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

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    , Volume 34 Issue 11 Previous Issue    Next Issue
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    INVESTIGATION ON MICROSTRUCTURE AND SUPERPLASTICITY OF A NiAL-BASED MULTIPHASE ALLOY
    CHEN Rongshi;GUO Jianting;YIN Weimin;ZHOU Jiyang (Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110015)(Department of Materials Engineering; Dalian University of Technology;Dalian 116023)
    Acta Metall Sin, 1998, 34 (11): 1121-1125. 
    Abstract   PDF (1862KB) ( 854 )

    The microstructure of a NiAl-based multiphase alloy with a composition of Ni-25Al-25Cr has been investigated, which consists of NiAl matrix surrounded by a eutectic of α-Cr, β-Ni(Al,Cr) and γ'-Ni3(Al,Cr), and a large amount of α-Cr precipitates distributed uniformly in NiAl matrix. This alloy exihibits superplasticity elongation as high as up to 480% at 1123-1223 K and strain rates of 2.2×10-4 -3.3×10-2 s-1. The fracture after superplasticity deformation results from cavities generated by grain boundary sliding and cleavage in the grains, the mechanism for superplasticity has also been discussed.

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    ELECTRICAL PROPERTIES OF Fe_3Al INTERMETALLICS
    YU Xinquan;SUN Yangshan;MEI Jianping;SUN Guoxiong (Department of Materials Science and Engineering;Southeast University; Nanjing 210096)
    Acta Metall Sin, 1998, 34 (11): 1126-1130. 
    Abstract   PDF (441KB) ( 795 )

    The electrical properties of Fe3Al intermetallics have been studied. The results indicate that the binary Fe3Al alloys have high electrical resistivity which relates to Al content. Additions of alloying elements further increase the electrical resistivity. An anomalous relationship between resistivity and temperature has been found in the temperature range of 20-1100℃,and the mechanism of the phomenon has also been discussed.

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    OXIDATION RESISTANCE OF Fe_3Al INTERMETALLICS AT HIGH TEMPERATURES
    SUN Yangshan;YU Xinquan;HUANG Haibo;SUN Guoxiong (Department of Materials Science and Engineering; Southeast University; Nanjing 210096)
    Acta Metall Sin, 1998, 34 (11): 1131-1136. 
    Abstract   PDF (2002KB) ( 993 )

    The oxidation resistance of the binary Fe3Al decreases rapidly with the increase of temperature when the temperature is above 1000℃. SEM observations have revealed wisker-shaped oxides on specimen surface oxidized at 1200℃. Cavities and internal oxidation have been observed between the oxidation layer and the matrix of oxidized specimen. Microalloying of Ce increases the oxidation resistance of Fe3Al based alloys significantly. After oxidizing at 1200℃ for a long time (120 h), the specimen surface of the Fe3Al alloy containing cerium is still smooth without spalling and its oxidation resistance is one order of magnitude higher than that of the alloy without cerium addition.

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    ROOM TEMPERATURE MECHANICAL BEHAVIOR OF B2-ORDERED Fe_3Al SINGLE CRYSTALS
    ZHENG Weiwei;YANG Wangyue;LIU Qing;SUN Zuqing(Department of Materials Science and Engineering; University of Science and Technology Beijing; Beijing 100083)
    Acta Metall Sin, 1998, 34 (11): 1137-1142. 
    Abstract   PDF (2312KB) ( 573 )
    A detailed study of room temperature mechanical behavior of B2-ordered Fe3Alsingle crystals had been conducted. It was found that the yield strength, plastic elongation and work-hardening rate were changed with orientations. The highest ductility was measured from the specimen with the orientation near [110], where the plastic elongation is 42%. In contrast, at near [100] the plastic elongation is only 14.1%. The high work-hardening rate of the orientation near [110] was confirmed to be the results of superdislocation interaction, and the dissociation of two-fold superdislocations into single dislocations led to cross-slip, which resulted in further increase in elongation. The low work-hardening rate of near [211] was due to single active slip system and the superdislocations kept two-fold until the specimen was fractured.
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    ELEVATED TEMPERATURE DEFORMATION BEHAVIOR OF IN SITU MULTIPHASE COMPOSITE (NiAl-28Cr-6Mo)TiC
    JIANG Dongtao;GUO Jianting;LI Gusong;SHI Changxu (Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110015)
    Acta Metall Sin, 1998, 34 (11): 1143-1148. 
