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ISSN 1005-0302
CN 21-1315/TG
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      28 November 1999, Volume 15 Issue 06 Previous Issue    Next Issue
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    Research Articles
    Cyclic Deformation and Fatigue Damage Behavior of Cu Monocrystals, Bicrystals and Tricrystals
    Zhongguang WANG, Xiaowu LI, Zhefeng ZHANG, Weiping JIA, Shouxin LI
    J. Mater. Sci. Technol., 1999, 15 (06): 489-508. 
    In the present work, the cyclic deformation behavior of Cu single crystals oriented for double- and multiple slip as well as Cu bicrystals and tricrystals was investigated under constant plastic strain control at room temperature in air. The main objectives of the study are: (1) to find out the effects of crystallographic orientation and grain boundary (GB) on the cyclic stress-strain (CSS) curves; (2) to compare the cyclic deformation behavior of the double-, multiple-slip crystals, bicrystals and tricrystals with that of single-slip oriented crystals and to correlate the results with those of polycrystals; (3) to examine the corresponding dislocation structures; (4) to investigate the interactions of persistent slip bands (PSBs) with GBs and triple joint (TJ) as well as intergranular fatigue cracking in Cu bicrystals and tricrystals.
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    Effect of Crystallinity on Electrochemical Insertion/Extraction of Li in Transition Metal Oxides Part I: LiMn2O4 and LiCo0.5Ni0.5O2
    Tomoki TSUMURA, Michio INAGAKI
    J. Mater. Sci. Technol., 1999, 15 (06): 509-514. 
    Electrochemical insertion/extraction of Li on cathode materials of spinel type LiMn2O4 and ordered rock-salt type LiCo0.5Ni0.5O2 was measured on samples of which structures were well characterized. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materials on electrochemical Li insertion/extraction performance was discussed. These two transition metal oxides belong to one group that the crystallinity of these oxides affects to the performance.
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    Carbide Behavior during High Temperature Creep in DZ40M Co-base Superalloy
    Wenhui JIANG, Xiangdong YAO, Hengrong GUAN, Zhuangqi HU
    J. Mater. Sci. Technol., 1999, 15 (06): 515-518. 
    The carbide behavior of a directionally solidified Co-base superalloy DZ40M has been investigated after creep at 700 and 900℃. During the high temperature creep, a great amount of secondary carbide, M23C6 precipitated in alloy matrix. At 700℃, the M23C6 precipitation occurred in slip bands, indicating that it was stress-induced, while at 900℃, M23C6 formed surrounding the primary carbides, which is a characteristic of thermally aged alloy. The M23C6 particles pinned up dislocations and subgrain boundaries, strengthening the alloy matrix effectively. The creep crack initiation of DZ40M alloy was exclusively related to the primary carbides. The fracture of the primary carbide and the crack at the interface between them and matrix resulted in the crack formation. Furthermore, it was found that at 900℃, the surface of specimens was oxidized severely and the preferentially oxidized primary carbides acted as crack initiation sites.
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    Effect of Prior Deformation on Aging Process in a Cu-30Ni-25Fe Spinodal Alloy
    Xinjiang HAO, Hongxiao LI, Gang ZHAO, Shiming HAO
    J. Mater. Sci. Technol., 1999, 15 (06): 519-522. 
    The effect of prior deformation on the mechanical properties and microstructural evolution of aging process in a Cu-30Ni-25Fe (in at. pct) alloy has been studied by tensile test, hardness measurement, SEM and optical microscopy analysis. The results show that spinodal decomposition and recovery process interact on each other when aged at low temperature (600℃), and most of the defects induced by cold-work did not disappear in 100 h. When aged at high temperature (850℃), the discontinuous coarsening of the spinodal products takes place. The increase in yield strength and elongation of the sample aged at 850℃ for 5 h after deformation mainly results from the submicrometer grains produced by discontinous coarsening of spinodal products.
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    Indium Composition Dependence of the Size Uniformity of InGaAs Quantum Dots on (311)B GaAs Grown by Molecular Beam Epitaxy
    Weihong JIANG, Huaizhe XU, Bo XU, Wei ZHOU, Qian GONG, Ding DING, Jiben LIANG, Zhanguo WANG
    J. Mater. Sci. Technol., 1999, 15 (06): 523-526. 
    The deposition of InxGa1-xAs (0.2≤x≤0.5) on (311)B GaAs surfaces using solid source molecular beam epitaxy (MBE) has been studied. Both AFM and photoluminescence emission showed that homogeneous quantum dots could be formed on (311)B GaAs surface when indium composition was around 0.4. Indium composition had a strong influence on the size uniformity and the lateral alignment of quantum dots. Compared with other surface orientation, (100) and (n11)A/B (n=1,2,3), photoluminescence measurement confirmed that (311)B surface is the most advantageous in fabricating uniform and dense quantum dots.
