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ISSN 1005-0302
CN 21-1315/TG
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      28 March 2006, Volume 22 Issue 02 Previous Issue    Next Issue
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    Research Articles
    Microstructures of an Ultrafine Grained SS400 Steel in an Industrial Scale
    Hua DING, Long LI, Chunzheng YANG, Dan SONG, Linxiu DU
    J. Mater. Sci. Technol., 2006, 22 (02): 145-148. 
    Abstract   HTML   PDF (1030KB)
    The microstructures of a SS400 steel after thermomechanical control process (TMCP) in an industrial production were observed by optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results indicated that the size of ferrite grains was 4 ~μm, and the volume fraction of ferrite was around 70%. The types of the ultrafine ferrite grains were analyzed and the strengthening mechanisms were discussed. The results show that the ultrafine ferrite grains came from three processes, i.e. deformation induced ferrite transformation (DIFT), dynamic recrystallization of ferrite and accelerated cooling process. The increase in the strength of the material was mainly due to the grain refining.
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    Mathematical Modelling of Carbonitride Precipitation during Hot Working in Nb Microalloyed Steels
    Yunbo XU, Yongmei YU, Xianghua LIU, Guodong WANG
    J. Mater. Sci. Technol., 2006, 22 (02): 149-152. 
    Abstract   HTML   PDF (475KB)
    Based on thermodynamics and kinetics, precipitation behavior of microalloyed steels was analyzed. Deformation greatly promotes isothermal carbonitride precipitation and makes C-curve shift leftwards. The position and shape of C-curve also depend on the content of Nb and N. C-curve shifts leftwards a little when N content increases and the nose temperature is raised with increasing Nb content. Deformation shortened precipitation start time during continuous cooling, raised precipitation start temperature, accelerated precipitation kinetics of carbonitrides. With decreasing the finishing temperature and coiling temperature, the precipitates volume fraction increases and strength increment is raised during hot rolling. The simulated results are in agreement with experiment results.
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    Simulations of Coarsening Behavior for M23C6 Carbides in AISI H13 Steel
    Xinbin HU, Mei ZHANG, Xiaochun WU, Lin LI
    J. Mater. Sci. Technol., 2006, 22 (02): 153-158. 
    Abstract   HTML   PDF (2728KB)
    Based on the local equilibrium assumption, coarsening behavior of M23C6 carbide at 700℃ in H13 steel was simulated by DICTRA software. The results from the calculations were compared with transmission electron microscopy (TEM) observations. The results show the interfacial energy for M23C6 in H13 steel at 700℃ is thus probably 0.7 J•m-2, which fits the experiments well. The influence of composition and temperature on the coarsening rate was also investigated by simulations. Simulations show a decrease in the coarsening rate when V/Mo ratio is increased, while the coarsening rate increases with increasing temperature.
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    Effect of V and V-N Microalloying on Deformation-Induced Ferrite Transformation in Low Carbon Steels
    Kai WANG, Lijun WANG, Wenfang CUI, Chunming LIU
    J. Mater. Sci. Technol., 2006, 22 (02): 159-163. 
    Abstract   HTML   PDF (4357KB)
    Deformation-induced ferrite transformation (DIFT) has been proved to be an effective approach to refine ferrite grains. This paper shows that the ferrite grains can further be refined through combination of DIFT and V or V-N microalloying. Vanadium dissolved in γ matrix restrains DIFT. During deformation, vanadium carbonitrides rapidly precipitate due to strain-induced precipitation, which causes decrease in vanadium dissolved in matrix and indirectly accelerates DIFT. Under heavy deformation, deformation induced ferrite (DIF) grains in V microalloyed steel were finer than those in V free steel. The more V added to steel, the finer DIF grains obtained. Moreover, the addition of N to V microalloyed steels can remarkably accelerate precipitation of V, and then promote DIFT. However, DIF grains in V-N microalloyed steel easily coarsen.