    Abstract   PDF (1062KB) ( 609 )
    An intermetallic matrix composite (NiAl-28Cr-6Mo)-TiC has been successfully fabricated by using reaction synthesis method. The elevated temperature deformation behavior of the in situ multiphase composite was investigated. The flow stress decreases with increasing temperature or decreasing initial strain rate. The deformation behavior of the composite can be adequately described by the power law. The stress exponent and activation energy are calculated and compared with other similar NiAl-based composites.
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    TEM STUDY ON THE MICROSTRUCTURE OF THE NiCrAlYSi COATING/IC6 ALLOY SUBSTRATE
    XING Zhanping;HAN Yafang(Beijing Institute of Aeronautical Materials; Beijing 100095)CHENG Zhiying (Tsinghua University; Beijing 100084)
    Acta Metall Sin, 1998, 34 (11): 1149-1152. 
    Abstract   PDF (1953KB) ( 507 )
    Using vacuum arc deposition technology NiCrAlYSi coating was deposited on the Ni3Al based alloy IC6. The microstructure between the coating and the substrate interface was investigated by the transmission electron microscopy (TEM). The results show that the coating mainly consisted of the γ twins, but the fine γ' precipitates existed in the γtwin plates. These precipitates were coherent with the γ phases. In the influence zone which consisted of γ+γ' phases, fine γ'precipitates also existed in the γ phases.
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    EFFECT OF YTTRIUM AND SILICON ON MICROSTRUCTURE AND PROPERTIES OF Ni_3Al BASE ALLOY IC6
    HAN Yafang;XIAO Chengbo (Beijing institute of Aeronautical Materials; Beliing 100095)
    Acta Metall Sin, 1998, 34 (11): 1153-1157. 
    Abstract   PDF (1305KB) ( 617 )
    The effect of different amounts of yttrium and silicon on the microstructure of directionally solidified Ni3Al base alloy IC6 was studied with electron probe microstructural analysis(EPMA). The oxidation resistance at 1100℃, stress rupture property under 1100℃ /80MPa, thermal fatigue property at 1100℃ and tensile properties at different temperatures were tested, the results show that the high temperature oxidation resistance, stress rupture property and thermal fatigue property of alloy IC6 are increased by adding proper amounts of yttrium. Silicon is beneficial to the high temperature oxidation resistance but harmful to the stress rupture property and thermal fatigue property. The addition of yttrium and silicon has no obvious influence on the tensile properties.
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    MECHANISM OF IMPROVING THE COHERENCE BETWEEN OXIDE SCALE AND SUBSTRATE OF Ni_3Al BASE ALLOY IC6 BY YTTRIUM
    XIAO Chengbo;HAN Yafang (Beijing institute of Aeronautical Materials; Beijing 100095)
    Acta Metall Sin, 1998, 34 (11): 1158-1162. 
    Abstract   PDF (1642KB) ( 550 )
    The oxidation resistance of Ni3Al base alloy IC6 with different amounts of yttrium at 1100℃ was determined. The results showed that the coherence between the oxide scale and the substrate is substantially improved by adding 0.04% -0.30%Y. The results of the X-ray line scan of EPMA showed that a diffusion layer rich in Ni, Mo and poor in Al is formed during the oxidation process, and that segregation of sulfur to the interface between the oxide scale and the substrate is inhibited by yttrium, which results in the improvement of the coherence between the oxide scale and the substrate. The results of X-ray diffraction analysis of the spalled oxides showed that yttrium can promote the slective oxidation of aluminum and hence improve the high temperature oxidation resistance of alloy IC6.
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    EFFECT OF METALLURGICAL FACTORS ON THE RESISTANCE OF CAVITATION EROSION OF Ni_3Al BASED ALLOYS
    YE Wujun;FENG Di;CHEN Beijing;LUO Heli (Central Iron and Steel Research institute; BeiJing 100081)
    Acta Metall Sin, 1998, 34 (11): 1163-1166. 
    Abstract   PDF (362KB) ( 585 )
    Effect of Al, Cr, Fe and Mo concentrate on the resistance of cavitation erosion of Ni3Al based alloys was studies, the results show that Zr and B toughened Ni3Al alloy with Al concentrate of 6%-9% possesses excellent resistance of cavitation erosion and the decrease of the γ' forming elements concentrate causes the decline of the resistance of cavitation erosion. The introduction of Fe and Mo somewhat decreases the resistance to cavitation erosion.
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    SOLID-STATE JOINING OF TiAl BASED ALLOYS
    HE Yuehui;HUANG Baiyun;WANG Bin;LIU Yong;WANG Jiannong(State Key Laboratory for Powder Metallurgy;Central South University of Technology; Changsha 410083) GUO Jingjie (Materials Science College; Harbin University of Technology; Harbin 150001)
    Acta Metall Sin, 1998, 34 (11): 1167-1172. 
