Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
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Current Issue
 29 March 2004, Volume 20 Issue 02 Previous Issue    Next Issue
Research Articles
 Select Effect of Notch Location on Fatigue Life Prediction of Strength Mismatched HSLA Steel Weldments S.Ravi, V.Balasubramanian, S.Nemat Nasser J. Mater. Sci. Technol., 2004, 20 (02): 129-135.  Abstract   HTML   PDF (3743KB) Welding of high strength low alloy steels (HSLA) involves usage of low, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the availability of the ˉller material. In the present investigation, the fatigue crack growth behaviour of weld metal (WM) and heat affected zone (HAZ) regions of under matched (UM), equal matched (EM) and over matched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) process has been used to fabricate the butt joints. Centre cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behaviour of the welded joints. Fatigue crack growth experiments have been conducted using servo hydraulic controlled fatigue testing machine at constant amplitude loading (R=0). A method has been proposed to predict the fatigue life of HSLA steel welds using fracture mechanics approach by incorporating influences of mismatch ratio (MMR) and notch location.
 Select Effect of Aluminum and Silicon on Transformation Induced Plasticity of the TRIP Steel Lin LI, B.C.De Cooman, P.Wollants, Yanlin HE, Xiaodong ZHOU J. Mater. Sci. Technol., 2004, 20 (02): 135-138.  Abstract   HTML   PDF (1102KB) With the sublattice model, equilibrium compositions of ferrite (α) and austenite (γ ) phases, as well as the volume percent of austenite (γ) at 780℃ in different TRIP steels were calculated. Concentration profiles of carbon, Mn, Al and Si in the steels were also estimated under the lattice fixed frame of reference so as to understand the complex mechanical behavior of TRIP steels after different isothermal bainitic transformation treatments. The effect of Si and Mn on transformation induced plasticity (TRIP) was discussed according to thermodynamic and kinetic analyses. It is recognized that Al also induces phase transformation in the steels but its TRIP effect is not as strong as that of Si.
 Select Emission Properties of Yb3+/Er3+ Doped TeO2-WO3-ZnO Glasses for Broadband Optical Amplifiers Jiacheng LI, Shunguang LI, Hefang HU, Fuxi GAN J. Mater. Sci. Technol., 2004, 20 (02): 139-142.  Abstract   HTML   PDF (391KB) The Yb3+/Er3+ doped TeO2-WO3-ZnO glasses were prepared. The absorption spectra, emission spectra and fluorescence lifetime of Er3+ at 1.5 um, excited by 970 nm were measured. The influence of Er2O3, Yb2O3 and OH- contents on emission properties of Er3+ at 1.5 um was investigated. The optimum doping concentrations for Er3+ and Yb3+ is around 3.34×1020ions/cm3 and 6.63×1020 ions/cm3, respectively. The peak emission cross section is 0.83~0.87 pm2. With the increasing concentration of Yb3+, the FWHM of Er3+ emission at 1.5 um in the glass increases from 77 nm to 83 nm. The results show that Yb3+/Er3+ doped TeO2-WO3-ZnO glasses are promising candidate for Er3+-doped broadband optical amplifier.
 Select Study on Two-phase Nanocrystalline Nd8.5Fe74Co5Cu1Nb1Zr3Cr1B6.5 Permanent Magnet Jiansen NI, Hui XU, Mingyuan ZHU, Qiang LI, Bangxin ZHOU, Yu, a DON J. Mater. Sci. Technol., 2004, 20 (02): 142-144.  Abstract   HTML   PDF (1004KB) Nd8.5Fe74Co5Cu1Nb1Zr3Cr1B6.5 bonded magnets were prepared by melt-spun and subsequent heat treatment. Magnetic properties of Br=0.68 T, JHc=716 kA/m, (BH) max=77 kJ/m3 were achieved. The addition of Cr element shows to be significantly advantageous in reducing grain size and increasing the intrinsic coercivity.
