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CN 21-1315/TG
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      28 July 2000, Volume 16 Issue 04 Previous Issue    Next Issue
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    Research Articles
    Structure Evolution of Bulk Metallic Glass Zr52.5Ni14.6Al10Cu17.9Ti5 during Annealing
    Guo HE, Zan BIAN, Guoliang CHEN
    J. Mater. Sci. Technol., 2000, 16 (04): 357-361. 
    Abstract   HTML   PDF (1305KB)
    Bulk metallic glass Zr52.5Ni14.6Al10Cu17.9Ti5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively. By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM), the predominant crystallized phase of Zr2Ni0.67O0.33 distributed an glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr2Ni0.67O0.33 and a small amount of ZrAl and Zr2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr2Ni0.67O0.33 is interface-controlled, but is diffusion-controlled to Zr2Cu and ZrAl. With increasing annealing temperature up to 200 K above T-x, the nanometer grains became very fine because of the increase of nucleation rate for Zr2Cu and ZrAl.
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    Study on the diffraction patterns of alpha α''-Fe16N2 with Jack-1 and Jack-2 structural parameters
    Zhiquan LIU, Douxing LI, Xiaolei XU, Liang WANG, Zukun HEI
    J. Mater. Sci. Technol., 2000, 16 (04): 362-366. 
    Abstract   HTML   PDF (940KB)
    Two body centered tetragonal (bct) crystal structures of alpha"-Fe16N2 with x=0.25, z=0.3125 (Jack-1) and x=0.222, z=0.306 (Jack-2) respectively, were analyzed theoretically with EMS software package. The simulation of diffraction patterns indicates that both diffraction patterns of the same axis in these two structures obey bcc extinction rule. The conclusion is also obtained from the analyses of the diffracted waves. alpha"-Fe16N2 precipitates in the diffusion layer of ion-nitrided alpha-iron have been studied with transmission electron microscope (TEM). We have distinctly observed the electron diffraction patterns of alpha"-Fe16N2 in [100], [111], [110], [011], [210], [021], [311], [113], [331] and [133] zone axes with perfect symmetry, which indicate the parallel orientation relationship with alpha matrix: <001>(alpha")//<001>(alpha), {100}(alpha")// {100}(alpha). The analyses of diffraction patterns, which obey bcc extinction rule, verify the bet structure of alpha"-Fe16N2 discovered by X-ray diffraction.
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    Effective-medium theory for two-phase random composites with an interfacial shell
    Qingzhong XUE
    J. Mater. Sci. Technol., 2000, 16 (04): 367-369. 
    Abstract   HTML   PDF (371KB)
    According to the Bruggeman theory and Maxwell-Garnett theory, the effective dielectric constant of a two-phase random composite with an interfacial shell is presented. The nonlinearity of the theory is obvious. Especially, the theory is suited to study the dielectric properties of two-phase random composites with a spherical interfacial shell. The theoretical results on dielectric properties of polystyrene-barium titanate composites with an interfacial shell are in good agreement with experimental data.
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    Dislocation model and morphology simulation of bcc <-> fcc martensitic transformation
    Xiumu ZHANG, Bin LI, Xianwei SHA, Zongqi SUN, Rong LI
    J. Mater. Sci. Technol., 2000, 16 (04): 370-374. 
    Abstract   HTML   PDF (1227KB)
    By using molecular dynamics computer simulation at atomic level, the effects of single dislocation and dipole dislocations on nucleation and growth of martensitic transformation have been studied. It was found that only the location of tension or compression stress fields of the dislocations are favorable for martensite nucleation in NiAl alloy and the dislocations can move to accommodate partly the transformation strain during the nucleation and growth of martensite. Combined with the molecular dynamics simulation, a two dimensional simulation for martensite morphology based on a dislocation model has been performed. Many factors related to martensitic transformation were considered, such as supercooling, interface energy, shear strain, normal strain and hydrostatic pressure. Different morphologies of martensites, similar to lath, lenticular, thin plate, couple-plate and lenticular couple-plate martensites observed in Fe-C and Fe-Ni-C alloys, were obtained.
