical magnetic field increases with increasing temperature, and whenplotted against the temporature difference from M_s, it lies on a straight line notpassing through the origin. This result and thermodynamical analysis suggest thatpulsed magnetic field strongly promotes the athermal martensitic transformation andrestrains tht isothermal one. The influence of magnetic field on martensitic trans-formation in the present Fe-Ni-Mn alloy is mainly due to Zeeman effect. Theentropy change for athermal transformation at M_s, S_Ms~at is obtained to be 4.13J/mol.K. The amount of magnetic field-induced martensites increases linearly withthe maximum strength of pulsed magnetic field. Lath, plate and butterfly martensi-tes are formed under magnetic field.
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    COMPUTER SIMULATION OF EFFECT OF ORIENTATION DIFFERENCE ON MECHANICAL PROPERTIES OF BICRYSTALLINE SPECIMENS
    WEI Chao;QIAN Rengen;LIN Shi;XIAO Jimei University of Science and Technology Beijing Department of mathematics and mechanics; University of Science and Technology Beijing; Beijing 100083
    Acta Metall Sin, 1990, 26 (4): 18-21. 
    Abstract   PDF (324KB) ( 524 )
    By means of the crystalline elastic-plastic finite element method, theeffect of orientation difference on the mechanical properties and stress distributionof the bicrystalline specimens of Al were simulated by computer.
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    GROWTH OF Bi(Pb)-Sr-Ca-Cu-O SUPERCONDUCTING WHISKERS
    GE Yunlong;LIU Qingmin;ZHOU Jing;CHANG Xin;HU Zhuangqi Institute of Metal Research; Academia Sinica; Shenyang associate professor
    Acta Metall Sin, 1990, 26 (4): 22-26. 
    Abstract   PDF (2633KB) ( 788 )
    Amorphous Bi(Pb)-Sr-Ca-Cu-O strips of (1112) and (2212) types weremade by non-equilibrium solidification of melt-quenching method. On the surfaceof glassy strip, the flexible (2212) superconducting whiskers have been obtained at840-850℃ in a stream of O_2 for a long time. The growth and feature of supercon-ducting whiskers were studied in deteil.
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    INFLUENCE OF GRAIN SIZE ON STRENGTH AND HYDROGEN INDUCED CRACKING OF DUPLEX STAINLESS STEELS
    HE Jianhong;TANG Xiangyun;CHEN Nanping Huazhong University of Science and Technology; Wuhan Tsinghua University; Beijing Department of Materials Science and Engineering; Huazhong University of Science and Technology; Wuhan 430074
    Acta Metall Sin, 1990, 26 (4): 27-31. 
    Abstract   PDF (1096KB) ( 754 )
    The relation between grain size and strength of the duplex stainlesssteels and the influence of grain size on the properties of hydrogen induced crack-ing in these steels have been investigated. The Hall-Petch relation between grainsize and strength of the duplex stainless steels is also followed. The susceptibilityto hydrogen induced cracking of the present steels increases with increasing grainsize.
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    EFFECTS OF AGING TEMPERATURE AND TIME ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF GH35A SUPERALLOY
    GUO Shouren;LU Dezhong;GUO Jianting;WU Xi Institute of Metal Research; Academia Sinica; Shenyang Fushun Steel Works associate professor
    Acta Metall Sin, 1990, 26 (4): 32-39. 
    Abstract   PDF (1484KB) ( 608 )
    The mechanical properties and microstructures of an Fe-base GH35Asuperalloy have been examined during aging at 650--750℃ for 100--10000h. Thetensile strength of the alloy changes no more with aging temperature and time atroom temperature, but the ductility and impact toughness at room temperature, aswell as stress-rupture life up to 700℃ decrease slowly during aging even till10000h. And the initiation time to worsen its properties becomes shorter as theaging temperature increasing. The mechanical properties of the alloy are found tobe mainly varied with the formation, morphology, distribution and character of theσ-phase precipitation.
