Table of Content

23 October 2008, Volume 14 Issue 5

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Articles

Relationship between Nodular Corrosion Resistance and Textures for Zircaloy-4 Strip

ZHOU Bang-xin;YAO Mei-yi;LI Qiang;XIA Shuang;LIU Wen-qing

2008, 14(5):  441-445 . 

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The effects of heat treatments and textures on the nodular corrosion resistance of Zircaloy-4 strip have been investigated in superheated steam of 500 °Cand 10.3 MPa by autoclave tests. After heat treatment at 820 °C-1 h and fast cooling, concentrated textures with (0001) ［11 20］ and (0001) ［10 10］ orientations were obtained after grain growth, and the supersaturated solid solution of alloying elements of Fe and Cr in α-Zr matrix was increased simultaneously. (0001) planes with better corrosion resistance were mainly parallel to the rolling plane of the specimens, while (10 10) and (11 20) planes with worse corrosion resistance were on the side planes around the specimens. In this case, the nodular corrosion resistance on the rolling plane of the specimens was improved but the nodular corrosion phenomena could also appear on the side planes around the specimens. The nodular corrosion behavior was closely related to the texture orientations. And it could be completely suppressed when the supersaturated solid solution contents of Fe and Cr in α-Zr matrix were further increased after heat treatment in β phase.

Progress in Applications of Strong Magnetic Field in Processing Metallic Materials

REN Zhong-ming;JIN Fang-wei

2008, 14(5):  446-455 . 

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Processing metallic materials under a strong magnetic field is a newly emerging research area, and undergoes fast development. Main progresses in this area are reviewed, with the focus on the influence of strong magnetic field on alignment and orientation of crystals, solidification of metals, heat treatment of alloys, and thermodynamics of phase transformation. It is shown that the influence of strong magnetic field is unique and complicated, with promising prospects. Problems in this area that need further research are discussed.

Diffusion of Hydrogen in Disordered and Ordered Ni₃Fe Alloys


CHEN Ye-xin;MA Jie;SHI Dan-dan;C. T. LIU

2008, 14(5):  456-460 . 

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Diffusion of hydrogen for disordered and ordered Ni₃Fe alloys at room temperature has been studied by cathodic charging with hydrogen. At the same temperature of precharging, the elongation decreases and intergranular (IG) depth increases with increasing precharging time respectively for Ni₃Fe precharged hydrogen. At the same time of precharging, the depth of IG increases with increase of precharging temperature. Relationship between IG depth and temperature and time is in accordance with the solution of Fick law. Based on the time-lag method, the apparent diffusion coefficient of hydrogen in disordered Ni₃Fe alloy is larger than that in ordered Ni₃Fe alloy. The activation energy of hydrogen diffusion in disordered and ordered Ni₃Fe alloys is 44.9 kJ/mol and 29.5 kJ/mol respectively.

Effect of Temper Rolling on Formation of Cubic Texture in Electrical Steels

WANG Jun-an;HE Ying;QIU Zhen-wei;ZHOU Bang-xin;Frantisek Kovac

2008, 14(5):  461-466 . 

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Effects of temper rolling on the cubic texture formation in primary recrystallized electrical steel were investigated. The results show that the cubic texture with columnar structure is obtained in the Fe-3.2%Si electrical steels through temper rolling and final annealing of primary recystallized sheets. In the formation of columnar structure, ∑5 and ∑11 grain boundaries decrease and finally disappear. This is beneficial to the growth of (100)［001］ grains. The migration of those grain boundaries is due to the special misorientation of 36.9°/〈100〉and 50.5°/〈110〉between (100)［001］ grains and primaries and the beneficial annealing environment.

Development of TRIP Steel with Good Weldability and Galvanizing Property


LI Lin;SHI Wen;ZHANG Mei;HE Yanlin;LIU Hua-chu;FU Ren-yu

2008, 14(5):  467-471 . 

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TRIP steel is less popular in automobile industry as compared with DP steel although the latter has much lower strength and ductility. Reasons for this are listed. By careful calculation based on thermodynamics and kinetics, a new type of TRIP steel with good weldability and galvanizing property is successfully developed both in the university laboratory and on a modern production line of steel plant. In order to make the steel suitable for domestic metallurgy processing, phosphorus is used to substitute silicon instead of aluminum.

Structure and Properties of 00Cr25Ni2Mo3Mn10N High Nitrogen Super Duplex Stainless Steel

XIAO Xue-shan;LI Jun;JIANG Lai-zhu;ZHAO Jun-liang

2008, 14(5):  472-474 . 

