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ISSN 1005-0302
CN 21-1315/TG
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      28 July 2001, Volume 17 Issue 04 Previous Issue    Next Issue
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    Research Articles
    Crystalline precipitate in a bulk glass forming Zr-based alloy and its effect on mechanical properties
    Guo HE, Zan BIAN, Guoliang CHEN, Jian LU, Dianjing CHEN, Guochao TU, Guojun CHEN, Xiaojun HU
    J. Mater. Sci. Technol., 2001, 17 (04): 389-398. 
    Abstract   HTML   PDF (3064KB)
    Cylindrical and sheet samples of bulk metallic glassy with a nominal composition of Zr52.5N14.6Al10CU17.9Ti5 (at. pct) were prepared by melt injection casting. The crystalline precipitates formed during the casting were studied by metallographic observations and selected-area electron diffractions. The effect of crystalline precipitates on the mechanical properties were investigated by tensile and compressive tests at room temperature. Oxygen contents and the sample sizes (or cooling rates) strongly affect the formation of the crystalline precipitates. Overheating the alloy melt up to 200 K above its melting temperature can effectively prevent the formation of the crystalline precipitates to get fully glass samples with diameters up to 2 mm for cylinders and thickness up to 1 mm for sheets even the oxygen content is as higher as 0.08 wt pct. With increasing the sample sizes, the crystalline precipitates increase in volume fraction and size. The formation of the precipitates experienced two stages, i.e., initially nucleation and isotropic growth, and then anisotropic growth, finally forming faceted morphologies. Fully glassy Zr52.5Ni14.6Al10Cu17.9Ti5 alloy exhibits excellent tensile and compressive properties at room temperature. The presence of crystalline precipitates significantly decreases the tensile and compressive properties. With increasing the crystalline precipitates, the area of vein patterns on the fracture surface decreases, but the fracture steps increase, and the fracture mode changes from ductile to brittle resulting from the larger stress concentration caused by the larger sizes and faceted shapes of the crystalline precipitates.
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    Role of P, S and B on creep behavior of alloy 718
    Zhuangqi HU, Hongwei SONG, Shouren GUO, Wenru SUN
    J. Mater. Sci. Technol., 2001, 17 (04): 399-402. 
    Abstract   HTML   PDF (996KB)
    The doping of phosphorus, sulfur and boron in IN718 superalloy can remarkably influence the creep behavior. The modifications of the minor elements seem not to vary the stress exponent and the influences primarily concentrate on the effective diffusion coefficient. A pronounced beneficial interaction between P and B and a weaker detrimental interaction between P and S have been obtained. The preexponential frequency constant is proved to be strongly related with the creep activation energy because of the so-called compensation effect. The compensation temperature has been determined to be about 1080 K, which corresponds to the transformation temperature from rapidly coarsened gamma " phase to delta phase. It has been proposed that trace elements can influence the effective diffusion coefficient individually or cooperatively, which in turn either retard or speed the creep process.
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    Fatigue crack propagation behavior of TiNi50.6 shape memory alloy
    Guangbin RAO, Jianqiu WANG, We KE, Enhou HAN
    J. Mater. Sci. Technol., 2001, 17 (04): 403-408. 
    Abstract   HTML   PDF (2862KB)
    The fatigue crack propagation behavior of TiNi50.6 shape memory alloy was studied. The experiment results showed that the crack propagation properties of this alloy display difference and similarity in comparison with common metallic materials. Because of the stress concentration there was stress induced martensite transformation (SIMT) near the crack tip though the nominal stress was lower than the threshold stress of SIMT. The position and the amount of SIMT was in situ observed by a quester remote measurement system (QRMS). The observation results showed that the position of SIMT was beside the crack tip and was not in the plastic, zone of common metallic materials (in front of the crack tip). The SIMT zone at an angle of about 45 degrees to the direction of the crack propagation, like a butterfly, appeared in the loading process, disappeared in the unloading process and grew larger with the increase of DeltaK. The crack propagation rate(da/dN) followed the linear law in Ig-Ig plot. Observation of the crack surface showed fatigue striation clearly. The relationship between the site and the size of the plastic zone and the SIMT zone is discussed and a model is given to explain both the similarity and the difference of the crack propagation property of TiNi50.6 to common metal materials.
