bluuebunny/crossref_metadata_2025 huggingface dataset:
A New AC-Driving Method for Active-Matrix OLED Displays
Authors: Chen Xin Fa , Si Yujuan , Zhao Yi , Liu Shi Yong
Published: March 2009

The lifetime of organic light-emitting devices can be influenced by the OLED material and structure, electrode material, driving mode and so on. Among all these factors, OLED driving method has been regarded as one of the most important factors, and it is well known that ac-driving mode improves the lifetime of OLED, especially pulse-driving mode with a reversed-biased voltage on OLED. In this article, a new ac-driving mode for Active-Matrix OLED is proposed on basic fabrication of two-TFT current source pixel circuit. Simulation has been done on the pixel and 1×4 matrix circuits, and simulation results have demonstrated that OLED is in reversed-biased state during recovery time. At last, a practical peripheral circuit that can provide achieve an ac-driving mode has been designed.
Influence of Cyclic Deformation on Shape Memory Characteristics of Ti-Ni-Cu Alloys Fabricated by Pulse-Current Pressure Sintering Method
Authors: Kyogoku H. , Kadomura T. , Komatsu S. , Yoshida Fusahito , Sakuma Toshio
Published: March 2009

Ti-Ni-Cu shape memory alloy by elemental powders was fabricated by using a pulse-current pressure sintering method, and it was subjected to solid-solution heat treatment after sintering to homogenize the microstructure of the alloy. The influence of the thermo-mechanical cyclic deformation on the shape memory and thermo-mechanical characteristics of Ti-Ni-Cu alloy was investigated. The thermo-mechanical cyclic deformation improved the deformation behavior of the sintered alloy and made the thermo-mechanical behavior of the alloy stable caused by the introduction of dislocations. As a result, the recovery stress of the alloy after the cyclic deformation fairly increased. The transformation temperatures of the alloy after the cyclic deformation became lower than those of the alloy before the cyclic deformation. Therefore, the superelastic-like behavior of the alloy after the cyclic deformation appeared in an isothermal tensile test at lower holding temperature.
Magnetic Field-Induced Strain of Martensite and Parent Phases in a Ferromagnetic Shape Memory Iron-Palladium Alloy
Authors: Kakeshita Tomoyuki , Fukuda Takashi , Sakamoto Tatsuaki
Published: March 2009

We have investigated the magnetic field-induced strain (MFIS) of the martensite and the parent phases in an Fe-31.2Pd(at.%) single crystal, which exhibits a martensitic transformation at TM = 230K. Below TM, a large MFIS of several percent appears due to rearrangement of martensite variants and this strain remains when a magnetic field is removed. Such rearrangement depends on magnetic field direction; Variants are perfectly rearranged into the variant, which lowers the magnetocrystalline anisotropy energy most, when a magnetic field is applied along [001]P, and partially when [011]P and hardly when [111]P (“P” represents “parent” phase). The dependence on the field direction can be explained by comparing the magnetic shear stress tmag with the shear stress t
req required for rearrangement of variants. Above the temperature, TM, a relatively large MFIS appears and it increases up to about 10-3 with decreasing temperature from 280 K toward TM. This MFIS is probably caused by anomalies of some physical properties, such as elastic constant and dipole-dipole interaction coefficient in the parent phase.
Martensitic Transformation and Magnetic-Field-Induced Strain in Magnetic Shape Memory Alloy NiMnGa Melt-Spun Ribbon
Authors: Guo Shi Hai , Zhang Yang Huan , Quan Bai Yun , Li Jian Liang , Wang Xin Lin
Published: March 2009

A non-stoichiometric polycrystalline Ni50Mn27Ga23 magnetic shape memory alloy was prepared by melt-spinning technology. The effects of melt-spinning on the martensitic transformation and magnetic-field-induced strain (MFIS) of the melt-spun ribbon were investigated. The experimental results show that the melt-spun ribbon undergoes the thermal-elastic martensitic transformation and exhibits the thermo-elastic shape memory effect. But the martensitic transformation temperature decreases and Curie temperature remains unchanged. A particular internal stress induced by melt-spinning made a texture structure in the melt-spun ribbon, which
made the melt-spun ribbon obtain larger transition-induced strain and MFIS. The internal stress was released under cycling of magnetic field. This resulted in a decrease of MFIS of the melt-spun ribbon.
Stress Induced and Magnetic Field Enhanced Twin Variants Reorientation in NiMnGa Single Crystal
Authors: Wang Jing Min , Jiang Cheng Bao , Xu Hui Bin
Published: March 2009

The behavior of twin variants reorientation in Ni50Mn27.5Ga22.5 single crystal under the applied mechanical stress and magnetic field was investigated. Through three times of compression, the twinning stress was reduced from 4.4MPa to 0.4MPa, and 2.5% stress induced strain was obtained. During the succedent MFIS measurement, with the increase of measurement number of times, the critical field (μ0H)c at which the MFIS jumps became lower, and the corresponding jumping magnetostrain ε j, and the maximal magnetostrain εmax ascended. At last, a quasi
single-variant state was realized, and the sample showed repeatable 6.21% MFIS, which is close to the theoretical value (1-c/a)*100%. The results are discussed from the point of martensitic microstructure evolution.
Characterization of High-Speed Microactuator Utilizing Shape Memory Alloy Thin Films
Authors: Tomozawa M. , Okutsu K. , Kim Hee Young , Miyazaki Shuichi
Published: March 2009