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    Effect of some admixtures on the hydration of silica fume and hydrated lime
    Eisa E.Hekal
    J. Mater. Sci. Technol., 2000, 16 (04): 375-378. 
    Abstract   HTML   PDF (924KB)
    The effects of sodium salt of naphthalene formaldehyde sulfonic acid and stearic acid on the hydration of silica fume and Ca(OH)(2) have been investigated. The hydration was carried out at 60 degrees C and W/S ratio of 4 for various time intervals namely, 1, 3, 7 and 28 days and in the presence of 0, 2% and 5% superplasticizer and stearic acid. The results of the hydration kinetics show that both admixtures accelerate the hydration reaction of silica fume and calcium hydroxide during the first 7 days. Whereas, after 28 days hydration there is no significant effect. Generally, most of free calcium hydroxide seems to be consumed after 28 days. In addition, the phase composition as well as the microstructure of the formed hydrates was examined by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) respectively.
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    Positron lifetime study of the single-phase B2Ni(100-x)Al(x) and Ni50-xCOxAl50 intermetallics
    Rongshi CHEN, Jianting GUO, Wenlong ZHOU, Liangyue XIONG
    J. Mater. Sci. Technol., 2000, 16 (04): 379-382. 
    Abstract   HTML   PDF (701KB)
    In order to understand the point defect structure in NiAl Intermetallic compound, the positron lifetime in binary Ni100-xAlx (53 greater than or equal to x greater than or equal to 45) and ternary B2 Ni50-xCoxAl50 (x=0, 5, 10, 15) intermetallic compounds as a function of composition were measured. It is shown that the positron lifetime spectra of these compounds can be consistently expressed by single-component lifetimes. The positron lifetime value in ternary Ni50-xCoxAl50 alloy is independent of Co content and equal to that detected in both stoichiometric and Al-rich NiAl. From an analysis of the present results, it is suggested that the constant lifetime of tau approximate to 180 ps should be ascribed to saturation trapping and annihilation of positron exclusively at Ni vacancy, no evidence for the presence of Al vacancy is available.
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    A resistivity gradient piezoelectric FGM actuator
    S. U.Adikary, Zhongyan MENG, Dengren JIN
    J. Mater. Sci. Technol., 2000, 16 (04): 383-386. 
    Abstract   HTML   PDF (726KB)
    A resistivity gradient actuator based on lead zirconate titanate ceramics was successfully developed and the bending deflections up to 140 mu m were obtained. The actuator material was a matrix of PZT ceramic into which smooth gradient of piezoelectric activity was introduced. The application of an electric field then causes the actuator to bend due to differential strains induced by the piezoelectric effect. The resistivity gradient of the actuator was achieved by doping PZT with suitable donor and acceptor dopants. PZT powder was modified and synthesized by using two stage powder fabrication method. The actuator was fabricated by uniaxial pressing followed by isostatic pressing with two layers of different resistivities.
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    Preparation of TiC/Ni3Al composites by upward melt infiltration
    Yi PAN, Kewei SUN
    J. Mater. Sci. Technol., 2000, 16 (04): 387-392. 
    Abstract   HTML   PDF (1361KB)
    TiC/Ni3Al composites have been prepared using upward infiltration method. The densification was performed by both Ni3Al melt filling and TiC sintering during the infiltration. The dissolution of TiC in liquid Ni3Al has been evidenced by finding Ni-3(Al,Ti)C after fast cooling in the TiC/Ni3Al composites. The dissolution may be responsible for the infiltration and sintering. Compared with downward infiltration, the upward infiltration brought about higher strength and fracture toughness and shorter infiltration time. TiC/20 vol. pct Ni3Al composite processed by upward infiltration had a flexural strength of 1476 MPa with a statistic Weibull modulus of 20.2 and a fracture toughness of 20.4 MPa root m. Better mechanical properties may be attributed to melt unidirectional movement in upward infiltration.
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    Particle size distribution, powder agglomerates and their effects on sinterability of ultrafine alumina powders
    Renjie ZENG, B.R
    J. Mater. Sci. Technol., 2000, 16 (04): 393-396. 
    Abstract   HTML   PDF (794KB)
    An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.
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    Inhibiting effect of indole and some of its derivatives on corrosion of C-steel in HCl
    A.A.Ismail, S.H.Sanad, A.A.El-Meligi
    J. Mater. Sci. Technol., 2000, 16 (04): 397-400. 
    Abstract   HTML   PDF (584KB)
    The Inhibiting effect of indole (A), indole acetic acid (B), indole buteric acid (C), and 3-acetyl indole (D), on the corrosion of three carbon steels in 10% HCl was investigated by using galvanostatic polarization method and open circuit potential measurements. It was observed that the inhibiting action of inhibitors increased with increasing inhibitor concentration. The best inhibiting effect obtained at the highest concentration (200x10(-6) g/L) of the inhibitors for the three carbon steels. According to polarization and open circuit potential methods the inhibitors have effect on both anodic and cathodic area.
