bluuebunny/crossref_metadata_2025 huggingface dataset:
Microscopic Investigation of Strain Localization and Fatigue Damage in Thin Cu Films
Authors: Zhang G.P. , Volkert Cynthia A. , Schwaiger Ruth , Kraft Oliver
Published: March 2009

Fatigue damage behaviour in micron and sub-micron thick Cu films has been
investigated using focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). The observations show that cyclic strain localization in the fatigued thin films is affected by the physical dimensions of the material, as evidenced by changes in the extrusion dimensions and by changes in the dislocation structures. The significant decrease in extrusion dimensions and the
suppression of the development of bulk-like dislocation structures with decreasing film thickness and grain size is attributed to the strong inhibition of dislocation mobility and activity at small length scales.
Effect of Annealing Temperature on Characteristics of Ni76Fe24 Films Deposited on SiO2/Si(100) by DC Magnetron Co-Sputtering
Authors: Chen Xiao Bai , Qiu Hong , Qian Hao , Wu Ping , Wang Feng Ping , Pan Liqing , Tian Yue
Published: March 2009

185 nm-thick Ni76Fe24 films were deposited on SiO2/Si(100) substrates at room
temperature by DC magnetron co-sputtering and they were annealed in a vacuum of 5×10-4 Pa at 300 , 400 and 480 °C for 1 hour, respectively. The as-deposited film grows with thin columnar grains and has void networks in the grain boundaries. As the annealing temperature increases, the grain size gradually increases and the void networks decrease. Besides, the void networks shorten and widen
with annealing temperature. The resistivity of the film decreases with increasing annealing temperature. The magnetic hysteresis loop of the as-deposited film shows a hard magnetization requiring a saturation field of 1050 Oe while that of the film annealed at 480 °C represents an easy magnetization. For the film annealed at 480 °C the coercivity is 78 Oe and the ratio of remanent magnetization to saturation magnetization is 0.72. The as-deposited and annealed films have an isotropic magnetization characteristic.
Studies on the Heterostructure of Fe Film on Si Substrate
Authors: Ge Y.F. , Zhang Rong , Xiu Xiang Qian , Xie Zi Li , Gu Shu Lin , Shi Yi , Zheng You Dou
Published: March 2009

Fe films have been grown on different oriented Si substrates by metal organic chemical vapor deposition (MOCVD), and then samples are put in the air without any protection for nearly fifteen years. In this paper, using methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM), we make a detailed research on the
samples. We identify the composition and structure of the epitaxial films on different oriented substrates and compare the difference both in composition and magnetic properties. Different orientation of the substrates results in different epitaxial film with different characteristic. We also confirm the existence of single crystal iron in the heteroepitaxial film grown on Si (001), and discuss the possible reason why the single crystal iron film still exists without complete oxidation in air for such a long time.
The Evaluation of Elastic Modulus at Grain Boundaries for Polycrystalline Materials
Authors: Zheng Lei , Deng Q. , Xu Ting Dong
Published: March 2009

The elastic modulus in the region of a grain boundary for a commercial 2.6Ni-Cr-Mo-V steel has been obtained from Misra’s observation of grain-boundary segregation of sulphur under a tensile stress. The result is in agreement with the theoretical estimation.
Distribution of Plane Matching Boundaries for Different Types and Sharpness of Textures
Authors: Kawahara Koichi , Ibaraki Ken-ichiro , Tsurekawa Sadahiro , Watanabe Tadao
Published: March 2009

The stability of the plane matching boundary is discussed in connection with the
deviation from the exact plane matching orientation and the atomic density per unit area of the lattice plane. The statistic calculation of the plane matching boundary distribution in the different types and sharpness of texture revealed that the coverage by plane matching boundaries (>80%) is much higher than the coverage by CSL boundaries (~60%). The sharpness of texture strongly
affects the distribution of plane matching boundaries.
Study of Electronic Structure In Ni3Fe/Al2O3/Ni3Fe Magnetic Tunnel Junction with Various Ferromagnetic Layer Thicknesses
Authors: Zhou Yuan , Bi Xiao Fang , Shang Jia Xiang , Xu Hui Bin
Published: March 2009

