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

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    , Volume 19 Issue 6 Previous Issue    Next Issue
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    THE HARDENABILITY OF BORON STEEL AND THE SEGREGATION OF BORON
    HE Xinlai; CHU Youyi; KE Jun (T. Ko) (Beijing University of Iron and Steel Technology)
    Acta Metall Sin, 1983, 19 (6): 5-114. 
    Abstract   PDF (5111KB) ( 916 )
    The process of boron segregation to austenite grain boundary has been investigated by particle-tracking autoradiography of Jominy bar of a medium carbon boron steel (0.54%C, 0.75%Mn and 0.0027% acid soluble boron) quenched from different temperatures (800—1150℃) after heating to a same high austenitizing temperature (1150℃). It has been shown that the boron segregation to austenite grain boundary in quenched specimens increases with increasing quenching temperature and is related to and dominated by a process other than equilibrium adsorption. In the present work, it has been found that at any position of the Jominy bar, the grain boundary segregation develops continuously during cooling and the final extent of segregation varies with Jominy distance. The grain boundary segregation intensifies as the cooling rate decreases and changes from continuous boronenriched networks to discontinuous aggregation and even to discrete precipitation of boron constitutents. The developing rate of grain boundary segregation increases with increase of the quenching temperature. The boron concentration profiles and the widths of boron-depleted zone have been experimentally measured, and the developing rate of grain boundary segregation estimated and related to the hardenability of boron steel.Under a given quenching temperature, the width of the boron depleted zone x_i is inversely proportional to A~(1/2), where A is the cooling rate or x=H(T_i)/A~(1/2). H(T_i) increase with increasing quenching temperature and is a reflection of the rate of grain boundary segregation and effects of composition and other structural factors. It is suggested that the effect of boron on the hardenability depends on the relative rate of segregation to austenite grain boundary and the incubation of the austenite decomposition, and is at its best when the correlation of both rates is optimum.
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    EFFECT OF WAVY GRAIN BOUNDARY ON CREEP FRACTURE BEHAVIOUR IN ASTROLOY ALLOY
    GUO Guixiong; CAI Qigong; SHEN Huiwang (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Beijing)
    Acta Metall Sin, 1983, 19 (6): 13-23. 
    Abstract   PDF (1158KB) ( 610 )
    By comparing the measurement and the prediction of the creep crack initiation life at the sharp notch root, it is demonstrated that the creep J~*-integral is the effective parameter controlling the asymptotic field at the tip of the notch (and so the crack). Accordingly, a combined analysis on the linear damage model and the HRR singularity is carried out and an expression for the creep crack growth rate is derived as:da/dt=Ba k/n+1 D(x_0)J~* kn/n+1which is in good agreement with the experimental results of material with smooth and wavy grain boundaries. A microscopic mechanism of the creep damage in the material with the wavy grain boundaries has been discussed from the view point of the cavity formation along the grain boundary.
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    STUDIES OF FATIGUE CRACK PROPAGATION AND MICROFRACTUREGRAPHY IN HIGH STRENGTH STEELS
    OUYANG Hui; WANG Yansheng (Institute of Aeronautical Materials Beijing)
    Acta Metall Sin, 1983, 19 (6): 24-116. 
    Abstract   PDF (2739KB) ( 655 )
    The studies were carried out of the test of fatigue crack growth rate and relative to the microscopic morphology of fracture surface in certain high-strength steels. It was found that the results measured by both macro-and microscopic examinations are identical. The fatigue striation of the subcritical crack propagation is quantitatively related to the mean stress. In the same range of stress intensity factors the crack growth rate increases with the mean stress. The fractographic observations of the fatigue crack propagation on specimens of 18CrMn2MoBA steel reveal that the microstructural particle phase constituent with martensite and austenite can be responsible for the reduction of the fatigue crack growth rate.
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    THE FINE STRUCTURE OF Nb AND V PRECIPITATES IN Nb-V STEEL
    XU Wenchong; SUN Fuyu (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Beijing)
    Acta Metall Sin, 1983, 19 (6): 29-118. 
