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ISSN 1005-0302
CN 21-1315/TG
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      28 September 2002, Volume 18 Issue 05 Previous Issue    Next Issue
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    Research Articles
    In-situ Al/24Si Functional Graded Materials Prepared by Electromagnetic Separation
    Ke LI, Jun WANG, Da SHU, Baode SUN, Yaohe ZHOU
    J. Mater. Sci. Technol., 2002, 18 (05): 385-386. 
    Abstract   HTML   PDF (1119KB)
    Cylinder-like in-situ Al/24Si FGMs were produced by using electromagnetic separating process. Si primary phase reinforced layer with volume fraction as high as 16 pct was formed at the outer region of the cylinder-like samples where the local hardness and wear resistance were enhanced remarkably. Moreover, both of strength and ductility in the inner region provided insurance of reliable strength for this as-cast gradient material. It indicated that general mechanical properties such as good wear resistance at the outer region and good ductility in the central part could be obtained with the optimized redistribution of the Si primary particles under the electromagnetic force.
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    Stress Corrosion Crack Growth Behavior of Titanium Alloy/Bioactive Glasses Sandwiches in Simulated Human Physiological Environment
    Da CHEN, J.M.McNaney, E.Saiz, A.P.Tomsia, R.O.Ritchie
    J. Mater. Sci. Technol., 2002, 18 (05): 387-391. 
    Abstract   HTML   PDF (658KB)
    Based on a series of newly developed bioactive glasses having suitable thermo-mechanical properties to allow application as fixation agents between bone and titanium alloy biomedical implants, the stress corrosion crack growth (SCCG) behavior of their interfaces with Ti6Al4V was investigated in simulated body fluid (SBF) with the objective of discerning the salient mechanisms of crack advance and to assess the reliability of the bonds. Results indicated that crack growth rates in Ti6Al4V/glass/Ti6Al4V sandwich specimens were nearly the same as or slightly lower than those in the bulk glasses at comparable stress intensities; indeed, cracks would prefer to propagate off the interface,suggesting that the Ti6Al4V/glass interface has relatively good crack-growth resistance. Mechanistically, interfacial crack growth appears to be controlled by the classic stress corrosion mechanisms for silicate glasses, with no discernible effect of bioactivity on the SCCG behavior being observed.
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    Effect of Pb Ions on the Ionic Conductivity of Some Silicate Glass Systems
    A.G.Mostafa, M.A.Salem, Z.A.El-Hadi
    J. Mater. Sci. Technol., 2002, 18 (05): 391-394. 
    Abstract   HTML   PDF (355KB)
    Conductivity of glasses in the systems SiO2•PbO•RO, (where R=Ca, Sr or Ba) was investigated between room temperature and 530 K. The dependence of log resistivity as well as the activation energy on the PbO content has been studied. Based on the present experimental results, the possible different conduction mechanisms in such glasses are discussed. It was postulated that Pb2+ ions may represent the major charge carrying species in these glasses. This assumption was confirmed by the calculations of the mean distance between the interstitial Pb2+ ions and the effective center of the O2- ions in the glass networks. The variation in the values of the density and the molar volume with PbO content is also discussed in view of the obtained activation energies for the studied glass-systems.
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    Effect of Porosity and Cell Size on the Dynamic Compressive Properties of Aluminum Alloy Foams
    Yi FENG, Zhengang ZHU, Shisheng HU, Yi PAN
    J. Mater. Sci. Technol., 2002, 18 (05): 395-397. 
    Abstract   HTML   PDF (613KB)
    The dynamic mechanical properties of open-cell aluminum alloy foams with different relative densities and cell sizes have been investigated by compressive tests. The strain rates varied from 700 s-1 to 2600 s-1. The experimental results showed that the dynamic compressive stress-strain curves exhibited a typical three-stage behavior: elastic, plateau and densification. The dynamic compressive strength of foams is affected not only by the relative density but also by the strain rate and cell size. Aluminum alloy foams with higher relative density or smaller cell size are more sensitive to the strain rate than foams with lower relative density or larger cell size.