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    Effect of Nb on the Microstructure and Mechanical Properties of Cast NiAl-Cr(Mo) Eutectic Alloy
    Kaiwen HUAI, Jianting GUO, Zirong REN, Qiang GAO, Rui YANG
    J. Mater. Sci. Technol., 2006, 22 (02): 164-168. 
    Abstract   HTML   PDF (603KB)
    The microstructure and mechanical behaviors of NiAl-28Cr-5Mo-1Nb eutectic alloy were investigated by using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and compression tests, respectively. The alloy is mainly composed of three phases, which are the gray lamellar Cr(Mo) plate, black NiAl matrix and semicontinuously distributed Cr2Nb-type Laves phase. Through Nb addition, NiAl-Cr(Mo)/Nb alloy exhibits a reasonable balance of high temperature strength and room temperature compression ductility and its mechanical behaviors are superior to the NiAl-28Cr-6Mo eutectic alloy at all temperature. The elevated temperature compression deformation behavior of NiAl-Cr(Mo)/Nb alloy can be properly described by power-law equation.
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    Influence of Co, W and Ti on the Stress-rupture Lives of a Single Crystal Nickel-base Superalloy
    Dayun YANG, Tao JIN, Nairen ZHAO, Zhihui WANG, Xiaofeng SUN, Hengrong GUAN, Zhuangqi HU
    J. Mater. Sci. Technol., 2006, 22 (02): 169-172. 
    Abstract   HTML   PDF (418KB)
    The influence of Co, W and Ti on stress-rupture lives of a Ni-Cr-Al-Mo-Ta-Co-W-Ti single crystal nickel-base superalloy has been investigated using a L9 (34) orthogonal array design (OAD) by statistical analysis. At a selected composition range, Ti content was the most important factor to the effect of the stress-rupture lives and then followed by Co content. W content had the minimum effect on stress-rupture lives. The optimal alloy should contain 10 wt pct Co, 8 wt pct W and zero Ti. The optimized alloy also had good microstructural stability during thermal exposure at 870℃ for 500 h.
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    Optimal Control of Oxygen Concentration in a Magnetic Czochralski Crystal Growth by Response Surface Methodology
    Huiping YU, Yunkan SUI, Jing WANG, Fengyi ZHANG, Xiaolin DAI
    J. Mater. Sci. Technol., 2006, 22 (02): 173-178. 
    Abstract   HTML   PDF (1200KB)
    Concepts and techniques of response surface methodology have been widely applied in many branches of engineering, especially in the chemical and manufacturing areas. This paper presents an application of the methodology in a magnetic crystal Czochralski growth system for single crystal silicon to optimize the oxygen concentration at the crystal growth interface in a cusp magnetic field. The simulation demonstrates that the response surface methodology is a feasible algorithm for the optimization of the Czochralski crystal growth process.
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    Effect of 0.1 wt pct Dy Addition on Morphology and Compressive Behavior of Cast NiAl-28Cr-5.8Mo-0.2Hf
    Qiang GAO, Jianting GUO, Kaiwen HUAI, Hutian LI, Junshan ZHANG
    J. Mater. Sci. Technol., 2006, 22 (02): 179-182. 
    Abstract   HTML   PDF (911KB)
    Effect of 0.1 wt pct Dy addition on microstructure and compressive behavior of NiAl-28Cr-5.8Mo-0.2 Hf eutectic alloy was investigated. The results showed that remarkable lamellar refinement can be achieved with the addition of 0.1 wt pct Dy. The Dy addition results in the decrease in Young's modulus of alloy and the enhancement of the compressive strength and ductility of alloy at all testing temperatures. The lamellar refinement, the increased dislocation networks located at the interfaces of NiAl/Cr(Mo) and the strengthening of cell boundary are benefical to the improvement of compressive properties of the alloy.
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    Growth of Casting Microcrack and Micropore in Single-crystal Superalloys Analysed by Three-Dimensional Unit Cell
    Jiansong WAN, Zhenzhou LU, Zhufeng YUE
    J. Mater. Sci. Technol., 2006, 22 (02): 183-189. 
    Abstract   HTML   PDF (2584KB)
    Finite element (FE) analysis was employed to investigate the casting microcrack and micropore growth in nickel-base single-crystal superalloys DD3. Based on the finite deformation rate-dependent crystallographic constitutive equation, the simulations of casting microcrack and micropore growth in three-dimensional unit cell model were carried out in a range of parameters including stress triaxiality, Lode parameter and type of activated slip systems. The FE results show that the stress triaxiality has profound effects on growth behavior, and the Lode parameter is also important for the casting microcrack and micropore growth. The type of operative slip systems has remarkable effect on casting microcrack and micropore growth, so the life of single-crystal component is associated with the type of activated slip systems, which is related to Schmid factor and the number of activated slip systems. The growth comparison between microcrack and micropore reveals that when the material is subjected to large deformation, the growth rate of microcrack is faster than that of micropore, i.e. microcrack is more dangerous than micropore; the microcrack is easier to result in brittle fracture than micropore. The stress triaxiality and Lode parameter have strong influence on the growth of microcrack and micropore.