    Abstract   PDF (2836KB) ( 571 )
    The precipitation of Nb and V in Nb-V steel has been investigated by means of STEM and EDAX. It Was found that a complex ordered carbonitride is formed on hot-rolling and continuous cooling by the precipitation of Nb and V together with C and N in which the contents of Nb and V are changeable. Its concentration ratio, C_(Nb)/C_v, decreases with the decrease of the grain size precipitated. The stoichiometric formula of the precipitate may be (Nb, V) (C_(1-x), N_(1-y)). Electronic microscopic observation revealed that both the morphology characteristics and the crystallographic orientation of the precipitate seem to be identical with ones either in the Nb- or V-steel.
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    EFFECT OF STRUCTURE AND TEXTURE ON COLD WORKABILITY OF 3%-AND 4%Si-Fe ALLOYS
    LU Qichun; ZHANG Wenrun; SHUAI Renjie; LI Junyi (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Beijing)
    Acta Metall Sin, 1983, 19 (6): 36-44. 
    Abstract   PDF (2810KB) ( 475 )
    The effect of the hot-rolling microstructure and texture on the cold workability of 3%-and 4%Si-Fe alloys has been studied by the cold-rolling and bending tests. The plasticity of the hot-rolled plate would be better by making the grains fine and improving the homogeneity in the hot-rolled structure. The cold-rolling test of the single crystal with specific orientation shows that it is benefited in the ductility of cold-rolling by increasing {112} <110> and {111} <112> among the main hotrolled texture.
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    WORK STRENGTHENING OF BIPHASE W-Ni-Fe ALLOYS AND THEIR MICROSTRUCTURE
    ZHU Guisen; LIU Mingcheng; ZHEN Zhenxian (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry Beijing)
    Acta Metall Sin, 1983, 19 (6): 45-120. 
    Abstract   PDF (2235KB) ( 672 )
    The correlation among the percentage reduction, mechanical properties and microstructure of 3 biphase W-Ni-Fe alloys swaged under lower temperature has been investigated. It was resulted that the strength and hardness of the alloys increase with the increase of their W contents. However, the alloys of higher W contents have no more strengthened under the reduction beyond 15%. The room temperature tensile strength and hardness may be increased about 50% if it is of 93% W. Their microstructure markedly shows that the W grains are elongated along the longitudinal working direction. The cleavage failure across W grains becomes the main mode of fracture and the slip bands can be observed on them. The deformation feature and the mechanism of these biphase W alloys have been also discussed. Furthermore, it is suggested that the superior mechnical properties as a whole of the alloys may be produced by the vacuum annealing at the temperature between 800—1200℃.
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    DIFFUSION OF CARBON DURING FORMATION OF LOW-CARBON MARTENSITE (Continued)
    XU Zuyao (T. Y. Hsu); LI Xuemin (Shanghai Jiaotong University)
    Acta Metall Sin, 1983, 19 (6): 51-56. 
    Abstract   PDF (358KB) ( 635 )
    The time required for carbon diffusion to enrich the retained austenite is 7×10~(-3) —3×10~(-4) s as calculated. In comparison with the time of formation of a martensite lath——10~(-3)—10~(-6) s, the result of calculation implies that the diffusion of carbon can keep pace with or slightly lags behind the formation of lath martensite. The time required for equalizing the carbon concentration enriched in the retained austenite is at least one order of magnitude lower than that for the formation of lath martensite. These results show that there may exist the carbon diffusion in the course of formation of low-carbon martensite, however, the carbon diffusion is not a main or required process in the martensitie transformation. Supposing that the growth of low-carbon martensite is analogous to that of upper bainite, we obtain the growth rate is only 3×10~(-4)cm/s, at least two orders of magnitude lower than the available experimental data at present. The present work proves once more the formation mechanism of low-carbon martensite differs from that of upper hainite.
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    MICROSTRUCTURAL CHANGE OF TC9 Ti-ALLOY DURING THERMAL EXPOSURE AT 500℃
    ZHANG Shaoqing (Institute of Aeronautical Materials; Beijing)
    Acta Metall Sin, 1983, 19 (6): 57-122. 
