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

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    , Volume 33 Issue 12 Previous Issue    Next Issue
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    论文
    OBSERVATION OF COMPETITIVE GROWTH IN A DIRECTIONALLY SOLIDIFIED NICKEL BASE SINGLE CRYSTAL SUPERALLOY
    FU Hengzhi; HE Guo; LI Jianguo (State Key Laboratory of Solidification Processing;Northwestern Polytechnical University; Xi'an 710072)
    Acta Metall Sin, 1997, 33 (12): 1233-1238. 
    Abstract   PDF (2185KB) ( 983 )

    Experiments have been done on bi and tetra-crystal competitive growth in a nickel base single crystal superalloy to imitate the competitive growth during directional solidification. The grain orientations were controlled by seed crystals. Results show that the competitive growth is dependent on the relative orientations of grains and their relation with the direction of maximum temperature gradient. Grains with their preferred growth direction (<001> in nickel base superalloy) nearer to maximum temperature gradient will grow faster than those with their preferred growth direction far away from maximum temperature gradient in the condition of bi-crystal as well as tetra-crystal competitive growth. A third grain may appear and grow as a single crystal if two seed crystals with their preferred growth directions are far away from that of maximum temperature gradient in a divergent way in bicrystal competitive growth.

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    LOW CYCLE FATIGUE BEHAVIOR OF A DZX40M DIRECTIONALLY SOLIDIFIED Co-BASED SUPERALLOY──Ⅰ.Fatigue and Its Mechanism at Room Temperature
    LU Zheng; ZHOU Huihua; XU Yongbo; HU Zhuannqi (State Key Laboratory for Fatigue and Fracture of Materials; Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)
    Acta Metall Sin, 1997, 33 (12): 1239-1245. 
    Abstract   PDF (1830KB) ( 741 )

    Low cycle fatigue behavior of a DZX40M directionally solidified Co-based superalloy has been investigated at room temperature in air under different total strain amplitudes ranging from 2.5 × 10(-3) to 6.0 × 10(-3). The results show that the cyclic hardening of the alloy appears at the first few cycles in the initial hardening stage, and then the saturation stage which is the major part of the whole fatigue life begins. Examination by TEM indicates that the initial hardening of the alloy is caused by the pile-up of the stacking faults at the intersection of stacking fault, while the saturation of the alloy during low cycle fatigue is arising from the transition of the stacking fault on the (111) to the closely spaced stacking fault ribbon on the (111).