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    A New Physical Metallurgy Phenomenon—the Shock Wave Nanocrystallization of Amorphous Alloys
    Heyun ZHAO, Zuoquan LIU, Xinghui WU, Hai WANG, Yuhua HE
    J. Mater. Sci. Technol., 2002, 18 (05): 398-400. 
    Abstract   HTML   PDF (640KB)
    Some results of amorphous alloy nanocrystallization by shock wave are presented. Compared with the well known annealing crystallization, these results seem novel and are very difficult to be explained by the diffusion theory, such as nucleation and growth mechanism in the solid state phase transitions. The shock wave crystallization of amorphous alloy is a new metallurgical phenomenon with possibilities for improving the crystallization theory in physics.
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    Effect of Electromagnetic Frequency on Microstructures of Continuous Casting Aluminum Alloys
    Beijiang ZHANG, Guimin LU, Jianzhong CUI
    J. Mater. Sci. Technol., 2002, 18 (05): 401-403. 
    Abstract   HTML   PDF (429KB)
    The relationship between electromagnetic frequency and microstructures of continuous casting aluminum alloys was studied. 7075 aluminum alloy ingot of 100 mm in diameter was produced by electromagnetic continuous casting process, the microstructures of as-cast ingot was examined by scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). The results showed that electromagnetic frequency greatly influenced segregation and microstructures of as-cast ingot, and product quality can be guaranteed by the application of a proper frequency. Electromagnetic frequency plays a significant role in solute redistribution; low frequency is more efficient for promoting solution of alloying elements.
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    Mathematical Modelling of Particle Movement Ahead of the Solid-liquid Interface in Continuous Casting
    Hong LEI, Yongli JIN, Miaoyong ZHU, Jicheng HE
    J. Mater. Sci. Technol., 2002, 18 (05): 403-406. 
    Abstract   HTML   PDF (746KB)
    Whether the particle will be trapped by the solid-liquid interface or not is dependent on its moving behavior ahead of the interface, so a mathematical model has been developed to investigate the movement of the particle ahead of the solid-liquid interface. Based on the theory for the boundary layer, the fluid velocity field near the solid-liquid interface was obtained, and the trajectories of particles were calculated by the equations of motion for particles. In this model, the drag force, the added mass force, the buoyance force, the gravitational force, the Saffman force and the Basset history force are considered. The results show that the behavior of the particle ahead of the solid-liquid interface is affected by the physical property of the particle and fluid flow.And in the continuous casting process, if it moves in the stream directed upward or downward near vertical solid-liquid interface or in the horizontal flow under the solid-liquid interface, the particle with the diameter from 5 mm to 60 mm can reach the solid-liquid interface. But if it moves in horizontal flow above the solid-liquid interface, only the particle with the diameter from 5 mm to 10 mm can reach the solid-liquid interface.
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    Effect of Processing Parameters on Microstructures of Melt-Spun Al-In Immiscible Alloys
    Yuan LIU, Jingjie GUO, Yanqing SU, Hongsheng DING, Jun JIA
    J. Mater. Sci. Technol., 2002, 18 (05): 407-410. 
    Abstract   HTML   PDF (1903KB)
    Melt spinning rapid solidification technique was employed to fabricate homogeneous Al-In immiscible alloys and their final microstructures and morphologies were investigated. There existed a transition of columnar Al grain®equiaxed grain for the thicker ribbon, butonly columnar Al grain for the thinner ribbon throughout the thickness. In the columnar grain field, most of the fine In particles was distributed within the cells, but a minority of bigger In particles or short rods was perpendicularly distributed at the grain boundaries. In the equiaxed grain field, the fine In particles were located in Al grains and coarser particles were situated at the boundaries. The average particle size increased with increasing distance from the chilled surface throughout the ribbon. At the same wheel speed (same cooling rate), the average particle size increased with raising In content. At the same composition condition, the average particle size decreased with increasing wheel speed and/or decreasing ejection temperature.