A series models of Ni3Fe/Al2O3/Ni3Fe magnetic tunnel junction with Al-terminated
interfaces have been established for investigating the influence of ferromagnetic layer thickness on the electronic structure, employing first-principle methods based on local spin-density approximation theory. The spin polarization of the interfacial Ni3Fe monolayer shows a maximum value as the thickness of ferromagnetic layer increases. The Al monolayers at the ferromagnetic/insulating interface and the O monolayer in the interior of insulating layer are also studied in terms of the change
of spin polarization with the ferromagnetic layer thickness. In addition, we have found that the structure of Ni3Fe monolayer has a great influence on the spin polarization.
Mechanical and Tribological Properties of Ti6Al4V Hardened by Double Glow Plasma Hydrogen-Free Carbonitriding
Authors: Zhang Gao Hui , He Zhi Yong , Pan Jun De , Zhang Ping Ze , Xu Zhong
Published: March 2009

By means of double glow plasma surface alloying process, Ti6Al4V surface was
successively carbonitrided forming a layer with special physical and chemical properties. The depth profile of C and N elements showed a tendency of gradual decrease on the Ti6Al4V as well as the depth profile of its hardness. Friction and wear test indicate that the wear resistant property is increased greatly after carbonitriding the Ti6Al4V.
Plasma Surface Alloying W-Mo Low-Alloy HSS
Authors: Xu Jin Yong , Liu Yan Ping , Gao Yuan , Xu Zhong
Published: March 2009

The plasma surface alloying low-alloy high speed steel (HSS) is carried out in vacuum chamber where a source electrode (W-Mo) and a work piece are properly placed. By using the sputter of glow-discharge, under the common function of electric field and temperature field, the desired alloying elements (W- Mo) are sputtered from the source cathode, traveling toward the
substrate. Subsequently the alloying elements deposit onto the surface of the substrate, forming alloy diffusion layer which the depth may vary from several micron to several hundreds micron. In the end a surface low-alloy HSS steel would be produced after ultra-saturation ion carbonization. The composition of the alloyed layer is equal or similar with it of low-alloy HSS. The carbonized layer, without coarse eutectic ledeburite structure, possesses high density of finely and dispersed
alloy carbides with tungsten equivalent 10% above and a significant improvement in surface hardness and wear resistance. The principle of plasma surface alloying and its test results and commercial products application are introduced in this paper.
Improving the Microwave Absorbing Property of Fiber Reinforced/Resin by Surface Modification of Fiber through Ion Implantation
Authors: Bi Yun Fei , Tao Ye , Liu Pei Ying
Published: March 2009

Metal ions were implanted into the surface of fiber with metal vapor vacuum arc source implanter. The resin matrix composite was made of the surface modified fibers. The microwave absorbing property of the composite was measured. It is shown that the microwave absorbing property of the composite was improved effectively by the ion implantation and the extreme reflectivity reached -6.13dB. The paper studied the microwave absorbing property of the composite material treated by ion impregnation and discussed mechanism.
The Influence of Impulse Electroless Plating on Amorphous Ni-P Alloys in Structure and Hot Stability
Authors: Liu Yan Ping , Zhang Yan Mei , Gao Yuan , Xu Zhong
Published: March 2009

Using a special impulse device, the impulse electroless Ni-P alloy plating were
prepared. The microstructure、crystallization and the starting activation energy for crystallization was investigated by TEM、XRD and DTA, compared with electroless Ni-P alloys plating. The results showed that the diffractive ring was wider when using impulse, depositing temperature dropped up to 65°C,and crystallization temperature rose up to 310°C. Furthermore , the starting activation energy for crystallization and crystallization temperature of impulse electroless Ni-P
alloys plating measured were more than that of electroless plating in the heating rate at 5、10、20、 40K/min, and it was also higher in the amorphous disorder degree and the starting crystallization temperature. Impulse electroless Ni-P alloys plating had better performance of thermal stability.
The Effect of Electromagnetic Vibration on the Continuous Elimination of Inclusions in Molten Aluminum Alloy by Electromagnetic Force
Authors: Kim Y.G. , Choi Jung Pyung , Park Joon Pyo , Kim Ki Bae , Yoon Eui Pak , Nam T.W.
Published: March 2009

