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

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    DEVELOPMENT AND INNOVATION OF SUPERALLOY IN CHINA
    SHI Changxu ZHONG Zengyong
    Acta Metall Sin, 2010, 46 (11): 1281-1288.  DOI: 10.3724/SP.J.1037.2010.00309
    Abstract   PDF (916KB) ( 2986 )
    In this paper the development course of superalloy in China, the technical progress and innovation in recent years and works in the future are described.
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    RESEARCH AND DEVELOPMENT OF γ´´ AND γ´ STRENGTHENED Ni-Fe BASE SUPERALLOY GH4169
    XIE Xishan DONG Jianxin FU Shuhong ZHANG Maicang
    Acta Metall Sin, 2010, 46 (11): 1289-1302.  DOI: 10.3724/SP.J.1037.2010.00436
    Abstract   PDF (1881KB) ( 2425 )
    γ´´ and γ´ strengthened Ni-Fe base superalloy Inconel 718 (GH4169) is world-widely used under 650 ℃ because of its excellent mechanical properties and metallurgical workability. The effects of main strengthening elements Nb, Ti, Al, minor elements P, S and micro-alloying element Mg on mechanical properties and structure stability have been studied for this alloy at standard heat treatment and long time aging conditions both by means of mechanical tests (tensile, stress rupture and creep, cyclic stress rupture and crack propagation etc.) and detail structure analyses (SEM, TEM, EDS, SAED, phase separation and micro-chemical analyses etc.) and also Auger analyses on grain boundary segregation behavior. For quality improvement of conventional GH4169, Nb content should be controlled at high level (5.4%-5.5%) with low content of S (<10×10-6) and high level of P (but less than 150×10-6) and with micro-alloying element Mg also. For 680 ℃ even higher temperature used modified GH4169 the γ´´/γ´ highest stable temperature must be raised and the grain boundary precipitates should be controlled. Nb content should be still controlled at high level (5.4%-5.5%), Al content should be raised to 1.0%-1.5% and Ti content still be kept at 1%; S must be controlled to less than 10×10-6 and P should be raised to a high level but less than 150×10-6 and also with micro-alloying element Mg. The modified GH4169 to be used at 680 ℃ or even higher temperature has good thermal structure stability and high mechanical properties above 650 ℃.
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    PROCESSING, MICROSTRUCTURE AND MECHANICAL PROPERTIES OF LARGE DIRECTIONALLY SOLIDIFIED CASTINGS FOR INDUSTRIAL GAS TURBINE APPLICATIONS
    ZHANG Jian SHEN Jian LU Yuzhang LOU Langhong
    Acta Metall Sin, 2010, 46 (11): 1322-1326.  DOI: 10.3724/SP.J.1037.2010.00509
    Abstract   PDF (725KB) ( 1367 )
    Contamination of low melting point metal and distortion and fracture of ceramic shell during directional solidification assisted by liquid metal cooling (LMC) were discussed. Large DS castings with 430 mm in length were produced by optimizing the processing parameters. The microstructure, heat treatment response and typical creep rupture properties of the large casting were analyzed. Results of the preliminary casting trials of large blades were also reported.
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    STRUCTURE EVOLUTION IN DIRECTIONALLY SOLIDIFIED BICRYSTALS OF NICKEL BASE SUPERALLOYS
    ZHOU Yizhou JIN Tao SUN Xiaofeng
    Acta Metall Sin, 2010, 46 (11): 1327-1334.  DOI: 10.3724/SP.J.1037.2010.00280
    Abstract   PDF (929KB) ( 1763 )
    Bicrystal samples of Ni base superalloy IN792 were produced to study the structure evolution in directional solidification process. In the case of converging grains, the misaligned dendrites were able to block the better aligned dendrites at the grain boundary. The dendrite blocking leaded to inclination of the grain boundary from the misaligned grain to the better aligned grain. Thus, the better aligned grain was overgrown by the misaligned grain. In the case of diverging grains, dendrite development at the grain boundary leaded to inclination of the grain boundary from the better aligned grain to the misaligned grain. Consequently, the better aligned grain overgrew the misaligned grain.