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    A Novel near Net-Shape Technique for P/M Parts with Large H/D Ratio
    Yong LIU, Baiyun HUANG, Kechao ZHOU, Hongwu OUYANG, Yuehui HE
    J. Mater. Sci. Technol., 2002, 18 (05): 410-412. 
    Abstract   HTML   PDF (1173KB)
    In order to overcome the shortcomings of conventional hot pressing, a novel near net-shape technique, called radial hot pressing, for P/M parts with large height-to-diameter (H/D) ratio was introduced. Effects of processing parameters on the microstructures and density of P/M TiAl base alloy valves were studied. Results show that the radial hot pressing is an effective technique for manufacturing valves with a H/D ratio of about 10:1, and the perfect joint interface between the Mo sheet and the parts is helpful for subsequent HIPing.
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    Study on Numerical Simulation of Mold Filling and Solidification Processes under Pressure Conditions
    Shoumei XIONG, Baicheng LIU, Liangrong JIA, Xinghuo WEN
    J. Mater. Sci. Technol., 2002, 18 (05): 413-416. 
    Abstract   HTML   PDF (1010KB)
    The mold filling and solidification simulation for the high pressure die casting (HPDC) and low pressure die casting (LPDC) processes were studied. A mathematical model considering the turbulent flow and heat transfer phenomenon during the HPDC process has been established and parallel computation technique was used for the mold filling simulation of the process. The laminar flow characteristics of the LPDC process were studied and a simplified model for the mold filling process of wheel castings has been developed. For the solidification simulation under pressure conditions, the cyclic characteristics and the complicated boundary conditions were considered and techniques to improve the computational efficiency are discussed. A new criterion for predicting shrinkage porosity of Al alloy under low pressure condition has been developed in the solidification simulation process.
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    Analysis of Equivalent Oxygen Diffusivity of Particle Dispersed Composites
    Mingwei LI, Jingchuan ZHU, Zhongda YIN, Gang ZENG
    J. Mater. Sci. Technol., 2002, 18 (05): 416-418. 
    Abstract   HTML   PDF (562KB)
    This paper presents a new method to determine the equivalent oxygen diffusivities of particle dispersed composites. This method can be used to design FGM thermal barrier systems with the function of oxygen barrier. A qualitative explanation of the oxidation of nickel with the increment of zirconia contents in the composite samples can be accepted by this method. The values of equivalent oxygen diffusivities obtained with this method are in excellent agreement with those from the EMT method for the composites with ZrO2 particle dispersed phase when the volume fractions of dispersed phase are lower than 25%.
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    In-situ Composite Based on Poly (ethylene terephthalate), Polyamide and Polyethylene with Microfibres Formed through Extrusion and Hot Stretching
    Zhongming LI, Mingbo YANG, Rui HUANG, Ai LU, Jianmin FENG
    J. Mater. Sci. Technol., 2002, 18 (05): 419-422. 
    Abstract   HTML   PDF (2024KB)
    In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die relatively small in diameter. The extrudate was drawn at a drawing ratio of 3.1, and then quickly cooled in cold water. The specimens were obtained by injection molding at processing temperatures less than 190°C, far below the melting temperature of PET (265°C) and PA (230°C), which can maintain the solid state of PET and PA microfiber phase in the composites. Morphological observation with scanning electron microscopy (SEM) indicated that PET and PA can more or less form in-situ microfibers at compositions studied (0~20 wt pct PET or PA), and especially, PET and PA were almost deformed into fibers at the concentration of 15 wt pct. Tensile strength and modulus of the blends reinforced by PET or PA microfibers showed to be increased from the tensile test results. The most noticeable improvement of the tensile properties occurred at 15 wt pct of PET in PET/PE system, corresponding to the highest microfiber content, where the tensile strength reached 32.5 MPa, whereas only 19.5 Mpa for the pure PE.