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    PRECIPITATION HARDENING OF ELINVAR ALLOY
    LIU Zhiguo;CHEN Yong;CAO Yanni;ZHU Zhengsheng Nanjing University Shanxi Iron and Steel Institute; Xi'an professor;Department of Physics;Nanjing University;Nanjing 210008
    Acta Metall Sin, 1990, 26 (4): 40-44. 
    Abstract   PDF (601KB) ( 537 )
    The microstructural evolution and precipitation hardening of an Elin-var alloy doped with Ti and Al during isothermal aging at 700℃ have been inves-tigated by atom probe field ion microscopy and microhardness measurement. Theγ′ precipitates formed are spherical and coherent with the matrix. The chemical com-position of the precipitates are (Ni_(0.53)Fe_(0.47))_3(Ti_(0.6)Al_(0.4)). During aging, a Lifshitz-Wanger type dissolution and coarsening reaction of the precipitates has been obse-rved. The hardness of the material varies with the aging time and reaches maxi-mum when the average diameter of the precipitates was about 11 nm.
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    BEHAVIOUR OF AUSTENITE UNDER IMPACT ABRASION
    WANG Huaming;ZHANG Qing;SHAO Hesheng Institute of Metal Research; Academia Sinica; Shenyang Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Beijing Beijing Graduate School; China University of Mining and Technology
    Acta Metall Sin, 1990, 26 (4): 45-49. 
    Abstract   PDF (1165KB) ( 434 )
    On the basis of the experimental results of resistance to impact-abra-sion of a newly developed austenite-bainitic ferrite dual-phase high carbon lowalloy steel with high strength, toughness and strain-hardening ability, discussionwas made on the behaviour of austenite under impact abrasion. It was found thata favourable austenite resisting to impact abrasion is only more stable and fine onewith certain high dispersion in the matrix of high strength and proper toughnesssteel. But the mechanically poor stable and coarse austenite in quantity, especiallydistributed as continuous matrix, is extremly harmful to impact abrasion resistance.
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    A PHENOMENOLOGICAL MODEL FOR GRAIN BOUNDARY PRECIPITATION STRENGTHENING IN HIGH TEMPERATURE CREEP
    LI Peien;ZHANG Junshan;JIN Junze Dalian University of Technology Department of Materials Engineering;Dalian University of Technology; Dalian 116024
    Acta Metall Sin, 1990, 26 (4): 50-53. 
    Abstract   PDF (351KB) ( 506 )
    Considering the effect of intergranular carbides density, a modifiedmodel has been proposed to try to suit any common case of the fraction of theintergranular carbides to the total grain boundary less than 1, on the basis of theprevious model for the grain boundary precipitation strengthening. This modifiedmodel may be available to predict the changes in creep rate and its stress and tem-perature dependence of alloys by intergranular carbides.
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    CRYOGENIC MECHANICAL BEHAVIOUR OF MARAGING STEEL CONTAINING HYDROGEN
    LIU Zhonghao;CHEN Lian Institute of Metal Research; Academia Sinica; Shenyang research assistant;Institute of Metal Research;Academia Sinica; Shenyang 110015
    Acta Metall Sin, 1990, 26 (4): 54-61. 
    Abstract   PDF (1779KB) ( 575 )
    Within the range of 77 to 295 K, the strength and plasticity of 18Nimaraging steel containing hydrogen increase with the decreasing temperature anddecrease with the increasing hydrogen content. The susceptibility to hydrogen em-brittlement of the maraged specimens is superior to solid solution treated ones evendown to 77K. The dislocations after plastically deformed will be tangled into cellswhich reduce themself in size as decreasing temperature and coarsen as increasinghydrogen concentration. No cryogenic deformation twin was found. The tensile frac-ture surfaces of the solution and maraged specimens containing 5.90 ppm hydrogenunder 295--223 K are revealed as quasi-cleavage and intergranular features respec-tively and as transgranular one at all under other experimental conditions. Theinfluence of hydrogen on the mechanical behaviour of steel and the mechanism ifhydrogen induced deformation and fracture were also discussed.