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    HYDROGEN EMBRITTLEMENT RESISTANCE OF AUSTENITIC ALLOYS AND ALUMINIUM ALLOYS
    LI Yiyi FAN Cungan RONG Lijian YAN Desheng LI Xiuyan
    Acta Metall Sin, 2010, 46 (11): 1335-1346.  DOI: 10.3724/SP.J.1037.2010.00433
    Abstract   PDF (1076KB) ( 2568 )
    Hydrogen embrittlement is of the technological importance in which the hydrogen in metallic materials can cause the loss in tensile ductility, cracking or damage and degradation of other mechanical properties. The common hydrogen resistant alloys are austenitic stainless steels, precipitation-strengthened austenitic alloys, low alloy steels and aluminum alloys etc.. As austenitic alloys have high hydrogen resistance properties and their strength can be improved by precipitation strengthening, they are commonly used in hydrogen conditions. IMR had developed a series hydrogen resistant steels, such as HR-1, HR-2, HR-3, J75 and J100 as well as Al-6Mg-0.2Sc-0.15Zr hydrogen resistant aluminum alloy. These alloys posses comprehensive mechanical properties and high hydrogen resistant ability. In addition, alloy smelting, casting, forging, welding and heat treatment should be followed the laws of the preparation. It is important to control the microstructures in order to improve the performance of resistant hydrogen.
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    HIGH EFFICIENCY WELDING PROCESS FOR STAINLESS STEEL MATERIALS
    LU Shanping DONG Wenchao LI Dianzhong LI Yiyi
    Acta Metall Sin, 2010, 46 (11): 1347-1364.  DOI: 10.3724/SP.J.1037.2010.00437
    Abstract   PDF (2252KB) ( 1855 )
    The high efficiency tungsten inert gas (TIG) welding process has been developed, including active flux welding process, mixed shielded welding process and double shielded welding process, to increase the weld depth/width ratio (D/W$) of conventional TIG welding method. Compared to the active flux method, mixed shielding method can make penetration deeper and the industrialization can be realized easily due to the simplification in operation. Double shielded method can avoid the oxidation of tungsten electrode. The results of experiment and simulation show that the change of the Marangoni convection direction which arises from the adjustment of the oxygen content in the weld pool is one of the main factors contributing to the increase in TIG weld penetration, and the large D/W ratio can be obtained by adjusting the active element content in the liquid pool. High efficiency TIG welding process is not sensitive to welding parameters (welding speed, welding current and electrode gap) and therefore is suitable to be applied in industry easily.
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    STUDY ON THE RUSTING EVOLUTION AND THE PERFORMANCE OF RESISTING TO ATMOSPHERIC CORROSION FOR Mn-Cu STEEL
    KE Wei DONG Junhua
    Acta Metall Sin, 2010, 46 (11): 1365-1378.  DOI: 10.3724/SP.J.1037.2010.00489
    Abstract   PDF (2915KB) ( 1457 )
    The rust evolutions of the corrosion mass gain, the corrosion rate, the chemical composition, and the cross-section of the rust layer versus cycles of dry/wet alternate corrosion test were summarized on the basis of the study progress on the rust layer of Mn-Cu weathering steel. The validity of the cyclic dry/wet corrosion acceleration test simulating the atmospheric corrosion has also been discussed. Moreover, we have described the principle of synergistically improving the corrosion resistance of the rust layer resisting to both coastal atmospheric corrosion and industrial acidic rain atmospheric corrosion through adding alloying elements Cu, Mn and P. Meanwhile, the mechanism of P in the rust layer and the relationship of the ion-selectivity of Mn-Cu steel rust layer and its structure have been discussed.