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    Surface modification of ceramic materials using excimer laser
    Yingna WU, Zhongchao FENG, Jing LIANG
    J. Mater. Sci. Technol., 2000, 16 (04): 401-404. 
    Abstract   HTML   PDF (1280KB)
    Changes of surface morphology following XeCl excimer laser irradiation were investigated for three engineering ceramic materials (Al2O3, Al2O3-SiC nanocomposite and Si3N4) Al2O3 and Al2O3-SiC nanocomposite samples exhibit a smooth rapid melt layer on the surface, and the formation of the metastable gamma-Al2O3 was observed. A silicon-rich layer on the surface was formed after laser irradiation of Si3N4. The toughness K-1c of the materials was measured by the indentation fracture method. After laser irradiation, the toughness of Al2O3, Al2O3-SiC nanocomposite and Si3N4 was improved to various degrees: Al2O3-SiC nanocomposite, 60% (max.), Al2O3, 40% (max.), Si3N4, 12% (max.).
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    Fracture mechanics, crack propagation and microhardness studies on flux grown ErAlO3 single crystals
    K.K.Bamzai, P.N.Kotru, B.M.Wanklyn
    J. Mater. Sci. Technol., 2000, 16 (04): 405-410. 
    Abstract   HTML   PDF (850KB)
    Results on fracture mechanics and crack propagation have been obtained, making use of Vickers microhardness studies on two different crystallographic planes [(110) and (001)] of flux grown erbium aluminate crystals in the load ranging from 10 similar to 100 g. The variation of microhardness with load which is best explained by Hays and Kendall's law leads to the load independent values of hardness. Classification of cracks is dealt with and it is reported that the transition from Palmqvist to median types of cracks occurs at higher loads. The values of fracture toughness (K-C), and brittleness index (B-i) are calculated using median types of cracks.
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    Effect of microstructure and sulfide on corrosion of Cu-Ni alloys in seawater
    Xiaolong ZHU
    J. Mater. Sci. Technol., 2000, 16 (04): 411-415. 
    Abstract   HTML   PDF (1320KB)
    The microstructure and the corrosion product films have been investigated on Cu-Ni alloys by TEM, SEM, AES and electrochemical technique as well as natural seawater exposure tests. Experimental results showed that the alloys had two kinds of microstructure, i.e. recrystallization and incomplete recrystallization. In synthetic seawater containing 2x10(-6) S2-, the stability of the alloy increased with the increase of deformation and annealing temperature, i.e., the degree of recrystallization. After exposure to natural seawater for different periods of time, the corrosion product films of the: recrystallized alloy were rich in Ni and compact, and there were cracks in the outer layer which contained a small amount of S, the films of the alloy of incomplete recrystallization became thick, loose and porous, and obviously of layered structure, and the intergranular corrosion took place in the underlying substrate. Besides, a great amount of seawater substance existed in the outer layer and some sulfur was found within the grain boundaries that prefer to corrode. The accelerating effect of sulfides in corrosion of Cu-Ni alloys in seawater is attributed to the coexistence and absorption of sulfides and carbides promoting the preference of corrosion where they absorb, and the formation of dissolvable Cu2S results in keeping the surface of the alloys in the active state.
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    Effect of trace Sc and Zr on the mechanical properties and microstructure of Al alloy 2618
    Kun YU, Songrui LI, Wenxian LI
    J. Mater. Sci. Technol., 2000, 16 (04): 416-420. 
    Abstract   HTML   PDF (1382KB)
    An experimental 2618(Al-Cu-Mg-Fe-Ni) alloy added with trace Sc and Zr was prepared by ingot metallurgy (IM) method. The aging behavior of the alloy was studied by Vickers hardness measurement at 200 degrees C and 300 degrees C, and the tensile properties of alloy specimens were measured at 20 degrees C, 200 degrees C, 250 degrees C and 300 degrees C. The microstructure was observed by using optical microscope, SEM and TEM. It was found that the addition of Sc and Zr to 2618 alloy resulted in a primary Al-3(Sc,Zr) phase which could refine the grain because it acts as nuclei of heterogeneous crystallization in the melt during solidification. The secondary Al-3(Sc,Zr) particles were full coherent with matrix and had obvious precipitation hardening effect. They also made the S' phase precipitate more homogeneous. So the strength of alloy increases at both ambient and elevated temperatures without a decrease of ductility. The ductile fracture of alloy occurs by microvoid nucleation, growth and coalescence, so the microvoid coalescence is the dominant fracture mechanism.