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    THERMAL FATIGUE CRACK IN 5CrMnMo STEEL
    HE Shiyu;LI Ying;LIU Jianhong Harbin Institute of Technology Faculty of Metal;Harbin Institute of Technology; Harbin
    Acta Metall Sin, 1990, 26 (4): 62-65. 
    Abstract   PDF (1856KB) ( 644 )
    The thermal fatigue behaviour of 5CrMnMo steel after various heattreatments has been examined by means of Coffin-model and self-strained thermalfatigue testing machines, The thermal fatigue crack initiation and propagation havebeen observed under SEM and TEM. The majority of thermal fatigue crack was in-itiated through the grain boundaries for the quenched steel and through the breakof interface between carbide and matrix or crack of grain boundary for quenchedand tempered one. The thermal fatigue crack propagated mainly through the break-age of the interface of carbide and grain boundaries for either quenched or quen-ched and tempered steel.
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    EFFECT OF NON-PROPORTIONAL OVERLOADINGON FATIGUE CRACK GROWTH
    GAO Hua;CHEN Youxuan;LI Ming;CHEN Dehai Shanghai University of Engineering Science Shanghai Dalong Machinery associate professor;Department of Materials;Shanghai University of Engineering Science;Shanghai 200051
    Acta Metall Sin, 1990, 26 (4): 66-72. 
    Abstract   PDF (707KB) ( 464 )
    The effects of proportional and non-proportional overloading on modeⅠ fatigue crack growth have been studied, and the influences of crack tip plasticzone, crack tip blunting as well as crack closure were discussed. The proportional(mode Ⅰ) overloading may cause more serious crack growth retardation than non-proportional (mixed mode) overloading. Therefore, for estimating fatigue life ofengineering structures to simplify a real overload which may often be non-propor-tional as a proportional one is not always safe.
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    MICROSTRUCTURE AND FATIGUE PROPERTIES OF RAIL STEELS
    ZHOU Qingyue;ZHOU Chenguang (China Academy of Railway Sciences; Beijing Engineer;Metal and Chemistry Research Institute;China Academy of Railway Sciences;Beijing 100081
    Acta Metall Sin, 1990, 26 (4): 73-78. 
    Abstract   PDF (484KB) ( 518 )
    The subcritical propagation of fatigue crack and the microstructure ofthe rail steels with relation to stress ratio have been studied. The effect of micros-tructure of the rail steels on their fatigue lives has been discussed preliminarily.
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    INTERFACE MORPHOLOGIES AND MICROSTRUCTURES DURING DENDRITE-TO-CELL TRANSITION AT HIGH GROWTH RATE
    LI Jianguo;MAO Xiemin;FU Hengzhi Northwestern Polytechnical University; Xi'an lecturer;Faculty No.403;Northwestern Polytechnical University; Xi'an 710072
    Acta Metall Sin, 1990, 26 (4): 79-82. 
    Abstract   PDF (1251KB) ( 471 )
    The interface morphologies and microstructures of the directionally solidifiedNi-5wt-%Cu alloy during the dendrite-to-cell transition at high growth rate have been investi-gated by a newly developed equipment for directional solidification. The results show in thevicinity of dendrite-to-cell transition, the well developed sidebranches become shrivelled withthe increase of growth rate and disappear at the dendrite-to-cell transition, and at the sametime the primary spacing decreases. Moreover, the length of mushy zone decreases greatlyduring the dendrite-to-cell transition. Cells obtained at high growth rate have much in commonwith those at low growth rate, but with much smaller cell spacing.