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    Microstructural evolution during forming of metals
    N.Hansen
    J. Mater. Sci. Technol., 2001, 17 (04): 409-412. 
    Abstract   HTML   PDF (1051KB)
    The microstructural evolution during plastic deformation is described as grain subdivision on a finer and finer scale with increasing strain. Key structural features are dislocation boundaries and high angle boundaries. These boundaries have characteristic parameters which are used in a comparison of deformation microstructures produced under different conditions.
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    Stress corrosion cracking and passive film-induced tensile stress in alpha-Ti
    Hong LU, Kewei GAO, Hui LIU, Lijie QIAO, Wuyang CHU
    J. Mater. Sci. Technol., 2001, 17 (04): 413-416. 
    Abstract   HTML   PDF (1104KB)
    alpha -Ti foil with a protective layer formed on one side was deflected during corrosion in a methanol solution containing 0.6 mol/L KCl and then a tensile stress was generated at or near the metal passive film interface. The in situ TEM observation showed that corrosion process could facilitate dislocation emission and motion. Adding 10% H2O into the methanol solution decreased the passive film-induced stress from 320 MPa to zero, and the susceptibility to SCC measured in slow strain rate tests decreased correspondingly from 98% to zero.
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    Electrochromic properties of sol-gel deposited V2O5 and TiO2-V2O5 binary thin films
    Qinyuan ZHANG, Guangming WU, Bin ZHOU, Jun SHEN, Jue WANG, Zhonggang WU, Xiaohong JI
    J. Mater. Sci. Technol., 2001, 17 (04): 417-420. 
    Abstract   HTML   PDF (815KB)
    Transparent mixed phase (1 - x)V2O5 -xTiO(2) (x=0,0.1,0.2,0.3,0.4) thin films were prepared on indium tin oxide (ITO) coated glass via sol-gel process. The films were characterized by cyclic voltammetry, optical spectroscopy, scanning electron microscopy, IR and X-ray diffractometer. Electrochemical lithium insertion/extraction showed that the porous structure of sol-gel (1 - x)V2O5-xTiO(2) thin films exhibited good recharge ability of Li+/e(-) insertion/extraction process. For a 220 nm thick (1 - x)V2O5-xTiO(2) film with 90% V2O5, the capacity of charge exchange reached 9 mC/cm(2). In both Li+ intercalated and free states, the films were highly transparent to visible light. Such films have potential applications in counter electrodes for electrochromic smart windows and other electrochemical devices.
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    Crystallization kinetics of NiTi films with different Ni contents
    Xunyong JIANG, Huibin XU, Shengkai GONG
    J. Mater. Sci. Technol., 2001, 17 (04): 421-424. 
    Abstract   HTML   PDF (774KB)
    Three kinds of NiTi films with different Ni contents were prepared by DC magnetron sputtering. The crystallization kinetics of amorphous films was determined by using non-isothermal single-scan techniques. The results show that the activation energy of crystallization of Ni-rich NiTi film(Ni 51.10 at. pct, Ti 48.90 at. pct) is 715 kJ/mol, while that of Ti-rich films are similar: one is 445 kJ/mol (Ni 46.74 at. pct, Ti 53.26 at. pct), the other is 418 kJ/mol (Ni 43.21 at. pct, Ti 56.79 at. pct), which is lower than Ni-rich film. The Avrami parameter n of different films are 0.92 and 0.74 for Ni-rich film and Ti-rich films, respectively. The difference of kinetic parameters for NiTi films with various Ni contents implies that the crystallization behaviors of these films are distinct, which is confirmed by the calculated isothermal kinetics at different temperatures. The thorough research on this phenomenon is in progress.
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    Characteristics of high temperature rupture of a cast Ni-based superalloy M963
    Chao YUAN, Xiaofeng SUN, Fengshi YIN, Hengrong GUAN, Zhuangqi HU, Qi ZHENG, Yang YU
    J. Mater. Sci. Technol., 2001, 17 (04): 425-428. 
    Abstract   HTML   PDF (1419KB)
    The rupture behavior of a cast Ni-base superalloy M963 at high temperature has been investigated. The microstructure examination shows that there exists a large amount of the carbide and gamma-gamma ' eutectic, which is very harmful to the mechanical properties of M963 superalloy. The tensile strength of M963 superalloy both at room temperature and at high temperatures is higher than that of K17G alloy, but the tensile ductility of the former is much lower than that of the latter. In tensile fracture process with the high strain rate, the open carbides are the initiation site and the carbide/matrix interface is the propagation path of cracks. But in fracture process with the low strain rate, the carbide/matrix interface and cast microvoids are the initiation sites, and the carbide/matrix interface is the propagation path of cracks. The effective ways to improve ductility of M963 superalloy are also suggested.