 Select Luminescent Properties of Porous Si Passivated by Diamond Film and DLC Film Linjun WANG, Yiben XIA, Weili ZHANG, Minglong ZHANG, Weimin SHI J. Mater. Sci. Technol., 2004, 20 (02): 145-148.  Abstract   HTML   PDF (1489KB) Surface passivation methods for porous Si (PS) surfaces, i.e., depositing diamond film or diamond-like carbon (DLC) film on PS surfaces, were attempted. Two emission bands, weak blue band and strong red band existed in the PL spectrum of diamond film coated on PS, were discovered by the photoluminescence measurements. The luminescent mechanism and stability were discussed. The results indicated that diamond film may stabilize the PL wavelength and intensity of PS, and therefore could become a promising passivation film of porous Si. The PL properties of PS coated by DLC films, including hydrogenated diamond like carbon (DLC:H) film and nitrogen doped DLC film (DLC:N) were also studied in this paper. The DLC films may stabilize the PL of PS, but the photoluminescent intensity was obviously weaker than that of diamond film coated PS.
 Select Effect of Spraying Condition and Material Properties on the Residual Stress in Plasma Spraying Xiancheng ZHANG, Jianming GONG, Sh, ong TU J. Mater. Sci. Technol., 2004, 20 (02): 149-153.  Abstract   HTML   PDF (3769KB) The thermomechanical behavior and the distribution of residual stresses due to thermal spraying of NiCoCrAlY coating were studied by thermomechanical finite element analysis. The effects of phase transformation due to solidifying process of coating particles, thickness and material properties of coating on the residual stresses were discussed. Results showed that residual stress decreases little with the stress relaxation due to the phase transformation. For the substrates with the same thickness, the residual stress increases with the increase in coating thickness. The state of residual stresses relates to the material properties of coating and substrate closely. The stress-induced failure model of coating is also discussed.
 Select Research on Thermal Deep-drawing Technology of Magnesium Alloy (AZ31B) Sheets Shihong ZHANG, Kun ZHANG, Zhongtang WANG, Chuanfu YU, Yi XU, Qiang WANG J. Mater. Sci. Technol., 2004, 20 (02): 153-156.  Abstract   HTML   PDF (1943KB) Forming technology of Mg alloy (AZ31B) sheets can be investigated by thermal deep drawing experiments. In the experiments, the blank holder and die contacting with the blank were heated to the same temperature as the blank by using the heating facility. The circular blank heated in an oven is formed at a temperature range of 100～400℃ to obtain the optimum forming temperature range and the effects of major technical parameters on the workpiece quality. It is found that the blank is brittle at temperatures lower than 200℃. Temperatures higher than 400℃ are not suitable for forming of the sheets because of severe oxidation and wrinkling. AZ31B shows an excellent formability at temperatures from 300 to 350℃ and can be formed into a workpiece with good quality. When the blank holder force is 9 kN, extruded sheets with a thickness of 1 mm can be formed into cups without wrinkling. Workpieces show strong anisotropic deformation behavior on the flanges.
 Select Kinetic Characteristic of Hydrogenation Zr-Ti-Cu-Ni-Be Bulk Delin PENG, Jun SHEN, Jianfei SUN, Yuyong CHEN J. Mater. Sci. Technol., 2004, 20 (02): 157-159.  Abstract   HTML   PDF (447KB) The relationship between the hydrogen content and the microhardness and the charging period, the effect of hydrogen on the activation energy, the kinetics of glass transition and crystallization of Zr-Ti-Cu-Ni-Be bulk amorphous alloy were studied by differential scanning calorimetry (DSC) and the Kissinger equation. It shows that both of the hydrogen content and the microhardness are related to the charging period, and that the glass transition and crystallization behavior are associated with the heating rate, and possess the kinetic effect. Hydrogen increases the glass transition temperature and the crystallization temperature, decreasing the enthalpies in the different stages of crystallization. Hydrogen increases the activation energies of the glass transition and the crystallization and changes the kinetic effect. The dependent extent between the glass transition, the crystallization and heating rate decreases after hydrogen charging.
 Select Effect of Pd on GFA and Thermal Stability of Zr-based Bulk Amorphous Alloy Fengxiang QIN, Haifeng ZHANG, Aimin WANG, Bingzhe DING, Zhuangqi HU J. Mater. Sci. Technol., 2004, 20 (02): 160-163.  Abstract   HTML   PDF (1191KB) The effect of Pd addition on the glass-forming ability and thermal stability of the Zr55Al10Cu30Ni5-xPdx (x=0, 1, 3, 5 at. pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region △Tx of 100 K is obtained with substituting Ni by 1 at. pct Pd. However, the addition of 3 at. pct Pd causes a little increase of thermal stability and an evident decrease of the GFA. The full substitution Ni by 5 at. Pct Pd induces the thermal stability and GFA to decrease simultaneously. It indicates that the thermal stability increases and the GFA decreases with the increasing of Pd content.