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    INFLUENCE OF ELECTROMAGNETIC STIRRING ON DENDRITIC STRUCTURE AND MECHANICAL PROPERTIES OF LOW SULPHUR STEEL
    HU Hanqi;ZHENG Riqi University of Science and Technology Beijing professor;Faculty of Casting;University of Science and Technology Beijing;Beijing 100083
    Acta Metall Sin, 1990, 26 (4): 83-86. 
    Abstract   PDF (1074KB) ( 574 )
    The melt flow induced by the electromagnetic stirring in the molten low sulphursteel may fine the original austenite grains, but widen the secondary dendritic arm spacings.As a result, the ultimate tensile strength of the steel will be improved and the reduction ofarea will be remarkably decreased. The microalloying by an addition of Ce may retard the un-favourable effect of the electromagnetic stirring.
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    EXTRACTION OF Zn AND Cd FROM CHLORIDE SOLUTIONS BY TRI-n-BUTYL PHOSPHATE
    JIANG Tao;SU Yuanfu East China University of Chemical Technology; Shanghai
    Acta Metall Sin, 1990, 26 (4): 87-92. 
    Abstract   PDF (533KB) ( 712 )
    Studies have been made on the extraction of Zn and Cd by TBP (tri-n-butyl phosphate) from diluent HCl solutions of NaCl. The experiments show thatthe species extracted from dilueat HCl solutions of NaCl appear to be predominatelyZnCl_2·2TBP and CdCl_2·2TBP. For Cd, at lower acidities, anionic complexes of thetype HCdCl_3 are also extracted. As the acidity is increased, the type H_2CdCl_4 ap-pears to be predominate complexes in organic phase. For Zn, the acido-complexes ofthe type HZnCl_3 appear in organic phase after the acidity of solutions reachs a cer-tain value ([HCl]>0.1 mol/L). Furthermore, the ultraviolet absorption spectra ofboth aqueous and organic phases have been studied, and the infrared spectra of theorganic phases have been examined. The extraction mechanism and temperaturedependence are also discussed.
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    KINETICS OF COPPER EXTRACTION BY N530-HEPTANE
    LIU Jincai;LU Jiufang Department of Chemical Engineering; Tsinghua University; Beijing Department of Chemical Engineering; Tsinghua University;Beijing 100084
    Acta Metall Sin, 1990, 26 (4): 93-97. 
    Abstract   PDF (429KB) ( 471 )
    The activity coefficieni of each compound in H_2SO_4-CuSO_4 solutionwas calculated by applying the Pitzer's equation and 6 Pitzer's mixing parametersθ and ψ were evaluated. The change of the activities of the metallic ions duringextraction was examined. The interfacial tension of the system was also measuredby drop weight method. The interfacial excesses of all compounds were calculatedfrom the interfacial tension equation which is expressed in the terms of activities.The results show that H~+ and Cu~(2+) are positive adsorption but CuR_2, (HR)_2, SO_4~(2-)and HSO_4~- are negative adsorption.
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    EQUILIBRIA OF Sr, Ba AND O, S IN LIQUID Fe
    YUE Kexiang;DONG Yuanchi East China Institute of Metallurgy; Maanshan Department of Metallurgy;East China Institute of Metallurgy; Maanshan 243004
    Acta Metall Sin, 1990, 26 (4): 98-102. 
    Abstract   PDF (326KB) ( 510 )
    The reaction equilibrium constants and inieraction coefficients of SrO,Ba-O, Sr-S and Ba-S in liquid Fe at 1570℃ have been determined as follows:K_(SrO)=1.897×10~(-7) e_O~(Sr)=-43.8 e_(Sr)~O=-240.0K_(BaO)=8.204×10~(-8) e_O~(Ba)=-98.0 e_(Ba)~O=-841.2K_(SrS)=8.356×10~(-7) e_S~(Sr)=-3.9 e_(Sr)~S=-10.6K_(BaS)=4.083×10~(-7) e_S~(Ba)=-3.5 e_(Ba)~S=-14.9
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    DISSOLUTION BEHAVIOURS OF La IN KCl-NaCl AND LaCl_3-KCo-NaCl MELTS
    GUO Chuntai;FENG Li;DU Senlin;YANG Zhongbao;TANG Dingxiang Changchun Institute of Applied Chemistry; Laboratory of Rare Earth Chemistry and Physics; Academia Sinica Lab.No.22;Changchun Institute of Applied Chemistry; Academia Sinica;Changchun 130022
    Acta Metall Sin, 1990, 26 (4): 103-107. 