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    Creep behavior of mullite short fiber reinforced ZL109 alloy composites at high temperature
    Shanling WANG, Baoluo SHEN Shengji GAO, Da LI, Mingjing TU, Weicheng YU, Ge YAO
    J. Mater. Sci. Technol., 2001, 17 (04): 429-432. 
    Abstract   HTML   PDF (982KB)
    The creep behavior of Al2O3. SiO2 fiber reinforced ZL109 composites has been investigated at four temperatures ranging from 553 to 623 K. The results show high stress exponent and high apparent creep activation energy. A good correlation between the normalized creep rate and normalized effective stress means that the true stress exponent of minimum creep strain rate of the composite is very close to 5, and the minimum creep strain rate is matrix lattice diffusion controlled. The threshold stress decreases with increasing temperature linearly and disappears at a temperature close to 623 K. It is assumed that the long range internal back stresses generated in creep reduce the load transfer to fibers and the interaction between dislocations and strengthening precipitates decreases at high temperature. At a high temperature where the long range internal back stresses is very close to the applied stress, the threshold stress disappears.
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    A rationalization of sympathetic nucleation-ledgewise growth theory of bainite transformation in Fe-C alloys
    Zhigang YANG, Chi ZHANG, Hongsheng FANG, Jinbo YANG, Bingzhe BAI, Jiajun WANG
    J. Mater. Sci. Technol., 2001, 17 (04): 433-438. 
    Abstract   HTML   PDF (1286KB)
    Based on the classic diffusion controlled nucleation and growth theory, the sympathetic nucleation-ledgewise growth mechanism of bainite was studied theoretically for low carbon F-e-C alloys. The rationality of the occurrence of sympathetic nucleation on the terraces of ledges competing with lateral ledge growth and other sites nucleation was demonstrated by the present work quantitatively. The calculations indicated that low reaction temperatures and high carbon concentrations may favor the sympathetic nucleation, thus accounting for the formation of multilayer structures of bainite.
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    Titanium technology in the USA - an overview
    D.Eylon, S.R.Seagle
    J. Mater. Sci. Technol., 2001, 17 (04): 439-443. 
    Abstract   HTML   PDF (1168KB)
    The state of Ti research, development and industry is reviewed in this article. The fifty-year anniversary of Ti technology commercialization in the USA provides an opportunity for a historical perspective. Incorporation of "information-age" tools into alloy development, processing, and production invigorates the technology. Consolidation, diversification and globalization have been transforming the Ti industry in the recent years.
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    Effect of hydrogen charging on the tensile and constant load properties of an austenitic stainless steel weldment
    A.M.Nasreldin, M.M.A.Gad, I.T.Hassan, M.M.Ghoneim, A.A.El-sayed
    J. Mater. Sci. Technol., 2001, 17 (04): 444-448. 
    Abstract   HTML   PDF (1643KB)
    The effect of cathodic hydrogen charging on the tensile and constant load properties was determined for an austenitic stainless steel weldment comprising a 304L steel in the solution treated condition as a base metal and a 308L filler steel as a weld metal. Part of the 304L solution treated steel was separately given additional sensitization treatment to simulate the microstructure that would develop in the heat affected zone. Tests were performed at room temperature on notched round bar specimens. Hydrogen charging resulted in a pronounced embrittlement of the tested materials. This was manifested mainly as a considerable loss in the ductility of tensile specimens and a decrease in the time to failure and threshold stress of constant load specimens. The 308L weld metal exhibited the highest, and the 304L solution treated steel the lowest, resistance to hydrogen embrittlement. Hydrogen embrittlement was associated with the formation of strain induced martensite as well as a transition from brittle to ductile fracture morphology onwards the centre of the specimens.