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    Investigation on the Microstructure Homogenization in a TiAl Based Alloy Prepared by Elemental Powder Metallurgy
    Yong LIU, Baiyun HUANG, Yuehui HE, Jiannong WANG
    J. Mater. Sci. Technol., 1999, 15 (06): 527-530. 
    A Ti-48Al (at. pct) alloy prepared by elemental powder metallurgy (EPM) has been heat treated under various conditions. Through optical and scanning electronic microscopy, EDAX, XRD analysis, and DTA, it was shown that the hot pressed microstructure consisted of α2-Ti3Al and TiAl phases. The α2-Ti3Al phase was island-like, and had a high stability and heredity in subsequent heat treatments. The supersaturation of Al in the island-likeα-Ti3Al phase strongly influenced the transformation of α (or α2) to α2/γ lamellar colonies. After a heat treatment at 1380℃ for 0.5 h and 1000℃ for 8 h, a fully lamellar microstructure with a colony size of 50 μm was obtained. This result indicates that a homogeneous composition and an equilibrium microstructure in EPM TiAl-base alloys can only be obtained after heat treatment at temperatures above α transus temperature (Tα).
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    Structure of the Intermetallic Compound Ni3Al Synthesized under Compression of the Powder Mixture of Pure Elements Part I: Phase Composition and Microstructure of Main Phase
    M.V.Fedorischeva, V.E.Ovcharenko, O.B.Perevalova, E.V.Kozlov
    J. Mater. Sci. Technol., 1999, 15 (06): 531-535. 
    It was shown by TEM and X-ray analysis that there are four types of grains of the main Ni3Al phase in the structure of the intermetallic obtained by the self-propagation high temperature method (SHS). Every type of grains has its own domain and dislocation structure. There are mono- and polydomains with and without dislocations. The grains of the main phase of mono- and polydomains without dislocations and polydomains with dislocations were formed by diffusion in the solid phase. In these conditions NiAl3 phase is located on the grain boundary of the main phase. The Ni2Al3 phase is located at the triple joints of the main phase.
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    Compression Properties of Ti-Al-X Alloys in Relation to Site Occupancies of Alloying Elements in TiAl and Ti3Al
    Yulin HAO, Rui YANG, Yuyou CUI, Dong LI, Wanfu GAO
    J. Mater. Sci. Technol., 1999, 15 (06): 536-540. 
    Room temperature compression properties of Ti-51Al-(1-2)X and Ti-26Al-(1-2)X alloys (X = V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Ta, Ga or Sn) were measured in oder to examine how the compression deformability correlates with the site occupancies of the alloying elements in γ-TiAl and α2-Ti3Al. The results showed that, for the γ phase, the compression ratio is not related to the site preference of the alloying elements in a simple way. For the α2 phase, the following correlation was observed between the compression ratio and the site occupancies of the investigated elements, those which occupy Al sites decrease the deformability, while those occupying Ti sites (except V) improve the deformability of the α2 phase. Compression properties of dual-phase TiAl alloys based on Ti-46Al-(1, 3, 5)X were also measured at room temperature to test a hypothetical mechanism of ductilization based on mechanical compatibility at phase interface. It was concluded that no simple relationship exists between the deformability of the dual-phase alloys and the properties of their constituent phases.
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    Nonequilibrium Microstructures and Phase Evolutions of an Iron-based Laser Clad Coating
    Xiaolei WU, Guangnan CHEN
    J. Mater. Sci. Technol., 1999, 15 (06): 541-547. 
    The microstructural and compositional features of the laser-solidified microstructures and phase evolutions occurring during high temperature tempering were investigated by using analytical electron microscopy with energy dispersive X-ray analysis. The cladded alloy, a powder mixture of Fe, Cr, W, Ni and C with a weight ratio of 10:5:1:1:1, was processed with a 3 kW continuous wave CO2 laser. The cladded coating possessed the hypoeutectic microstructure of the primary dendritic γ-austenite and interdendritic eutectic consisting of (γ+M7C3). Theγ-austenite is a nonequilibrium phase with extended solid solution of alloying elements. And, a great deal of fine structures, i.e., a high density of dislocations, twins, and stacking faults existed in austenite phase. During high temperature aging, the precipitation of M23C6, MC and M2C in austenite and in situ transformation of M7C3(+γ)→ M23C6 and M7C3+γ→M6C occurred. The laser clad coating revealed an evident secondary hardening and superior impact wear resistance.
