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

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    , Volume 32 Issue 5 Previous Issue    Next Issue
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    DISLOCATION FEATURES IN POLYSYNTHETICALLY TWINNED TiAl CRYSTALS AFTER DEFORMATION AT ROOM TEMPERATURE
    LIU Yi; LIN Dongliang; WANG Dening; CHEN Da; CHEN Shipu (Shanghai Jiaotong University; Shanghai 200030;State Key Laboratory of Solid State Microstructures; Nanjing University; Nanjing 210008); LIU Zhiguo; MENG Xiangkang (Nanjing University; Nanjing 210008)(Manuscript received 1995-09-07)
    Acta Metall Sin, 1996, 32 (5): 449-455. 
    Abstract   PDF (520KB) ( 573 )
    The dislocation features in polysynthetically twinned (PST) TiAl crystal deformed at room temperature have been investigated by TEM. Large amount of microtwins,1 / 2< 110] ordinary dislocations, < 011] and 1 / 2<112] superlattice dislocations have been found. The <011] dislocations often dissociate according to the following mode:[101]→1 / 2[101] + APB + 1 / 6[211] + SISF+1 / 6[12] The 1 / 2< 112] dislocations often dissociate to form faulted dipoles bounded by 1 / 6< 1 12]partial dislocations. The effects of these features on the deformation of PST TiAl crystal at room temperature have been discussed.
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    DISLOCATION FEATURES IN POLYSYNTHETICALLY TWINNED TiAl CRYSTALS AFTER DEFORMATION AT HIGH TEMPERATURE
    LIU Yi;LIN Dongliang; WANG Dening; CHEN Da; CHEN Shipu(Shanghai Jiaotong University; Shanghai 200030; State Key Laboratory of Solid State Microstructures; Nanjing University; Nanjing 210008); LIU Zhiguo; MENG Xiangkang (Nanjing University; Nanjing 210008)(Manuscript received 1995-09-07)
    Acta Metall Sin, 1996, 32 (5): 456-461. 
    Abstract   PDF (549KB) ( 589 )
    The dislocation features in polysynthetically twinned (PST) TiAl crystal deformed at 400, 600 and 850℃ have been investgated by TEM. Screw <011] superdislocations turned to dissociate on {100} planes to form Kear-Wilsdorf locks. Faulted dipoles were found in specimens deformed below 600℃ , whereas no faulted dipole was found at 850℃.In-situ heating observations on the faulted dipoles formed during deformation at room temperature indicated that the faulted dipole disappeared at about 600℃. Based on these experimental results, the mechanism of brittle-to-ductile of TiAl alloy has been discussed.
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    COMPOUND LAYER STRUCTURE OF NITROCARBURIZING 120 STEEL AETER QUENCHING AND AGING
    RONG Yonghua; WANG Yongrui; WANG Jiwen; CHEN Xingkang; HU Gengxiang(Shanghai Jiaotong University; Shanghai 200030)(Manuscript received 1995-09-21)
    Acta Metall Sin, 1996, 32 (5): 462-468. 
    Abstract   PDF (414KB) ( 508 )
    The structures of the quenched and aged compound layers of 0.2% C steel formed by austenitic nitrocarburizing treatment have been investigated. By comparing the intensities of superlattice spots in electron diffration patterns with that of the simulated patterns, the quenched compound layer is confirmed to be ε-Fe(2-3)N which is one of three structural types of ε phase. The γ'- Fe4N plates precipitated from the grey regions of aged compound layer are sometimes observed to be 180°related to each other. A model has been suggested to explain this 180°rotation relationship.
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    M SSBAUER SPECTRA OF FOUR Fe-BASED ALLOYS
    WANG Kuixiang; HAO Zhaoyin; DENG Jingchuan; LIU Milan; LU Guohui(Jilin University; Changchun 130073)(Manuscript received 1995-06-19; in revised form 1995-09-16)
    Acta Metall Sin, 1996, 32 (5): 469-473. 