The separation system including a DC electric field with steady magnetic field was
adopted for removal of inclusion in molten Al alloy. But, very small inclusions, which less than 10 ㎛ are not eliminated. So, firstly, small inclusions are agglomerated by low frequency electromagnetic vibration. And then, we adopting the previously used electromagnetically inclusion removal process. Experiments were carried out on commercial die casting aluminum alloy A380 (JIS: ADC 10). Inclusion was separated continuously. XRF was used for compositional test and PoDFA for cleanliness test. Chemical composition of specimen was not changed and UTS,
elongation and cleanliness were increased.
Electron Holography Characterization of Potential Barrier in a Spin Valve Structure with Nano-Oxide Layers
Authors: Wang Y.G.
Published: March 2009

The potential barrier at the metal/oxide junction in a specular spin valve structure with nano-oxide layers has been mapped by off-axis electron holography in a field emission gun transmission electron microscope. A potential jump of ~3V across the metal/oxide junction was detected. Presence of the potential barrier confirms formation of metal/insulator/metal structure, which contributes to confinement of conductance electrons with spin polarity characteristic in the key SV structure by the specular reflection of the spin-polarized electrons at the metal/oxide junction and
leads to nearly double enhancement of magnetoresistance (MR) ratio from 8% to ~16%.
Effect of Inhomogeneity of Carbide Precipitation on Nanohardness Distribution for Martensitic Steels
Authors: Li Jin Xu , Ohmura Takahito , Wei Fu Gao , Tsuzaki Kaneaki
Published: March 2009

Nanoindentation technique was applied to evaluate nanohardness distribution in a submicron scale for two kinds of martensitic steels: Fe-0.4C binary steel and Fe-0.05C-0.22Ti steel with a stoichiometric composition of TiC. AFM images showed that Fe-C steel includes relatively coarse cementite particles with about 100~200 nm in diameter and a couple of hundreds nanometer in average spacing, while high-resolution TEM observation showed that the Fe-C-Ti steel has fine TiC precipitates with 5 nm in diameter and 15 nm for average spacing. Nanoindentation results
revealed that the standard deviation was much higher for the Fe-C than that for the Fe-C-Ti. Since the typical indent size was a couple of hundreds nanometer, which was about two orders larger than the size of the TiC and comparable to the cementite size, the small distribution of nanohardness of the Fe-C-Ti was attributed to the homogeneous microstructure in sub-micron scale, while the inhomogeneity of cementite particles in the Fe-C steel leaded to large nanohardness.
Evaluation of Grain Boundary Effect on the Strength of Fe-C Martensitic Steels through Nanoindentation Technique
Authors: Ohmura Takahito , Tsuzaki Kaneaki
Published: March 2009

Nanoindentation measurements were performed for Fe-C based martensitic steels,
and then the strengthening factors such as grain boundary effect were evaluated.
Nanohardness of the matrix of the martensite is lower than that expected from macroscopic hardness, indicating that the grain boundary effect is significant for the macroscopic strength of the Fe-C martensite. A remarkable decrease of the grain boundary effect was found at the tempering temperature of 673 K, which is due to a disappearance of film-like carbides on grain boundaries. These results will be discussed in light of the interpretations of grain boundary strengthening.
The Effect of Frequency of Electromagnetic Vibration on the Primary Silicon Size in Hypereutectic Al-Si Alloy
Authors: Yoon Eui Pak , Choi Jung Pyung , Park Joon Pyo , Kim Ki Bae , Yoon W.Y. , Kim Myung Ho , Kim Kwon H. , Nam T.W.
Published: March 2009

In this study, the electromagnetic vibration is adopted for control of the size of primary Si phase. The higher the current density and frequency of electromagnetic vibration (EMV), the finer the size of primary Si phase. The higher the current density but the lower frequency of EMV, the bigger the size of primary Si phase. This phenomenon considered to be related the collision, agglomeration and diffusion of silicon atoms.
High-Temperature Wear Properties of the Nitrided Alloys for Steam Turbine Valve System Parts
Authors: Kim I.S. , Kim H.S. , Hur I.C. , Son K.S. , Lee Je Hyun , Yoon J.H. , Kim H.S.
Published: March 2009

