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

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    RECALESCENCE AND SOLIDIFICATION MICROSTRUCTURE OF HIGHLY UNDERCOOLED ALLOY Ni_(68)B_(21)Si_(11).
    LI Delin; YANG Gencang; ZHOU Yaohe (Northwestern Polytechnical University; Xi'an)
    Acta Metall Sin, 1992, 28 (10): 1-5. 
    Abstract   PDF (1316KB) ( 644 )
    One, two and three recalescence events in the solidification of highly undercooled Ni_(68)B_(21)Si_(11) alloy melt and the conditions of undercooled together with the effect on solidification morphologies were revealed. The solidification morphologies of the undercooled alloy may be examined in the light of two aspects, i.e., growth of either Ni_3B Ni_6Si_2B and Ni_2B eutectic or dendrite cluster with Ni_3B as leading phase. When the degree of undercooling below 200 or over 310 K, the solidification of alloy is accompannied by one recalescene only, and the crystals grow according to the first mode of solidification. While undercooling at other temperatures, two or three events of recalescence may occur and the dendrite cluster may solidify.
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    MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TiAI ALLOY POWDER
    CAO Mingzhou; HAN Dong; ZHANG Tao; LI Dong (Institute of Metal Research; Academia Sinica; Shenyang)
    Acta Metall Sin, 1992, 28 (10): 6-10. 
    Abstract   PDF (1028KB) ( 692 )
    The rapidly solidified powder of Ti-34Al-2Mn alloy was produced by gas atomization. The typical value of the size of RS powder is 27μm. X-ray diffraction results show that the microstructure of RS powder consists of major α_2-phase and minor γ-phase. On the optical micrograph there are equiaxed and dendritic grains. After annealing at 900℃, 2 h in vacuum, most of α_2-phase transformed into γ-phase and the microstructure becomes finer.
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    IMPROVEMENT IN TENSILE PROPERTIES OF α+β TYPE Ti ALLOYS BY HYDROGEN TREATMENT
    GONG Bo; LAI Zuhan (Northeast University of Technology; Shenyang); NIINOMI Mitsuo; KOBAYASHI Toshiro (Toyohashi University of Technology; Japan)
    Acta Metall Sin, 1992, 28 (10): 11-14. 
    Abstract   PDF (850KB) ( 417 )
    A process by using hydrogen as a temporary alloying element to refine the microstructrue of α+β type Ti alloys was newly developed. It involves hydrogenating the alloy at 0—40K below the hydrogenated β transition temperature, air cooling to room temperature and dehydrogenating at 948K. Ti-6Al-4V and Ti-SAl-2.5Fe alloys treated by the process show much refined microstructures, and the yield strength, ultimate strength and elongation increase by 8—15, 5—13 and 7—14% respectively.
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    MICROSTRUCTURE OF BORONITRIDING LAYER ON AUSTENITIC STAINLESS STEEL
    QI Lian; HUANG Qingzhu; ZHONG Sunuo (Zhongshan University; Guangzhou); LU Yaokun; LI Jianguo; RUAN Guangde (Guangzhou Institute of Mechanical and Electrical Industry)
    Acta Metall Sin, 1992, 28 (10): 15-20. 
    Abstract   PDF (1487KB) ( 594 )
    Microstructure of the boronitriding layer on austenitic stainless steel and the transition zone between the layer and matrix has been examined. The boronitrided layer is an even spreaded coating containing (FeM)B and (FeM)_2B borides. After boronitriding, the A_1 and A_3 line for γ region of austenitic stainless steel may be elevated over room temperature. In the B solution region, the α-phase is formed. The black dense band is an easily etched region of co-existence between α-phase and the fine borides.
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    INVESTIGATION OF BEHAVIOUR OF B IN Ni_3AI ALLOYS BY POSITRON ANNIHILATION TECHNIQUE
    DENG Wen; XIONG Liangyue; LONG Qiwei (International centre for Materials Physics; Institute of Metal Research; Academia Sinica; Shenyang); WANG Shuhe; GUO Jianting (Institute of Metal Research; Academia Sinica; Shenyang)
    Acta Metall Sin, 1992, 28 (10): 21-24. 