Dynamic actuation properties of two types of high-speed microactuators utilizing
Ti-Ni-based thin films were investigated. One type is a microactuator utilizing a Ti-Ni-Pd thin film which has high transformation temperatures. Cooling rate of a microactuator increases with increasing temperature difference between transformation and atmosphere temperatures, thus the increase in transformation temperature is effective to increase the actuation response. The other type is a microactuator using R-phase transformation of a Ti-Ni thin film which has a narrow
transformation temperature hysteresis. The narrow transformation temperature hysteresis of the R-phase transformation is effective to increase the actuation response. Both types of actuators are promising for high response applications. The working frequency of the microactuators reached 100Hz in the two types of microactuators utilizing the martensitic transformation of the Ti-Ni-Pd thin film and the R-phase transformation of the Ti-Ni thin film.
Shape Memory Behavior of NiMnGa/Epoxy Smart Composites
Authors: Hosoda Hideki , Takeuchi Shinsuke , Inamura Tomonari , Wakashima Kenji , Miyazaki Shuichi
Published: March 2009

A new type of smart composite developed in our group was studied in terms of shape memory behavior. The smart composites were composed of NiMnGa ferromagnetic shape memory alloy particles (FSMAP) and a polymer matrix, where NiMnGa FSMAP will bring shape memory effect and the matrix polymer enhances ductility. Two kinds of NiMnGa were selected by taking the phase constitution into account (parent or martensite state at room temperature). The
shape memory properties are reported in terms of transformation temperature, powder size, applied stress and heating/cooling rate. It was found that martensitic transformation temperatures of the smart composites obtained by differential scanning calorimetry (DSC) were almost equal to those of NiMnGa FSMAPs. The shape recovery of the composites was confirmed in the strain-temperature
curves obtained by dynamic mechanical analysis. Clear shape change was recognized corresponding to the martensitic transformation temperatures. The shape memory properties depend on heating/cooling rate, particle size and applied stress. Lower heating/cooling rate and smaller particle size brings better shape memory properties. This is because thermal conductivity of polymer is low and the amount of defects such as pores introduced during curing decreases with
decreasing particle size. The improvement of processing is needed to reduce material defects.
A New Method to Identify the Preisach Distribution Function of Hysteresis
Authors: Li Fan , Mao Jian Qin , Ding Hai Shan , Zhang Wen Bo , Xu Hui Bin , Jiang Cheng Bao
Published: March 2009

In this paper, a new method which combines the least square method with Tree-Structured fuzzy inference system is presented to approximate the Preisach distribution function. Firstly, by devising the input sequence and measure the output, discrete Preisach measure can be identified by the use of the least squares method. Then, the Preisach function can be obtained with Tree-Structured fuzzy inference system without any special smoothing means. So, this new method is not sensitive to
noise, and is a universal approximator of the Preisach function. It collect the merit and overcome the deficiency of the existing methods.
Exchange-Coupling Interaction and Effective Anisotropy in Two-Phase Nanocomposite Permanent Magnetic Materials
Authors: Liu L.M. , Chen Wei , Zhu M.G. , Nie L.Y. , Li Ai Jun , Hu J.J.
Published: March 2009

Using the part exchange-coupling model, the exchange-coupling interaction between
magnetically soft and hard grains in Nd2Fe14B/α-Fe nanocomposite and its effect on the effective anisotropy of the material have been investigated. By testing six different functions, series curves of effective anisotropy constant versus the mean grain size were obtained. The calculation results show that the effective anisotropy of the composite increases slightly with decreasing grain size, reaches the maximum at about 23nm, and then decreases abruptly. The calculated curves resemble the experimental results of the coercivity versus grain size in nanocomposite.
Investigation of Hard Magnetic Behaviors for Nd-Fe-B Based Magnets Prepared by Hydrogen Decrepitation Technique
Authors: Li Bo , Wang Dongling , Guo Bing Lin , Yu Xiaojun , Qin Hong Wei , Hu Ji Fan
Published: March 2009

In the present work, we investigated the hard magnetic properties of Nd-Fe-B magnets prepared by the decrepitation technique. The microstructure of (Nd0.935Dy0.065)14.5Fe79.4B6.1 HD - magnet was observed and the average grain size is about 6-15 µm. The HD alignment degree f is about 93%. Most rich-Nd phase can be found at grain boundaries of main phase, but a few rich – Nd phase occurs within main phase grains. The magnetizing field dependence of the hardmagnetic properties for the (Nd0.935Dy0.065)14.5Fe79.4B6.1 were investigated. The value of magnetizing field for the saturation coercivity is smaller than the value of the saturation coercivity, showing that the coercivity for the (Nd0.935Dy0.065)14.5Fe79.4B6.1 HD-magnet is controlled by the nucleation
mechanism. Meanwhile, the temperature dependence of coercivity for HD magnet Nd14.5Fe79.4B6.1 was analyzed.
Growth and Properties of Half-Metallic Double Perovskite Thin Films
Authors: Asano Hidefumi , Koduka Norihito , Sugiyama Mikito , Matsui Masaaki
Published: March 2009

Ferromagnetic oxides with ordered double-perovskites Sr2FeMoO6 and Sr2CrReO6 are known to be in a half-metallic ground state with high Curie temperatures Tc, and hence one of the promising materials for spin electronics. This paper reports epitaxial growth and micro-structural, magnetic, and electrical characterization of thin films of these oxides. It is shown that a coherent growth without strain relaxation, which is accomplished by the use of substrate or buffer layers with a small (0.1%) lattice match, is essential to obtain high quality films with both atomically flat surface and high magnetization values expected for their half-metallicity
Magnetoresistance and Current-Controlled Electric Transport Properties of Fe-C Film on Si Substrate
Authors: Xue Q.Z. , Zhang X.
Published: March 2009