 Select The Role of Nd Solid-Solution and Grain-Boundary Segregation in Binary NiAl Intermetallic Compound Weili REN, Jiangting GUO, Gusong LI, Jiyang ZHOU J. Mater. Sci. Technol., 2004, 20 (02): 163-166.  Abstract   HTML   PDF (725KB) The role of Nd solid-solution and grain-boundary segregation in binary NiAl alloy was studied based on microhardness and compressive macrostrain. X-ray and Auger spectra studies indicate that Nd not only is soluble in grain interiors, but also segregates to the grain boundaries. Nd solid-solution induces an increase of the microhardness from 269 to 290 HV in grain interiors and segregation results in an enhancement of hardness from 252 to 342 HV on grain boundaries. Thus, the cohesion of grain boundaries is enhanced by Nd segregation, which make the alloy doped with 0.05 wt pct Nd exhibit more compressive microstrain, i.e. the higher the compressive ductility at room temperature, the better the final surface condition at elevated temperature. Finally, a discussion was made on the reason that Nd strengthens the grain boundaries in NiAl intermetallic alloy.
 Select Aging Behavior of High Volume Fraction SiC Particles Reinforced 2024Al Composite Xiufang WANG, Gaohui WU, Dongli SUN, Longtao JIANG, Yuanyuan HAN J. Mater. Sci. Technol., 2004, 20 (02): 167-172.  Abstract   HTML   PDF (3002KB) 2024 Al matrix composite reinforced by SiC particles with 45% volume fraction and um diameter was successfully fabricated by squeeze-exhaust casting method. The aging behavior of SiCp/2024Al composite at four temperatures was investigated and compared to 2024 alloy. It was found that the addition of high volume fraction SiC particles does not alter the aging sequence, but it significantly accelerates the kinetics of precipitation in the composite matrices. Therefore, the aging peak of the composite appears earlier than that of 2024Al alloy. This is attributed to the decrease in the activation energy for the precipitate formation and the increase in the precipitate growth rate due to the high density dislocations in the composite with high volume fraction particles. The high density dislocations, as preferential nucleation sites for precipitates, bring about the tiny and dense precipitates in the composite.
 Select Superplasticity of a SiCw/Zn-22Al Composites Xiaojing XU, Wei WANG, Lan CAI J. Mater. Sci. Technol., 2004, 20 (02): 172-174.  Abstract   HTML   PDF (1001KB) n this paper, the superplastic characteristics of a 15 SiC(vol. pct) whisker reinforced Zn-22Al alloy composites, fabricated by low pressure infiltration and solute treatment after extrusion with the extrusion rate of 10:1, was investigated. The result showed that the composite exhibited a tensile elongation of 150% and a strain rate sensitivity value of about 0.33 at the initial strain rate of 6.67×10-2 s-1 and at 658 K where an appropriate amount of liquid phase was presented in the composite.
 Select Creep Rupture Behavior of K40S Alloy at Elevated Temperatures Fumin YANG, Xiaofeng SUN, Hengrong GUAN, Zhuangqi HU J. Mater. Sci. Technol., 2004, 20 (02): 175-179.  Abstract   HTML   PDF (3392KB) Creep testing was conducted on K40S alloy. The detailed creep deformation and fracture mechanisms under constant load were studied. The results show that the stress exponent ranges between 7 and 14.4 at elevated temperature 973～1173 K, and that the activation energy is approximately 449.1 kJ/mol. During creep, the grain boundary sliding cut off primary carbides at the boundary, generating the "O" model cracks. The creep failure mode of K40S alloy is transgranular ductile and cracks originate at the primary carbides. A long carbide and matrix interface is often a preferential path for crack propagation. The creep mechanism is discussed in light of the creep microstructure, the stress exponent and the activation energy.
 Select Effect of Annealing Temperature on GMR of [NiFeCo(10 nm)/Ag(10 nm)]×20 Multilayer Yuding HE, Shejun HU, Jian LI, Guangrong XIE J. Mater. Sci. Technol., 2004, 20 (02): 179-181.  Abstract   HTML   PDF (2142KB) The composition, phase structure, and microstructure of the discontinuous multilayer films [NiFeCo(10 nm)/Ag(10 nm)]×20 annealed at temperature 280, 320, 360 and 400℃, respectively were investigated GMR (giant magnetoresistance) ratios of the multilayer films were measured at different temperature. The results showed that FeNi3 precipitated at 360℃ and dissolved at 400℃. The films annealed at 360℃ for 1 h exhibited the highest GMR ratio 11% when saturation field was equal to 79.6 kA/m.