    Abstract   PDF (372KB) ( 477 )
    Mssbauer spectra of four Fe-based alloys before and after quenching at high temperature and high pressure were studied and the relationships of the hyporfine field H(nf),magnetization M and correlated parametiers to electron concentration of alloys have been obtained. Based on Stoner's rigid band model the variational regulations of H(nf)and M for the carburized alloys were discussed. It was revealed that the 2p electrons of carbon atom filled the 3d holes of iron atom, and there exists Fe-C bond.
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    PHOSPHOROUS DISTRIBUTION IN Pd_(40)Ni_(40)P_(20) ALLOY SOLIDIFIED UNDER MICROGRAVITY CONDITION
    SUN Liling; WU Qi; QIN Zhicheng; WANG Wenkui(Institute of Physics; Chinese Academy of Sciences; Beijing 100080)(Centre of International Material Physics; Shenyang 110015)(Manuscript received 1995-09-15; in revised form 1995-12-20)
    Acta Metall Sin, 1996, 32 (5): 474-478. 
    Abstract   PDF (357KB) ( 430 )
    Phosphorous atom distribution in Pd(40)N(40)P(20) alloy solidified in a China-made recoverable satellite was studied. It was found that the amount of phosphorus in the primary phase formed under μ-g is lower than that under l-g, but in the eutectic region under μ-g is higher than that under l-g. In addition, the microstructure morphology and phosphorous content of the phase, which appeared in the eutectic region and has the lattice of Pd-Ni solid solution, were changed remarkablely. The distribution regulation of solute atoms under μ-g and l-g was discussed and the behaviour of solute atoms (P) distribution in the alloy solidification process was analysed.
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    EFFECTS OF TRACE Li ADDITION ON MECHANICAL PROPERTIES OF Ni_3Al
    (ZHANG Yingjiu; XIE Youqing; LI Weimin; TANG Renzheng; GAO Kunyuan; LU Weijie; CHEN Linghui (Central South University of Technology; Changsha 410083)(Manuscript received 1 995-07-20; in revised form 1995-12-01)
    Acta Metall Sin, 1996, 32 (5): 479-483. 
    Abstract   PDF (322KB) ( 530 )
    The mechanical properties of Ni3Al alloys containing trace Li have been studied. It is found that trace Li may improve their yield strength and a proper amount may improve the ductility of polycrystalline Ni3Al alloys and change the fracture model from the inter-granular to the mixture of inter-and trans-granular. But neither improvement over brittleness at medium temperature nor effect on the ductility of polycrystalline Ni3Al+B alloys is satisfactory. XPS seems to indicate that Li atoms segregate to grain boundaries of Ni3Al alloys. According to this, preliminary explications of Li ductiling Ni3Al alloys might been made.
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    EFFECTS OF EQUILIBRIUM PHASES ON MECHANICAL PROPERTIES OF 8090 Al-Li ALLOY
    ZHANG Wanming; ZHANG Yun; HU Zhuangqi; LIU Yulin; ZHAO Hong'en;(Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110015)(Manuscript received 1995-09-15)
    Acta Metall Sin, 1996, 32 (5): 484-488. 
    Abstract   PDF (458KB) ( 476 )
    Effects of contents of equilibrium phases T2 and δ in 8090 Al-Li alloy with composition (mass fraction, %) of Al-2.45Li-1.21Cu-1.20Mg-0.15Zr on its mechanical properties had been studied. The results show that, after double-aging treatments (210-300℃, 4h+retrogression+160℃, 100h), a large amount of precipitation of T2 may reduce the strength and improve the enlongation of the alloy to a certain extent, but a large amount of precipitation of δ may reduce the strength and improve the elongation of the alloy greatly.
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    EFFECTS OF In ADDITION ON Pd HYDRIDING
    CHEN Yanglin (Zhejiang University; Hangzhou 310027) (Manuscript received 1995-09-12; in revised form 1996-01-19)
    Acta Metall Sin, 1996, 32 (5): 489-494. 