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    Microstructure Evolution and Tensile Properties of Pure Ti Subjected to Rapidly Heating and Quenching
    Weisong ZHAO, Wei ZHANG, Jinyu GUO, Boquan WANG, Jingdong GUO, Ke LU
    J. Mater. Sci. Technol., 2006, 22 (02): 190-194. 
    Abstract   HTML   PDF (1383KB)
    The pure α-Ti samples were heated at an extremely high rate (~106 K/s) to the temperature of β phase zone followed by a rapidly quenching in an electro-pulsing treatment. After the treatment, micrometer-thick lamellar substructures were generated within the original equiaxed α-Ti coarse grains. Misorientations across adjacent lamellae are of a few degrees. The ultrafine lamellar substructures originated from a non-equilibrium α-β-α' phase transformation during rapidly heating-quenching process with a short exposure time at high temperatures. Tensile strength was increased by about 100 MPa due to the formation of the ultrafine lamellar substructure while the same tensile plasticity (elongation-to-failure) was maintained relative to the original sample. The strengthening effect could be attributed to the effective blockage of dislocation motions by a high density of sub-boundaries.
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    Formation and Evolution of Non-dendritic Microstructures of Semi-solid Alloys Prepared by Shearing/Cooling Roll Process
    Shuncheng WANG, Furong CAO, Renguo GUAN, Jinglin WEN
    J. Mater. Sci. Technol., 2006, 22 (02): 195-199. 
    Abstract   HTML   PDF (847KB)
    The shearing/cooling roll (SCR) process was adopted to prepare semi-solid A2017 alloy. The formation and evolution of non-dendritic microstructures in semi-solid A2017 alloy were studied. It is shown that the microstructures of semi-solid billets transform from coarse dendrites into fine equiaxed grains as the pouring temperature of molten alloy decreases or roll-shoe cavity height is reduced. From the inlet to the exit of roll-shoe cavity, microstructure of semi-solid slurry near the shoe surface is in the order of coarse dendrites, degenerated dendrites or equiaxed grains, but fine equiaxed grains are near the roll surface. Microstructural evolution of semi-solid slurry prepared by SCR process is that the molten alloy nucleates and grows into dendrite firstly on the roll and shoe's surface. Under the shearing and stirring given by the rotating roll, the dendrites crush off and disperse into the melt. Under the shearing and stirring on semi-solid slurry with high volume fraction of solid, the dendrite arms fracture and form equiaxed grain microstructures.
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    Anti Cervix Cancer Activity of Co-immobilized Tumor Necrosis Factor-α and Interferon-γ
    Yanqing GUAN, Limei HE, Shumei, Tianhong ZHOU
    J. Mater. Sci. Technol., 2006, 22 (02): 200-204. 
    Abstract   HTML   PDF (882KB)
    Tumor necrosis factor α (TNF-α) and interferon-γ (IFN-γ) are cytokines with strong antitumor activities. They were reacted with a photoactive arylazide-4-azidobenzoic acid, resulting in photoactive TNF-α and IFN-γ. The infrared (IR) spectra of these products showed the characteristic absorption of an azido group at 2127 cm-1. By photo-immobilization, this modified TNF-α and IFN-γ were immobilized on polystyrene membranes for cell culture to prepare biomaterials. The micro-morphology of photoactive cytokines was observed with a scanning electron microscope (SEM). The inhibitory effect on growth of Hela cells and inducing apoptosis activity of these two cytokines were analyzed by growth curve, transmission electron microscope (TEM) and fluorescence active cell sorter (FACS). The results showed that co-immobilization of IFN-γ and TNF-α had significant inhibitory effect on growth of Hela cells, inhibitory rate up to 82%, and IFN-γ had obviously synergistic action.