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A new resource-saving high nitrogen super duplex stainless steel 00Cr25Ni2Mo3Mn10N has been developed, in which the nitrogen content reaches 0.5%. The results indicate that the alloy is made up of ferrite and austenite after hot forge and 1 050 ℃ solid solution treatment, and the ferrite content is about 47%. Mechanical and corrosion property are noticeably enhanced with the increase of nitrogen. The comprehensive performance of 00Cr25Ni2Mo3Mn10N alloy is as good as that of 00Cr25Ni7Mo4N super duplex stainless steel, and even better.

Oxidative Photoelectrochemical Technology with Titanium/Transition Metal Doped-TiO2 Multi-nanoporous Thin-Film Anodes

SHEN Jia-nian;LIU Dong;WAN Bin;LI Mou-cheng;ZHONG Xiang-yu

2008, 14(5):  475-480 . 

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The present investigation reports the preparation of platinum and nickel doped-anatase multi-nanoporous thin film electrodes. These doped electrodes were prepared from titanium plates by a three step electrochemical method. Investigations concerning degradation of a non-biodegradable azo dye (acid red G) in the presence of these electrodes irradiated by artificial UV-light were carried out. It has been found that the presence of Pt⁴⁺ into TiO₂ can cause a significant increase in the catalytic activity, especially in the photodegradation of the dye. Incorporation of Ni²⁺ was detrimental to this process. Efficiency of metal-doped TiO₂ electrodes was explained on the basis of electroaffinity and the electron work function. It was observed that photocatalytic degradation of the dye was strongly favored in acidic solutions.


Numerical Simulation on Fluid Flow and Mixing Behavior in Twin-Roll Strip Cas
ting Pool

ZHANG Jie-yu;WANG Bo;K.C. Chou;FAN Jun-fei;REN San-bing;ZHAO Shun-li

2008, 14(5):  481-486 . 

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Transport phenomena of the molten steel in a twin-roll strip casting pool have been studied numerically by solving the momentum equation, k-ε two equations along with the species concentration equation. Flow and mixing characteristics of molten steel in the pool was analyzed using a V-type delivery system. Turbulence kinetic energy and residence time distribution (RTD) of the fluid near the free surface were calculated. It was shown that fluid can be uniformly distributed which was benefit to uniform solidification of the strip. The regeneration rate of fluid and level fluctuation increased near side dams. This is desirable to prevent formation of crust.

Multiferroic BiFeO₃-CoFe₂O₄ Composite Films Prepared by Pulded Laser Deposition

CHENG Jin-rong;ZHU Yan-yan;CHEN Jian-guo;YU Sheng-wen;WU Wen-biao;JIN Deng-ren;MENG Zhong-yan

2008, 14(5):  487-491 . 

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Multiferroic 0.7BiFeO₃-0.3CoFe₂O₄(BFO-CFO) composite films were prepared on the Pt（111）/Ti/SiO₂/Si substrate by the pulsed laser deposition method. In the deposition process, the perovskite BiFeO₃ and the spinel structured CoFe₂O₄ phases were formed and separated by selfassembling growth. The growth condition and mechanism of BFO-CFO composite films, and the effect of film thickness on the structure and properties of BFO-CFO films were investigated.

Composition Optimization of Zn-Al Hot-Dip Coatings Using Combinatorial Material Chip Approach

ZHU Li-hui;ZHU Shuo-jin;LIU Qian;LIU Qing-feng;WANG Li

2008, 14(5):  492-497 . 

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Combinatorial material chip approach is innovation in materials research. It can discover and optimize new materials efficiently and quickly. Combinatorial material chip approach suggests that Al content should be controlled in the range of 50%~75% for Zn-Al hot-dip coatings with good mechanical properties and anticorrosion behavior. Especially, 72.6Al-Zn has excellent properties. Corrosion behaviors of hot-dip Zn, 55Al-Zn and 72Al-Zn coatings were compared and the corrosion mechanisms were studied. The results show that the anticorrosion property of 72Al-Zn coating is slightly better than 55Al-Zn coating, and both are much better than Zn coating. It indicates that combinatorial material chip approach can be applied for the composition optimization of anticorrosion Zn-Al hot-dip coatings.