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    PZN-PZT piezoelectric multilayer actuator with Ag/Pd electrodes
    Xiangping JIANG, Jun LIAO, Wangzhong ZHANG, Guorong LI, Daren CHEN, Qingrui YIN
    J. Mater. Sci. Technol., 2000, 16 (04): 421-423. 
    Abstract   HTML   PDF (1104KB)
    The PZN-PZT ceramic with high piezoelectric constant d(33) sintered at 1130 degrees C was prepared. The PZN-PZT multilayer actuator (MLA) with Ag/Pd as an internal electrode was fabricated by tape casting.
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    Shape memory effect of As-aged Fe-14Mn-5Si-8Cr-4Ni-0.2C alloy
    Yuhua WEN, Ning LI, Mingjing TU
    J. Mater. Sci. Technol., 2000, 16 (04): 424-426. 
    Abstract   HTML   PDF (1337KB)
    The effects of aging temperature on shape memory effect, mechanical properties and microstructure of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles rich in chromium, manganese and silicon precipitate during aging, and thereby increase the hardness and strength of the alloy. The shape recovery ratio can be remarkably improved by aging and a maximum value can be obtained at 1223 K, which is 68% higher than that of the specimen in solid solution state. When the aging temperature is below 1223 K, the amount of second phase particles increases as the aging temperature increases. The size of austenite grain increases with increasing aging temperature. When the temperature is over 1223 K, the second phase particles can not precipitate. The lack of second phase particles and the increase of grain size make the hardness and shape recovery ratio drastically decrease, when the temperature is over 1223 K.
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    Study on the miscibility and phase behavior of polyoxymethylene with Novolak
    Xiaodong WANG, Hangquan LI, Riguang JIN
    J. Mater. Sci. Technol., 2000, 16 (04): 427-430. 
    Abstract   HTML   PDF (1063KB)
    The miscibility and phase behavior of the blends of polyoxymethylene (POM)/Novolak were investigated by the cloud point method, which showed that the POM/Novolak blends exhibited a lower critical solution temperature. The melting point of POM decreased when diluted with Novolak. From the melting temperature depression of POM, a negative interaction parameter (chi) between POM and Novolak was obtained. The IR spectrum revealed that the miscibility between POM and Novolak was caused by the specific interaction between the OH groups of Novolak and the ether oxygen atoms of POM. The morphology of the blends investigated by polarized light microscopy showed that the size of spherulites of POM was sharply decreased by its mixing with Novolak. This suggests that Novolak be used as a compatibilizer for POM.
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    The effect of Al and Fe on the intergranular embrittlement of Co3Ti alloys by hydrogen transport from the external surface
    Xiaoying CHENG, Xiaojing WAN, Yexin CHEN, Meiyi YAO
    J. Mater. Sci. Technol., 2000, 16 (04): 431-434. 
    Abstract   HTML   PDF (745KB)
    Some observation relating tp the solubility, diffusivity and intergranular cracking by hydrogen transport from the external surface in Co3Ti, Co3Ti-Al and Co3Ti-Fe alloys have been carried out. The results show that the addition of alloying elements Al or Fe to Co3Ti alloy can increase the critical hydrogen concentration for changing from transgranular to brittle intergranular fracture, therefore suppress the moisture induced environmental embrittlement.
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    Prediction of superconductivity for oxides based on structural parameters and artificial neural network method
    Xueye WANG, Huang SONG, Guanzhou QIU, Dianzuo WANG
    J. Mater. Sci. Technol., 2000, 16 (04): 435-438. 
    Abstract   HTML   PDF (722KB)
    Superconductive properties for oxides were predicted by artificial neural network (ANN) method with structural and chemical parameters as inputs. The predicted properties include superconductivity for oxides, distributed ranges of the superconductive transition temperature (T-c) for complex oxides, and T-c values for cuprate superconductors. The calculated results indicated that the adjusted ANN can be used to predict superconductive properties for unknown oxides.