    Abstract   PDF (2170KB) ( 494 )
    The microstructural change of TC9 Ti-alloy(Ti-6.5Al-3.5Mo-2.SSn-0.3Si)during 500℃ long-term exposure has been investigated by TEM. Such phase changes in the alloy on exposure have been observed that the Ti_3Al phase precipitates and disperses in primary a-phase; and the retained β-phase decomposes to cause the precipitation of secondary a-phase and the growth of original secondary a-phase, and the existence of type 1 and 2 of the secondary a-phase is confirmed. As the exposure prolonged, the Ti_3Al phase may gradually be increased and grew up. It is suggested that the precipitation of Ti_3Al in primary a-phase may embrittle the alloy during 500℃ exposure. Experiments identified that the orientation relation ship between Ti_3Al and a-phase is (0001)_a//(0001)_(Ti_3Al) and <2(?)0>_a//[2(?)0]_(Ti_3Al).
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    AN INVESTIGATION ON LIQUIDUS OF Al-RICH CORNER OF Al-Mg-La SYSTEM
    ZHENG Chaogui; XING Ya; QIAN Jiuxin; YE Yupu (Department of Chemistry; peking University)
    Acta Metall Sin, 1983, 19 (6): 61-66. 
    Abstract   PDF (495KB) ( 579 )
    The liquidus of the Al-rich corner in the phase diagram of Al-Mg-La system has been investigated by means of thermal, metallographic and X-ray diffraction techniques. The composition of all samples was determined accurately by chemical analysis. It was found that the pseudo-ternary system Al-Mg_5Al_8-LaAl_4 is of the ternary eutectic type. There are three surfaces corresponding to the primary crystallization of a-Al, Mg_5Al_8 and LaAl_4 respectively, and three univariant lines related to the secondary crystallization. The temperature of the ternary eutectic, composed of 11.3 wt-% La, 62.9 wt-% Al and 25.8 wt-% Mg, was determined to be 445℃.
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    METASTABLE EXTENSION OF SOLID SOLUBILITY OF CERTAIN LIGHT RARE-EARTH METALS IN Ag
    NING Yuantao; ZHENG Yun (Institute of Precious Metals Research; Kunming)
    Acta Metall Sin, 1983, 19 (6): 67-71. 
    Abstract   PDF (374KB) ( 471 )
    The metastable extension of solid solubility of certain light rare-earth, i.e. La, Ce, Pr, Nd and Gd, in Ag has evaluated by measurement of the lattice parameters of the quenched melts, made of separate metal with Ag. It was resulted that at the cooling rate about 10~5—10~6 K/s, their metastable limit solid solubility is 1.0, 1.5, 2.5, 3.0 and 6.0 at.-% respectively, which is directly proportional to the contractions of the lanthanide and conform to the authors' proposal on a(A)-A_mB_n eutectic systems. The solid solubility in equilibrium has been discussed.
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    STUDIES ON KINETICS OF LEACHING OF Ca-CONTAINING VANADATES IN CARBONATEBICARBONATE BUFFER SOLUTION
    LIU Houyuan; KE Jiajun; CHEN Jiayong (Chen Chia-yung) (Institute of Chemical Metallurgy. Academia Sinica; Beijing)
    Acta Metall Sin, 1983, 19 (6): 72-78. 
    Abstract   PDF (529KB) ( 695 )
    The kinetics of V leaching from Ca(VO_3)_2 and NaCaVO_4 in Na_2CO_3-NaHCO_3 buffer solution has been investigated. It has been shown that the kinetics of these two samples is rather different. The rate of leaching of Ca(VO_3)_2 is controlled by the parallel reactions between Ca(VO_3)_2 with Na_2CO_3 and NaHCO_3 respectively. No reaction occurs between NaCaVO_4 and Na_2CO_3 at least in the experimental range of the present study, the leaching rate of NaCaVO_4 with NaHCO_3 is controlled by the chemical adsorption of HCO_3~- ions on the solid surface.
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    DISCUSSION ON OFF-FURNACE STEEL REFINING SLAG ATTACK UPON MgO-CaO REFRACTORIES FROM ASPECT OF CaO-SiO_2-Al_2O_3-MgO QUARTERNARY PHASE DIAGRAM
    CHEN Zhaoyou (Luoyang Institute of Refractory Research; Ministry of Metallurgical Industry)
    Acta Metall Sin, 1983, 19 (6): 79-85. 