    Abstract   PDF (304KB) ( 432 )
    The behaviour of B atoms added to mono- and poly-crystalline Ni_3Al alloys has been investigated by positron annihilation technique. If an additive of B less than 1.37 at.-%, some of B atoms solid-dissolved interstitially into matrix and distorted the lattice, thus the lifetime of positron in matrix dilated; the others of them segregated on vacancy-like defects and formed" filling effect", thus the mean lifetime and S parameters decreased. If B added up to 2.22 at.-%, more defects having larger free volume were induced by boride eutectic occurred along grain boundaries and grain interior, thus the positron lifetime in vacancy-like defects, mean lifetime and S parameters increased remarkably.
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    FLAKES AND HYDROGEN CONTENT IN U71Mn HEAVY RAIL STEEL
    LI Peiji; XIAN Aiping; WANG Yikang (Institute of Metal Research; Academia Sinica; Shenyang); CHEN Renyi; MEI Dongsheng(Panzhihua Institute of Iron and Steel Re search; Ministry of Metallurgical Industry)
    Acta Metall Sin, 1992, 28 (10): 25-28. 
    Abstract   PDF (275KB) ( 476 )
    The content of hydrogen allowed in U71Mn heavy rail steel, produced by the Panzhihua Iron and Steel Company, was investigated by technique of hydrogen blowing into molten steel. Experimental results revealed that the critical hydrogen content is limited to 2.5 ppm. If the content in melt increases to 3.3—5.8 ppm, the flakes may form in the steel. And it will further drop as the increase of Mn contained. It was also observed that the incubation period for flake forming seems to be undetermined.
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    EMBRITTLEMENT OF Fe-Cr-Al ALLOYS AND EFFECT OF YTTRIUM ADDITION
    LI Bei; WU Shuangxia; LI Dianchen (Baotou Research Institute of Rare Earth; Ministry of Metallurgical Industry); MA Ruzhang (University of Science and Technology Beijing)
    Acta Metall Sin, 1992, 28 (10): 29-35. 
    Abstract   PDF (1084KB) ( 510 )
    A high temperature embrittlement occures in Fe-15Cr-4Al and Fe-20Cr-41Al alloys treated over 1000℃. It is caused mainly by 475℃ brittleness during cooling. When a secondary treatment at 500℃ was conducted, the 475℃ brittleness developed very rapidly. After only 15 min of the treating, little plasticity was remained for all samples pretreated at the temperatures over 1000℃ and cooled in water. However, no 475℃ brittleness was generated when pretreating temperature was below 1000℃ . Addition of Yttrium can inhibit not only grain growth, but also 475℃ brittleness. For the alloys with 0.2 —0.4wt-%Y, after treating at 800—1300℃, the plasticity did not decrease and the properties of furnace cooled samples were not lower than those of water cooled samples.
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    MECHANISM OF DEUTERIUM CRACKING IN PALLADIUM
    SUN Dalin; LEI Yongquan; CHEN Yanglin; WU Jing; WANG Qidong (Zhejiang University; Hangzhou)
    Acta Metall Sin, 1992, 28 (10): 36-40. 
    Abstract   PDF (1251KB) ( 525 )
    After 290 h electrochemically deuterium charged, the density of dislocations in well-annealled Pd increased from 10~8/cm~2 to 10~(12)/cm~2 above, and a large amount of bubble-like structure or cracks have been observed by optical and transmission electronic microscopes. The mechanism of deuterium cracking was considered to be the formation of D_2 due to the segregation and recombination of deuterium atoms around dislocations. XRD results showed that the lattice constant of Pd increased from 0.3890 to 0.4034 nm.
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    DIMPLE FORMATION ON FRACTURE SURFACE OF STEEL 55SiMnMo
    LIANG Sizu; LIANG Yaoneng; LIU Zhengyi (South China University of Technology; Guangzhou)
    Acta Metall Sin, 1992, 28 (10): 41-44. 
    Abstract   PDF (894KB) ( 502 )
    The fracture surface of the normalized steel 55SiMnMo was observed, under tensile testing device equipped on SEM, to be of ductile dimple feature in the bainite which are composed of austenite and ferrite. The dimple is almost nucleated in the ferrite. Because the austenitic plastic deformation is remarkable during fracturing, the tear ridge of dimple is very sharp.