ASTM A355, SUS422 and Nimonic 901 steel were nitrided and their wear characteristics such as the wear coefficient, amount of wear, shape and composition of wear debris were evaluated. Fe3N and Fe4N were observed in the nitrided layer of ASTM A355. Fe3N, Fe4N and CrN were appeared in the nitride of SUS422. However, only CrN phase was observed in the layer of Nimonic
901. The amount of wear and wear coefficient for the nitride specimen decreased remarkably compared with non-nitrided specimens. Also, the surface hardness and ductility increased and small debris was formed in the nitrided specimen.
Characteristics of Photocatalytic Titania Fabricated by Anodization
Authors: Lee J.H. , Oh H.J. , Jeong Y. , Lee Y.J. , Kim J.S. , Chi C.-S.
Published: March 2009

The anodic titanium dioxide (TiO2) films for photocatalyst were prepared by anodization in acid solution. The characteristics of surface layer and the photocatalytic efficiency of the anodic film have been investigated. The chemical states of anodic film were analyzed using XPS, and the photocatalytic efficiency was evaluated by the degradation rate of aniline blue. From XPS results the
component elements of the electrolyte, P and S, were observed in the anodic film, which were incorporated from the electrolyte into the oxide layer during anodization. The porous TiO2 film exhibited high photocatalytic efficiency for degradation of aniline blue.
The Effect of the Graphitizing Heat Treatment and Boron Content on Boron Distribution in High Carbon Steel
Authors: Woo Kee Do , Kim S.W. , Kim Dong Ki
Published: March 2009

It is convenient to analyze the distribution of boron in high carbon steel with boron,
simply using neutron-induced radiography with a neutron fluency of 1.9 x 1013 [cm-2]. It was revealed by the neutron-induced radiography that the distribution of boron was dependent on boron contents, graphitizing temperature and time. The density of boron track increased with increasing boron contents. But the density of the boron track and graphite in high carbon steel graphitized at 700°C is higher than that of high carbon steel graphitized at 750°C. The density of graphite in high carbon steel also depends upon the content of boron and the graphitizing temperature. The shape of the boron track was changed from sphere to rod type when annealed at 800°C, in steel containing 50ppm of boron, due to different phases of boride. The distribution of boron segregation or boronrich precipitates in high carbon steel was well documented with a neutron-induced radiography, but the direct relationship between graphite and boron was not clarified by it. Furthermore, the analysis
of electron probe X-ray microanalyzer (EPMA) also showed that the high amount of boron coexisted with carbon in graphite in high carbon steel.
The Forming Characteristics of Simultaneous Radial-Forward Extrusion Processes
Authors: Hwang Sun Keun , Jang D.H. , Ko B.D. , Hwang Beong Bok
Published: March 2009

Numerical simulations are applied to investigate the simultaneous radial-forward extrusion process in a combined extrusion such as subsequent radial-forward extrusion after radial extrusion. Design factors for the process such as gap height, deflection angle into annular gap and frictional condition are employed in the analysis. The analysis is focused to see the influence of design factors
on the maximum force requirement for the forming process. One of the selected simulation results is compared with the experiments in terms of load-stroke relationships. The pressure distributions exerted on the die-wall interfaces are also investigated to reveal if the tooling system is safe, especially the die set. The plastic stress-strain relationship is derived analytically from the material constants used in elastic deformation analysis. It is revealed from the simulation results that the
influence of the deflection angle on the maximum force requirement for the process is greatest among design parameters. AA 6063 alloy is selected as a model material for the analyses in this study.
Flux Growth and Dielectric Properties of Relaxor-Based Pb(In1/2Nb1/2)O3-PbTiO3 Single Crystals
Authors: Fan Hui Qing
Published: March 2009