Preparation of SandwichLike Multilayered PbxSr1-xTiO3 Thin

Film wit
h Study of Dielectric Tunability and Temperature Stability


WU Wen-biao;ZHOU Dong-yi;JIN Deng-ren;MENG Zhong-yan

2008, 14(5):  498-502 . 

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A sandwich-like multilayered lead strontium titanate Pb_xSr_1-xTiO₃ (PST20-40) thin film was fabricated on Pt/Ti/SiO₂/Si substrates using the sol-gel technique. PST20-40-20 thin films have high tunability and low loss tangent. Tunability and FOM of PST20-40-20 thin films are 52 and 45, respectively. PST20-40-20 thin films have weaker temperature dependence, and the decreasing rate of tunability for PST20-40-20 thin films is about 8% at 20 °C to 100 °C.

Alloying Characteristics of Two Sucker-Rod Steels Analyzed with JMatPro


MIN Yong-an;LIU Xiang-jiang;MAO Yuan-jian

2008, 14(5):  503-508 . 

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Equilibrium phases and their compositions under different temperature are studied in two sucker-rod steels with JMatPro software. Compared with those in 17Mn2SiCr steel, more alloying elements of Cr, Mo and Si are saturated in austenite and ferrite respectively, while the amount of carbides decreases by about 30% in 12MnSi2Cr steel. Stability of M(C, N) carbide is increased by the addition of micro alloying element Nb. Based on this study, high toughness of the sucker-rod of 12MnSi2Cr steel is discussed.

BiFeO₃ Thin Films Fabricated by Sol-gel Method and Its Thickness Dependence

YU Sheng-wen;CAI Jin-yu;YAN Yun-fei;CHENG Jin-rong

2008, 14(5):  509-513 . 

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BiFeO₃ thin films with different layers/thicknesses were fabricated on Pt(111)/Si(100) substrates by sol-gel method. XRD results indicate that a phase transition from pseudocubic to rhombohedral might happen between the films with thicknesses of 4 layers/200 nm and 8 layers/400 nm. With increasing thickness, the films exhibit better crystallinity and dielectric properties. Meanwhile, insulation and ferroelectricy are improved as well.

Tunable Morphology of ZnO Nanostructures Self-Assembled by Polymer Complexation Process

HE Ying;WANG Jun-an;ZHANG Wen-fei;CHEN Xiao-ban;HUANG Zong-hao

2008, 14(5):  514-520 . 

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Influence of various factors on the growth behavior of ZnO nanostructures self-assembled by polymer complexation process and growth mechanism is discussed. Investigation on the self-assembling formation mechanism of ZnO nanostructures revealed that the growth of ZnO nanostructures was in well accordance with the polar growth behavior and polymer grid backbone localization model. The ZnO nanostructures can be tailored by using different complexing media. The regular wire-like, flower-like, flake-like and club-like ZnO nanostructures were obtained by using polymer such as PVA and PAM, ammonia, trisodium citrate (TSC) and hexamethylene tetraamine (HMTA) as complexing media, respectively. The weak base of the complexing solution at suitable pH value promoted the ［0001］ oriented growth of ZnO in the selfassembling process thus leading to the ZnO nanorods/nanowires. By reasonable selection and adjusting the factors such as complexing media and the basicity of the complexing solution, the crystal growth and morphologies of the ZnO nanostructures can well be controlled.

Electroless Plating Kinetics of Ag₈₀(WC₇₀TiC₃₀)₁₇C₃ Silver-Based Electric Contact Material


ZHANG Xiao-yan;REN Hai-feng;GAO Li-cong;CAO Ze-chun

2008, 14(5):  521-524 . 

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This paper introduces the chemical dynamics mechanism during an electroless plating process of silver on the mixture of WC, TiC, C powders. The reaction rate of electroless plating is determined by the pH value. A kinetic equation is derived from the curves of pH measurements versus time at different temperat
ures, i.e. c=c₀e^-kt.


3D Atom Probe Characterization of Precipitation of Cu-rich Clusters in Pressure Vessel Model Steel

ZHU Juan-juan;WANG Wei;LIN Min-dong;LIU Wen-qing;WANG Jun-an;ZHOU Bang-xin

2008, 14(5):  525-530 . 