    Abstract   PDF (382KB) ( 548 )
    The dissolution behaviours of La in KCl-NaCl and LaCl_3-KCl-NaClmelts have been studied by means of the see-through cell, cyclic voltammetry andEHMO of quantum chemistry. The La dissolved in KCl-NaCl melt is found to be ina metallic state, and dissolved in LaCl_3-KCl-NaCl melt ionized into La~(2+) which mayreact furthermore with surrounding La~(3+) to form atom cluster La_m~(n+).
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    0412-1961
    CALCULATION OF THERMODYNAMIC PROPERTIES OF In-Bi-Tl TERNARY ALLOYS
    Acta Metall Sin, 1990, 26 (4): 108-112. 
    Abstract   PDF (360KB) ( 531 )
    ZHENG Minhui;KOZUKA Zensaku University of Science and Technology Beijing Faculty of Engineering, Osaka University Department of Physical Chemistry,University of Science and Technology Beijing, Beijing 100083
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    EFFECT OF PRE-ANNEALING ON CRYSTALLIZATION KINETICS OF Cu-Ti GLASS
    MIAO Weifang;WANG Jingtang;LI Shuling Institute of Metal Research; Academia Sinica; Shenyang research assistant
    Acta Metall Sin, 1990, 26 (4): 113-118. 
    Abstract   PDF (873KB) ( 495 )
    The crystallizatiin kinetics of the Cu_(40)Ti_(60) glasses, either as-quenchedor pre-annealed, has been studied by differential scanning calorimetery. The crystal-lization temperature, activation energy for crystallization and Avrami exponent werefound to be lowered by pre-annealing. Both activation energies of nucleation andgrowth of the amorphous Cu_(40)Ti_(60) alloys were obtained on the basis of experimen-tal results and theoretical analysis.
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    MAGNETIC MOMENT, CURIE TEMPERATURE AND SPIN WAVE EXCITATION FOR AMORPHOUS Fe_(90-x) Si_x Zr_(10) ALLOYS
    SHEN Baogen;ZHANG Zhiying;GUO Huiqun;ZHAO Jiangao;GU Benxi Institute of Physics; Academia Sinica; Beijing Department of Physics; Nanjing University research assistant
    Acta Metall Sin, 1990, 26 (4): 119-124. 
    Abstract   PDF (527KB) ( 575 )
    The magnetization curves at 1.5K and thermomagnetization curves forthe amorphous Fe_(90-x)Si_(x)Zr_(10) (x=0, 4,7 or 10) alloys prepared by the drum spinningtechnique bave been measured with an extracting sample magnetometer. It is obtain-ed that the average magnetic moment, μ, per magnetic atom and Curie temperature,T_c, in the amorphous FeSiZr alloys increase with increasing Si content. The μ andT_c are found to be quite small, compared with amorphous FeSiB alloys. This unu-sual behaviour is suggested to be due to the presence of the Fe-Fe antiferromagneticinteractions. The temperature dependence of magnetization at low temperature is inaccordance with Bloch T~(3/2) law. Calculation shows that the spin wave stiffnessconstant, D, increases with increasing Si conteat from 0.37 meV·nm~2 for x=0 to0.538 meV·nm~2 for x=10. The values of 〈r~2〉 indicate that the range of the exchangeinteraction is roughly the mean atomic distance of nearest neighbours.