Using pulsed laser deposition we prepared Fex-C1-x films on Si (100) substrates. We show that the lightly Fe-doped amorphous carbon films on Si substrate have large MR at room temperature. At T=300K and B=5T a large positive MR of 138% was found in Fe0.011-C0.989 film. Furthermore, we find that when temperature T<258K, the MR of Fe0.011-C0.989 film on Si substrate is negative and
when 258K<T<340K the MR is positive. Besides, the resistance of the material is controlled by the measuring current and therefore its I-V curve is unusual asymmetric. The current-controlled electric transport properties have a potential to achieve higher density magnetic random access memory (MRAM).
Magnetoresistance in the Hard/Cu/Soft Sandwiches: Dependence on Layer Thickness and Field Annealing
Authors: Yang Bai , Bi Xiao Fang , Yang Fan , Gong Sheng Kai , Xu Hui Bin
Published: March 2009

NiFe(2nm)/Cu(tCu)/Co(1.5nm) sandwiches were deposited on Ta buffer layer by magnetron sputtering method. Small angle X-ray diffraction analysis was made to investigate the structural characterizations of the sandwiches. It has been obtained that MR value showed a maximum at tCu=2nm when Cu spacer thickness changed, which is contributed by the effect of shutting and interlayer coupling. The Cu layer was deposited at two different rates. Larger MR ratio was observed with a lower deposition rate. The result was discussed in terms of magnetic reversal fields. In addition, the sandwiches were subjected to field annealing at different annealing
temperatures. MR ratio has exhibited a largest increase after annealing at 175oC with a magnetic field of 750Oe applied.
Giant Magnetoimpedance in as Quenched Fe Based Nanocrystalline Ribbons
Authors: Hu Ji Fan , Qin Hong Wei , Jiang Minhua , Li Bo , Zhao Dongliang , Yu Xiaojun , Wang Dongling , Wang Xin Lin
Published: March 2009

FeCuNbSiB and FeZrBCu nanocrystalline ribbons can be obtained directly through the melt- spinning technique without additional annealing processes. The giant magnetoimpedance can be observed in FeCuNbSiB and FeZrBCu as quenched ribbons. The addition of Cu improves the nano-crystallization of a-Fe(Si) or a-Fe phase and reduces the grain size in FeCuNbSiB and FeZrBCu as quenched ribbons, which enhances the magnetoimpedance via increasing the variation of permeability under fields. The present experimental results reveal a novel route to
fabricate the Fe based nanocrystalline soft magnetic materials with giant magnetoimpedance effect.
Micro-Mechanism and Impurity Influence of Ferromagnetic Shape Memory Alloy Ni2MnGa Investigation
Authors: Mu Jiangang , Zhao Dongliang
Published: March 2009

In this paper the perfect Ni2MnGa cluster model is studied by use of the first principles discrete variational method (DVM), which is based on the framework of density- function theory. To study the characteristic properties of the alloy and the influence of the impurities which substitute for Mn at the central, the electronic structure、the binding energy and site energy are calculated. The result illuminates that Ni2MnGa complex obviously has metallic property. Ga plays to transmit electron for the exchange actions between Mn and Mn. And the periodic influence of 11 impurity elements on the binding energy and the site energy is gived. From the microcosmic the reason of the martensitic temperature changed with the concentration of element is analyzed.
The First-Principles Study of Electronic Structure of Fe/MgO/Fe Magnetic Tunnel Junctions Interface
Authors: Shang Jia Xiang , Wang Fu He , Bi Xiao Fang , Xu Hui Bin
Published: March 2009

In this work series of models were constructed in order to investigate the relationship between atomic and electronic structure and TMR property. Models with normal component interface of Fe/MgO/Fe magnetic tunnel junctions were calculated by first-principles discrete variational method (DVM) within the framework of local spin density functional theory. The SP and TMR ratio of Fe at interface of ferromagnetic layer as well as density of states are analyzed. Our
research shows that the thickness of ferromagnetic layers effect much on electronic structure. The interface and surface Fe layers have different feature from that of interior.
Magnetotransport Behaviors in Electron-Doped Manganese Oxide La0.9Te0.1MnO3
Authors: Tan Guotai , Zhang X. , Chen Zhao Hui
Published: March 2009

The magnetotransport behaviors of electron-doped colossal magnetoresistance (CMR) manganites La0.9Te0.1MnO3 have been investigated in external magnetic fields up to 4 T. The temperature dependence of the resistivity shows that the transport mechanisms of the sample below the metal-insulator transition temperature are attributed to the electron-phonon and magnon scattering behaviors. While the resistivity above Curie temperature (Tc=240 K) can be fitted with either polaron transport or variable-range hopping, and the fitting results are affected significantly by the magnetic fields. The electron spin resonance investigation indicated that there exist the ferromagnetic clusters up to 280 K in the paramagnetic phase of the sample. As a result, a possible correlation between the resistivty and phase separation is considered.
The Precipitation of Copper in the Non-Oriental Electrical Steel
Authors: Xu Ben , Li Youguo , Gong Yong Feng
Published: March 2009