Relaxor-based piezoelectric single crystals of lead indium niobate-lead titanate
(0.63Pb(In1/2Nb1/2)-0.37PbTiO3, abbreviated as PIN-PT), in the vicinity of the morphotropic phase boundary, were prepared by a flux method. The compositions of the flux, Pb3O4 or PbF2, play different role in perovskite stability and phase development. Thus, pure perovskite PIN-PT single crystals with the size of 2~5 mm were obtained by using Pb3O4 flux as well as a small amount of B2O3
additive. The microstructure and the phase development of the as-grown single crystals were investigated by scanning electron microscopy and transmission electron microscopy and X-ray diffraction. Furthermore, the dielectric properties of the <100>-oriented PIN-PT single crystals were measured in the temperature range between 20°C and 400°C.
A Process Sequence Design of Multi-Step Cold Extrusion Process for Hollow Parts
Authors: Shim Jae Hyun , Ok J.H. , Choi Hyoung Jin , Koo H.S. , Hwang Beong Bok
Published: March 2009

Conventional multi-step extrusion processes with solid billet are examined by the
rigid-plastic finite element method in order to provide criteria for new process sequence for hollow parts. Two examples are taken for the analyses such as the current three-stage cold extrusion process for a hollow flange part and five-stage process for manufacturing an axle housing. Based on the results of simulation of the current three-stage and five-stage manufacturing processes, new design
strategy for improving the process sequences is developed simply by replacing the initial billet from solid to hollow one. The developed new process sequences are applied for simulation by FEM and they are compared with the existing processes to confirm the usefulness of new process sequences with hollow initial billets. The results of simulation show that the newly proposed process sequences
with hollow billet instead of solid one are more economical way to manufacture required parts, respectively.
Localized Deformation of Equal Channel Angular Extruded Aluminum
Authors: Yang Fuqian , Peng Lingling , Okazaki Kenji
Published: March 2009

The localized deformation behavior of annealed Al and Al severely deformed by ECAE process was determined by using microindentation test. Using the method proposed by Tabor, the indentation stress-strain curves of annealed Al and as-ECAE deformed Al were constructed, which display similar work-hardening behavior. For annealed Al, the altitude of the indentation stressstrain curves is a function of the indenter size. A master curve then is constructed, which displays
different work-hardening behavior. For the ECAE deformed Al, the indentation stress-strain curves are independent of the indenter size, suggesting that the microstructure inside the as-ECAE deformed Al is different from the annealed Al.
Well-Ordered Self-Assembly Growth of Strain-Modulated SrTiO3 Thin Films: Templates for Complex Oxide Quantum Wires
Authors: Li Yan Rong , Li Jin Long , Zhang Ying , Deng Xin Wu , Yang Fan , Fei Wei Dong
Published: March 2009

Well-ordered self-assembled SrTiO3 thin film, as a template for complex oxide quantum wires, was fabricated on LaAlO3 (100) single crystal substrates with laser molecular beam epitaxy. The self-assembled growth was in-situ monitored by reflective high energy electron diffraction. The morphology evolutions of the films as a function of thickness were studied by ex-situ atomic force microscopy. As the thickness of the films increased from 3.875nm to 46.5nm gradually, the
compressive stress-induced SrTiO3 films exhibited a periodic well-ordered ripple structure, which formed a unique nanoassembled template for the fabrication of quantum wires. Small angle X-ray scattering technique was employed to investigate the structure. Symmetric satellite peaks were discovered, indicating the well-ordered superstructure. In contrast, the similar superstructure was not observed during the growth of the tensile stress-induced LaAlO3 films on SrTiO3 substrates.
The Compressive stress was considered as the main reason of the self-assembled growth, and systematical elucidation about strain mechanism was discussed. These results might provide an efficient method for the controllable formation of well-aligned template of quantum wire for complex oxide with desirable structure via proper modulation of strains.
A Simplified Model for Velocity and Temperature Evolution of Alloy Droplets in Centrifugal Atomisation and Spray Deposition
Authors: Zhao Y.Y.
Published: March 2009