 Select First-Principle Investigation of O2 Adsorption on the NiTi Alloy (110) Surface Yingjie HUA, Xin LIU, Changgong MENG, Dazhi YANG J. Mater. Sci. Technol., 2004, 20 (02): 182-185.  Abstract   HTML   PDF (532KB) The discrete-variational method within the framework of density functional theory was used to investigate the process of O2 adsorption occurring on the surface of NiTi alloy. The calculated results showed that O2 exhibits the adsorption state of Odelta2 (0.36
 Select Nature of Surface Layer and Electrochemical Behavior of NaOH Hydrothermally Treated NiTi Alloy P.Shi, F.T.Cheng, H.C.Man J. Mater. Sci. Technol., 2004, 20 (02): 185-188.  Abstract   HTML   PDF (2984KB) NiTi samples were hydrothermally treated in NaOH at 200℃ with different soaking times. The morphology of the surface layer formed was studied by scanning electron microscopy (SEM). The composition of the layer and the major phases present were determined by energy-dispersive spectroscopy (EDS) and X-ray diffractometry (XRD), respectively. In contrast to the results reported by some authors, the surface layer was essentially Ni(OH) 2 instead of being TiO2. The electrochemical behavior of the samples was studied by electrochemical impedance spectroscopy (EIS) in 3.5 % NaCl solution at 23℃, and analyzed using a simplified Randle circuit consisting of a resistance R and a capacitance C in parallel. After hydrothermal treatment, R was increased by a factor ranging from 1.5 to 5.0 times, depending on the treatment time. The value of R of all the samples became steady within a period of less than 15 h. Results of the present study indicate that alkaline treatment leads to the growth of an insulating layer on NiTi, but the method is not suitable for surface modification of NiTi implants due to the enhanced Ni content in the surface layer.
 Select Theoretical Calculation of the Real Vapor Pressure of Al during ISM Processing of Ni-xAl (at. pct) (x=25～50) Alloy Jingjie GUO, Guizhong LIU, Yanqing SU, Jun JIA, Hengzhi FU J. Mater. Sci. Technol., 2004, 20 (02): 189-192.  Abstract   HTML   PDF (920KB) A new model was established to calculate the real vapor pressure of Al in the molten Ni-xAl (at. pct) (x=25～50) alloy. The effects of the holding time, chamber pressure, mole fraction of Al and melting temperature on the real vapor pressure of Al in the vacuum chamber were analyzed. Because of the impeding effect of the real vapor pressure on the evaporation loss rate, within a short time (less than 10 s), the real vapor pressure tends to a constant value. When the chamber pressure is less than the saturated vapor pressure of Al, the real vapor pressure of Al is equal to the chamber pressure. While when the chamber pressure is higher than the saturated vapor pressure, the real vapor pressure of Al approaches to the saturated vapor pressure of Al of the same condition.
 Select Interfacial Structure of Steel-Mushy Al-20Sn Bonding Plate Peng ZHANG, Yunhui DU, Hanwu LIU, Daben ZENG, Jianzhong CUI, Limin BA J. Mater. Sci. Technol., 2004, 20 (02): 193-195.  Abstract   HTML   PDF (533KB) Fe-Al compound at the interface of steel-mushy Al-20Sn bonding plate was studied quantitatively. The relationship between ratio of Fe-Al compound at interface and bonding parameters (such as preheat temperature of steel plate, solid fraction of Al-20Sn slurry and rolling speed) was established by artificial neural networks perfectly. The results show that when the bonding parameters are 505℃ for preheat temperature of steel plate, 34.3% for solid fraction of Al-20Sn slurry and 10 mm/s for rolling speed, the reasonable ratio of Fe-Al compound corresponding to the largest interfacial shear strength of bonding plate is obtained. Its value is 72%. This reasonable ratio of Fe-Al compound is a quantitative criterion of interfacial embrittlement, that is, when the ratio of Fe-Al compound at interface is larger than 72%, interfacial embrittlement will occur.