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    Fibroblast Adhesion and Proliferation on a New β Type Ti-39Nb-13Ta-4.6Zr Alloy for Biomedical Application
    Yongkang ZHAO, Yang YAO, Weixian LIU, Caiyun ZHENG, Shujun LI
    J. Mater. Sci. Technol., 2006, 22 (02): 205-210. 
    Abstract   HTML   PDF (1701KB)
    Cell attachment and spreading on Ti-based alloy surfaces is a major parameter in implant technology. Ti-39Nb-13Ta-4.6Zr alloy is a new β type Ti alloy developed for biomedical application. This alloy has low modulus and high strength, which indicates that it can be used for medical purposes such as surgical implants. To evaluate the biocompatibility and effects of the surface morphology of Ti-39Nb-13Ta-4.6Zr on the cellular behaviour, the adhesion and proliferation of rat gingival fibroblasts were studied with substrates having different surface roughness and the results were also compared with commercial pure titanium and Ti-6Al-4V. The results indicate that fibroblast shows similar adhesion and proliferation on the smooth surfaces of commercial pure titanium (Cp Ti), Ti-39Nb-13Ta-4.6Zr, and Ti-6Al-4V, suggesting that Ti-39Nb-13Ta-4.6Zr has similar biocompatibility to Cp Ti and Ti-6Al-4V. The fibroblast adhesion and spreading was lower on rough surfaces of Cp Ti, Ti-39Nb-13Ta-4.6Zr and Ti-6Al-4V than on smooth ones. Surface roughness appeared to be a dominant factor that determines the fibroblast adhesion and proliferation.
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    Crystallization Kinetics of Nanophase Glass-Ceramics as Magnetic Disk Substrate
    Shengyu JIANG, Jiancheng ZHANG, Feng GU, Yue SHEN, Hua WANG
    J. Mater. Sci. Technol., 2006, 22 (02): 211-214. 
    Abstract   HTML   PDF (475KB)
    Glass-ceramics containing β-quartz as a main crystal phase based on the system of SiO2-Al2O3-Li2O-K2O-MgO-ZnO were investigated for the application to magnetic storage substrate for higher storage capacity. Parent glasses were prepared, then nucleated and crystallized at certain temperatures for 3~4 h. The crystallization kinetics of glass-ceramics was also studied. The grain size was estimated by Scherrer formula and image treatment of transmission electron microscopy (TEM). The results π showed that the Avrami exponent was determined to be 3.88, the activation energy 189±7 kJ/mol and the grain size 30~60 nm. A detailed microstructure of the glass-ceramics, including grain distribution and the morphology of nano-crystalline was characterized by TEM, X-ray diffraction (XRD), differential scanning calorimeter (DSC), differential thermal analysis (DTA). The relationship between microstructure and mechanical properties was also discussed.
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    A Valence Electron Structure Criterion of Ionic Conductivity of Sr- and Mg-doped LaGaO3 Ceramics
    Min SHI, Ning LIU, Yudong XU, Can WANG, Yupeng YUAN, P.Majewski
    J. Mater. Sci. Technol., 2006, 22 (02): 215-219. 
    Abstract   HTML   PDF (706KB)
    The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules (EET). A criterion for the ionic conductivity was proposed, i.e. the 1/(nAnB) increases with increasing the ionic conductivity when x or y≤% (in molar fraction).
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    Matrix Crack Detection by an Embedded Polarimetric Sensor
    H.Wang, S.L.Ogin, A.M.Thorne, G.T.Reed
    J. Mater. Sci. Technol., 2006, 22 (02): 220-224. 
    Abstract   HTML   PDF (1224KB)
    Polarimetric optical fibre sensors have been embedded within the 0℃ ply and close to the 0/90 interface of transparent cross-ply GFRP coupons. The laminate ply cracks may initiate and propagate across the coupon when the coupons were subjected to an increasing quasi-static load in a servo-hydraulic testing machine. Crack accumulation have been monitored using a long gauge-length extensometer. The response of the strain signal, the optical signal and the load signal to cracks at different positions in the coupon in relation to the extensometer and optical sensor positions have been acquired and compared by means of video images of the crack growth. The relationship between crack growth and sensor response was demonstrated. The displacement induced by a new transverse crack has been predicted and compared with experimental data.