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    Experimental study of monitoring and controlling of composite cure process in autoclave featured with fiber optic sensor
    Boming ZHANG, Zhanjun WU, Dianfu WANG, Shanyi DU
    J. Mater. Sci. Technol., 2001, 17 (04): 449-452. 
    Abstract   HTML   PDF (879KB)
    With the aid of the latest fiber optic sensing technology, parameters in the cure process of thermosetting resin-matrix composite, such as temperature, viscosity, void and residual stress, can be monitored entirely and efficiently. In this paper, experiment results of viscosity measurement in composite cure process in autoclave using fiber optic sensors are presented. Based on the sensed information, a computer program is utilized to control the cure process. With this technology, the cure process becomes more apparent and controllable, which will greatly improve the cured products and reduce the cost.
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    Positron annihilation behaviors and magnetic properties of single-phase Nd2Fe14B and nanocomposite Nd2Fe14B/alpha-Fe magnets
    Dingkang XIONG, Xiaokai SUN, Liangyue XIONG, Wei LIU, Tong ZHAO, Zhidong ZHANG
    J. Mater. Sci. Technol., 2001, 17 (04): 453-456. 
    Abstract   HTML   PDF (908KB)
    Positron annihilation behaviors have been studied in the single phase Nd2Fe14B magnet and the nanocomposite Nd2Fe14B/alpha -Fe magnet, prepared by melt spinning. The results showed that the number of vacancy-cluster at grain boundaries increases with increasing annealing temperature for the both types of magnets. The increase of this kind of defect can improve the coercivity of the single-phase magnet. Conversely, the increase of vacancy-cluster amount leads to decreasing of the coercivity for the nanocomposite magnet. It implies that the mechanism of dominant magnetic hardening for the two types of magnets is different, and the domain walls pinning mechanism in the single-phase magnet and the reversal magnetization nucleation mechanism in the nanocomposite magnet operate, respectively.
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    Magnetization-enhanced dislocation motion and decreased yield strength of 60Fe40Ni alloy
    Hongqi LI, Yanbin WANG, Wuyang CHU
    J. Mater. Sci. Technol., 2001, 17 (04): 457-459. 
    Abstract   HTML   PDF (568KB)
    Using a special constant deflection device, the changes in dislocation configuration ahead of a loaded crack tip for 60Fe40Ni alloy, before and after magnetization in a magnetic field, have been studied in TEM. The results showed that the magnetization for 60Fe40Ni alloy could enhance dislocation emission, multiplication and motion. Also, the mechanical properties of 60Fe40Ni alloy, in air and in the magnetic field respectively, have been investigated using the slow strain rate tension. And the results indicated that magnetization could make the yield strength corresponding to decrease by 26 percent, but did not influence the ultimate tensile strength and the fracture strain, which showed that magnetization could enhance plastic deformation.
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    Embedded-atom potential for oxygen
    Yifang OUYANG, Hongmei CHENG, Zhanpeng JIN
    J. Mater. Sci. Technol., 2001, 17 (04): 460-462. 
    Abstract   HTML   PDF (432KB)
    The analytic embedded-atom potential for oxygen is developed from the experimental data and the results of the first-principle. The potential is used to predict the geometries and energies of O-3, fcc, bcc, sc and diamond. The predictions are in good agreement with experimental data available and other theoretical results.
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    Physical simulation of nonmetallic particle movement in Al melt under electromagnetic field
    Tianxiao LI, Zhenming XU, Baode SUN, Da SHU, Yaohe ZHOU
    J. Mater. Sci. Technol., 2001, 17 (04): 463-465. 
    Abstract   HTML   PDF (568KB)
    Physical simulation is used to study the movement of nonmetallic particles in Al melt in electromagnetic field. It is found that the terminal velocity of particles in different Reynolds number range has different functions. By confirming drag force coefficient of nonmetallic particles with Reynolds number in the range of 0.2 similar to 10 and 10 similar to 25 respectively, two functions of terminal velocity for spherical nonmetallic particles have been got accordingly, which provide a theoretical basis for separating nonmetallic inclusions from Al melt in electromagnetic field.
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    Stress field analyses of functionally gradient ceramic tool by FEM
    Ning FAN, Xing AI, Jun ZHAO
    J. Mater. Sci. Technol., 2001, 17 (04): 466-468. 
    Abstract   HTML   PDF (537KB)
    The cutting properties of the functionally gradient ceramic cutting tools relate closely to the gradient distribution. A cutting model of the functionally gradient ceramic tool is firstly designed in the present paper. The optimum of gradient distribution is obtained by way of the FEM analyses.