    Abstract   PDF (1862KB) ( 600 )
    Solid-state joining between TiAl based alloy samples with various microstructures was investigated. When joining between coarse-grained TiAl based alloys, a fine recrystallized microstructure, which was different from those of the substrates, formed in the joining interface. When joining between a coarse-grained TiAl based alloy and an alloy of fine duplex microstructure, the coarse-grained part was penetrated by the fine-grained part due to its high superplasticity, and good joining interface was obtained. When solid joining between fine-grained parts, because both parts had high superplasticity, perfect joining interface with the microstructure of substrate was obtained through grains sliding in thermal plastic deformation, and the joining component had high mechanical properties (σba=533 MPa and δ≈2%). So all the fracture occurred away from the joining interface.
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    SUPERPLASTICITY BEHAVIORS OF THERMALLY DEFORMED TiAl BASED ALLOYS
    HUANG Baiyun;HE Yuehui;DENG Zhongyong;WANG Jiannong (State Key Laboratory for Powder Metallurgy;Central South University of Technology; Changsha 410083)SUN Jiang (Department of Materials Science;Shanghai Jiaotong University;Shanghai 200030)
    Acta Metall Sin, 1998, 34 (11): 1173-1177. 
    Abstract   PDF (1648KB) ( 635 )
    Superplasticity behaviors under the conditions of a temperature range from 1000℃ to 1075℃ and strain rates varlying from 1×10-6 to 8×10-3 s-1 were investigated for Ti-33Al-3Cr alloy with 1 μm grain size obtained by multi-step thermal mechanical treatment. Test results show that this TiAl alloy possesses good superplasticity. It exhibits a strain rate sensitivity coefficient of 0.9 at the strain rate of 3×10-4 s-1 and temperatures from 1000℃ to 1075℃. Tensile elongation of 517% was obtained at the temperature of 1075℃ and the strain rate of 8×10-5 s-1. Test results also show that this alloy has a low thermal activation energy of about 250 kJ/mol. Superplasticity behavior obtained from this fine-grained TiAl is due to dynamic recrystallization during tensile deformation.
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    THE TRIBOLOGICAL AND WEAR BEHAVIOR OF ALUMINUM MATRIX COMPOSITES
    WANG Wenlong;WU Junhua;ZHANG Gooding (State Key Lab of Metal Matrix Composites;Shanghai Jiao Tong University;Shanghai;200030)
    Acta Metall Sin, 1998, 34 (11): 1178-1182. 
    Abstract   PDF (465KB) ( 702 )
    The tribological and wear behavior of aluminum matrix composites(AMC) under the condition of braking experiments was measured.The results indicate that compared with cast iron,AMC can greatly reduce the temperature of the friction surface and maintain a stable friction coefficient under high press and rotating brake speed.Therefore,AMC have an advantage over the traditional material of cast iron and demonstrate themselves to be appropriate materials for brake disk.It is also found out that the wear value of AMC has a relationship with the volume fraction of SiC particles and the type of matrix material. Under the same braking condition,the wear value of AMC is decreased by increasing the volume content of particles.
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    MECHANICAL PROPERTIES AND CRYSTALLITE ORIENTATION DISTRIBUTION OF SiC_p REINFORCED ALUMINIUM MATRIX COMPOSITE SHEETS
    CHEN Liqing;L U Yuxiong;BI Jing (Institute of Metal Research;Chinese Academy of Sciences;Shenyang 110015)
    Acta Metall Sin, 1998, 34 (11): 1183-1187. 
    Abstract   PDF (489KB) ( 693 )
    The mechanical properties of an aluminium alloy sheet (Al-3.OCu-1.5Mg-0.4Mn)reinforced by 15% silicon carbide particulate via powder metallurgy technique were investigated under hot-and cold-rolling conditions,and the crystallite orientation distribution in these sheets were also determined by ODF analysis.The hot-rolled sheet composite exhibits much higher ultimate tensile strength and elongation comparing to those of the cold-rolled one. However, the cold-rolled sheet has an elevated 0.2% yield strength.The texture of the cold-rolled sheet composite consists of three weak components, i.e. shear component {001}<110> and two other typical fcc components {110}<112> and {3 3 14}<773>, while the hot rolling texture is almost random. The textured microstructure has an effect on the 0.2% yield strength and do not have any influence on the ultimate tensile strength.The decrease in ultimate tensile strength of the cold-rolled sheet is attributed mainly to the micro-damages produced during cold rolling.