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    Optical Properties, Electronic Energy Level Structure and Electro-luminescent Characteristics of Salicylaldehyde Anil Zinc
    Yuying HAO, Bingshe XU, Zhixiang GAO, Hua WANG, Hefeng ZHOU, Xuguang LIU
    J. Mater. Sci. Technol., 2006, 22 (02): 225-229. 
    Abstract   HTML   PDF (5341KB)
    A new electroluminescent material, salicylaldehyde anil zinc (SAZ) was synthesized, which can form high quality, thermal stability, nano-scale amorphous films by vacuum evaporation. Its structure, thermal stability were characterized by infrared (IR) spectra, differential thermal analysis-thermogravimetry (DTA-TG) analysis, respectively. The optical properties of SAZ were investigated by UV absorption spectra, Photoluminescence (PL) excitation and emission spectra. The highest occupied molecular orbits (HOMO), lowest unoccupied molecular orbits (LUMO) and optical band gap were evaluated by cyclic voltammetry curve and optical absorption band edge. The electroluminescent devices using SAZ as the emissive layer emit green light with a peak wavelength at 509 nm and a brightness of about 3.1 cd/m2.
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    Structure and Optical Behavior of Nanocomposite Hybrid Films of Well Monodispersed ZnO Nanoparticles into Poly (vinylpyrrolidone)
    Wei FENG, Huichun TAO, Yan LIU, Yichun LIU
    J. Mater. Sci. Technol., 2006, 22 (02): 230-234. 
    Abstract   HTML   PDF (637KB)
    We fabricated an inorganic-polymeric photoluminescent thin film based on ZnO nanoparticles, which were grown directly in the poly(vinylpyrrolidone) (PVP) matrix. The microstructure, composition, thermal stability, and the temperature-dependent photoluminescence of the thin film were investigated. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that all the ZnO nanoparticles with a polycrystalline hexagonal wurzite structure were well separated from each other and were dispersed in the polymeric matrix homogeneously and randomly. Raman spectrum (Raman) showed a typical resonant multi-phonon process within the hybrid thin film. The shifts of infrared bands for PVP in the hybrid film should be attributed to strong coulombic interaction between ZnO and polymeric matrix. The stability of the hybrid film and the effect of the perturbation of ZnO on the stability were determined by means of the thermogravimetric analysis (TG) and differential thermal analysis (DTA). The ultraviolet-visible adsorption (UV-vis) showed distinct excitonic features. The photoluminescent spectrum (PL) of the ZnO nanoparticles modified by PVP molecules showed markedly enhanced ultraviolet emission and significantly reduced green emission, which was due to the perfect surface passivation of ZnO nanoparticles. Temperature dependent photoluminescent spectrum studies suggested that the ultraviolet emission was associated with bound exciton recombination.
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    Influence of Pressing Time on Steel-copper-graphite Bonding
    Peng ZHANG, Yunhui DU, Hanwu LIU, Jun ZHANG, Daben ZENG, Jianzhong CUI, Limin BA
    J. Mater. Sci. Technol., 2006, 22 (02): 235-238. 
    Abstract   HTML   PDF (926KB)
    The bonding of steel plate with QTi3.5-3.5 graphite slurry was studied by using pressing bonding technique. The influence of pressing time on the interfacial mechanical property of bonding plate was researched. The results show that: under the conditions of 620℃ preheating temperature of steel plate, 530℃ preheating temperature of dies, 46% solid fraction of QTi3.5-3.5 graphite slurry and 50 MPa pressure, there exists a nonlinear relationship between pressing time and interfacial shear strength. The interfacial shear strength of bonding plate increases with increasing pressing time and reaches a largest value about 127 MPa when pressing time is longer than 120 s. At the interface with the best mechanical property, there exists a continuous Fe-Cu inter-diffusion zone and a metallurgical bonding.