The precipitation of copper in the non-oriental electrical steel was studied in this article. These precipitation particles, which influenced both the texture development and the magnetic properties of the steel sheets, appeared in the hot-rolling strips and grew up in the later normalization process. Their composition, morphology and crystallography had been investigated using TEM. Differed from the MnS and AlN that studied in the previous papers, these precipitate particles were found to be CuAl2. It suggested that these particles might stimulate the recrystallization nucleation of the {110} oriented grains and restrain the development of {111}
oriented grains in the sheet of non-oriented electrical steel. This might be another explanation to the improvement on magnetic properties of the non-oriental electrical steel containing copper addition.
Long Magnetic Nanochains Assembled by Magnetotactic Bacteria in a Directional Field
Authors: Wu X.L. , Zhong W. , Gao Shy Ying , Qi X.H. , Tang N.J. , Jiang H.Y. , Du You Wei
Published: March 2009

A new species of single-cell magnetotactic bacteria, the NMV-1 bacteria, has been found by us. Each NMV-1 bacterium synthesizes itself a chain of magnetic nanoparticles inside its body. When an external magnetic field is applied, long bacteria chains come into being in the direction of the field in the water. More than 30 µm long chains of live bacteria have been observed. Length of bacteria chains is field dependant: the higher the magnetic field is, the longer the bacteria chains are. The bacteria chains orientation is controllable and the chains can be stably trapped. The mechanism of the assembly of long bacteria chains is also discussed. The
results show that, while an external magnetic field is applied, the NMV-1 bacteria have strong enough interactions between each other to assemble long bacteria chains. After positioning the bacteria chain, cellular membranes of the bacteria were removed by cell lysis, leaving long chains of magnetic nanoparticles on a substrate. These magnetic nanochains can be potentially used as building blocks for magnetic nanostructures.
Investigation of Cobalt-Free AB5-Type Hydrogen Storage Alloy
Authors: Zhang Yang Huan , Wang Guoqing , Dong Xiao Ping , Guo Shi Hai , Wang Xin Lin
Published: March 2009

Co-free AB5-type LaxMm1-x(NiMnSiAlFe)4.9 (x = 0, 0.45, 0.75, 1) hydrogen storage alloys were prepared by casting and rapid quenching. The phase structures and microstructures of the as-cast and quenched alloys were analyzed and observed by XRD and SEM. The electrochemical performances of the as-cast and quenched alloys were measured. The effects of La content and quenching rate on the microstructures and electrochemical properties of the alloys were investigated comprehensivel y. The obtained results indicate that the Co-free AB5-type hydrogen storage alloy with excellent synthetical electrochemical performances can be prepared by adjusting La content and employing appropriate rapid quenching technique.
Research on Molten Pool Shape during Laser Rapid Forming through the Close-Range Continuous Photography
Authors: Chen Jing , Yang Haiou , Wang Meng , Su Yun Peng , Huang Wei Dong
Published: March 2009

Laser Rapid Forming (LRF) is a new and advanced manufacture technology to
accomplish near net shape metal components with high performance for use in the aerospace, defense and chemical processing industries. In this paper the close-range continuous photography is used to take side views on the cladding zone in order to disclose inherent characteristic of the laser rapid forming process. The vivid molten pool shape is obtained by adopting image partition technology since the not molten area is eliminated from the photos. It is found that the molten pool size depended essentially on the LRF process parameters. With introducing the metal powders into the focus spot of the laser beam, the molten pool retains a segment arc raised outward and the molten pool free surface inclines to the axis of laser beam. Further results show that the molten pool inclination plays an important role on the microstructure of the LRF components.
Electrochemical and Optical Characterization of the Corrosion Resistivity of Explosively Bonded Al-Cu Bimetal
Authors: Ha Y.-C. , Bae J.H. , Ha T.-H. , Lee H.G. , Kim D.-K. , Lee B.I.
Published: March 2009

With the usage of Al-Cu bimetals to connect aluminum and copper in power distribution systems growing persistently, efforts to mitigate the mechanical, electrical and electrochemical degradation are widely made. The explosive bonding technology has been considered as a countermeasure for the degradation. In this paper, electrochemical analysis and optical microscopic observation are carried out in order to compare the corrosion resistivity of the explosion type bimetal to the commonly used compression type bimetal. In particular, the effect of anions in the interfacial electrolyte on corrosion susceptibility was also investigated. The results show that the explosive bonding technology can prevent the interfacial corrosion caused by the formation of crevices and pits as well as by galvanic potential difference between aluminum and copper.
The Interaction of Weld Defects under Plastic Collapse
Authors: De Waele Wim
Published: March 2009

Multiple defects in welds, when detected, have to be assessed for interaction. Current code rules are based on linear elastic fracture mechanics whereas the failure mode for welds in thin structures is primarily plastic collapse. Results of large-scale tests illustrate that current interaction rules have a high degree of conservatism for plastic collapse conditions. Guidance for the assessment of defect interaction under plastic collapse is proposed.
Microwave and Millimeter-Wave Processing of Materials
Authors: Lewis III D. , Bruce Ralph W. , Fliflet Arne W. , Kurihara L.K. , Bruce R.L.
Published: March 2009

We present results on microwave and millimeter-wave processing of materials. The research is primarily based on two systems– a 2.45 GHz, 6 kW S-band system and an 83 GHz, 15 kW gyrotron based quasi-optical system. These systems have been used for a wide range of material processing experiments. We describe the capabilities of these systems and discuss some of the results, including nanophase material production, rapid sintering, coating removal and joining of high temperature
ceramics.
Modelling Shape Evolution and Heat Flow of Spray-Formed Ring Preforms
Authors: Mi Jia Wei , Shi Z. , Grant Patrick S.
Published: March 2009