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    Study of Thermodynamic Properties of Nonstoichiometric Phase with Compound Energy Model
    Shuigen HUANG, Lin LI, O.V.D.Biest, J.Vleugels, Peiling WANG
    J. Mater. Sci. Technol., 2002, 18 (05): 422-426. 
    Abstract   HTML   PDF (914KB)
    Using compound energy model (CEM), the thermodynamic properties of and were evaluated. The evaluation was based on the optimization of ZrO2-CeO2 and ZrO2-CeO1.5 systems, as well as the miscibility gap in CeO1.5-CeO2 system. Except the cubic fluorite structure phase assessed with compound energy model, all the other solution phases were assessed with subsitutional solution model. The model parameters were evaluated through fitting the selected experimental data by means of thermodynamic optimization. A set of parameters with thermodynamics self-consistency was obtained and satisfactorily described the complex relation between y in and the partial pressure of oxygen at different temperatures, also the interdependence among miscellaneous factors such as temperature, oxygen partial pressure, the reduction amount of CeO2 as well as the nonstoichiometry in cubic phase . The calculated results seem to be reasonable when put into the explanation of pressureless sintering of CeO2-stabilized ZrO2 powder compacts at a controlled oxygen partial pressure.
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    Microstructure and Fracture Morphology in the Welding Zone of T91 Heat-resisting Steel Used in Power Station
    Yajiang LI, Bing ZHOU, Tao FENG, Jiangwei REN
    J. Mater. Sci. Technol., 2002, 18 (05): 427-430. 
    Abstract   HTML   PDF (458KB)
    Microstructure performance in the welding zone of T91 heat-resistant steel under the condition of TIG welding was researched by means of metallography, X-ray diffraction and scanning electron microscope (SEM).Experimental results indicated that microstructure of T91 weld metal was austenite + a little amount of d ferrite when using TGS-9cb filler wire.Substructure inside the austenite grain was crypto-crystal lath martensite, on which some Cr23C6 blocky carbides were distributed. The maximum hardness (HRC44) in the welding zone is near the fusion zone. There existed no obvious softening zone in the heat-affected zone (HAZ). For T91 steel tube of F63 mm×5 mm, when increasing welding heat input (E) from 4.8 kJ/cm to 12.5 kJ/cm, fracture morphology in the fusion zone and the HAZ changed from dimple fracture into quasi-cleavage fracture (QC). Controlling the welding heat input of about 9.8 kJ/cm is suitable in the welding of T91 heat-resistant steel.
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    Electrorheological Fluids Based on Titania Particles Coated with Silica and Their Application in Smart Windows
    Mengqiang WU, Ai CHEN, Zhuoya ZHU, Yongquan HAN
    J. Mater. Sci. Technol., 2002, 18 (05): 430-432. 
    Abstract   HTML   PDF (319KB)
    The electrorheological (ER) fluids are colloidal suspension of highly polarizable particles in a non-conducting solvent. Chains of submicron-sized particles formed along an applied DC electric field by the so-called electrorheological effect. According to the obvious change of transmittance of the ER fluids in a DC electric field when the polarized particles arranged along the field, the model of smart window was proposed by sandwiching the ER fluids based on titania particles coated with silica between a pair of In-Sn oxide (ITO) coated glasses. The solar transmittance change as much as 48.0% was obtained with the wavelength of 500 nm at the maximumm on applying and removing th electric field of 500 V/mm.
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    Concentration Heterogeneity in Structure of Ni3Al Intermetallic Synthesized under Compression
    O.B.Perevalova, M.B.Fedorischeva, V.E.Ovcharenko, Huihe SU
    J. Mater. Sci. Technol., 2002, 18 (05): 432-435. 
    Abstract   HTML   PDF (385KB)
    By X-ray analysis, TEM and SEM methods the phase composition, microstructure, and deviation from stoichiometric composition were investigated for the Ni3Al intermetallic compound obtained by cast and self-propagation high-temperature synthesis under compression with followed homogenization anneal, with the Al concentration being 24.0 and 25.0 at. pct with and without B (0.5 at. pct). It was discovered that in SHS intermetallic alloys an average local deviation from stoichiometric composition is significantly more than in the cast alloy. Dependence of the local deviation from the stoichiometric composition on the distance has a zig zag nature at the level of the grain groups. Deviation from the stoichiometric composition at the boundaries of the general type is less than at the boundaries of the special type. When the intensity of boundary migrations of the general type decreases, the degree of deviation from the stoichiometric composition increases. There is correlation between the solubility of B in the crystalline lattice of the Ni3Al phase and the value of the deviation from the stoichiometric composition in the grains. When the B concentration in a solid solution increases, the deviation from stoichiometric composition decreases.