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    Determination of Particle Sizes and Crystalline Phases on Colloidal Silicon Nanoparticle Suspensions
    S.M. Scholz, H. Hofmann
    J. Mater. Sci. Technol., 1999, 15 (06): 548-550. 
    Particle size and crystallinity of silicon nanoparticles were determined by analyzing the optical extinction spectra of colloidal suspensions. Experimental results from these colloids were analyzed using Mie theory in connection with effective medium theory, in order to determine particle sizes and their internal structure with the simple technique of optical transmission spectroscopy. By modeling an effective refractive index for the particles, the crystalline volume fraction can be extracted from extinction spectra in addition to information about the size. The crystalline volume fraction determined in this way were used to calibrate the ratio of the Raman cross sections for nanocrystalline and amorphous silicon, which was found to be σc/σa=0.66.
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    Valence Distribution in ATxV6-xO11 Compounds
    Hongchao LIU, Changlin KUO
    J. Mater. Sci. Technol., 1999, 15 (06): 551-554. 
    The distribution of trivalent and tetravalent cations in several ATxV6-xO11 compounds was quantitatively studied by the bond valence method. In SrV6O11, the M(3) sites were mainly occupied by trivalent cations; while M(1) and M(2) sites were shared by trivalent and tetravalent cations, the relative content of tetravalent at M(1) sites was higher than at M(2) sites. During substitution process, the trivalent cations preferred to occupy M(3) sites, tetravalent ones preferred to occupy M(2) sites. The occupancy of trivalent and tetravalent cations at M sites would change with the substitution.
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    Microstructure, Impact Toughness and TEM Analysis in the CGHAZ of HQ130 High Strength Steel
    Zengda ZOU, Yajiang LI, Shike YIN
    J. Mater. Sci. Technol., 1999, 15 (06): 555-558. 
    Microstructure and impact toughness in the coarse grain heat-affected zone (CGHAZ) of HQ130 high strength steel were studied by using the weld thermo-simulation test. Fracture morphology and fine structure in the CGHAZ were analyzed by means of SEM, TEM and electron diffraction. Experimental results indicated that the impact toughness and hardness in the CGHAZ (Tm= 1350 ℃) decreased with increasing cooling time (t8/5), and fracture morphology changed from dimple fracture into cleavage fracture. The reason for the toughness decrease is the formation of upper bainite. During application, the welding heat input should be strictly limited, to reduce brittleness in the CGHAZ of HQ130 steel.
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    Corrosion Inhibition of Carbon Steel in Hot Hydrochloric Acid Solutions
    T.Y.Soror, H.A.El Dahan, N.G.El Sayed Ammer
    J. Mater. Sci. Technol., 1999, 15 (06): 559-562. 
    The dissolution of carbon steel in 5% HCl in the temperature range of 30-90℃ was inhibited by two organic compounds having the general formula: ClR NH2(CH2)n NH2 RCl where R is a benzyl group. The behavior of these inhibitors in acidic medium was investigated using weight loss method, open circuit potential and linear polarization technique. These inhibitors provided satisfactory corrosion inhibition for carbon steel in hydrochloric acid solutions even at higher temperature and acid concentration (10%). The electrochemical results showed that the polarization resistance (Rp) values increased with increasing inhibitor concentration, also the corrosion current decreased and a higher inhibition efficiency was obtained. The protective properties of these two organic inhibitors were attributed to the chemisorption mechanism.
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    Laser and Fluorescence Properties of Organic Dye DCM Doped Sol-Gel-Derived Solid-State Materials
    Qinyuan ZHANG, Zhonghong JIANG
    J. Mater. Sci. Technol., 1999, 15 (06): 563-566. 
    Two kinds of new Ormosil xerogels derived from GPTMS (3-glycidyl propyl trimethoxisilane) and TEOS (tetraethoxysilane) or GPTMS and Ti(OBu)4 (tetrabutoxytitanate) were synthesized via the sol-gel method as dye laser host. Their optical properties, microstructure characteristics and surface laser damage thresholds have been reported. The effects of dye matrix combination on the fluorescence emission, slope efficiency, photostability and tunable bandwidth were examined. Laser oscillation was easily achieved near 620 nm with a slope efficiency of 29% from DCM doped SiO2-Ormosil pumped by a frequency-doubled radiation from a Q-switched Nd:YAG laser. The laser wavelength was tunable over 59nm, and the laser output energy had only a 10% reduction after 2.5×104 pulses at a pump repetition rate of 1 Hz and a pump intensity of 1 J/cm2.