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    Low-temperature Preparation of Photocatalytic TiO2 Thin Films on Polymer Substrates by Direct Deposition from Anatase Sol
    Yan HU, Chunwei YUAN
    J. Mater. Sci. Technol., 2006, 22 (02): 239-244. 
    Abstract   HTML   PDF (4287KB)
    Anatase TiO2 sol was synthesized under mild conditions (75℃ and ambient pressure) by hydrolysis of titanium-n-butoxide in abundant acidic aqueous solution and subsequent reflux to enhance crystallization. At room temperature and in ambient atmosphere, crystalline TiO2 thin films were deposited on polymethylmethacrylate (PMMA), SiO2-coated PMMA and SiO2-coated silicone rubber substrates from the as-prepared TiO2 sol by a dip-coating process. SiO2 layers prior to TiO2 thin films on polymer substrates could not only protect the substrates from the photocatalytic decomposition of the TiO2 thin films but also enhance the adhesion of the TiO2 thin films to the substrates. Field-emission type scanning electron microscope (FE-SEM) investigations revealed that the average particle sizes of the nanoparticles composing the TiO2 thin films were about 35~47 nm. The TiO2 thin films exhibited high photocatalytic activities in the degradation of reactive brilliant red dye X-3B in aqueous solution under aerated conditions. The preparation process of photocatalytic TiO2 thin films on the polymer substrates was quite simple and a low temperature route.
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    Electrical Conductivity of Sintered Chromia Mixed with TiO2, CuO and Mn-Oxides
    K.El-Menshawy, H.P.Buchkremer, F.Tietz, D.Stoever
    J. Mater. Sci. Technol., 2006, 22 (02): 245-251. 
    Abstract   HTML   PDF (4262KB)
    The electrical conductivity of sintered Cr2O3 mixed with 2% and 5% (in molar fraction) TiO2 or CuO was investigated in the temperature range 500~900℃ in air and in Ar/4 vol. pct H2 atmospheres. The effect of different Mn-oxides on the electrical conductivity of Cr2O3 was also studied under the same conditions. From the conductivity measurements it is established that additions of TiO2 change the defect structure of Cr2O3 and the effect of TiO2 on the electrical conductivity is controlled by TiO2 concentration as well as temperature and O2 partial pressure of the surrounding atmosphere. The conductivity of Cr2O3 increased in air and decreased in the Ar/H2 atmosphere by CuO additions. The effect of CuO was discussed with possible changes in the defect concentration in Cr2O3. Mixing of Cr2O3 with different Mn-oxides at the same Mn to metal atom fraction decreased the conductivity in air and in Ar/H2 atmospheres. No clear correlation between the spinel fraction and the changes in conductivity could be found.
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    Intercalation and Stability of Layered Semiconductive Material in Corrosive Environment
    A.A.El-Meligi
    J. Mater. Sci. Technol., 2006, 22 (02): 252-256. 
    Abstract   HTML   PDF (2845KB)
    The intercalation of 4-methyl pyridine (4-picoline) into layered semiconductive material (MnPS3) and the stability of the resulting materials in corrosive environments (water, HCl and open atmosphere) were investigated. Powder X-ray diffraction (XRD) indicated that the presence of water and hydrochloric acid greatly influenced the existing form of intercalation and its orientation in the interlayer of the host. Atmospheric environment (open air) affected the guest orientation in the interlayer of the host material. Phase transformation occurred and the material was stable. The intercalated compounds could be indexed in the trigonal unit cell. The XRD patterns exhibited sharp hkl reflections of the intercalated compounds, which formed in water and HCl, confirming that the materials were well crystalline and stable in corrosive environments.
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    Fabrication of Iron-base Alloy by Spark Plasma Sintering
    Yuanyuan LI, Xiaoqiang LI, Yan LONG, Wei XIA, Min ZHU, Weiping CHEN
    J. Mater. Sci. Technol., 2006, 22 (02): 257-260. 
    Abstract   HTML   PDF (330KB)
    Fe-2Cu-2Ni-1Mo-0.8C (wt pct) elemental mixed powders were rapidly sintered within 6~min by spark plasma sintering, and the effects of sintering parameters on the densification degree and performance of the as-sintered materials were investigated. Results showed that when a proper combination of pulse electric current and constant electric current was employed for sintering, the density and bend strength of the as-sintered material reached the maxima, being 7.61×103 kg/m3 and 1540 MPa, respectively. Its corresponding fracture morphology was characterized as the mix of ductile, intergranular and cleavage fractures.
