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

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    , Volume 31 Issue 6 Previous Issue    Next Issue
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    MORPHOLOGY AND HIGH RESOLUTION IMAGE OF EUTECTOID TRANSFORMATION PRODUCTS OF Ti-H ALLOYS
    KANG Qiang;ZHANG Caibei;LAI Zuhan;NING Xiaoguang(Laboratory of Atomic Imaging of Solids; Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110015)(Department of Materials Science; College of Science; Northeastern University;Shenyang 110006)
    Acta Metall Sin, 1995, 31 (6): 241-247. 
    Abstract   PDF (596KB) ( 528 )
    The morphology and the fine structure of the hydrides in Ti-H alloys, containing 0.2-1.53 wt-% hydrogen, were investigated by TEM. It was found that the eutectoid transformation products from β-Ti(H) were consisted of δ hydrides and α-Ti,forming a micro-polycrystalline aggregate, while γ hydride was precipitated from α-Ti(H) directly. The atomic structure of these microcrystals were carefully delineated by HRTEM, showing that there may be ten variants of α-Ti around δ hydrides, which can keep two definite crystallographic relationships with α-Ti. The shear mechanism of the eutectoid transformation is discussed.
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    CORRELATION BETWEEN YIELD STRESS AND STRAIN RATE FOR METALLIC MATERIALS AND THERMAL ACTIVATION APPROACH
    TANG Changguo (Northwestern Polytechnical University; Xi'an 710072)ZHU Jinhua;ZHOU Huijiu (State Laboratory for Mechanical Behaviour of Materials;Xi'an Jiaotong University 710049)
    Acta Metall Sin, 1995, 31 (6): 248-253. 
    Abstract   PDF (376KB) ( 929 )
    The effect of the strain rate on tensile behaviour has been investigated for 4 metallic materials. From the tests, a two-stage linear relation has been found between yield stress(σ_s) and strain rate(ε),σ_s=σ_0+klgε. A new mechanism of thermal activation produced by the response of thermal vibration of dislocation lines to loading frequences was suggested, from which the critical strain rate calculated is in agreement with the measured one.Base on these studies the disspative map of the effect of ε on σs can be re-divided into rich-, poor-thermal activation region.
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    MICROSTRUCTURE AND PROPERTIES OF HIGH Si ALLOY ZA27 PRODUCED BY SPRAY DEPOSITION
    YANG Liushuan; PANGLijun;YANG Gencang; ZHOU Yaohe (State Key Laboratory of Solidification Processing; Northwestern Polytechnical University;Xi'an; 710072)
    Acta Metall Sin, 1995, 31 (6): 254-260. 
    Abstract   PDF (547KB) ( 531 )
    The microstructure and high-temperature properties of ZA27 alloy containing 4% Si and 0.3 % Fe produced by spray deposition are investigated. The microstructure of the alloy was made up of porosity(2%—4%), spheroial and uniform silicon-riched phases(30%—40%) and three kinds of substrate. The micro-hardness(HV) and high-temperature hardness(HB) of the alloy produced by spray deposition or conventional casting process make no difference before aging, but all the above properties is greatly improved by spray deposition after aging.
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    EFFECTS OF SULPHUR CONTENT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ALLOY K4169
    ZHOU Lanzhang; GUO Jianting (Institute of Metal Research; Chinese Academy of Sciences;Shenyang 110015)
    Acta Metall Sin, 1995, 31 (6): 261-265. 
    Abstract   PDF (419KB) ( 772 )
    Sulphur segregated strongly to interdendritic regions and promoted to form Y-M_2SC phase during solidification, and it also promoted segregation of Nb to form Laves phase. The more sulphur in the alloy, the more Laves phase formed. Mechanical Properties test showed that sulphur had bad effects on tensile properties at room temperature and at 650℃, and strongly decreased stress-rupture properties at 650℃, 620 MPa. Observation under SEM revealed that in high sulphur content alloy the fracture feature of Laves phase was of cleavage,and cracks initiated at Laves-matrix interfaces.