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    Dependence of Magnetoresistance on the Thickness of a Dusted Al Spacer Inserted in CoFe/Cu/CoFe Sandwiches
    Yanxue CHEN, Shouguo WANG, Liangmo MEI, Kungwon Rhie, Sangjin Byeun
    J. Mater. Sci. Technol., 2002, 18 (05): 436-438. 
    Abstract   HTML   PDF (216KB)
    A series of CoFe (4 nm)/ Cu(X nm) Al (Y nm)/ CoFe(6 nm) samples have been prepared at room temperature. An exponential decay of the GMR (Giant Magnetoresistance) with Y was observed for fixed X=2nm. The characteristic decay parameter of Al is obtained to be about 0.26nm, which is rather close to 1 monolayer for Al. A coexistant state of GMR and AMR (anisotropic magnetoresistance) was observed when Y=2 nm. As the Cu spacer is replaced by Al layer, only AMR effect dominates. The experimental data further underline the important role played by the nonmagnetic spacers.
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    Kinetic Model of TiN Particle Dissolution and Coarsening during Welding Thermal Cycle
    Mao'ai CHEN, Chuansong WU, Jinqiang GAO, Yimin TANG
    J. Mater. Sci. Technol., 2002, 18 (05): 439-442. 
    Abstract   HTML   PDF (368KB)
    With carbon extraction replica technique, electron diffraction and EDAX analysis, second particle size distribution in two Ti microalloyed steels and their heat-affected zones were investigated. The results show that the particles in the Ti microalloyed steels are TiN particles, and the TiN particles in the steel with lower Ti/N ratio exhibit smaller size and lower dissolution and coarsening rate and extent. Based on the investigation results, kinetic models for TiN particle dissolution and coarsening during welding thermal cycle were developed. The predicted values calculated by using the models are in good agreement with the experimental ones.
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    Formation of Copper Type Texture in Cold Rolled Aluminum Sheet
    Weimin MAO
    J. Mater. Sci. Technol., 2002, 18 (05): 443-446. 
    Abstract   HTML   PDF (385KB)
    The formation process of copper type rolling texture in f.c.c. metals was simulated based on a deformation model considering internal reaction stresses induced by the neighboring matrix as well as external shear stress induced by rollers. It is indicated that the external shear stress will reduce the brass type texture and increase the copper type texture obviously.
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    Characterization of the Diamond-like Carbon Based Functionally Gradient Film
    Feng MA, Xun CAI, Gang LI, Qiulong CHEN, Hongtao MA
    J. Mater. Sci. Technol., 2002, 18 (05): 447-450. 
    Abstract   HTML   PDF (407KB)
    Diamond-like carbon coatings have been used as solid lubricating coatings in vacuum technology for their good physical and chemical properties. In this paper, the hybrid technique of unbalanced magnetron sputtering and plasma immersion ion implantation (PIII) was adopted to fabricate diamond-like carbon-based functionally gradient film, N/TiN/Ti (N, C)/DLC, on the 304 stainless steel substrate. The film was characterized by using Raman spectroscopy and glancing X-ray diffraction (GXRD), and the topography and surface roughness of the film was observed using AFM. The mechanical properties of the film were evaluated by nano-indentation. The results showed that the surface roughness of the film was approximately 0.732 nm. The hardness and elastic modulus, fracture toughness and interfacial fracture toughness of N/TiN/Ti(N,C)/DLC functionally gradient film were about 19.84 GPa, 190.03 GPa, 3.75 MPa•m1/2 and 5.68 MPa•m1/2, respectively. Compared with that of DLC monolayer and C/TiC/DLC multilayer, this DLC gradient film has better qualities as a solid lubricating coating.