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    EFFECTS OF PARTICLE SIZE AND MATRIX STRENGTH ON THE FAILURE MECHANISM OF SiC_p REINFORCED ALUMINIUM MATRIX COMPOSITES
    LU Yuxiong;BI Jing;CHEN Liqing;ZHAO Mingjiu (Institute of Metal Research;Chinese Academy of Sciences;Shenyang 110015)
    Acta Metall Sin, 1998, 34 (11): 1188-1192. 
    Abstract   PDF (1660KB) ( 790 )
    Three different sizes(3.5, 10, 20μm) of SiC particulate and Al-Cu alloy powder were employed to fabricate composites via powder metallurgy technique. The fracture surfaces of the tensile specimen and EDX analysis show that the reinforcement size has a prominent effect on the failure mechanism of the composites. When the reinforcement size exceeds 10 μm, the failure of the MMC results from the SiC.cleavage crack.The breakage is due to the cavity and micro-crack formed by Al-SiC interfacial tearing,however,when the reinforcement size is 3.5 μm. The Al tearing ridge on the SiCp. surface is similar to the conglutination of Al by pulling-out of whisker in SiCw/Al. The tensile test result shows that the MMCs reinforced with small size of particulate has an elevated ultimate tensile strength and elongation. The low strength MMCs, due to their lower matrix strength, has increased plastics and their failure under tensile load is dominated by cavity nucleation, growth and coalescence nearby the SiCp.
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    THE EFFECT OF PARTICLE SHAPE ON DUCTILITIES OF SiC_p/LD2 COMPOSITES
    QIN Shuyi;WANG Wenlong;ZHANG Gooding (State Key Lab of Metal Matrix Composites;Shanghai Jiao Tong University;Shanghai 200030)
    Acta Metall Sin, 1998, 34 (11): 1193-1198. 
    Abstract   PDF (2715KB) ( 734 )
    Blunted SiC particles were selected as reinforcement to fabricate SiC./LD2 composites. Compared with a general SiC particle,the blunted SiC. reinforced composite has higher ductility.Analysises of finite element method(FEM) and tensile fractographic scanning electron microscope(SEM)show that particle fracture is the main failure mechanism of composites after T6 treatment.The ductility improvement of processed SiCp/LD2 is attributed to decrease the heat-residual-strain concentration near penetrating particle corner and the possibility of penetrating particle corner fracturing at low level of external strain when the penetrating particle corner has been blunted. The main failure mechanism of composites after extruded but no T6 treatment is matrix failure. Therefore, extent of ductility improving of composites after T6 treatment is higher than that of composites after extruded.
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    THE SPATIAL DISTRIBUTION OF REINFORCEMENTS IN ALUMINIUM MATRIX COMPOSITES
    FAN Jianzhong;SANG Jimei;ZHANG Yongzhong;ZHANG Kui;ZHANG Shaoming;SHI Likai (General Research Institute for Non-ferrous Metal; Beijing 100088)
    Acta Metall Sin, 1998, 34 (11): 1199-1204. 
    Abstract   PDF (3327KB) ( 1099 )
    Effect of high energy ball milling and general mixing on the spatial distribution of reinforcements of SiCp (B4Cp)/Al composites was investigated systematically at qualitative and quantitative level. High energy ball milling,which leads to the dispersed homogeneous distribution of reinforcements in the matrix, is the most effective method for obtaining homogeneous distribution of reinforcements. There are clusters of reinforcements in the composites fabricated by general mixing. The degree of reinforcement clusters is related to mixing medium and mixing time. For uniform distribution of reinforcements by dry blending procedure there is a optimum mixing time, however, by wet blending procedure the distribution of reinforcement is improved with the increasement of mixing time.
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    THERMODYNAMIC AND KINETIC ANALYSIS OF IN SITU SYNTHESIS OF MoSi_2-SiC COMPOSITE
    ZHANG Laiqi;SUN Zuqing;ZHANG Yue;YANG Wangyue(State Key Laboratory of Advanced Metal Materials; University of Science & Technology Beijing; Beijing 100083)
    Acta Metall Sin, 1998, 34 (11): 1205-1209. 
    Abstract   PDF (418KB) ( 669 )
    On the basis of the thermodynamic calculation,XRD and DTA measurements, in view of thermodynamics and kinetics, the phase formation involved in the processing of reactively in situ reactive synthesis of MoSi2-SiC composites are systematically analyzed. Proper heating rate, sintering temperature, and sintering time are recommended.