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Three-dimensional atom probe (3DAP) and thermal aged method were used to characterize precipitation of Cu-rich clusters in pressure vessel model steel. Pressure vessel model steel specimens were quenched at 880 °C , then aged at 400 °C and 500 °C for different time. The results of hardness test show that peak hardness reached for 100 h aged at 400 °C and 5 h aged at 500 °C, respectively. Analysis results of 3DAP indicate that the number density of Cu-rich clusters increases from 1.5×10²³ m^-3 to 6.2×10²³m^-3, and equivalent diameter of the biggest clusters increases from 2 nm to 3.5 nm after aging 100 h and 300 h at 400 °C . It shows that the growth of Cu-rich clusters is very slow. The content of Cu in Cu-rich clusters is about 20%. Both Mn and Ni atoms are also segregated in Cu-rich clusters and distribution riched at the αFe matrix/clusters interfaces.

Effect of Alloying Element (Cu and Mn) Additions on the Precipitates of Zr Alloys


ZENG Qi-feng;ZHOU Bang-xin;YAO Mei-yi;PENG Jian-chao;XIA Shuang

2008, 14(5):  531-536 . 

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A series of zirconium alloys with copper and manganese additions in Zircaloy-4 were prepared using a vacuum non-consumable arc melting method. TEM observationwas carried out to characterize precipitates in alloys. The crystal structure was determined by a selected area electron diffraction (SAD) pattern, and the composition of precipitates was analyzed with energy dispersion spectroscopy (EDS). In the copper-added Zircaloy-4 specimens, three main precipitates were detected: (1) Zr(Fe,Cr)₂ precipitates, (2) Zr(Fe,Cr,Cu)₂ precipitates, and (3) Zr₂Cuprecipitates with a bit of Fe or without Fe. In the manganese-added Zircaloy-4 specimens, only one kind of Zr(Fe,Cr,Mn)₂ precipitate was observed. Mn content in the precipitates increased as the increase of Mn content from 0.07% to 0.35% in the alloy.

Interaction between Boron Nitride and the Melted TiNi Alloy

ZHANG Qiang;ZHOU Xing;LIU Hong-bao;ZHU Ming;KANG Di;WANG Xiao-kang;MAO Xie-min;LI Chong-he

2008, 14(5):  537-540 . 

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Interaction between high-purity boron nitride (BN) and melted TiNi alloy was studied to determine if BN could be used as crucible material for melting TiNi alloy. A series of interface actions between them were performed for differentmelt temperatures (1 450 °C, 1 520 °C) and different holding times (90 s, 180 s, 270 s, 360 s). These interfaces were then investigated with scanning electron microscopy (SEM), X-ray diffraction, and electron probe microanalysis. The results showed that TiNi melt was slightly contaminated due to the limited reaction between BN and Ti under the conditions.

Nanohardness and Elastic Modulus of Pyrocarbon

YANG Min;SUN Jin-liang;REN Mu-su;LI Hong;BAI Rui-cheng

2008, 14(5):  541-545 . 

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Nanoindentation experiments were made on pyrocarbon of samples with single phase before or after high-temperature heat treating, and of the 3DC/C composites. Nanohardness and elastic modulus were measured. Loading and unloading curves were analyzed. It was found that there was only elastic distortion happening for the single phase samples before heat treating, but the plastic deformation also happened for the heat-treated samples. Values of elastic modulus are 33.84 and 4.65 GPa for single phase samples before and after heat treating, respectively. The large difference is due to the structure transformation from turbostratic structure to graphite structure. The value of elastic modulus was30.08 GPa for the C/C composite pyrocarbon.

Effect of Nb on Hydrogen Storage Characteristics of TiV_0.9Cr_1.3 Alloy

MENG Xiang-hai;ZHANG Jin-long;JIN Hang-jun;ZHU Ming;LIN Gen-wen;GE Jian-sheng

2008, 14(5):  546-550 . 

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The effect of Nb on hydrogen storage properties of TiV_0.9Cr_1.3 alloy was nvestigated. It was found that all alloys were single phases with BCC structures and dendritic crystals, in which minor Laves（Cr₂Nb）phase were observed and the second dendritic crystals disappear ( x＞0.3). As x increases from 0 to 0.4，the lattice parameters increase and the maximum hydrogen storage capacities, efficient hydrogen storage capacities and the desorption plateau pressure of the alloys decrease, while flatness of the desorption plateau region is improved. Slope of the desorption plateau region decreases from 1.59 to 0.71. The absolute value of enthalpy and entropy for hydrides increase. The TiV_0.6Cr_1.3Nb_0.3 alloy exhibits the maximum hydrogen storage capacities of 3.254%,the efficient hydrogen capacity of 2.367%, desorption plateau pressure of 0.09 MPa and slope of the desorption plateau region of 1.0.