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    Electron beam irradiation-induced diffusion of oxygen in the Al particle encapsulated by Al2O3 shell
    Zhiqing YANG, Zhixiong JIN, Lianlong HE, Hengqiang YE
    J. Mater. Sci. Technol., 2001, 17 (04): 469-470. 
    Abstract   HTML   PDF (372KB)
    Transportation of oxygen from Al2O3 shell to the encapsulated Al core under the electron beam irradiation was achieved by field emission gun transmission electron microscope.
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    Development and application of universal formability technology
    Yanwu Xu
    J. Mater. Sci. Technol., 2001, 17 (04): 471-472. 
    Abstract   HTML   PDF (400KB)
    Using mathematical plasticity theories, universal formability (UF) technology has been developed and applied in the automotive stamping engineering and production. As a formability analysis tool, this technology is the major methodology for the development of stamping expert system (solution provider) for (a) product design and feasibility analysis, (b) material automatic selection using nomograms, (c) draw die design using pre-models, and (d) UF and robustness analysis of die performance in finite element analysis (FEA) environment.
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    Simulation on domain rotation path and magnetostriction of Terfenol-D alloy
    Jiuchun YAN, Wenbo HAN, Xaoqiu XIE, Shiqin YANG
    J. Mater. Sci. Technol., 2001, 17 (04): 473-475. 
    Abstract   HTML   PDF (498KB)
    Based on a simplified domain rotation model, the rotation path of internal domains and corresponding magnetostriction of [112], [111] oriented single Terfenol-D crystals under compressive prestresses have been simulated. Comparisons with results of experiment and other calculation have been made. Results of simulation showed that the [111] oriented single crystal has better low-field magnetostriction properties than the [112] oriented one. Under a compressive prestress of 10 MPa, up to 2300x10(-6) saturation magnetostriction of [111] oriented crystal has been obtained at 800 Oe, while for [112] oriented, 1600x10(-6) maximum magnetostriction has been reached at 1000 Oe.
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    Simulation of multiple cold rolls progressive forming for non-symmetrical channel section
    Zhiwu HAN, Cai LIU, Weiping LU, Luquan REN
    J. Mater. Sci. Technol., 2001, 17 (04): 476-478. 
    Abstract   HTML   PDF (585KB)
    In cold roll forming process, the sheet is progressively formed into a very complex three dimensional surface. The design procedure for the roll formed products, forming rolls, and roll pass sequences was considered more an art than a science. Good roll pass design was the key to successful roll forming. In order to reduce forming defects and trial production cost, computer simulation of cold roll forming was employed. Based on the Updated-Lagrange method in the deformation mechanics, a theoretical model of elastic-plastic large deformation spline finite strip method is proposed in this paper. The method is employed to analyze the progressive forming process of non-symmetrical section, and the displacement, the stress and the strain along rolling direction during the multiple cold rolls forming process are got. This program written in C Language can be used to analyze other simple cross sectional profiles also.
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    Formation and oxidation resistance of silicide coatings for Mo and Mo-based alloys
    Yu WANG, Yunpeng LI, Xingfang HU
    J. Mater. Sci. Technol., 2001, 17 (04): 479-481. 
    Abstract   HTML   PDF (734KB)
    The forming process of silicide coatings on pure Mo and Mo-base alloys, obtained by the gasphase deposition method, has been studied by examining the microstructure of coatings and the relationship between coating thickness and process parameters. It was shown that the growth of coatings was diffusion-control led, the diffusion of silicon to be coated into Mo or Mo-base alloys was mainly responsible for the formation of silicide. The relationship between initial silicide thickness and oxidation resistance was also investigated, and the equation of service life of the coatings at high temperature in air is presented.
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    Investigation of corrosion resistance using positron annihilation for an amorphous alloy
    Jingcheng WANG, Fuqiang YOU, Junlin YIN, Guohua GAO
    J. Mater. Sci. Technol., 2001, 17 (04): 482-484. 
    Abstract   HTML   PDF (503KB)
    An amorphous alloy with Ni-(17 similar to 19) at. pct P prepared by electrodeposition process was studied using positron annihilation technique (PAT) associated with X-ray diffraction and the measurement of corrosion rate. It is suggested that defect or the interface between precipitates and matrix is one of the important factors which decrease corrosion resistance of the alloy after crystallization.
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ISSN: 1005-0302
CN: 21-1315/TG
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