A finite element model has been developed to simulate the coupled effects of deposit
shape evolution and heat flow inside spray formed ring-shaped deposits. The shape model was developed using Matlab and included the features of: (1) atomiser scanning; (2) substrate movement relative to the atomiser; and (3) sticking efficiency. Atomiser scan and various substrate horizontal travel speeds were studied to optimise the ring shape in terms of useful materials suitable for downstream processing. The heat flow model was developed using the commercial finite element code Femlab. A data mapping technique was developed to transfer thermal data between different domains when the computational domains are subject to changing geometry and therefore the coupled effects of shape evolution and heat flow were addressed. Spray forming of ring deposits was performed on the large spray forming unit at Oxford University. In-situ temperature measurements were carried put for acquisition of boundary conditions and validation of the heat flow model. Heat flow modelling revealed that edge effects had a strong influence on the ring thermal history and the porosity distribution inside the deposits is closely related to the local solidification time.
PID Control of Deposit Dimension during Spray Forming
Authors: Qu Ying Dong , Cui Cheng Song , Chen San Ben , Li Qing Chun
Published: March 2009

A PID controller has been developed to improve the dimensional precision of a deposit during spray forming. Simulation has been carried out based on a dynamic neural network modeling of deposit dimension. The simulation results show that the PID controller is effective for the control of deposit dimension with short regulating time and low override. Experimental results show that the error between the actual size and the target value is very small even though a disturbance from unstable melt flow rate was introduced.
Evolution of SiC Particle Distribution in Spray Codeposited SiCp/ 7075 Al Composites during Extrusion
Authors: Zhan Meiyan , Chen Zhen Hua , Yan Hong Ge , Xia Weijun
Published: March 2009

The evolution of SiC particle distribution in spray codeposition SiCp/7075Al composite during extrusion was investigated. A unique metallurgical pattern designated as ring- and band-pattern in the cross section of the extruded products occurred which comprises areas with higher and lower concentrations of SiC particles. The factors that contributed to the evolution of SiC particles distribution feather during plastic deformation were analyzed. The difference of flowability between the matrix and SiC particles was supposed to be the main factor accounting for the forming of the ring- and band-pattern. In addition, concentration difference of SiC particles between different deposition layers will also contribute to the forming of the ring- and band-pattern. A simple model was proposed to describe the evolution of SiC particle distribution during extrusion.
Modeling and Numerical Calculation of Heat Transfer during Magnetic Field Quenching
Authors: Li Zhen Hua , Liu Mei Hong , Chen Jun Ruo , Zhou Rong Feng
Published: March 2009

A new nonlinear constructive model for description of temperature field of carbon steel axisymmetric body during the magnetic field quenching has been established based on thermo-magnetic coupling analysis. Using the model and finite element method, a numerical calculation program is developed with Microsoft FORTRAN 5.0, and cooling curves of center in a carbon steel sample of 30mm in diameter and 60mm in length during magnetic field quenching and common quenching are calculated and tested. Results showed that calculated cooling curves is accordant with corresponded tested cooling curves very well, and the calculated accuracy of
temperature field during magnetic field quenching based on the new model is satisfactory.
Novel Zirconia Composite Coatings Fabricated by Twin Hybrid Plasma Spraying
Authors: Huang Heji , Eguchi Keisuke , Kambara Makoto , Yoshida Toyonobu
Published: March 2009

With a newly established 300kW twin hybrid plasma spraying system, a peculiar layered composite zirconia coating was successfully deposited. The coating is consisting of splats and dendritic columns, which come from thermal plasma spraying and thermal plasma PVD, respectively. A 120µm-thick composite coating was deposited in 10 minutes at the corresponding growth rate of 100µm/min, if the rotation of the substrates is considered. The microstructure of such composite
coatings has been characterized using a variety of microscopic techniques as part of a process optimization study.
A Study on Mechanical Behavior and Microstructural Evolution in the Superplastic Deformation of Ti75 Alloy
Authors: Li Chang Liang , Ding Hua , Zhao Yong Qing , Zhou Lian
Published: March 2009

Superplastic forming provides a good way for Ti alloys which are usually difficult to
be deformed. Ti75 alloy with a nominal composition of Ti-3Al-2Mo-2Zr is a newly developed corrosion resistant alloy, with a middle strength and high toughness. In the present paper, superplastic behavior of the alloy was investigated, the microstructural evolution in superplastic deformation was observed and the superplastic deformation mechanisms were analyzed. The results showed that the strain rate sensitivity, m, of the Ti75 alloy was larger than 0.3 and the strain was over 2.0 without surface cracking at 800°C and 5×10-4s-1 in compressive testing.
During the first stage of superplastic deformation, a phase grains became equiaxed, fine and homogeneous due to the recrystallization in a phase and diffusion in b phase. Newly formed equiaxed a grains then could slide and rotate, exhibiting superplastic features. The stress concentration caused by grain sliding of a grains could be released by slip and diffusion in b phase between the a phase grains, which acted as accommodation mechanisms.
Phase Transformation in Fe-Based Alloys in High Magnetic Fields
Authors: Hao X.J. , Ohtsuka H.
Published: March 2009

The effects of a high magnetic field on phase transformation behaviors and microstructures in Fe-based alloys have been extensively studied. It was found that a magnetic field accelerates ferritic and martensitic transformation, changes the morphology of the transformed microstructures and increases the A3 and A1 temperature. In a magnetic field of 10 Tesla, the A1 temperature increases by about 15°C for Fe-0.8C, the A3 temperature for pure Fe increases by about 8°C and the martensitic transformation temperature Ms in 18Ni maraging steel increases by 20°C. Ferrite grains are elongated and aligned along the direction of magnetic field in Fe-0.4C and Fe-0.6C alloys by ferritic transformation, but elongation was not found in pure Fe, Fe-0.05C alloy and Fe-1.5Mn-0.11C-0.1V alloy. Aligned structure was not found either by pearlitic transformation in Fe-0.8C alloy or by cementite precipitation from martensite.
Superplasticity and Crystallographic Orientation Distribution in Friction Stir Processed Sheet of an Al-Mg-Mn Alloy
Authors: Takayama Yoshimasa , Nagai Takayuki , Shibayanagi Toshiya , Kato Hajime , Watanabe Hideo
Published: March 2009