 Select Effect of Substrate Characteristics on Interdiffusion Coefficients of Ni and Al Atoms in β-NiAl Phase of Aluminide Coatings Hua WEI, Xiaofeng SUN, Qi ZHENG, Guichen HOU, Hengrong GUAN, Zhuangqi HU J. Mater. Sci. Technol., 2004, 20 (02): 196-198.  Abstract   HTML   PDF (1523KB) Interdiffusion coefficients at 950℃ and 1050℃ are calculated by Wagner analysis method as a function of composition of beta-NiAl phase. The beta-NiAl phase was formed by pack cementation on surface of superalloy. Results of the calculation show that interdiffusion coefficients in $\beta$-NiAl phase strongly depend on the compositions and vary over several orders of magnitude. Compared with the interdiffusion coefficients in the stoichiometric beta-NiAl phase, the interdiffusion coefficients in beta-NiAl phase formed on superalloy is obviously small, probably due to the composition, complicated microstructure and precipitates. However, it could be seen clearly that the shapes of the diffusivity curves are very similar to each other. The similarity of the diffusion curves and the difference between interdiffusion coefficients imply that the compositions, microstructures and precipitates of superalloy have a distinctly adverse effect on the interdiffusion of Ni and Al atoms during aluminization, but do not change the essential characteristics of beta-NiAl phase.
 Select Internal Strain Measurement in 3D Braided Composites Using Co-braided Optical Fiber Sensors Shenfang YUAN, Rui HUANG, Yunjiang RAO J. Mater. Sci. Technol., 2004, 20 (02): 199-202.  Abstract   HTML   PDF (1523KB) 3D braided composite technology has stimulated a great deal of interest in the world at large. But due to the three-dimensional nature of these kinds of composites, coupled with the shortcomings of currently-adopted experimental test methods, it is difficult to measure the internal parameters of this materials, hence causes it difficult to understand the material performance. A new method is introduced herein to measure the internal strain of braided composite materials using co-braided fiber optic sensors. Two kinds of fiber optic sensors are co-braided into 3D braided composites to measure internal strain. One of these is the Fabry-Parrot (F-P) fiber optic sensor; the other is the polarimetric fiber optic sensor. Experiments are conducted to measure internal strain under tension, bending and thermal environments in the 3D carbon fiber braided composite specimens, both locally and globally. Experimental results show that multiple fiber optic sensors can be braided into the 3D braided composites to measure the interval parameters, providing a more accurate measurement method and leading to a better understanding of these materials.
 Select Electronic Structure of New Superconducting Perovskite MgCNi3 Li CHEN, Hua LI, Liangmo MEI J. Mater. Sci. Technol., 2004, 20 (02): 203-205.  Abstract   HTML   PDF (220KB) The electronic structures of new superconducting perovskite MgCNi3 and related compounds MgCNi2T (T=Co, Fe, and Cu) have been studied using MS-Xα method. In MgCNi3, the main peak of density of states is located below the Fermi level and dominated by Ni d. From the results of total energy calculations, it was found that the number of Ni valence electron decreases faster for the Fe-doped case than that for the Co-doped case. The valence state of Ni changes from +1.43 in MgCNi2Co to +3.02 in MgCNi2Fe. It was confirmed that Co and Fe dopants in MgCNi3 behave as a source of d-band holes and the suppression of superconductivity occurs faster for the Fe-doped case than that for the Co-doped case. In order to explain the fact that Co and Fe dopants in MgCNi3 behave as a source of d-band holes rather than magnetic scattering centers that quench superconductivity, we have also investigated the effects of electron (Cu) doping on the superconductivity and found that both electron (Cu) doping and hole (Co, Fe) doping quench superconductivity exist. Comparing with the hole (Co) doping, there was no much difference between Cu and Co doping. This suggests that Co and Fe doping do not act as magnetic impurity.
 Select Geometric and Electronic Structure of Squaric Acid from DFT Calculation Xuyan XUE, Chunlei WANG, Weilie ZHONG J. Mater. Sci. Technol., 2004, 20 (02): 206-208.  Abstract   HTML   PDF (1128KB) The crystal and electronic structure of antiferroelectric squaric acid is studied using density functional theory method, and the exchange correlation effects are treated by the generalized approximation. In order to understand the ferroelectricity of H2SQ in the molecular plane and the antiferroelectricity in whole crystal, the density of states, charge density distribution and band structure are calculated. The result showed that O2p and C2p play important roles in the interactions between layers. The hybridizations of O2s-H1s and O2p-H1s are responsible for the tendency to ferroelectricity within each layer.