A model has been developed for the velocity and temperature evolution of a metal alloy droplet with travel distance in centrifugal atomisation. The droplet velocity decreases rapidly with increasing travel distance. The degree of droplet cooling at a certain travel distance decreases with increasing droplet velocity, increasing diameter and decreasing temperature, and is also affected by the droplet physical properties. The solidification of the droplets is largely dependent upon the latent heat removal.
Effect of Section Thicknesses on Tensile Behavior and Microstructure of High Pressure Die Cast Magnesium Alloy AM50
Authors: Zhou Ming , Li Nai Yi , Hu Henry
Published: March 2009

High pressure die cast magnesium alloy AM50 is currently used extensively in complex shaped automotive components with various cross-section thicknesses. Understanding of the effect of section thicknesses on mechanical behavior of AM50 is critical for proper design of different applications. In the present study, magnesium alloy AM50 was high pressure die cast into rectangular coupons with section thicknesses of 2, 6 and 10 mm. The prepared coupons were tensile tested at room temperature. Microstructure analysis and porosity measurement were performed on
the representative specimens. The results of tensile testing show that the tensile properties including yield strength (YS), ultimate tensile strength (UTS) and elongation(Ef) decreases with an increase in section thicknesses of die cast AM50. Microstructure and porosity analyses indicate that the observed tensile behavior of die cast AM50 is primarily attributed to the level of porosity which
resulted from entrapped gases during the high pressure die casting process.
Microstructure, Texture and Deformation Behavior of Lithium Containing Magnesium Alloys
Authors: Feng Lin Ping , Chen Bin , Liu Pei Ying , Zhou Tie Tao
Published: March 2009

In the present work the deformation behavior of magnesium alloys with different
lithium content has been investigated in terms of microstructures, crystal parameters, textures and mechanical properties. The lattice constants of a phase (hcp) determined by XRD varied with its lithium content and at the same time there are some changes in the texture composition. The plasticity would remarkably increase while b phase (bcc) becomes dominant in the microstructure of alloys.
Magnesium Foam Produced from Bulk AZ31 Magnesium Alloy Sheets
Authors: Kikuchi Yusuke , Kakehi Koji , Kitazono Koichi , Sato Eiichi , Kuribayashi Kazuhiko
Published: March 2009

Using commercial AZ31 magnesium alloy sheets, we produced a foamable preform sheet containing titanium hydride (TiH2) powder through diffusion-bonding and hot-rolling of four cycles. Heating the preform sheets in Ar atmosphere, we obtained closed-cell magnesium alloy foams with various porosities. The foamed specimen at 883 K showed the maximum porosities of 77%.
Development of Creep Resistant Mg Alloys
Authors: Kang Dae H. , Yoo Min S. , Park Sung S. , Kim Nack
Published: March 2009

A study has been made on the tensile and creep properties of squeeze and die cast Mg alloys, with emphasis on the effect of second phase particles. Two different microstructures were compared; the microstructure with thermally unstable particles along grain boundaries (AZ91 alloy) and the microstructure with thermally stable particles along grain boundaries as well as within matrix (MX alloy). The experimental MX alloy has equivalent room temperature tensile strength to AZ91
alloy with higher ductility. Moreover, elevated temperature tensile properties and creep resistance of MX alloy are higher than those of AZ91 alloy. Such improved properties of MX alloy over those of AZ91 alloy are due to the optimized microstructure of the former.
Grain Refinement and Texture Evolution in AZ31 Alloy during ECAP Process and Their Effects on Mechanical Properties
Authors: Kim H.S. , Jeong Hyo Tae , Jeong Ha Guk , Kim Woo Jin
Published: March 2009

The softening of fine-grained ECAPed AZ31 Mg alloys could be ascribed to the texture modification during ECAP. Lower ECAP temperature is more effective in refining the microstructure. The strength of the ECAPed AZ 31 Mg alloys increased with decrease in grain size when they have similar texture.
Current Research Situation and Development of Titanium Alloy in China in Recent Five Years
Authors: Zhao Yong Qing , Zhou Lian
Published: March 2009

China pays great attentions to the development of titanium alloys and their basic theory because of their excellent properties. New titanium alloys and their new basic theories developed in China in recent five years were reviewed, for example, high temperature Ti alloys, burn resistant titanium alloys, high strength and middle strength titanium alloys and so on. The developing directions in the next 5 to 10 years were forecast.
Growth of Single Crystals and Low Temperature Oxidation Behaviors of MoSi2 and NbSi2
Authors: Zhang Fang , Zhang Lan Ting , Yu Jin Xing , Wu Jian Sheng
Published: March 2009