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    Microstructure-Properties Correlation of Dual Phase Steels Produced by Controlled Rolling Process
    A.Fallahi
    J. Mater. Sci. Technol., 2002, 18 (05): 451-454. 
    Abstract   HTML   PDF (396KB)
    The purpose of this research is to quantify the effects of compositional and processing parameters on the microstructure and properties of dual phase steel produced directly by hot rolling and rapid cooling.Steels with the base composition of 0.1%C, 1.4%Si, and 1.0%Mn with additions of 0.5%Cr to influence hardenability, 0.04%Nb to retard recrystallization in the latter stages of rolling, or 0.02%Ti to inhibit grain growth during and after reheating were investigated. Investigation was made to predict microstructure evolution and to correlate microstructure with processing parameters. The effects of the important microstructure parameters such as ferrite grain size, martensite volume fraction (VM) and morphology (polygonal or fibrous) on the tensile and impact properties are discussed. Multiple linear regression analysis of the ultimate tensile strength has shown that, increasing VM and martensite microhardness and grain refinement of ferrite are the major contributions to increase the strength of the steel. It was found that the dual-phase steel produced by controlled rolling process, with a microstructure which consisted of fine grained ferrite (4 mm) and 35%´40% fibrous martensite, presented optimum tensile and impact properties because of enhanced resistance to crack propagation.
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    Characterization of Rust Layer Formed on Low Alloy Steel Exposed in Marine Atmosphere
    Quancheng ZHANG, Jiansheng WU, Wenlong ZHENG, Jianjun WANG, Jiaguang CHEN, Xiaofang YANG, Aibai LI
    J. Mater. Sci. Technol., 2002, 18 (05): 455-458. 
    Abstract   HTML   PDF (363KB)
    The iron rust phases formed on low alloy steels containing different quantities of Cr element have been characterized using EPMA, Raman spectroscopy, TEM, optical microscopy etc. The ion selective properties of synthesized rust films with the same phase constituent as the atmospheric corrosion products were investigated using self-made apparatus. The results showed that corrosion loss of steels exposed in marine atmosphere decreased rapidly as the Cr content of the steel was increased. Cr-containing steels were covered by a uniform compacted rust layer composed of fine particles with an average diameter of several nanometers. Inner rust layer of Cr-containing steel (2 mass fraction) was composed of a-CrxFe1-xOOH, with Cr content of about 5 mass fraction. Such rust layer showed cation selective property, and could depress the penetration of Cl- to contact substrate steel directly.
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    X-ray Peak-Shift Determination of Deformation Fault Probability in Fe-Mn-Si Alloys
    Yonghua RONG, Gang HE, Zhenghong GUO, Shipu CHEN, T.Y.Hsu XU Zuyao
    J. Mater. Sci. Technol., 2002, 18 (05): 459-461. 
    Abstract   HTML   PDF (286KB)
    The X-ray diffraction peak-shift method was introduced into the determination of deformation fault probability (a) of Fe-Mn-Si alloys with various Mn contents and thermomechanical cycling numbers. The precise lattice constants required were obtained by numerical calculation instead of using standard sample without any fault. The influence of internal stress on the determined a has been evaluated, and the caused relative error was determined as about 4% and thus negligible. The results show that the deformation fault probability increases with decreasing Mn-content and increasing cycle number, which are qualitatively consistent with those results of Psf determined by peak-broadening method.
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    Formation of Omega-like Nanocrystalline in the Melt-Spun Nd85Al15 Alloy by Phase Transformation
    Jia ZHANG, Wensheng SUN, Mingxiu QUAN, Zhuangqi HU
    J. Mater. Sci. Technol., 2002, 18 (05): 462-464. 
    Abstract   HTML   PDF (330KB)
    Microstructure and subsequent phase transformations on heating of the melt-spun Nd85Al15 alloy have been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The melt-spun Nd85Al15 alloy shows two-stage transformation processes as follows: amorphous+72 nm supersaturated bcc-Nd(Al) solid solution→7 nm omega-like phase→AlNd3+hexagonal Nd. The activation energies for the first and second transformation were found to be 100 kJ/mol and 188 kJ/mol, respectively. The formation mechanism of nanoscale omega-like phase is discussed.