    Abstract   PDF (553KB) ( 810 )
    From the aspect of the phase diagram, the slags of the off-furnace steel refinement may be substantially considered similar in nature of a CaO-SiO_2-Al_2O_3-MgO quarternary system. The liquid zone and the saturation surface at 1600℃ of this system and the MgO solubility line at 1600℃ in CaO-SiO_2-Al_2O_3 slags as well as the quantity of liquid formed in different compositions of MgO-CaO system refractories after absorbed a certain amount of SiO_2 and Al_2O_3 at 1700℃ have been constructed by the allied ternary phase diagrams and the published data. Based upon above-mentioned, the off-furnace steel refining slags attack upon the MgO-CaO system refractories was discussed. Suggestion may be made of the improvements upon the service life of the linings either by controlling the composition of slags or by selecting properly the constituents of MgO-CaO refractories.
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    SPATIAL ORIENTATION DISTRIBUTION OF CRYSTALLITES IN COLD-ROLLED Al-KILLED STEEL SHEET DURING RECRYSTALLIZATION ANNEALING
    HUANG Qingzhu; KONG Bingyu; ZHU Congxun (Research Institute of Wuhan Iron and Steel Company)
    Acta Metall Sin, 1983, 19 (6): 86-91. 
    Abstract   PDF (538KB) ( 455 )
    The change of texture during recrystallization annealing in low carbon Alkilled steel sheet containing 0.13% Cu has been studied by function of crystal orientation distribution. It is shown that the cold-rolled texture is composed of one component of the <111> fibre texture with fibre axis parallel to the plane normal and another component of {001} <110>. The <110> partial fibre texture with fibre axis parallel to the rolling direction is formed by the diffusion of the two components. During the recrystallization, <111> fibre texture becomes prevailing and {001} <110> component diminishes while the <110> partial fibre texture contracts gradually, therefore, the <110> partial fibre texture is not an independent one.
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    STRUCTURE MICROANALYSIS OF INTERFACE BETWEEN Cu-Ti ALLOY AND DIAMOND (OR GRAPHITE)
    GAO Qiaojun (Department of Physics; Peking University)
    Acta Metall Sin, 1983, 19 (6): 92-99. 
    Abstract   PDF (2188KB) ( 879 )
    The structure of micro-region along the interfacial section between Cu-Ti alloy and graphite (or diamond) has been analyzed by using SEM-EDS and SEMWDS as well as in-depth metallography and X-ray diffraction. It was revealed that the wetting and bonding behaviour on diamond surface by Cu-Ti melt is realized through the stable TiC film which is produced by interaction between Ti atoms of Cu-Ti alloy and C atoms of graphite (or diamond) surface at elevated temperatures.
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    A STUDY OF THE SURFACE TREATED WITH SULF BT BY XPS
    WANG Tanghan (Institute of Chemistry; Academia Sinica; Beijing); WU Yan (Harbin Institute of Technology)
    Acta Metall Sin, 1983, 19 (6): 100-103. 
    Abstract   PDF (328KB) ( 522 )
    The main component in the surface treated with SULF BT has been recognized to be a category of iron sulphide (FeS) so far, however, the XPS results in the present paper show that the surface contains not only iron sulphide (FeS), but also iron sulphite (FeSO_3), and both relative amounts in the surface are the same.
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    OBSERVATION OF CRYSTALLOGRAPHIC CONTRAST ON POLYCRYSTALLINE SPECIMENS BY MEANS OF CHANNELLING MICROGRAPHY TECHNIQUE
    LAN Fenlan; LIAO Qianchu; WANG Hongjun; WANG Yun (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Beijing)
    Acta Metall Sin, 1983, 19 (6): 104-110. 
    Abstract   PDF (1254KB) ( 658 )
    In order to reveal the crystallographic contrast from the surface of the polycrystalline specimen, two electron optical paths were analyzed. For the standard scanning path, the magnification of the channelling micrograph is controlled by the electron beam scanning angular field. The ratio between geometric and crystallographic contrast can be modulated by the signal processing method. For the defocused beam rocking path, the magnification is controlled by the defocused distance. The anomalous effects of the orientation contrast resulted by the deformed specimen may be interpreted by means of ECP superimposed on the channelling photograph.Observations were made of certain specimens such as W, Mo and 304 austenitic stainless steel. It seems that the present technique is available for study of both the orientation distribution and the deformation behaviour of the polycrystalline materials.
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