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    NUMERICAL SIMULATION OF HEAT, MASS AND MOMENTUM TRANSFERS IN METALLIC INGOTS AND PRE-DICTION OF MACROSEGREGATION
    XU Daming;LI Qingchun Harbin Institute of Technology associate professor;Faculty of Casting;Harbin Institute of Technology; Harbin 150006
    Acta Metall Sin, 1990, 26 (4): 125-129. 
    Abstract   PDF (435KB) ( 569 )
    A continuum model and numerical method were established for des-cription of heat, mass and momentum transfers as well as macrosegregation forma-tions in metallic alloy ingots. Numerical simulation of temperature, composition andliquid flow fields during solidification were made on an Al-4.5%Cu ingot. Themodel and numerical method were verified through two experiments.
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    BEHAVIOUR OF Ti IN AS-CAST MEDIUM MANGANESE AUSTENITIC STEEL
    JIANG Qichuan;LI Zhang;WANG Shoushi;HE Zhenming Jilin University of Technology; Changchun associate professor;Faculty of foundary Jilin University of Technology;Changchun 130025
    Acta Metall Sin, 1990, 26 (4): 130-134. 
    Abstract   PDF (1538KB) ( 530 )
    The majority of Ti is found to be preferentially precipitated in theform of TiC from medium manganese steel melt. The TiC may contribute to theheterogeneous nuclei of fine austenite crystallization, to the retardation of disloca-tion movement, as well as, to pile-up and proliferation of dislocations, thus, thematrix of the as-cast austenitic medium manganese steel will be effectively strength-ened. It was also found that the TiC can be acted as the heterogeneous nuclei ofthe nodular eutectic carbides formation and caused the dispersion of an abundanceof the carbides in the interstices between austenite dendrite arms.
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    CRYSTALLIZATION AND FRACTAL STRUCTURE OF MOLYBDENA SINGLE CRYSTALS
    ZHANG Jizhong;LI Hengde Tsinghua University; Beijing Lecturer;Department of Materials Science and Engineering; Tsinghua University; Beijing 100084
    Acta Metall Sin, 1990, 26 (4): 135-138. 
    Abstract   PDF (975KB) ( 556 )
    During a molybdenum metal sheet heated properly at 900℃ in an oxi-dizing ambient, the Mo_5O_(14) single crystals will grow. The size of the most coarsesingle crystals is up to 15×1.1 mm and 310 nm thick as measured by Rutherfordback scattering spectrometry. Some fractal structure consisting of many molybdenawhiskers are observed after heating at 750℃. An approach to explain the crystalgrowth and fractal structure has been discussed.
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    NETWORK FRACTAL AND ANNEALING-INDUCED AGGREGATION OF Cu/a-C:H BILAYER FILMS
    ZHANG Renji;WANG Wangdi;HE Daren Tsinghua University Northwest University; Xi'an Department of Mechanical Engineering;Tsinghua University;Beijing 100084
    Acta Metall Sin, 1990, 26 (4): 139-143. 
    Abstract   PDF (902KB) ( 483 )
    The Cu/a--C:H blayer films, grown far from the equilibrium, havethe network fractal structure. Their fractal dimension value D_f=1 .83. An in situdynamic observation of these films under TEM with slowly heating revealed that theinitial network fractal structure was damaged gradually and broken down completelyat 535℃. And as the annealing-induced aggregation developed, the random spreadaggregated gradually, the fractal dimension of the new structure decreased with theincreasing of annealing temperature. Finally, the D_f=1.63 at 850℃. Based on thesurface and interface diffusion model of the metallic atoms, the variation of thestructural character could be explained.
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    FRACTAL DIMENSION OF CAVITIES SHAPE CHANGES DURING SUPERPLASTIC DEFORMATION OF HIGH STRENGTH Al ALLOY 7475
    JIANG Xinggang;CUI Jianzhoug;MA Longxiang Northeast University of Technology; Shenyang Box 317; Northeast University of Technology; Shenyang 110006
    Acta Metall Sin, 1990, 26 (4): 144-147. 