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    CORROSION MECHANISMS OF STAINLESS STEEL AND NICKEL BASE ALLOYS IN HIGH TEMPERATURE HIGH PRESSURE WATER
    HAN En-Hou WANG Jianqiu WU Xinqiang KE Wei
    Acta Metall Sin, 2010, 46 (11): 1379-1390.  DOI: 10.3724/SP.J.1037.2010.00468
    Abstract   PDF (2405KB) ( 1909 )
    The electrochemical corrosion behavior and the chemical components, structures and electronic characters of oxide films for stainless steels and Ni base alloys used in nuclear power plant were reviewed. The effects of water chemistry and microstructure of materials on oxide films were analyzed in order to relate the oxide film properties with electrochemical behaviors. The corrosion mechanism of the materials used in high temperature pressurized water is different with that used in room temperature water. The corrosion mechanism of the materials in high temperature pressurized water is controlled by electrochemistry and oxidation, whereas in room temperature water it is controlled only by electrochemistry. Oxide films has double-layer structure. The outer layer is porous, and the inner layer is composed by nano-crystalline and has semiconductivity which controlled the corrosion process. The microstructure, chemical composition, surface status of materials and water chemistry parameters are the key parameters which affect corrosion. The wedging stress of oxide inside the flaw could induce localized tensile stress at the tip of the flaw, which caused stress corrosion cracking initiation and propagation even in macro-compressive stressed region. The wedging stress of oxide is the key factor to induce stress corrosion cracking in compressive stressed region.
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    RECENT PROGRESS IN THE AREA OF BULK AMORPHOUS ALLOYS AND COMPOSITES
    HU Zhuangqi ZHANG Haifeng
    Acta Metall Sin, 2010, 46 (11): 1391-1421.  DOI: 10.3724/SP.J.1037.2010.00381
    Abstract   PDF (3716KB) ( 2561 )
    Bulk metallic glass (BMG) and its composite (BMGC) are new members in the area of materials science and engineering. In this paper, we simply reviewed the development history, especially introduced our recent progress referred to Ti-, Ni-, Zr- and Mg-based BMGs and BMGCs. The study of the microstructures of BMGs prepared by controlling the solidification conditions indicates that the microstructure of BMG is flexible. Several factors including the casting temperature, the mold temperature and the mold material etc. influencing on the glass formation, microstructures and properties were studied. The relationship among processes, structures and properties of BMGs is furthermore illustrated. Some BMGs and BMGCs were prepared by mediating the solidification conditions and designing the novel composite structures, of which the size of Ti-based BMG reaches 50 mm,\linebreak and crystal/BMG bi-continuous phase composites exhibit good properties. Investigations reveal that the application of these BMG and BMGCs will be expected in the near future.
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    METALLIC MATERIALS WITH NANO--SCALE TWINS
    LU Lei LU Ke
    Acta Metall Sin, 2010, 46 (11): 1422-1427.  DOI: 10.3724/SP.J.1037.2010.00462
    Abstract   PDF (784KB) ( 2763 )
    Strengthening materials is a central objective of materials research. Traditional approaches to strengthen materials, including solid solution strengthening, second phase strengthening, grain refinement strengthening, dispersion strengthening and work hardening strengthening etc., aim at creation of internal defects and boundaries so as to obstruct the motion of dislocations. Such strategies for strengthening invariably compromise the ductility and electrical conductivity of the material. By reviewing recent advances in our understanding of nanostructured metals and alloys, we propose a novel approach to optimize the strength, ductility and the electrical conductivity of materials by means of coherent twin boundaries at nano-meter scale. We assess current understanding of strengthening mechanism of twin boundaries (instead of incoherent boundaries as conventionally used). Additionally, some mechanical properties (such as strength, ductility, strain rate sensitivity, work hardening) and the physical properties (electrical conductivity and electrical migration) as well as the relative preparation techniques of the metallic materials with nano-scale twins will be reviewed in this paper.