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    LOW CYCLE FATIGUE BEHAVIOR OF A DZX40M DIRECTIONALLY SOLIDIFIED Co-BASE SUPERALLOY──Ⅱ.Fatigue and Its Mechanism at 700℃
    LU Zheng; LIU Lu; XY Yongbo; HU Zhuangqi (Stale Key Laboratory for Fatigue and Fracture of Materials; Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)
    Acta Metall Sin, 1997, 33 (12): 1246-1251. 
    Abstract   PDF (2935KB) ( 602 )
    An investigation has been made on the low cycle fatigue behavior of a DZX40M Co-base directionally solidified superalloy at 700℃ in air under the control of different total strain amplitudes ranging from 3.0 × 10(-3) to 6.0 ×10(-3). The results show that the alloy exhibits a pronounced initial hardening, and secondary hardening after a short saturation. Examination by TEM reveals that the initial hardening is arising from the pile-up of the stacking faults at the intersection of stacking faults, while the stress saturation is due to the obstacle to the motion of the stacking faults at the intersection becomes weaker, arising from the thermal activation, and the stress concentration of the pile-up of the stacking faults at the intersection. The secondary hardening is contributed to the formation of the dislocation tangle.
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    SOME REGULARITIES OF MONOTECTIC BINARY ALLOY SYSTEMS OF NON-TRANSITION METALS
    ZHANG Zhaochun; LI Chonghe; CHEN Nianyi (Shanghai Institute of Metallurgy;The Chinese Academy of Sciences Shanghai 200050)
    Acta Metall Sin, 1997, 33 (12): 1252-1255. 
    Abstract   PDF (383KB) ( 455 )
    An extended Miedema's cellular model of alloy systems has been applied to study the regularities of binary monotectic systems consisting of non-transition metals. It has been found that larger and smaller enhance liquid--liquid immiscibility. In the three-dimensional space spanned by atomic parameters, and △Z the representative points of the non-monotectic and monotectic systems with and without solid intermetallic compounds distributed in different regions separately. The criteria of the occurrence of two layer region can be obtained by artificial neural network trained by known data of phase diagrams.
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    PROCESS OF FORMATION OF CORROSION FILMS ON ALLOY 70Cu-30Ni IN SEAWATER
    ZHU Xiaolong; LIN Leyun (General Research Institute for Nonferrous Metals; China Nonferrous Metals Industry Corporation; Beijing 100088); LEI Tingquan (Harbin Institute of Technology; Harbin 150001)
    Acta Metall Sin, 1997, 33 (12): 1256-1261. 
    Abstract   PDF (1368KB) ( 789 )
    The characteristics and composition changes of the corrosion films of alloy 70Cu-30Ni immersed in seawater for different times were investigated.The results show that there is a Ni-rich zone in the films, which becomes wider and higher in the degree of Ni enrichment with increasing the immersed time. The film rich in Ni serves as an anode so as to protect the matrix. For the change of the structure or composition or for inner stress making the film broken, cracks or trenches appear in the film immersed in seawater for long time.With the solution and scaling off of the outer layer,the cracks or trenches become convex lines. Because the concentration ratio Ni / Cu at the convex lines is higher than average ratio Ni/Cu in the zone between convex lines,the preferred dissolution of convex lines leads the surface of the film to smoothness.The carbon in the film increases with increasing immersion time and can be thought to be from seawater not from residual carbon films.
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    INVESTIGATION OF TENSILE STRESS GENERATED BY PASSIVE FILM DURING CORROSION PROCESS FOR α-Ti
    LU Hong; GAO Kewei; NIE Yifan; CHU Wuyang (University of Science and Technology Beijing; Beijing 100083)
    Acta Metall Sin, 1997, 33 (12): 1262-1267. 
    Abstract   PDF (566KB) ( 537 )
    The α-Ti foil with protective layer in one side bended to corrosion surface gradually during corrosion process in 0.1 mol / L H2SO4, while the passive film was formed,i.e. a tensile stress was developed in the surface layer of the sample. The extra tensile stress grew gradually, whose maximum value was 313 MPa (average value of 5 samples),which was near or reached the yield stress. The extra tensile stress would be added to the load stress during SCC to facilitate the emission and motion of dislocation, so that SCC cracks could nucleate in lower stress(or lower KI).
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    CORROSIVE WEAR BEHAVIOR OF COPPER ALLOYS IN 3.5% NaCl+NH_3(NH_4~+) SOLUTION
    WANG Jihui; JIANG Xiaoxia; LI Shizhuo (Institute of Metal Research; The Chinese Academy of Sciences; Shenyang 110015)
    Acta Metall Sin, 1997, 33 (12): 1268-1274. 
    Abstract   PDF (1387KB) ( 581 )
    The corrosion rate, corrosive wear rate and polarization curves of aluminium brass and cupronickel alloy were determined in 3.5%NaCl and 3.5%NaCl+NH3(NH4+)solutions, the wear tracks of copper alloys were observed by SEM, the specific energy of the surface layer after corrosion was also measured by single pendulum scratching test. Experimental results show that the addition of ammonia or ammonium in 3.5%NaCl solution can accelerate the corrosion and corrosive wear of copper alloys, the corrosion potential shifts negativly,the corrosion current density increases. The ammonia or ammonium caused the surface embrittlement of copper alloys during corrosive wear.
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    DYNAMIC RECRYSTALLIZATION OF STEEL X65 DURING HIGH TEMPERATURE DEFORMATION
    CHENG Xiaoru; LI Huxing; GE Maoqi; CHEN Yihong; HU Yansheng (Wuhan Yejin University of Science and Technology. Wuhan 430081); ZHENG Lin; LUO Dexin;WEN Aqing; LUO Gang (Wuhan Iron & Steel Co.; Wuhan 430081)
    Acta Metall Sin, 1997, 33 (12): 1275-1281. 
    Abstract   PDF (508KB) ( 1243 )
    The high temperature compression tests of X65 steel have been carried out by using THERMECMASTOR-Z simulator. The hot deformation equation of austenite and the critical regression equations of dynamic recrystallization have been established. On the basis of recrystallization dynamics, the dynamic recrystallization rate equation has been established by means of σ-εcurves as followsXd=1-exp[-2.58(ε/εp-0.83)1.52] εp=1.25×(1Nz-26.97)/17.14 Z= ·exp(364.5/RT)
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    HEAT DAMAGE OF LASER CLAD Ni-BASED WC COATING
    WU Xinwei; ZENG Xiaoyan; ZHU Beidi; TAO Zengyi; CUI Kun (Huazhong University of Science and Technology; Wuhan 430074)
    Acta Metall Sin, 1997, 33 (12): 1282-1288. 
    Abstract   PDF (1366KB) ( 797 )
    A 2 kW CO2 laser has been used to deposit Ni based WC alloy onto steel A3 substrate. The effects of ceramic-metal ingredient and laser processing conditions on the heat damage of coatings are studied. Results show that the heat damage level of WC particles in ceramic-metal composite coatings is mainly determinated by the chemical reaction between WC and binder. Further research shows that the mass fractions of carbon in binder, the kind,size and content of WC particles and the laser processing condition all directly affect the heat damage level of composite coatings.
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    MAGNETOTHERMAL ANALYSIS OF Fe_(72.7)Cu_1Nb_2V_(1.8)Si_(13.5)B_9 ALLOY
    WANG Zhi;HE Kaiyuan;ZHANG Luo (Northeastern University; Shenyang 110006)(Tianjin Institute of Technology; Tianjin 300191)(Shanghai Iron and Steel Research Institute; Shanghai 200940)
    Acta Metall Sin, 1997, 33 (12): 1289-1294. 
    Abstract   PDF (583KB) ( 436 )
    Thermomagnetic curves (σs-T curve) of Fe(72.7)Cu1Nb2V(1.8)Si(13.5)B9 alloy annealed at different temperatures (763-883 K) for 1h were investigated by magnetic analysis.Based on theσs1/8 -T curve and X-ray diffraction analysis, the changes in volume fraction,saturation magnetization and Curie temperature of α-Fe(Si) phase and residual amorphous phase with annealing temperatures as well as the correlation between them were determined.The results showed that the saturation magnetization and Curie temperature of α-Fe(Si)phase, σsαand were decreased a little with increasing of Ta when Ta< 823 K and then invariable for Ta≥823K. The saturation magnetization and Curie temperature of residual amorphous phase,σsα and TCα were all decreased monotonically with increasing of Ta in the whole annealing process and had a linear correlation between them. The dependences of magnetic coupling between α-Fe(Si) grains and of saturation magnetostriction on volume fractions of each phase were also discussed.
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