    Abstract   PDF (1418KB) ( 440 )
    The fractal dimension changes of cavities have been determined duringsuperplastic deformation of the high strength Al alloy 7475 with different strain,temperature, strain rate and grain size. The fractal dimension of cavities may in-crease with the increase of strain. It becomes higher as the alloy deformed underthe lower temperature, the greater strain rate and the coarser grain size. The alloywould be approaching to rupture if the fractal dimension of cavities raised to acertain extent.
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    BOUNDARY MICROSTRUCTURE AND MAGNETIC HARDENING OF SINTERED NdFeB MAGNET
    ZHOU Shouzeng;TANG Weizhong;WANG Run University of Science and Technology Beijing associate professor;Department of Materials Science;University of Science and Technology Beijing; Beijing 100083
    Acta Metall Sin, 1990, 26 (4): 148-152. 
    Abstract   PDF (1372KB) ( 815 )
    The boundary microstructure of the sintered alloy Nd_(15.5)Fe_(77)B_(7.5) hasbeen studied by TEM, ASE and SAED. It may distinguish the boundaries into 4types. The first three types remain the same during annealing, and the 4th changesits microstructure remarkably. The 4th type of boundary microstructure is composedof two different regions, i. e., the central Nd-rich phase and the epitaxial layer ofthe Nd_2Fe_(14)B grains. Owing to the atomic diffusion and other types of masstransport,magnetic hardening occurred in the epitaxial layers, thus the coercivity of the alloywill be improved.
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    LIQUIDUS OF Au-Cu-Si SYSTEM
    LIU Shuqi;YI Tao Department of Chemistry; Peking University; Beijing
    Acta Metall Sin, 1990, 26 (4): 153-154. 
    Abstract   PDF (103KB) ( 407 )
    The diagram of srstem AU-Cu-Si was constructed from data of 9 internal sectionsby DTA in an atmosphere of dry N_2. The composition of ternary eutectic point melting at337℃ lies in Au(74.7)-Cu(6.1)-Si(19.2) at.-%. The liquidus of the 3 side-binary systems havebeen redetermined.
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    PREDICTION OF MAGNETOCRYSTALLINE ANISOTROPY OF POLYCRYSTALLINE MATERIALS WITH GENERALIZED VECTOR METHOD
    ZUO Liang;WANG Yandong;XU Jiazhen;LIANG Zhide Northeast University of Technology; Shenyang Department of Materials Science and Engineering;Northeast University of Technology; Shenyang 110006
    Acta Metall Sin, 1990, 26 (4): 155-157. 
    Abstract   PDF (275KB) ( 485 )
    The orientation distribution function of the crystallites in a cold-rolled W20non-oriented Si steel sheet was determined for the layers along surface, 1/4 depth and centre, res-pectively, with the generalized vector method. The angular variation of magnetic torque in thesheet plane was quantitatively calculated by extending the theory of magnetic anisotropy to thepolycrystalline materials with no sample symmetry. The values predicted theoretically are wellfit to the magnetic torque plot measured.
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    SUPERPLASTIC DEFORMATION BEHAVIOUR OF SUPERHARD Al ALLOY LC4
    JIANG Xinggang;WU Qingling;CUI Jianzhong;MA Longxiang Northeast University of Technology; Shenyang Department of Metal Working; Northeast University of Technclogy;Shenyang 110006
    Acta Metall Sin, 1990, 26 (4): 158-160. 
    Abstract   PDF (704KB) ( 425 )
    The superplasticity of the high strength and hard Al alloy LC4 was improved toa great extent by modified thermomechanic treatment. Its maximum elongation may be up to2100% under deformation with initial strain rate 8.33×10~(-4)s~(-1) at 510℃. The optical and TEMobservations of the microstructure changes revealed that with thein crease of deformation, the dis-location density increases, the grain grows and the alloy exhibits strain hardening. The excel-lent elongation of the alloy seems due to the increase of grain stability under deformation.
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