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

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    , Volume 30 Issue 13 Previous Issue    Next Issue
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    PHASE TRANSFORMATION FROM AN AMORPHOUS ALLOY INTO NANOCRYSTALLINE MATERIALS
    LU Ke (National Key Laboratory for RSA; Institurte of Metal Research;Chinese Academy of Sciences;Shenyang)
    Acta Metall Sin, 1994, 30 (13): 1-21. 
    Abstract   PDF (1576KB) ( 1463 )
    Polycrystalline materials with nanometer-sized grains,or called nanocrystalline materials, can be synthesized by crystallization of amorphous alloys. This new method for preparation of nanocrystalline materials has drawn much intensive investigations in recent years. A review is made of the synthesis method and the transformation process from the amorphous to the nanocrystalline phases, including the transformation kinetics,thermodynamics, and the transformation micromechanism.
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    ARTIFICIAL NEURAL NETWORK APPLIED TO PREDICTION OF INTERMEDIATE PHASES IN MOLTEN SALT PHASE DIAGRAMS
    TANG BO; QIN Pei; LIU Miaoxiu;ZHANG Weiming;CHEN Nianyi(Shanghai institute of Metallurgy; Chinese Academy of Sciences)
    Acta Metall Sin, 1994, 30 (13): 22-26. 
    Abstract   PDF (336KB) ( 607 )
    Artificial neural network is a new type ofinfonnation processing system based on modelling the neural system structure of human brain. Together with chemical bond parameters, it can be used to extract useful information from the experimental data of molten salt phase diagrams.The semi-empirical rules found can be used for the computerized prediction of the stoichiometry, the melting or decomposition temperature, and the melting behavior(congruent or incongruent melting) of the intermediate phases in unknown molten saltphase diagrams.
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    DISPERSOID AND SiC PARTICULATE STRENGTHENED Al COMPOSITES Ⅰ.FABRICATION AND MICROSTRUCTURE
    MA Zongyi;WU Shengjin; NING Hiaoguang; LUO Ming;LU Yuxiong;BI Jing (Institute of Metal Research;Chinese Academy of Sciences; Shenyang);ZHANG Yuzheng (Northeastern University; Shenyang)
    Acta Metall Sin, 1994, 30 (13): 27-32. 
    Abstract   PDF (443KB) ( 494 )
    The Al_4C_3 and Al_2O_3 dispersoids and SiC particulate strengthened aluminum composites were successfully fabricated by mechanical alloying of Al powder,C powder and SiC particulates, followed by heat treatment, cold compaction and hot extrusion.Metallography, TEM and HREM observations indicate that the interfacial bonding between SiC particulates and Al matrix is fair, and the characteristics of matrix powders affects the unifromity of SiC particulate distribution in matrix. The existence of Al_2O_3 cannot be determined by XRD and TEM due to low content and fine size of Al_2O_3 . Rod-like Al_4C_3 single crystals with a mean diameter of 0.02 μm and a meam length of 0.2 μm are uniformly distributed in matrix, and have no consistent orientation relationship with Al matrix. The interfacial bonding between Al_4C_3 and Al is excellent, no transitional layer exists.
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    DISPERSOID AND SiC PARTICULATE STRENGTHENED Al COMPOSITES Ⅱ. PROPERTIES AND FRACTURE BEHAVIOUR
    MA Zongyi;WU Shengjin;LUO Ming;LU Yuxiong;BI Jing(Institute of Metal Researth; Chinese Academy of Scicnces; Shenyang);ZHANG Yuzheng (NorlheasternUniversity; Shenyang)
    Acta Metall Sin, 1994, 30 (13): 33-38. 
    Abstract   PDF (431KB) ( 520 )
    The tenisle tests and fracture surface analyses on the Al_4C_3. Al_2O_3 dispersoids and SiC particulate strengthened aluminum composites fabricated by mechanical alloying were carried out, as well as elastic modulus and CTE of the composites were measured.It was indicated that the strength of SiC_p/ Al composites is obviously improved due to the formation of Al_4C_3 and Al_2O_3 dispersoids, and increases with increasing C content or oxidation time of aluminum powder. The elevated temperature strength of Al_4C_3 dispersoid and SiC particulate reinforced aluminum composite is superior to that of SiC whisker reinforced 2024Al composite. The elastic modulus of Al_4C_3/ Al composite is raised due to the addition of SiC particulates, and CTE is reduced further.The fracture surfaces of the composites display mixture type of large dimples and fine dimples. The amount of cracked SiC particulates on tensile fracture surfaces of the compsites increases with increasing the strength of compsite matrix.
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    MICROSTRUC TURE AND PROPERTIES OF IN-SITU TiC PARTICULATE REINFORCED Al-Si ALLOY COMPOSITE
    Wang Zidong; Li Qingchun(Harbin Institute of Technology)Li Chunyu; Zhang Lusan; Yu Guifu(Beijing Institute of Aeronutical Materials)
    Acta Metall Sin, 1994, 30 (13): 39-44. 
    Abstract   PDF (401KB) ( 652 )
    A novel technique to make in-situ TiC Particulate in an Al-5.6Wt%Si matrix has been developed through direct-contact reaction.An Al-Ti-C compact is pushed into Al-Si alloy at 750℃. The titanium and carbon react directly to form fine TiC particulates (0.1-1.0μm) in liquid Al-Si alloy.The structures indicate that TiC enters into α-Al matrix during solidification and α-Al matrix is reinforced by the dispersion of TiC particulates. This new way to produce cast metal matrix composites is of great future.
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    XRD STUDIES ON A PHASE TRANSFORMATION OF Co
    HAO fianmin;WANG Lijie(Wianjin Electronic Materials Research Institute)LIU Shourong;LIANG Fuqi (Tianjin Hard Metal Institute)
    Acta Metall Sin, 1994, 30 (13): 45-48. 
    Abstract   PDF (233KB) ( 697 )
    Phase transformation of Co has been studied by using high temperature X-ray diffraction.At a temperature above 425℃ the hcp structure of Co transformed to an fcc phase. The most finding is that the transformation below 425℃ is very difficult to induce by simple cooling. If fcc-Co deformed by grinding,it is easy to transform into hcp phase at room temperature.So, at the process of transformation from fec into hcp, deformation is very important.
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