Superplasticity and crystallographic orientation distribution of an Al-Mg-Mn sheet
subjected to friction stir processing (FSP) have been investigated. The FSP was developed by adapting the concepts of friction stir welding to obtain a fine grain size in a stirred zone. Grain refinement was achieved by the FSP to give a smaller grain size of about 4µm than a value of 26µm in the as-received sheet. The SEM/EBSP analysis of the specimen before and after the FSP revealed a fraction of high angle grain boundaries became a higher percentage of 83% due to the FSP than 75% before. The elongation to failure in the FSPed sample had a maximum value of 361% at 773K and 1.1×10-3 s-1. Further, change in crystallographic orientation distribution is investigated during tensile testing in consideration of deformation mechanism.
Variant Selection in Fcc-to-Bcc Precipitation at Grain Boundaries in Ni-43Cr Alloy
Authors: Adachi Yoshitaka , Yin Fu Xing , Hakata Kazunari , Tsuzaki Kaneaki
Published: March 2009

Variant selection of bcc-Cr at the grain boundaries in a supersaturated fcc matrix was studied using a Ni-43Cr alloy. The preferentially selected variant was examined as a function of the grain boundary misorientation, the tilt angle between the {111}fcc plane and the grain boundary plane, and the orientation relationships with respect to both of the adjacent matrix grains.
A Study on Material Flow in Combined Extrusion Process
Authors: Ok J.H. , Hwang Beong Bok , Choi Hyoung Jin , Ham B.S. , Hwang Sun Keun
Published: March 2009

This paper deals with an analysis of material flow in an extrusion process with a divide flow. The billet material flows easily into the corners of the die cavity and/or the material flow is controlled by the help of the ratio in reduction area, thikness ratio of backward can thickness to forward can thickness. So the influences of this tool geometry and process condition on balanced material flow in a combined forward and backward can extrusion process are explained. The FEM simulation has been conducted in order to investigate the effect of process parameters such as
thickness ratio on the material flow. Deformation pattern and flow characteristics were examined in terms of design parameters such as extruded length ratio etc. Based on the simulation results, die pressure exerted on the die-workpiece interface is calculated and anaylsied for safe tooling. Therefore the numerical simulation works provide a combined extrusion process of stable cold forging process planning to avoid the severe damages on the tool.
Stability and Structures of Constitutional Defects in Nonstoichiometric Intermetallic Compounds by First-Principles Calculations
Authors: Mizuno Masataka , Araki Hideki , Shirai Yasuharu
Published: March 2009

Some of intermetallic compounds exist in a wide range of concentration around the
stoichiometric composition. First-principles electronic structure calculations have been performed for constitutional defects in non-stoichiometric CoAl and CoTi in order to investigate their stabilities and structural relaxations induced by constitutional defects. For the evaluation of stabilities of constitutional defects, the compositional dependence curves both of formation energies and of lattice parameters are obtained by the calculations employing supercells in various sizes. The lattice relaxations around constitutional defects are discussed by analyzing the change in electronic structures induced by constitutional defects.
Atomic-Scale Computer Simulation of Mixture Precipitation Mechanism for Ni75AlxV25-x Alloy
Authors: Zhao Yu Hong , Ju Dong Ying , Hou Hua
Published: March 2009

With the microscopic phase-field model, the early precipitation mechanisms of the
ternary Ni75AlxV25-x alloys with middle Al composition were explored by computer simulation in this paper. Through the simulated atomic pictures and composition order parameters of precipitates, we can explain the complex precipitation mechanisms of θ (Ni3V) and γ′ (Ni3Al) ordered phases. Simulated results also show that the precipitation characteristic of γ′ phase transforms from
non-classical nucleation and growth to congruent ordering + Spinodal decomposition gradually, otherwise, the precipitation characteristic of θ phase transforms from congruent ordering + Spinodal decomposition to non-classical nucleation and growth mechanism gradually.
Alloying Effect on the Electronic Structure of LaNi5-Based Hydrogen Storage Alloys
Authors: Lin Yu Fang , Zhao Dongliang , Wang Xin Lin
Published: March 2009

Employing the first principles discrete variational method(DVM), we investigated the electronic structure of LaNi5 hydrogen storage alloys containing various alloying elements, M=Mn,Fe,Co. The results showed that s electrons of H mainly interact with s electrons of hydride-non-forming element Ni, though hydride forming element La have stronger affinity to hydrogen atom. And alloying elements strengthened the bond between B-H, so decreased the capacity of doped-system.
Electron Structure and Interface Energy of GP Zone in Al-Zn Alloy
Authors: Gao Ying Jun , Han Yongjian
Published: March 2009

The valence electron structure of GP Zone in Al-Zn alloy was calculated according to the Empirical Electron Theory(EET). The result of valence electron structure was further applied to analyze the interface energy between GP Zone and matrix. The reason that the GP Zones were formed even at the highest quenching speed and the hardness was stably ascended as soon as GP zones were formed and reached the maximum before the precipitation of metastable phase, was that
the amoumt of the strongest covalent bond in the GP Zone was far more than that in α-Al cell and the Al atom in GP Zone was easily prone to forming covalent bond with Zn atom. It was an easy and effective method to apply the EET theory with the hardball model to calculation of interface energy.
Thermo-Calc Program Interface and Their Applications - Direct Insertion of Thermodynamic and Kinetic Data into Modelling of Materials Processing, Structure and Property
Authors: Chen Qing , Engström Anders , Höglund Lars , Strandlund Henrik , Sundman Bo
Published: March 2009