    Abstract   PDF (378KB) ( 439 )
    Hydrogen absorption and desorption isotherms were measured in a microbalance in the pressure range from 0.001 to 3.5 MPa and at seven temperatures from 381 to 621 K for four Pd-In alloys containing in from 3.6 to 15 atomin percent as well as pure Pd. The results are similar to those obtained for the analogous alloys Pd-Ag and Pd-Sn, and are interpreted in the same manner. In has two opposing effects upon the solubility of H in the Pd alloys: the first is the increase in the Fermi energy due to the donation of valence electrons and the second a lattice dilatation. When valence electron concentration is below 0.5, the lattice dilatation predominates and the H solubility is increased with addition of In. When valence electron concentration is above 0.5,the influence of the elevated Fermi energy predominates and the H solubility is lowered by additions of In. The molar enthalpy of Pd hydriding at infinite dilution is strongly increased with increasing in content, but the molar entropy is not affected abviously by the presence in In. The excess chemical potential of hydrogen at small hydrogen concentrations and at a given temperature increases with an increase in In content. The apparent H-H attractive interaction energy, w(HH) , is decreased by the presence of In. The trend is also similar to that found for the Pd-Ag-H and Pd-Sn-H system.
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    NUMERICAL COMPUTATION OF MIXING PROCESSES IN BATH OF BOTTOM STIRRING ELECTRIC ARC FURNACE
    LI Baokuan; HE Jicheng (Northeastern University; Shenyang 110006)(Manuscript received 1995-09-21;in revised form 1995-12-08)
    Acta Metall Sin, 1996, 32 (5): 495-501. 
    Abstract   PDF (448KB) ( 502 )
    The flow field and the mixing time in the water model of the bath of bottom stirring electric arc furnace(EAF) for single-and multi-plug are numerically and experimentally studied. The mixing time is the function of the diameter, number, location of plugs and the tracer injection situation. It was shown that the variation of mixing time is not obvious with the increasing of plug diameter, the stirring efficiency is better if plug number is increased and plugs are distributed in deep and off-central region in vessel, since the angular velocities occur and the more stirring power is obtained in these layouts.
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    KINETICS OF CARBON CATALYTIC REDUCTION OF TITANOMAGNETITE CONCENTRATE
    LAN Yaozhong(Yunnan Normal University; Kunming 650092); LIU Chunpeng(Kunming Institute of Technology; Kunming 650092)(Manuscript received 1995-09-12)
    Acta Metall Sin, 1996, 32 (5): 502-503. 
    Abstract   PDF (136KB) ( 425 )
    Catalytic kinetics of the carbothermic reduction of titanomagnetite concentrate was examined in the temperature range from 900 to 1150℃ . An addition of alkali carbonate enhances the rate of the reduction of titanomagnetite, the catalytic effects are in the order: Na_2CO_3 > Li_2CO_3.
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    INFLUENCE OF SUPERPOSED SMALL LOADS ON FATIGUE CRACK PREPAGATION RATE OF A537 STEEL
    WEI Xuejun; LI Jin; KE Wei(State Key Laboratory of Corrosion and Protection; Institute of Corrosion and Protection of Metals; Chinese Academy of Sciences; Shenyang 110015); (State Key Laboratory of Fatigue and Fracture of Materials; Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110015)(Manuscript received 1995-08-23)
    Acta Metall Sin, 1996, 32 (5): 504-509. 
    Abstract   PDF (432KB) ( 483 )
    The influence of small loads superposed upon principal cyclic load △P on the fatigue crack growth rate da/ dN has been studied for the single edge notched plate specimens of A537 steel, and the crack closure behaviour has been investgated by measurement of crack opening displacement with speckle interferometry(SPI) technique. The results showed that the small loads with amplitude below 30% △P had little influence on da/ dN caused by the principal load when they superposed on the bottom of △P; whereas the small loads with amplitude above 30% △P enhanced the crack growth in the same condition. All small loads superposed on the top of △P made the da / dN increased. It could be proved by the analysis of measured crack closure effect that the influence of small loads on da / dN is determined by crack closure, and the damage of crack tip material caused by the superposed small loads comes from the irreversible plastic deformation which only appears in a certain range of applied load.
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    BEHAVIOUR OF AI-SINGLE CRYSTAL DURING EARLY STAGE OF PUSH-PULL FATIGUE
    LIU Guodong; ZHU Zhengang; WANG Jing (Institute of Solid State Physics; ChineseAcademy of Sciences; Hefei 230031)(Manuscript received 1995-08-22; in revised form 1995-12-14)
    Acta Metall Sin, 1996, 32 (5): 510-515. 