In this paper, single crystals, around 8mm in diameter, of MoSi2 and NbSi2 have been grown by optical heating floating zone method. X-ray analysis confirmed that the as-grown ingots were single phase and single crystalline material. Oxidation behavior of the poly-crystalline and single crystalline MoSi2 and NbSi2 were characterized by measuring their weight changes as a function of exposure time. For arc-melted poly-crystalline samples, MoSi2 and NbSi2 fully turned into white powders after 160 and 3hrs exposure at 773K and 1023K respectively, which is known as the “pesting” phenomenon. As a comparison, no pesting was found in the dense spark plasma sintered (SPS) poly-crystalline samples and single crystals. The weight change of single crystals during exposure is found to be much lower than that of the SPS sample, indicating grain boundary plays an important role in the low temperature oxidation behavior of these two silicides.
Mechanical Anisotropy of NiAl Alloys Processed by Hot Hydrostatic Extrusion
Authors: Witczak Zbigniew , Witczak Przemysław , Jemielniak Ryszard
Published: March 2009

Mechanical properties of two stoichiometric NiAl intermetallic alloys processed by hot
hydrostatic extrusion were investigated. The ingots for extrusion process were produced both by casting and by powder metallurgy route in which the self-sustained high-temperature synthesis (SHS) of elemental powders was initialized by the process of extrusion itself. Elastic anisotropy of the obtained products were determined using a resonant ultrasound spectroscopy (RUS) in measurements of the elastic constants. The anisotropy of plastic properties was estimated from uniaxial compression tests on specimens cut off from the material in the main directions of previous deformation. An acoustic emission (AE) method of monitoring of the microcracking process in the material was used for estimation the role of cataclastic mechanism of deformation. The effect of annealing of extruded materials on their plastic behavior was roughly investigated.
Tensile Creep Behavior of NiAl-9Mo Eutectic Alloy
Authors: Ren Wei Li , Guo Jian Ting , Li Gu Song , Wu Jian Sheng
Published: March 2009

The tensile creep behavior of NiAl-9Mo eutectic alloy has been investigated over a stress range of 50 to 100MPa at the temperatures ranging from 850 to 950°C. All of the creep curves exhibit the very long steady-state stage. The creep parameters and TEM observations indicates the kinetics of the steady-state creep deformation is governed by dislocation climb in the NiAl matrix phase. The crack origination and development at the colony boundary results in the onset of tertiary creep stage and final fracture of the alloy.
High Temperature Oxidation of Ti45.4Al4.8Nb and Ti46Al2Mo2Nb Alloys
Authors: Kim J.W. , Lee Dong Bok
Published: March 2009

The Ti46Al2Nb2Mo and Ti45.4Al4.8Nb alloys were oxidized isothermally and cyclically in air between 800 and 1000oC, and their oxidation characteristics were investigated. Nb and Mo were beneficial to oxidation resistance. The initially formed thin TiO2-rich scale changed to an outer, superficial TiO2 layer, a thick Al2O3-rich middle layer, and an inner (TiO2-rich, Al2O3-deficient) layer, as the extent of oxidation progressed. The dissolved ions of Mo and Nb had a tendency to be
expelled from the outer TiO2 layer, which was formed by the outward diffusion of Ti ions, to the inner (TiO2-rich, Al2O3-deficient) layer, which was formed by the inward transport of oxygen, owing to the nobility of Mo and Nb when compared to Ti and Al.
Skull Variation during the Induction Skull Melting Processing of γ-TiAl Alloy
Authors: Guo Jing Jie , Liu G.H. , Su Yan Qing , Ding Hong Sheng , Jia Jun , Fu Heng Zhi
Published: March 2009