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    Optimal Preform Die Design through Controlling Deformation Uniformity in Metal Forging
    Xinhai ZHAO, Guoqun ZHAO, Guangchun WANG, Tonghai WANG
    J. Mater. Sci. Technol., 2002, 18 (05): 465-467. 
    Abstract   HTML   PDF (255KB)
    A finite element based sensitivity analysis method for preform die shape design in metal forging is developed. The optimization goal is to obtain more uniform deformation within the final forging by controlling the deformation uniformity. The objective function expressed by the effective strain is constructed. The sensitivity equations of the objective function, elemental volume, elemental effective strain rate and the elemental strain rate with respect to the design variables are constituted. The preform die shapes of an H-shaped forging process in axisymmetric deformation are designed using this method.
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    Influence of Diffusion Time on Steel-Aluminum Solid to Liquid Bonding Interfacial Structure
    Peng ZHANG, Yunhui DU, Shuming XING, Lizhong ZHANG, Daben ZENG, Jianzhong CUI, Limin BA
    J. Mater. Sci. Technol., 2002, 18 (05): 468-470. 
    Abstract   HTML   PDF (258KB)
    The bonding of steel plate to aluminum liquid was conducted using rapid solidification.The influence of diffusion time on interfacial structure was studied. The results showed that under the condition of 750ºC for the temperature of aluminum liquid and 200ºC for the preheat temperature of steel plate, when diffusion time was shorter than 4.3 s, there was only Fe-Al solid solution at the interface. When diffusion time was longer than 4.3 s, Fe-Al compound began to form at the interface. The relationships between diffusion time t and thickness of Fe-Al compound layer H are H=-9.72+2.62t-0.08t2 (4.3 s[t[15 s) and H=2.79+0.647t-0.033t2 (t>15 s).
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    Corrosion Behavior of the Rare Earth Sealing Anodized Coating on Aluminum Alloy LY12
    Xingwen YU, Chuanwei YAN, Chunan CAO
    J. Mater. Sci. Technol., 2002, 18 (05): 471-474. 
    Abstract   HTML   PDF (357KB)
    Technological process of rare earth sealing anodized LY12 (2024) alloy is introduced. Corrosion behavior of the film was studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that the coating remained passivity at the potential range from the open circuit potential (-780 mV) to –250 mV in NaCl solution. When the potential exceeded -200 mV, corrosion reaction happened on the coating. the results of EIS analysis was consistent with the results of polarization curves.
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    Hydrothermal Characteristics of Blended Cement Pastes Containing Silica Sand Using Cement Kiln Dust as an Activator
    S.A.Abo-El-Enein, F.I.El-Hosiny, E.El-Shimy, T.A.Osman
    J. Mater. Sci. Technol., 2002, 18 (05): 474-478. 
    Abstract   HTML   PDF (560KB)
    The hydrothermal reactivity of silica sand was studied using cement kiln dust (CKD) as an activator in addition to the Portland cement fraction of El-Karnak cement (a blend of ordinary Portland cement and ground sand). Autoclaved El-Karnak cement pastes were studied at pressures of 0.507, 1.013 and 1.520 MPa of saturated steam with respect to their compressive strength, kinetics of hydrothermal reaction and the phase composition of the formed hydrates. The role of CKD in affecting the physicochemical and mechanical properties of El-Karnak cement pastes was studied by autoclaving of several pastes containing 5, 7.5, 10 and 20% CKD at a pressure of 1.013 MPa of saturated steam. CKD was added either as a raw CKD (unwashed) or after washing with water (washed CKD). The results of these physicochemical studies obtained could be related as much as possible to the role of CKD (raw or washed) in affecting the hydrothermal reactivity of silica sand in El-Karnak cement pastes.
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    AC Complex Impedance Analysis of Doped Strontium Titanate Multifunctional Ceramics
    Qing XU, Wen CHEN, Duanping HUANG, Runzhang YUAN
    J. Mater. Sci. Technol., 2002, 18 (05): 479-480. 
    Abstract   HTML   PDF (182KB)
    Doped SrTiO3 capacitor-varistor multifunctional ceramics were fabricated by a single sintering process. AC complex impedance analysis was performed to investigate electrical features of grains and grain boundaries for both as-reduced ceramic and reoxidized ceramics.The results showed that the as-reduced ceramic exhibited inductive response at high frequencies above 2 MHz, which is attributed to the contribution of electron behavior in semiconducting grains.The high frequency inductive response disappeared in impedance plots of reoxidized ceramics.
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