Thermodynamic and kinetic data are generally essential for quantitative modeling of
materials processing, structure, and property. Thermo-Calc program interfaces, including TQ, TCAPI, and TC MATLAB Toolbox, provides a hierarchy of APIs for application programmers to access thermodynamic and kinetic data via the kernel of Thermo-Calc and DICTRA, the most widely used software and database system for multi-component phase equilibrium and phase transformation calculations. With these program interfaces, variation of thermodynamic and kinetic properties can be directly obtained in real time as the local temperature, pressure, or composition
changes. The structure and usage of the Thermo-Calc program interfaces will be introduced in this article. Successful application examples will be illustrated.
Simulation and Determination of the Goss Texture in Grain-Oriented Silicon Steel
Authors: Chen Leng , Mao Wei Min
Published: March 2009

A new approach to simulating the orientation distribution function (ODF) using one
diffraction frame collected by X-ray two-dimensional detector is proposed. Based on the concept that the texture component presents a normal distribution form, the volume fraction and the orientation spread of texture component are obtained using curve fitting method from diffraction profile and, the pole figures as well as ODF can be calculated. Thus the texture of grain-oriented silicon steel is determined rapidly and conveniently. A comparison of the simulation ODF with that reconstructed from experimental pole figures by series expansion is presented and the results show
that the new approach works correctly.
Study for Step Instabilities Induced by ES Barrier
Authors: Kim Jin You , Yeon Dong Hee , Cha Pil Ryung , Yoon Jong Kyu
Published: March 2009

A phase field model for step dynamics on vicinal surface is presented. Using this model, time dependent, collective motions of steps were investigated. Through numerical simulations, morphological step instabilities induced by ES barrier were analyzed, and it is shown that this model could interpret various phenomena during step flow growth such as step bunching and meandering.
Production and Mechanical Properties of In-Situ Ti Alloying A356 Alloys
Authors: Liu Zhong Xia , Wang Ming Xing , Song Tian Fu , Weng Yong Gang , Xie Jing Pei , Liu Zhi Yong
Published: March 2009

The in-situ Ti alloying of low-Ti Al alloys and their application in A356 alloys were
studied. The results show that the currency efficiency is comparable to that of pure Al, which is about 92%. The absorptivity of Ti is over 95%. Such obtained A356 alloys with different Ti content have excellent grain refinement effect and fading resistance comparing with the tradition A356 alloys. The refinement of grain always companies the refinement of Si particles. The strength is comparable to that of the tradition A356 alloys whether the alloys are unmodified or modified with Sr, but the ductility and quality index are superior to that of the tradition A356 alloys. The alloys
with 0.1%Ti have the optimal mechanical properties.
Analysis of Alligatoring Behavior during Roll Pressing of DRI Powder with Flat Roller and Indentation-Type Roller
Authors: Joo S.H. , Chang H.J. , Bang Woong Ho , Han Heung Nam , Oh Kyu Hwan
Published: March 2009

A computational model for roll pressing of powder was developed based on an
elastoplastic finite element method, and was applied to predict the alligatoring behavior at roll nip during powder compacting process. The yield criterion for powder has been implanted for the simulation of the roll pressing of Direct Reduced Iron powder with both flat roller and indentationtype roller. Calculated results could well explain the experimental observation that the indentationtype roller is more useful to hinder in alligatoring.
Rigid-Plastic Finite Element Analysis Applied Frictional Contact Problem in the Composite Rod Extrusion Process
Authors: Jo S.H. , Hwang Sun Keun , Choi Hyoung Jin , Hwang Beong Bok , Ko B.D.
Published: March 2009

This paper presents the plastic deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. In this study, the finite element code, DEFORM commercial package, considering frictional contact problem was used to analyze the effects for the diameter ratio of the core to sleeve layer on the material flow. Different cases of initial composite material are simulated under different conditions of extrusion process, which includes the semi-die angle, reduction in area and end distance, from the end of sleeve to the end of core, with constant value of reduction area, die corner radius and die land. The main design parameters influencing on deformation pattern are diameter ratio of the composite components and semi-die angle. Simulation results indicate that there is an obvious difference of forming pattern with various
diameter ration and semi-die angle. The predicted forming load, the end distance and outer radius of sleeve of the rods are also obtained from numerical results. The analysis in this paper is concentrated on the evaluation of the design parameters on the deformation pattern of composite rod.
Tension-Compression Asymmetry in Plasticity Modeling of a Single Crystal Superalloy Using a "Unit Cell" Approach
Authors: Choi Y.S. , Parthasarathy T.A. , Dimiduk D.M. , Uchic M.D.
Published: March 2009

The [001] tensile and compressive flow behavior of a single crystal superalloy CMSX-4 was simulated using a “unit-cell” mesh to represent the γ/γ′ microstructure. The simulation results showed a tension-compression (T-C) asymmetry, where the magnitude of the flow stress is larger in the elastic-plastic transition regime in tension, and is larger in compression in the plastic (flow
softening) regime. The T-C flow behavior was related to the flow response of the γ-phase matrix under the geometric and kinematic constraint of the γ/γ′ unit cell.
Dissociated Domain Boundaries Attached to Meta-Dislocations in a Structurally Complicated Alloy Phase ξ'-Al-Pd-Mn
Authors: He T. , Sun W. , Zhang Z.
Published: March 2009