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    Simulation of Stable Crack Growth for Welded Joints Including Strength Mismatching
    Hongyang JING, Lixing HUO, Yufeng ZHANG, Fumiyoshi Minami
    J. Mater. Sci. Technol., 1999, 15 (06): 567-570. 
    A 3-D computational method to simulate stable growth of a macroscopic crack under model I condition is described in this paper. The Gurson-Tvergaard plasticity model for voided materials describes the damage process. Fixed-sized, computational cell elements (containing voids) defined over a thin layer at the crack plane simulate the ductile crack extension. Outside of this layer, the material remains undamaged by the void growth, follows the conventional J2 flow theory. The micromechanics parameters controlling crack growth are D, the thickness of computational cell layer and f0, the initial void porosity. Calibration of these parameters proceeds through analyses of ductile tearing to match R-curve obtained from testing of deep notch bend specimens for welded joints. The effect of the strength mismatching on ductile crack growth for welded joints is simulated also.
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    Phosphogypsum Utilization Part II: Preparation of Ammonium Sulphate
    A.A.Hanna, S.M.Ahmed
    J. Mater. Sci. Technol., 1999, 15 (06): 571-574. 
    The aim of this work was to describe the conversion of raw phosphogypsum, issued from the manufacture of H3PO4 by dissolving the phosphate rock in H2SO4, into (NH4)2SO4 and CaCO3. The thermal analysis technique was used to estimate the yield of conversion. (NH4)2CO3 or (NH4)2CO3 with excess NH4OH or (NH4)2CO3 with NH3 gas were used in the preparation of (NH4)2SO4 from phosphogypsum. The obtained samples were separated and tested by chemical and thermogravimetric analyses, infrared spectrum and X-ray diffraction and the optimum conditions of conversion were determined. The results indicated that the yield of conversion equals to 83.37 and 86.70% in case of using (NH4)2CO3 or (NH4)2CO3 with excess ammonia respectively, while by using NH3 gas the percentage of conversion increased to 94.2% at a flow rate of 6 ml/min. Chemical analysis, infrared spectrum and X-ray diffraction patterns of the yield, (NH4)2SO4 were nearly similar to the standard sample.
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    Application of Magnetic Treatment in Hot Water Boilers for Preventing Scale
    Dianyu GENG, Zhidong ZHANG, Baozhi CUI, Zhijun GUO, Wei LIU, Xinguo ZHAO, Jiwen LIU
    J. Mater. Sci. Technol., 1999, 15 (06): 575-577. 
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    Effects of Al Additions on Microstructure and Mechanical Properties of MoSi2
    Jianlin LI, Dongliang JIANG, Shouhong TAN
    J. Mater. Sci. Technol., 1999, 15 (06): 578-580. 
    The effects of Al additions on the microstructure and mechanical properties of MoSi2 have been studied. With the Al additions from 2.5 wt pct to 5 wt pct, the siliceous grain boundary phase in hot pressed samples was eliminated because of the formation of Al2O3 particles. It was shown that Al and SiO2 reacted at 860℃. During the reaction, Al atoms were mainly transferred to Al2O3 particles, and to some extent, diffused into MoSi2 grains. Both the toughness and strength of Al containing composites exceeded those of pure MoSi2 material. Bending strength and fracture toughness reach the highest value of 350 MPa, 4.05 MPa•m1/2, respectively, at ambient temperature when Al addition was of 3.5 wt pct.
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    About Nonlinear Mechanism of Energy Transformation Ion Implantation
    S.G.Psakhie, K.P.Zolnikov, R.I.Kadyrov, G.E.Rudenskii, S.A.Vassiliev, Yu.P.Sharkeev
    J. Mater. Sci. Technol., 1999, 15 (06): 581-582. 
    The peculiarities of energy dissipation transferred by solitary waves on defects such as free surface, grain boundary, region with high concentration of vacancies are studied. One of the ways of description of the long range effect taking place at ion implantation in metallic materials is suggested.
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    Spinodal Decomposition of Ultrahigh Strength Steel 23Co14Ni12Cr3
    Liuding WANG, Changle CHEN, Mokuang KANG
    J. Mater. Sci. Technol., 1999, 15 (06): 583-584. 
    The depleted and enriched regions of solute atoms formed by spinodal decomposition in the early stage of tempering for ultrahigh strength steel 23Co14Ni12Cr3 were first confirmed by means of transmission electron microscopy (TEM). The segregation of solute atoms provides favorable composition and structure fluctuationfor the formation of secondary hardening phase M2C and cementite Fe3C.
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ISSN: 1005-0302
CN: 21-1315/TG
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