    Abstract   PDF (484KB) ( 517 )
    Push-pull fatigue deformation of [110] and [100] Al-single crystals was performed at room temperature at strain amplitudes in the range (1 to 6) × 10~(-4). Variation of the stress σ, internal friction Q~(-1), and ultrasonic attenuation △α vs cycle number N under various strain amplitudes were measured systematically, and the relative dislocation configuration at different stages of fatigue was observed by TEM. The results indicate that the σ-N curve goes through a hardening -softening-secondary hardening sequence during push-pull fatigue in the two kinds of Al-single crystals. The change in the internal friction vs cycle N is synchronous and reverse with that of the stress. The ultrasonic attenuation △α increases with N at the beginning, after reaching a hump, decreases gradually. The variation of this three parameter is controled by the mechanism of interaction between dislocation segments.
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    EFFECTS OF RE ON PROCESS OF COMPOSITE PLATING AND PROPERTIES OF COATING
    GUO Zhongcheng(Department of Metallurgy; Kunming Institute of Technology;Kunming 650093)(Manuscript received 1995-09-20; in revised form 1995-12-05)
    Acta Metall Sin, 1996, 32 (5): 516-520. 
    Abstract   PDF (304KB) ( 539 )
    The effects of RE on the process of electroplating and electroless plating and properties of coating have been studied. The results show that SiC content, hardness and wear resistance of the composite coatings increase obviously when a few RE are added in the bath.
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    EFFECTS OF MINOR-CARBON CONTENT ON SURFACE STRUCTURES AND EMBRITTLEMENT OF AS-CAST Fe-Si-B AMORPHOUS ALLOY WIRE
    LIANG Nairu; LI Dianchen (Baotou Research institute of Rare Earth; Baotou 014010); HE Kaiyuan; LAI Zuhan (Northeastern University; Shenyang 110006)(Manuscript received 1995-03-28; in revised form 1995-10-30)
    Acta Metall Sin, 1996, 32 (5): 521-526. 
    Abstract   PDF (392KB) ( 506 )
    Fe-Si-B amorphous alloy wires were prepared by the melt spinning in rotating water and the tensile and bending properties of as-cast wires were maesured. Minor carbon, makes the wires embrittle. The enrichment of carbon and the precipatation Fe_(23) (C,B),_6 phases in the surface layer of wires were observed by SEM, TEM and SAM.It seems that Fe_(23) (C, B)_6 induced the embrittlement of as-cast amorphous wires.
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    BEHAVIOUR OF Nb BICRYSTALS UNDER TENSION AND CYCLIC DEFORMATION
    WU Jiansheng; LIN Dangling(Shanghai Jiaotong University; Shanghai 200030)(Manuscript received 1995-10-04)
    Acta Metall Sin, 1996, 32 (5): 527-531. 
    Abstract   PDF (380KB) ( 569 )
    Using Y shape seeds, Nb bicrystals with misorientations 7, 9 and 12°were grown respectively by floating zone method. The tension and cyclic deformation curves of Nb bicrystals have been obtained and compared with that of Nb single crystal. Slip lines on bicrystal specimens after deformation have been observed. It is found that the grain boundary of bicrystal did not affect the deformation bands. Finally the role of the grain boundary during deformation was discussed.
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    EFFECTS OF THE WELD THERMAL CYCLE ON MICROSTRUCTURE AND PROPERTIES OF THE HEAT-AFFECTED ZONE OF HQ130 STEEL
    LI Yajiang;ZOU Zengda;CHEN Zhunian;WEI Hing(Shandong Polytechnic University; Jinan 250014); JIANG Quanchang(Engineering Machinery Co. Ltd. Xiamen361004)(Manuscript received 1995-10-04)
    Acta Metall Sin, 1996, 32 (5): 532-537. 
    Abstract   PDF (509KB) ( 644 )
    The effects of the different peak temperatures(T_m) and cooling times(t) on the microstructure, hardness, impact toughness and fracture morphology of heat-affected zone(HAZ) of HQ130 steel were investigated by means of the weld thermo-simulation test.Experimental results indieated that the impact toughness and hardness were decreased with the decrease in T_m or increase in cooling time under the condition of single thermal cycle. There was brittle zone in the vicinity of T_m = 800℃ . where the impact toughness was obviously lower, and softened zone in 700℃, where the hardness obviously decreased but toughness increased. In practicalwelding, the multi-layer and multi-pass welding, in which the welding heat input was strictly limited (t≤20 s), should be applied to reduce softness and brittleness in HAZ of HQ130 steel.