 Select Characteristics of Hydrogen Storage Alloy Mg2Ni Produced by Hydriding Combustion Synthesis Qian LI, Qin LIN, Lijun JIANG, Guozhi ZHOU, Feng ZHAN, Qiang ZHENG J. Mater. Sci. Technol., 2004, 20 (02): 209-212.  Abstract   HTML   PDF (1416KB) A high activity and large capacity of hydrogen storage alloy Mg2Ni by hydriding combustion synthesis was investigated by means of pressure composition isotherms, X-ray diffraction and scanning electron microscopy. The results showed that the maximum hydrogen absorption capacity of Mg2Ni is 3.25 mass fraction at 523 K, just after synthesis without any activation. The relationships between the equilibrium plateau pressure and the temperature for Mg2Ni were lgp (0.1 MPa)=-3026/T+5.814 (523 K≤T ≤623 K) for hydriding and lgp (0.1 MPa)=-3613/T+6.715 (523 K≤T ≤623 K) for dehydriding. The kinetic equation is [-ln(1-α)]3/2 = kt and the apparent activation energy for the nucleation and growth-controlled hydrogen absorption and desorption were determined to be 64.3±2.31 kJ/(mol·H2) and 59.9±2.99 kJ/(mol·H2) respectively.
 Select Corrosion of Iron and Four Commercial Steels in a Cl-Containing Oxidizing Atmosphere at 500℃～600℃ Ke ZHANG, Yan NIU, Chaoliu ZENG, Weitao WU J. Mater. Sci. Technol., 2004, 20 (02): 213-216.  Abstract   HTML   PDF (5893KB) The corrosion behaviors of Fe and four commercial steels with different Cr contents were investigated in an oxidizing atmosphere containing HCl at 500~600℃, which simulated the environment to which materials are usually exposed in waste incineration. All the test materials underwent an accelerated corrosion in this atmosphere and small amounts of chlorine could be detected a t the metal/scale interface. The corrosion mechanism is discussed on the basis of thermodynamic considerations for the reactions between metals and mixed O-Cl gases.
 Select Corrosion and Runoff Behavior of Carbon Steel in Simulated Acid Rain Baigang AN, Xueyuan ZHANG, Enhou HAN, Hongxi LI J. Mater. Sci. Technol., 2004, 20 (02): 220-222.  Abstract   HTML   PDF (1936KB) Under the condition of simulated rain precipitation in the laboratory, with EIS and SEM observation, the effects of pH value of simulated rain on corrosion and runoff behavior of carbon steel A3 were studied. The corrosion rate of A3 steel increased and runoff action of rain precipitation on A3 steel surface was intensified with decreasing pH value, of simulated rainwater. The runoff and corrosion traces were formed along the flowing direction of rainwater, which appeared more apparently with decreasing pH value.
 Select Growth of Hydroxyapatite Crystal in the Presence of Organic Film Yong LIU, Suping HUANG, Xiaohong DAN, Kechao ZHOU J. Mater. Sci. Technol., 2004, 20 (02): 223-226.  Abstract   HTML   PDF (2962KB) The growth of hydroxyapatite (HAp) crystal in the presence of hexadecylamine was investigated. Due to its high polarity and high charge density, the organic film could increase the ion supersaturation on its surface. Therefore the growth of pure HAp crystals was accelerated. Moreover, the positive headgroups of the organic film could act as recognized nucleation sites and orient the growth of HAp crystals along the <0001> direction.
 Select Long Periodic Structure in ZrO2-Y2O3 Ceramics Jiancun RAO, Yu ZHOU, Douxing LI J. Mater. Sci. Technol., 2004, 20 (02): 226-227.  Abstract   HTML   PDF (2697KB) A new type of long periodic structure has been found in ZrO2-Y2O3 ceramics in annealed states. High resolution electron microscopy (HREM), selected area electron diffraction, and computer simulation have been used to reveal the presence of the long periodic structure. The unit cell of the long periodic structure consists of a cubic ZrO2 unit cell and L10- like phase one.