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    IMPROVEMENT OF MECHANICAL PROPERTIES AND CORROSION RESISTANCE OF Cu-Ni ALLOY BY TRACE OF BORON ADDITION
    WANG Jihui; JIANG Xiaoxia;LI Shizhuo (Institute of Metal Research; ChineseAcademy of Sciences; Shenyang 110015)
    Acta Metall Sin, 1995, 31 (6): 266-271. 
    Abstract   PDF (387KB) ( 493 )
    An attempt was made of to improve the mechanical properties but especially the corrosion resistance for 70Cu-30Ni alloy to marine supplies by trace of boron addition.Experiments of EMPA,XRD and SEM show that the strength of the alloy adding 0.005%-0.012%B may increase and the plasticity decreases somewhat. The improvement over the corrosion rate may be at a certain extent and of the corrosive wear rate quite obvious.
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    ELECTRIC FIELD MODIFICATION DURING SUPERPLASTIC DEFORMATION OF LY12CZ DURALUMIN
    LI Miaoquan; WU Shidun(Northwestern Polytechnical University; Xi'an 710072)
    Acta Metall Sin, 1995, 31 (6): 272-276. 
    Abstract   PDF (296KB) ( 551 )
    Quantitative examination was made of the influence of external intensive electric field on grain size and aspect ratio of grains during superplastic tension and free bulging of duralumin LY12CZ without any pretreatment by the Heyn's method. During tension subjected to electric field, more homogeneously distributed particulares of secondary phase,Al_2CuMg, may precipitate out to stabilize the microstructure and not only the coarsening of grains may be restrained in the primary stage but also the shape of grains may tend towards equiaxial state. Moreover, it is believed that the electric field improves firmly the superplasticity of LY12CZ duralumin alloy.
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    EFFECTS OF HEAT TREATMENT ON Pb-DOPED Bi-2223 SUPERCONDUCTOR
    ZHANG Liuwan; CHEN Tingguo; XIE Xiaoming; WU Xiaochu; SHITiansheng(Shanghai Institute of Metallurgy; Chinese Academy of Sciences;Shanghai 200050) LI Xiangting; GAO Jianhua; SUN Jing(Shanghai Institute of Ceramics;Chinese Academy of Sciences; Shanghai 200050)
    Acta Metall Sin, 1995, 31 (6): 277-285. 
    Abstract   PDF (697KB) ( 550 )
    The annealing effects on the Pb-doped BPSCCO 2223 phase were studied by in situ electric resistivity measurement, XRD, TGA, TEM and EPMA. Annealing at hight temperature ranging from 650℃ to 800℃under higher oxygen pressure will incur the precipitaion of a Ca_2PbO_4-modified phase. and the impurity phase would be decomposed upon annealing under lower oxygen pressure. With the formation of the impurity phase, the sample's mass and resistivity are increased. and the modulated structure is changed from pure Pb-type to pure Bi-type. While the impurity is decomposed, the mass and the resistiviey of the sample are decreased. and the modulated structure is back to original Pb-type. In addition, the proper amount of precipitation of the Ca_2PbO_4-modified phase has a positive influence on both superconductivity and the weak links between the superconducting grains.
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    TENSILE DEFORMATION AND FRACTURE OF Ti_3Al BASED ALLOY
    AI Suhua; GUAN Shaoxuan (State Key Laboratory Fatigue and Fracture of Materials; Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110015)FENG Zemin; GE Jingyan(Department Science and EngineeringNortheastern University; Shenyang 110006)
    Acta Metall Sin, 1995, 31 (6): 286-288. 
    Abstract   PDF (249KB) ( 482 )
    The tensile properties of Ti3Al based alloy undergone 3 different regimes of solutioning treatment have been examined at room and elevated temperatures. The deformation and fractrure feature of the typical specimens have been observed under SEM and TEM. It is found that the mechanical properties correlated closely with the changes of fracture surface and dislocation configuration. With increasing testing temperature the strength decreased and the ductility increased. but with increasing solution temperature the strength increased and the ductility decreased. The cleavage fracture is revealed at room temperature in the three microstructures and the mixed (cleavage and intergranular) fractrue at elevated temperature.
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