Dissociated domain boundaries (DBs) attached to meta-dislocations have been found in a structurally complicated alloy phase (SCAP) of ξ'-Al-Pd-Mn. On the basis of HREM observations and theoretical simulation, a structure model of DBs is proposed. The displacement vector R for the DB is determined to be 1/2 [1, 0, 1/τ] with a length of 12.37 Å.
Formation and Optimization of Cu-Based Cu-Zr-Al Bulk Metallic Glasses
Authors: Wang Qing , Qiang Jian Bing , Wang Ying Min , Xia Jun Hai , Zhang Xin Fang , Dong Chuang
Published: March 2009

The present paper covers in a comprehensive manner the formation of the Cu-based Cu-Zr-Al bulk metallic glasses (BMGs). Composition optimization for BMG formation is realized by using an “e/a-variant criterion”. This criterion is incorporated into the ternary phase diagram by a straight composition line, which is defined by linking a specific binary composition to the third element. There e/a-variant composition lines are constructed: (Cu9Zr4)1-xAl, (Cu61.8Zr38.2)1-xAlx and (Cu56Zr44)1-xAlx, where Cu9Zr4, Cu61.8Zr38.2 and Cu56Zr44 are specific cluster compositions in the Cu-rich Cu-Zr binary system. No Cu-based BMGs are obtained in the composition line (Cu9Zr4)1-xAlx using our suction casting techniques, while BMGs are obtained within an e/a span from 1.24 to 1.3
and from 1.28 to 1.36 respectively along the other two lines (Cu61.8Zr38.2)1-xAlx and (Cu56Zr44)1-xAlx. Thermal analysis results indicate that the BMGs on every composition line manifest increased thermal stability and glass forming ability (GFA) with increasing e/a ratios. The maximum appears in Cu58.1Zr35.9Al6 with the e/a value of 1.3, which belongs to the (Cu61.8Zr38.2)1-xAlx series. The
characteristic thermal parameters of this BMG are Tg = 760K, Tg/Tm = 0.659 and Tg/Tl = 0.648, which are all superior to those reported for the known Cu55Zr40Al5 BMG.
The Comparison Study of Field Emission Characteristics from (002)-Oriented AlN and W Tip
Authors: Yue Shuang Lin , Zhi C.Y. , Gu Chang Zhi
Published: March 2009

By using radio frequency magnetron reactive sputtering system, (002)-oriented AlN film was deposited on W tip. The field emission from (002)-oriented AlN film on W tip was studied and compared with that from the bare W tip in a high vacuum (≤10-6 Pa) chamber. It indicated that the enhanced electron emission could be obtained from the (002)-oriented AlN film on W tip. The corresponding Fowler-Nordheim plot of AlN presented a nonlinear behavior in nature related the
high resistivity of AlN. Furthermore, the current-electric field (I-E) curve presented excellent reproducibility checked by repeated measurements.
Preparation of Diamond Film Coatings on Multi-Spectrum ZnS
Authors: Lu Fan Xiu , Tong Yu Mei , Gao X.H. , Tang Wei Zhong , Li Cheng Ming , Chen Guang Chao
Published: March 2009

In the present investigation a specially designed ceramic interlayer, which is able to supply suitable protection of the ZnS substrate against chemical attack by atomic hydrogen, and is helpful to reduce the thermal stress, has been developed. Nano-crystalline diamond films were successfully deposited on to the pre-coated multi-spectrum ZnS. It was found that diamond nucleation on the ceramic interlayer could be greatly enhanced by a metal or semiconductor mask placed on top of the
pre-coated ZnS substrate, whereas diamond nucleation will not happen even by long time seeding in ultrasonic bath with fine diamond powder suspension. It was found that diamond nucleation is induced by the presence of the metal or semiconductor mask. To our knowledge this kind of phenomena of induced nucleation has not been reported. Detailed results and discussions were
presented.
Fabrication of Structure-Designed Free-Standing Diamond Film
Authors: Zhou Y.L. , Chen Guang Chao , Chen Guoan , Li Cheng Ming , Tong Yu Mei , Lu Fan Xiu
Published: March 2009

Structure-designed free-standing diamond films have been fabricated by DC plasma jet method. The different dominant crystalline surface distributions were obtained under different deposition conditions. The as-grown films were polished by thermal chemical method. For the same crystalline structure, the removal rate was strongly affected by polishing parameters, such as polishing temperature, polishing time and applied pressure. The experimental results also showed that the dominant surface distribution in the films affected the polishing removal rate very much.
Microstructures and Properties of the DLC Films Prepared by PLD Process Using High Power High Frequency 308 nm Laser Beam
Authors: Peng Hong Yan , Zhao Li Xin , Jin Zeng Sun , Chen Bao Ling , Zhang Bing , Zhou Chuansheng , Zhang Mei Heng , Yang Xinghui
Published: March 2009

DLC and nanocrystalline diamond films were prepared by PLD process using 308
nm(XeCl) laser beam with high power(200-500 W) and high frequency(200-500 Hz). The effects of some parameters such as the laser power density, the repetition rate on the structures and characters of the DLC films under such extreme power and repetition rate conditions were studied for the first
time. The results indicated that: (1) The microstructures of the films were varied from amorphous to nanocrystalline with the laser power density increased from 108 W/cm2 to 1010 W/cm2; (2) The properties of the films grew at 200 Hz and 300 Hz were better than that of the films grew at 500 Hz, with the laser power density remained constant at 1010 W/cm2.