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    Phosphogypsum utilization - Part III: as adhesive filler and composite materials
    A.A.Hanna, Y.M.Abu-Ayana, S.M.Ahmed
    J. Mater. Sci. Technol., 2000, 16 (04): 439-444. 
    Abstract   HTML   PDF (1121KB)
    The aim of this work is to make use of phosphogypsum (PG) waste material, which is produced in phosphoric acid and phosphate fertilizer manufactures. A number of wood adhesive formulations based on polyvinyl acetate (PVAc) polymer and phosphogypsum as a filler have been prepared, using different percentages of phosphogypsum, ranging between 5 similar to 20 wt pet. The prepared formulations were tested for adhesion strength and compared with both natural and pure gypsum fillers. The results indicate that PG improves the adhesion strength when 5 wt pet added, and that may be due to filling the porous surface of wood with the fine particles of PG, as well as coating the particles of the filler (PG) with PVAc units. Also, a number of formulations based on urea-formaldehyde polymer have been prepared using phosphogypsum as an active filler in the ratio of 40 similar to 75 wt pct to prepare composite materials used for some decoration purposes and construction. Mechanical, physical, and thermal properties of these formulations were studied. Also, the activation energy was calculated. The results indicate that PG without acid hardener can be used for preparation of composite materials based on urea-formaldehyde between 40 similar to 63.64 wt pct for construction purposes in the humid atmosphere, while between 63.64 similar to 75 wt pct for decoration purposes. The improvement of the physical, mechanical and thermal properties of the composite material may be attributed to the simultaneous hydration hardening action of phosphogypsum and the presence of 0.8% P2O5. These effects act as an active hardener for urea-formaldehyde resin and accelerate the cross-linking and network formation reinforced by the fine dusty inorganic particles of PG. The advantage of this method is to prepare composite material gypsum-urea-formaldehyde, which achieves the utilization of large amount of PG, reducing the price of the main product phosphate, minimizing the pollution and producing new materials which possess high thermal resistance, good mechanical properties and water resistance that are suitable for construction panels.
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    Demagnetization process and coercivity for anisotropic HDDR NdFeB bonded magnets
    Ruwei GAO, Jiancheng ZHANG, Xianhong DENG, Yongjun ZHANG
    J. Mater. Sci. Technol., 2000, 16 (04): 445-446. 
    Abstract   HTML   PDF (464KB)
    The demagnetization process and the coercivity mechanism for anisotropic HDDR Nd(Fe,Co)B bonded magnets were studied by comparing the dependence of coercivity on the alignment field applied while the powders were pressed. The results showed that both the remanence and the coercivity of magnet increased with increasing alignment field. The demagnetization process of the magnet can be classified as the nucleation process inside the grains and the domain-wall motion between the grains. The combined effect of two processes determines the coercivity of HDDR NdFeB bonded magnets.
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    Effect of annealing temperature on magnetic aftereffect and positron lifetime in Fe73.5Cu1Nb3Si13.5B9 alloy
    Qixian BA, Guiyi ZENG, Hualin ZENG
    J. Mater. Sci. Technol., 2000, 16 (04): 447-448. 
    Abstract   HTML   PDF (318KB)
    The magnetic aftereffect (MAE) and the positron lifetime were measured at room temperature on the Fe73.5Cu1Nb3Si13.5B9 alloy in as-cast and after annealing at temperature T-a in the range from 450 to 750℃. It was found that both the MAE and the positron lifetime decrease with increasing T-a when T-a less than or equal to 600 degrees C. While T-a greater than or equal to 650℃, MAE is essentially suppressed, and two positron lifetimes appear.
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    Thermodynamic analyses of strain-induced martensite transformation in Fe-7Mn-1.2C alloy
    Jingpei XIE, Yaomin ZHU, Xiaoping WANG
    J. Mater. Sci. Technol., 2000, 16 (04): 449-451. 
    Abstract   HTML   PDF (492KB)
    The M-s temperature, Delta G(gamma-->alpha), Delta G(gamma-->M) and mechanical energy under a non-severe impact loading in a medium manganese steel (Fe-7Mn-1.2C) have been calculated by means of Xu's Fe-X-C model. The relation between the yield strength of austenite and the driving force for martensite transformation has been established. It is proved that the martensite transformation can take place in a medium manganese steel (Fe-7Mn-1.2C alloy) under a non-severe impact loading.
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ISSN: 1005-0302
CN: 21-1315/TG
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