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    INSIGHT FOR MICROSTRUCTURE RESEARCH OF MATERIALS
    ZHU Jing YE Hengqiang
    Acta Metall Sin, 2010, 46 (11): 1428-1442.  DOI: 10.3724/SP.J.1037.2010.00487
    Abstract   PDF (1421KB) ( 1744 )
    In matter science to observe the structure and to understand it's correlation with property in atomic scale is among the aims. Nano-science and technology, microminiaturization of IT devices, higher precision in advanced manufacture $etc$. play an important role to promote microscopic characterization to go deeply to atomic and even electronic level. Based upon the break-through of the aberration corrector the three functions of morphology observation, crystal structure determination and element analysis, provided by transmission electron microscope in recent years have expected to reach atomic resolution standard. Here we introduce the capabilities and prospects for microstructure characterization of materials with these new electron microscopes: (1) aberration-corrected electron microscopy (improving resolution; reducing delocalization effect; negative spherical aberration imaging; defocus-series processing images); (2) a high-resolution probe for imaging and spectroscopy; (3) three-dimensional atomic imaging; (4) interfaces in the complicated structure; (5) time resolution electron microscopy; (6) electron holography; (7) in situ electron microscopy with larger gap in pole piece.
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    ORTHORHOMBIC PHASE TRANSFORMATIONS IN TITANIUM ALLOYS AND THEIR APPLICATIONS
    YANG Rui HAO Yulin Obbard E G DONG Limin LU Bin
    Acta Metall Sin, 2010, 46 (11): 1443-1449.  DOI: 10.3724/SP.J.1037.2010.00483
    Abstract   PDF (890KB) ( 1446 )
    The link and difference between orthorhombic phase transformations in β-type titanium alloys and in Ti3Al containing high concentrations of transition metal elements such as Nb are first outlined in this paper. Recent investigations on these transformations conducted in the authors' group are reviewed followed by discussions of remaining problems. Three examples were presented to illustrate the applications of the orthorhombic phase transformations: design and development of superelastic titanium alloys for biomedical use, preparation of ultra-fine basketweave microstructure of titanium alloy wire for fastener manufacturing, and sheet and foil production of alloys based on Ti2AlNb.
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    RESEARCH AND APPLICATIONS OF MAGNESIUM IN CHINA
    DING Wenjiang ZENG Xiaoqin
    Acta Metall Sin, 2010, 46 (11): 1450-1457.  DOI: 10.3724/SP.J.1037.2010.00386
    Abstract   PDF (1029KB) ( 1994 )
    After more than fifty years developing, China has become the largest raw magnesium production country. In the year of 2000, Shi Changxu and his four colleagues, all are academicians of Chinese Academic of Science (CAS), sent a suggestion letter to Minister of Science and Technology (MOST) of China titled “A proposal for speeding up the development of magnesium research and applications”. The suggestion was thus approved by MOST quickly and a major science and technology developing program titled “Developing and industrializing of magnesium alloy” was launched in China during ten--five period. After the ten years development, a great deal of achievements have been attained on advanced magnesium alloys, surface treatment technology and processing technology in our country, and China is stepping for the strong country in magnesium research and applications.
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    RESEARCH PROGRESS ON PLASTIC DEFORMATION MECHANISM OF Mg ALLOYS
    LIU Qing
    Acta Metall Sin, 2010, 46 (11): 1458-1472.  DOI: 10.3724/SP.J.1037.2010.00446
    Abstract   PDF (1882KB) ( 3486 )
    Possible slip and twinning systems and their critical resolved shear stresses of Mg alloys with hcp structure were described. Research works on plastic deformation behavior and micro-mechanism of different kinds of Mg alloys were reviewed. Both microstructure and texture evolutions during different thermomechanical processes, both dynamic and static recrystallization mechanisms of Mg alloys were described and discussed. Deformation and strengthening mechanisms of precipitates hardening Mg alloys were also addressed with emphasis on the interaction between precipitates and twinning/slip.
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