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    STRENGTHENING AND WEAR RESISTANCE OF Ni-Fe-Cr-B-Si SPRAY ALLOY COATING BY SUPERPLASTICAL DIFFUSION WELDING
    LI Yanxiang;WEN Jiuba;ZHU Yaomin(Luoyang Institute of Technology; Luoyang471039); HUANG Jinliang (Xi'an Jiaotong University; Xi'an 710049)(Manuscript received 1995-07-11)
    Acta Metall Sin, 1996, 32 (5): 538-543. 
    Abstract   PDF (450KB) ( 506 )
    The structural analysis and tests of hardness and wear resistance of Ni-Fe-Cr-B-Si coating indicated that the original coating particles and the interfaces between coating and substrate were readily jointed if the substrate of 5CrMnMo steel together with coating deformed superplastically. The hardness of the superplastical diffusion welded coating may be superior to that of high frequency induction or spray remelted coatings up to 100-150%, and wear resistance up to 30%. It is seemed that the major factors of the improvement of the strengthening and wear resistance of the coating welded may be precipiation hardening, fine grained structure and increasing in internal dislocation density.
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    NUMERICAL SIMULATION OF EXTRUSION DIRECTLY FOLLOWING LIQUID INFILTRATION FOR MANUFACTURING OF Al_2O_3sf/LY12 COMPOSITE SHAPES
    REN Xiangqian;HU Lianxia; SUN Xiaomei; LUO Shoujing(Wuhan Transportation University; Wuhan 430063)(Harbin Institute of Technology; Harbin 150001)(Manuscript received 1995-09-20)
    Acta Metall Sin, 1996, 32 (5): 544-551. 
    Abstract   PDF (516KB) ( 530 )
    A numerical simulation technique based on the stable alternating direction implicit (SADI) method and the upper bound element technique(UBET) is presented and applied to simulations of extrusion directly following liquid infiltration which involves infiltration,solidification, and large plastic deformation in one process. The computer-generated animation displayed the workpiece forming process lively. The simulative results are helpful fora better understanding of the technology of extrusion directly following liquid infiltration.
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    IMAGE PROCESSING TECHNIQUES IN ANALYSIS OF METAL FRACTURE SURFACE
    YAN Yunhui;WANG Dejun(Northeastern University; Shenyang 110006)(Manuscript received 1995-08-21)
    Acta Metall Sin, 1996, 32 (5): 552-556. 
    Abstract   PDF (344KB) ( 931 )
    On the base of establishment of a computer aided instrumentation and analysis system for analyzing metallic fracture surface, some methods in analysis of fracture surface, by means of computer graphics and image processing techniques for detecting of edges and corresponding points, are described in detail. A way based on the method of weighted least squares for measuring and calculating the sizes of fatigue slip band and fatigue striation spacing is presented. An improved Levine's algorithm of detecting a pair of corresponding points is proposed according to the principle of measuring distance from stereo vision , which is used in measuring the relative depth on metallic fracture surface so that the precision and efficiency of computations are all improved.
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    PLS METHOD APPLIED TO HYDROGEN STORAGE PROPERTIES OF BINARY TRANSITION METAL ALLOYS
    GUO Jin;LI Chonghe;CHEN Nianyi(Shanghai Institute of Metallurgy; Chinese Acadamy of Sciences; Shanghai 200050)(Manuscript received 1995-09-15; in revised form 1995-12-08)
    Acta Metall Sin, 1996, 32 (5): 557-560. 
    Abstract   PDF (267KB) ( 386 )
    The partial least square(PLS) method is applied to the formability of hydride and hydrogen storage properties of binary transition metal alloys. The results show that the mathematical model describing the formation of hydrogen storage materials of binary transition metal alloys can be built by using chemical bond parameters and pattern recognition method, which is useful for hydrogen storage materials design.
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