 Select Numerical Simulation of Current Density Distribution in Keyhole Double-Sided Arc Welding Junsheng SUN, Chuansong WU, Min ZHANG, Houxiao WANG J. Mater. Sci. Technol., 2004, 20 (02): 228-231.  Abstract   HTML   PDF (1748KB) In the double-sided arc welding system (DSAW) composing of PAW+TIG arcs, the PAW arc is guided by the TIG arc so that the current mostly flows through the direction of the workpiece thickness and the penetration is greatly improved. To analyze the current density distribution in DSAW is beneficial to understanding of this process. Considering all kinds of dynamic factors acting on the weldpool, this paper discusses firstly the surface deformation of the weldpool and the keyhole formation in PAW+TIG DSAW process on the basis of the magnetohydrodynamic theory and variation principles. Hence, a model of the current density distribution is developed. Through numerical simulation, the current density distribution in PAW+TIG DSAW process is quantitatively analyzed. It shows that the minimal radius of keyhole formed in PAW+TIG DSAW process is 0.5 mm and 89.5 percent of current flows through the keyhole.
 Select Influence of Slot Defect Length on Magnetic Flux Leakage Songling HUANG, Luming LI, Haiqing YANG, Keren SHI J. Mater. Sci. Technol., 2004, 20 (02): 231-232.  Abstract   HTML   PDF (497KB) A key issue, which influences the applications of magnetic flux leakage testing, is defect quantification. There have been many research on the relationship between width, depth and magnetic flux leakage of slot defect. However, the length factor is often ignored. The relationship between characteristics of defect leakage field and defect length was investigated. The magnetic flux leakages of a series of plate specimens with the same width, same depth and different length slot defects were tested under the same magnetizing conditions. Testing results show that defect length is an important parameter needed to consider in quantifying defects.
 Select NBCM with Flat Roll in the Finish Stand Xiangwei KONG, Hezhou YE, Jiangzhong XU, Guodong WANG, Xianghua LIU, Junwei ZHANG J. Mater. Sci. Technol., 2004, 20 (02): 233-235.  Abstract   HTML   PDF (802KB) With the development of the market, it becomes a demanding task for producers to make flexible production schedules to shorten production cycle. Schedule-free rolling is needed. If the CVC work roll of the F6 and F7 stands in certain 2050 mm hot rolled strip mill are substituted by flat roll (aim to SFR) and the strip profile is controlled by the existing bending force, the control ability is not adequate. This fact has been tested through on-line experiment and has been given in this article. The NBCM (new backup roll crowning method) is recommended to improve the profile control ability. Finally the plastic deformation of the strip and the elastic deformation of the roll are analyzed by employing coupled calculation of rigid-plastic finite element method and G-function method, and the optimal range of the crown of backup roll is given theoretically.
 Select Superplastic Microforming of Zn-A122 Alloy Ribs Changli WANG, Kaifeng ZHANG J. Mater. Sci. Technol., 2004, 20 (02): 236-238.  Abstract   HTML   PDF (740KB) Research on microforming of mine-grained superplastic Zn-Al22 alloy was carried out in this paper by means of superplastic forming. With the selected material, microformability tests have been carried out with the specially developed evaluation method by using two kinds of stainless steel dies. With these dies, micro-extrusion tests have been carried out and the characteristics of microformability of the material have been clarified. Effects of processing parameters and die structure on forming have been analyzed. SEM and metallographic microscope have been used to analyze the formed specimens. Through analysis of °ow lines of the formed specimen, behavior of material could be understood well.
 Select Interface Reaction of Ta/NiFe and NiFe/Ta and the Dead Layer Hongchen ZHAO, Guanghua YU, Hong SI J. Mater. Sci. Technol., 2004, 20 (02): 239-240.  Abstract   HTML   PDF (515KB) The structures of Ta/Ni81Fe19 and Ni81Fe19/Ta are commonly used in magnetoresistance multilayers. It is found that the thickness of dead layer in Ta/Ni81Fe19/Ta was about 1.6§0.2 nm. X-ray photoelectron spectroscopy (XPS) was used to study the interfaces of Ta/Ni81Fe19 and Ni81Fe19/Ta. The results show that there is a reaction at the two interfaces: 2Ta+Ni=NiTa2, which caused the thinning of the effective NiFe layer. Furthermore, this reaction could also explain the phenomenon that the dead layer thickness of spin valves multilayers prepared by MBE is thinner than those prepared by magnetron sputtering.
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