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    PROPERTY OF RESISTANCE TO IRRADIATION DAMAGE OF ODS FERRITIC ALLOYS
    SUN Jiguang;CHEN Chaoqing;ZHANG Xishun (General Research institute for Nonferrous Metals; Beijing 100088)TIAN Yan;SHAN Bingquan;PAN Qingchun (Central Iron & Steel Research institute; Beijing 100081)
    Acta Metall Sin, 1998, 34 (11): 1210-1216. 
    Abstract   PDF (2207KB) ( 823 )
    The property of resistance to irradiation swelling of oxide dispersion strengthened(ODS) ferritic alloys,prepared by mechanical alloying(MA), has been studied by means of electron and ion irradiation simulations.The results showed that ODS alloys are superior to austenitic alloys in the resistance to irradiation swelling and segregation. After high influx of 1.7×1017/cm2 argon ions implantation,bubbles were formed and the top of which chapped slightly on individual sections of the ODS material surface.In addition, ductile-to-brittle transition temperature(DBTT) of ODS alloys were higher than that of Fe-13%Cr alloy. There existed anisotropy of strength induced by rolling.Therefore,ductility of ODS needed to be enhanced.
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    EFFECTS OF Ti ON STRENGTHENING OF ODS FERRITIC ALLOY FOR ADVANCED FBR CLADDING APPLICATION
    TIAN Yun;PAN Qingchun;LIU Guangzu;SHAN Bingquan;YANG Fenglan (Central Iron and Steel Research Institute; Beijing 100081)
    Acta Metall Sin, 1998, 34 (11): 1217-1222. 
    Abstract   PDF (2069KB) ( 676 )
    When an optimum machanical alloying(MA) process was selected, the dispersoids (Y2O3) added in the ferritic alloy will initially dissolve into a matrix during MA, then a kind of super fine complex oxide(Y2Ti2O7) will precipitate during following hot consolidation process By this transition, the dispersoids can be obviously refined from 30 um (Y2O3) to smaller than 10 nm (Y2Ti2O7) and even more uniformly distributed in alloy matrix. It can remarkably enhance the effect of dispersion strengthening and enable the alloy's strength, especially creep strength,to reach a superior high level enough to satisfy the specification of commercial type FBR. But when a high content of Ti (>2%) is added in the alloy, X phase can easily precipitate in the alloy's matrix during aging the alloy at 800℃ for 24 h, which can not contribute to 650℃ tensile strength, and is very harmful to tensile ductility and creep strength of the alloy.
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    THE INFLUENCE OF SEVERAL FACTORS ON THE PREPARATION OF NITRIDE IRON MAGNETIC FLUID
    LIU Silin;YU Yingyi;TENG Ronghou;XU Jiaoren (Central Iron and Steel Research Institute; Beijing 100081)
    Acta Metall Sin, 1998, 34 (11): 1223-1226. 
    Abstract   PDF (731KB) ( 567 )
    The influences of Fe(CO)5 thermal decomposition temperature (iron nitriding temperature), the flow of NH3 and surface activated agent on the preparation of nitride iron magnetic fluid were discussed. The result shows that the appropriate Fe(CO)5 theraml decomposition temperature is 180 to 210℃. Excessive NH3 and surface activated agent suitable to nanometer iron nitride magnetic particle and carrier liquid are necessary to preparing nitride iron magnetic with favorable property.
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    RESEARCH OF GALVANIZED PROCESS OF ELECTROLYTIC COPPER FOIL
    LENG Daguang;HU Jingjiang;GUO Zongxun;XU Shumin (Zhaoyuan;JINBAO Electronics Co. Ltd; Shandong 265400)
    Acta Metall Sin, 1998, 34 (11): 1227-1229. 
    Abstract   PDF (223KB) ( 848 )
    This article discusses galvanizing methods adopted sulfate technology and researches a formula and conditions for manufacturing electrolytic copper foil. It shows that the technology can meet quality requirements and has the advantages of a stable process, easy to operate and a low cost. It is an ideal manufacturing process of galvanizing copper foil.
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    A NEW TECHNOLOGY OF OXIDATION RESISTANCE OF COPPER FOIL
    XU Shumin;LENG Daguang (Zhaoyuan JINBAO Electronics Co.Ltd;Zhaoyuan 265400)
    Acta Metall Sin, 1998, 34 (11): 1230-1232. 
    Abstract   PDF (276KB) ( 833 )
    The specification requirements of oxidation resistance of copper foil at 180℃ and the technological proceeding condition were briefly discussed. A new composition of passivating solution and conditions were suggested and verified to be effective for improving the oxidation resistance of copper foil.The mechanism of oxidation resistance was also discussed.
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