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    NUMERICAL ANALYSIS OF THREE-DIMENSIONAL FLUID FLOW AND HEAT TRANSFER IN TIG WELD POOL WITH FULL-PENETRATION
    WU Chuansong; CAO Zhenning; WU Lin (Harbin Institute of Technology)
    Acta Metall Sin, 1992, 28 (10): 47-52. 
    Abstract   PDF (424KB) ( 566 )
    A model is established to analyze three-dimensional fluid dynamics and heat transfer in TIG weld pools with full-penetration. It considers the deformation of molten pool surface at the condition of full-penetrated workpieces, takes the arc pressure as the driving force of weld pool surface depression, and determines the surface configuration of weld pool based on the dynamic balance of weld pool gravity, arc pressure and surface tension. The fluid flow and temperature fields in weld pools of stainless steel workpieces are analyzed by using SIMPLER algorithm. TIG welding experiments are made to verify the validity of the model. It shows that the predicted results by the model are in good agreement with experimental ones.
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    PREPARATION OF Sm-Fe ALLOY USING MECHANICAL ALLOYING AND ITS CRYSTALLIZATION AND NITROGINATION
    LU Manqi; SONG Qihong; SUN Wensheng; MIAO Weifang; WANG Kai yang; JWEI Wenduo; WANG Longbao (Institute of Metal Research; Academia Sinica; Shenyang)
    Acta Metall Sin, 1992, 28 (10): 53-59. 
    Abstract   PDF (614KB) ( 462 )
    The crystallization and nitrogination of a mechanically alloyed Sm-Fe alloy have been investigated. The results show that the alloy consists of amorphous Sm-Fe phase and crystalline α-Fe. The composition of the alloy is inhomogeneous, the surface of the as-milled powder is relatively poor in Fe. The crystallization process involves the long-range diffusion of iron atoms and solid state reaction. After proper crystallization, the as-milled powder transforms into a Sm_2Fe_(17) phase completely. A metastable phase, which may be a Sm_2Fe_(17) phase with the structure of hexagonal Th_2Ni_(17) type, appears during the crystallization process. Nitrogination of Sm_2Fe_(17) consists of the following processes: incubation period, coexistence of Sm_2Fe_(17) and its nitride, and transformation of residual Sm_2Fe_(17) into nitride phase. During nitrogination small amount of very fine α-Fe segregates.
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    CRYSTALLIZATION OF METALLIC GLASS Zr_(70)Cu_(30) UNDER HIGH PRESSURE
    SHEN Dejiu; WU Haoquan (Yanshan University; Qinhuangdao); SHEN Zhongyi; CHEN Guiyu; YIN Xiujun (Institute of Physics; Academia Sinica; Beijing)
    Acta Metall Sin, 1992, 28 (10): 60-62. 
    Abstract   PDF (226KB) ( 467 )
    Crystallization temperature of the metallic glass Zr_(70)Cu_(30), observed by X-ray diffraction analysis, may be increased about 20℃ under high pressure up to 2GPa. Besides α-Zr and CuZr_2 , the Cu_(10)Zr_7 phase was newly obtained as the another crystallization product.
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    INFLUENCE OF DEFECTS ON PROPERTIES OF SPUTTERED CoCrAIY COATINGS
    WANG Fuhui; LOU Hanyi; WU Weitao (Corrosion Science Laboratory; Institute of Corrosion and Protection of Metals; Academia Sinica; shenyang)
    Acta Metall Sin, 1992, 28 (10): 63-68. 
    Abstract   PDF (2396KB) ( 550 )
    Influence of defects on oxidation, hot corrosion and thermal shock properties of sputtered Co-30Cr- 6Al-0.5Y coatings was investigated. In the coating, the nodular defect was observed to worsen severely the properties. For testing under oxidation condition, the nodular defect results in the internal oxidation of Al. No single Al oxide scale may be formed at 1100℃ owing to consumption of Al. Under hot corrosion, it becomes as short-path for diffusion of S through the coating, thus sulphuring the coating together with the substrate. During thermal shock testing, it may act as the source of cracking, and moreover, if cyclic stress applied, the cracks propagate toward the substrate, the thermal fatigue properties of coating will be worsened.