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    Finite Element Simulation on the Spin-forming of the 3D Non-axisymmetric Thin-Walled Tubes
    Qinxiang XIA, Baixiang LIANG, Saijun ZHANG, Xiuquan CHENG, Feng RUAN
    J. Mater. Sci. Technol., 2006, 22 (02): 261-268. 
    Abstract   HTML   PDF (1226KB)
    The roller movement trace for the 3D non-axisymmetric thin-walled tubes is a complex space curve. Besides the roller rotation caused by contact with the blank, the roller rotates around the workpiece together with the main spindle, and also moves simultaneously along the direction of the revolution radius. The method to correctly establish the finite element (FE) models of the metal spinning is based on the MSC. MARC software was introduced. The calculation formulas considering both the revolution and rotation of the roller were obtained by the mathematical deduction. The saving calculation points m should be a multiple of 4 for one revolution of the roller around the workpiece to obtain the maximum forming force for the spinning of the 3D non-axisymmetric thin-walled tubes. The simulation results conform well to the experimental ones for several spinning methods; the maximum error is less than ±15%.
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    High Strength Silicon Carbide Foams and Their Deformation Behavior
    Chong TIAN, Jinsong ZHANG, Xiaoming CAO, Qiang LIU, Wanping HU
    J. Mater. Sci. Technol., 2006, 22 (02): 269-272. 
    Abstract   HTML   PDF (826KB)
    Silicon carbide (SiC) foams with a continuously connected open-cell structure were prepared and characterized for their mechanical performance. The apparent densities of SiC foams were controlled between about 0.4 and 1.3 g/cm3, with corresponding compressive strengths ranging from about 13 to 60 MPa and flexural strengths from about 8 to 30 MPa. Compressive testing of the SiC foams yielded stress-strain curves with only one linear-elastic region, which is different from those reported on ceramic foams in literature. This can possibly be attributed to the existence of filaments with fine, dense and high strength microstructures. The SiC and the filaments respond homogeneously to applied loading.
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    Sensitivity Analysis Based Multiple Objective Preform Die Shape Optimal Design in Metal Forging
    Xinhai ZHAO, Guoqun ZHAO, Guangchun WANG, Tonghai WANG
    J. Mater. Sci. Technol., 2006, 22 (02): 273-278. 
    Abstract   HTML   PDF (1508KB)
    The multiple objective preform design optimization was put forward. The final forging's shape and deformation uniformity were considered in the multiple objective. The objective is to optimize the shape and the deformation uniformity of the final forging at the same time so that a more high integrate quality of the final forging can be obtained. The total objective was assembled by the shape and uniformity objective using the weight adding method. The perform die shape is presented by cubic B-spline curves. The control points of B-spline curves are used as the design variables. The forms of the total objective function, shape and uniformity sub-objective function are given. The sensitivities of the total objective function and the sub-objective functions with respect to the design variables are developed. Using this method, the perform die shape of an H-shaped forging process is optimally designed. The optimization results are very satisfactory.
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    Numerical Methodology for Metal Forming Processes Using Elastoplastic Model with Damage Occurrence
    A.Cherouat, H.Borouchaki, K.Saanouni, P.Laug
    J. Mater. Sci. Technol., 2006, 22 (02): 279-283. 
    Abstract   HTML   PDF (3504KB)
    Ductile damage often occurs during metal forming processes due to the large thermo-elasto (visco) plastic flow localisation. This paper presents a numerical methodology, which aims to virtually improve any metal forming processes. The methodology is based on elastoplastic constitutive equations accounting for nonlinear mixed isotropic and kinematic hardening strongly coupled with isotropic ductile damage. An adaptive remeshing scheme based on geometrical and physical error estimates including a kill element procedure is used. Some numerical results are presented to show the capability of the model to predict the damage initiation and growth during the metal forming processes.
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    Analysis of the Internal Pressure in Tube Hydroforming and Its Experimental Investigation
    Hongyang LI, Zhongren, WANG, Qibin MIAO, Shijian YUAN, Xiaosong WANG
    J. Mater. Sci. Technol., 2006, 22 (02): 284-288. 
    Abstract   HTML   PDF (695KB)
    The internal pressure of the process was studied theoretically and experimentally. The external load character and internal stress character of tube hydroforming were discussed first. Then, according to the characters, the function and classification of internal pressure were presented in general. Base on the stress analysis, its effect on the yield criterion and calculation formula were also researched and derived. To verify the correction of the theoretical analysis and derived formula, experiments with different internal pressures were carried out and the result was compared and discussed. It demonstrates that internal pressure plays an important role in tube hydroforming and theory and formula discussed and derived by this paper are feasible in practice.
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