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    HIGH TEMPERATURE OXIDATION AND STRUCTURE OF SCALE AND WHISKERS FOR Fe-Ni-Cr SEALING ALLOYS
    DONG Zhili; MA Jusheng; TANG Xiangyun; YOU Liang (Tsinghua University; Beijing)
    Acta Metall Sin, 1992, 28 (10): 69-72. 
    Abstract   PDF (863KB) ( 449 )
    The oxidation rate, the growth, morphology and structure of oxide scale and whiskers for Fe-Ni-Cr sealing alloys in H_2-H_2O atmosphere at high temperatures have been studied. The growth rate of scale is controlled by diffusion. The scale is composed of Cr_2O_3 and spinel(Fe, Mn)O Cr_2O_3 and the oxide whiskers are spinel (Fe, Mn) O Cr_2O_3.
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    EFFECT OF NITROGEN ON GRAPHITE MORPHOLOGY IN GRAY CAST IRON
    ZHAI Qijie; HU Hanqi (University of Science and Technology Beijing)
    Acta Metall Sin, 1992, 28 (10): 73-78. 
    Abstract   PDF (1915KB) ( 555 )
    The distribution of nitrogen and morphology of graphite in the gray cast iron containing nitrogen were studied by adopting the man-made specimens of Fe-C-Si-Mn alloys with some nitrogen added. The nitrogen adsorbed along interfaces between graphite and matrix together with solid-solutioned in graphite is believed to be the principal cause of morphological variation of graphite.
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    SiO_2 ASHETEROGENEOUSNUCLEI OF INTERGROWTH EUTECTIC IN MODIFIED AS-CAST MEDIUM MANGANESE STEEL
    JIANG Qichuan; YAN Jiulin; GUAN Qingfeng; WANG Shoushi; RONG Fujie; LI Zhang(Jilin University of Technology; Changchun)
    Acta Metall Sin, 1992, 28 (10): 79-84. 
    Abstract   PDF (1125KB) ( 463 )
    By calculation of thermodynamics, analysis of crystal structure and study of TEM and eletron probe, it is first discovered that SiO_2 can be acted as one of the heterogeneous nuclei for lamellar intergrowth eutectic(austenite and cementite) crystallizing in modified as-cast medium manganese steel.
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    EFFECT OF REINFORCEMENT VOLUME FRACTION ON PRECIPITATION IN MATRIX OF SiCp/ AI COMPOSITE
    LIN Junshan; LI Pengxing; WU Renjie (Shanghai Jiaotong University)
    Acta Metall Sin, 1992, 28 (10): 85-90. 
    Abstract   PDF (802KB) ( 463 )
    The kinetic process of precipitation in matrix of cast SiCp / Al composite was studied by differential scanning calorimetry and transmission electron microanalysis techniques. In comparison with the matrix free from SiC, an additive of SiC in composite may accelerate the precipitation of GP zone and intermediate phase S'(Al_2CuMg) and decrease the peak temperature. The enthalpy of precipitation of both GP zone and S'-phase reduces substantially. TEM analysis showed that the alloying element Mg segregates at the SiC-Al interface. Thus, the Mg nearby the interfaces in matrix depleted, and the precipitate-free zone and precipitate-sparse zone formed near the interface, the amount of precipitate decreased.
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    ASPRES—AN EXPERT SYSTEM FOR ALLOY STEEL DEVELOPMENT
    CHEN Yu; CHEN Nianyi (Shanghai Institute of Metallurgy; Academia Sinica)PENG Ping; KONG Bingyu (Iron and Steel Research Institute; Shanghai Baoshan Iron and Steel Complex)
    Acta Metall Sin, 1992, 28 (10): 91-94. 
    Abstract   PDF (340KB) ( 512 )
    An alloy steel pattern recognition expert system, ASPRES, has been established for the purpose of computer-aided optimal design of alloy steel in compositions andprocess parameters. Pattern recognition techniques are used to abstract inner relationship between mechanical properties and process variables. The ASPRES uses 2-dimensional graph as visual knowledge to represent domain expertise of specific object. Forward and backward chaining can be utilized by researchers in predicting sample performances or giving helpful suggestions about the chemical compositions and process parameters according to desired properties.
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