The ratio of skull weight to charge weight (Rs) and the skull size during the
induction skull melting (ISM) processing of TiAl alloy were investigated. The effects of inputting power, charge weight, and holding time on them were studied theoretically. An experiment was carried out. The theoretical and experimental results are in good agreement.
Effects of Cooling Rate on the Microstructure and Room Temperature Tensile Properties of Orthorhombic Ti-22Al-21Nb-1Ta-1W Alloy
Authors: Luo Dong , Cui Yu You , Yang Rui
Published: March 2009

In order to improve high temperature mechanical properties of Ti2AlNb based alloys,
alloying with a combination of Ta and W was studied in the on-going work. The effects of cooling rate after solution heat treatment on the room temperature mechanical properties have been reported in this paper. All samples were solid solution treated at near β transus temperature, cooled at different cooling rates, and then aged at subtransus temperature. Experimental results showed that, with increasing cooling rate, room temperature yield strength decreased sharply to a minimum value, and then increased. Change of elongation exhibits a trend opposite to yield strength. Microstructure of the alloy varied from near lamellar to lamellar plus Widmanstätten, and then to full Widmanstätten structure with the increase of cooling rate, and the faster the cooling rate, the finer the laths of the O phase. The samples with near lamellar microstructure obtained at the cooling rate of 6oC/min possess the best ductility but relatively low yield strength.
Microstructure Control of Co3AlC-Base Heat Resistant Alloys Using Optical Floating Zone Melting
Authors: Kimura Yoshisato , Sakai Kiichi , Teramoto Shinya , Mishima Yoshinao
Published: March 2009

Aiming for further improvement of mechanical properties of Co3AlC-based heat resistant alloys, microstructure control was conducted using optical floating zone (OFZ) melting. Unidirectional solidification was performed to align Co3AlC/a(Co) two-phase eutectic microstructure. Co3AlC single phase poly-crystal alloys were successfully fabricated for the first time by taking advantage of OFZ. Mechanical properties were evaluated for selected alloys by compression tests at ambient temperature, 1073 K and 1273 K. Excellent elevated temperature strength is achieved in Co3AlC single phase alloys and ductility is sufficiently improved in Co3AlC/a(Co) two-phase alloys.
Substructure Development in Rapidly Solidified B2-Type TiCo Ribbons
Authors: Yoshimi Kyosuke , Sung Minseok , Tsurekawa Sadahiro , Yamauchi Akira , Nakamura Ryusuke , Hanada Shuji , Kawahara Koichi , Watanabe Tadao
Published: March 2009

Substructure development through aging and annealing treatments was studied for
rapidly solidified TiCo ribbons using TEM. In as-spun ribbons, equiaxed grain structure was developed and its crystal structure was B2-ordered immediately after melt-spinning, while a small amount of fine precipitates existed as second phase. Some grains were dislocation-free but others contained a certain amount of curved or helical dislocations and loops. The dislocation density in the ribbons annealed at 700 °C for 24 h was obviously higher than those in the as-spun ribbons and the ribbons aged at 200 °C for 100 h. The increase of the dislocation density in the annealed ribbons would result from the absorption of excess vacancies. Therefore, the obtained results indicated that a large amount of supersaturated thermal vacancies were retained in TiCo as-spun ribbons by the rapid solidification.
Manufacture of Al/SiC Composites by Pressure Infiltration Process
Authors: Yin Fa Zhang , Jia Cheng Chang , Mei Xuezhen , Ye Bin , Ping Yanlei , Qu Xuan Hui
Published: March 2009

The SiCp performing sample was made first then Al/SiCp (65%) was manufactured. Appropriate component and proportion of binder and process parameters were selected to control the porosity. Debinding has succeeded by extractive and thermal debinding processes. SiCp preforming samples with good appearance, enough strength, and right porosity were obtained by pre-sintering process at 1100°C. Composites with high density and homogeneous microstructure were manufactured by pressure infiltration under 1050°C and 15MPa. The distribution of aluminium and silicon elements was homogeneous. The primary components of materials are aluminium, β-SiC and α-SiC. The thermal expand coefficient of composites is 8.0×10-6/°C at room temperature, which increases with temperature and reaches to 11.0×10-6/°C at 300°C. The density is 2.92g/cm3, and relative density is more than 97 %. The strength is about 500MPa, approaching to the upper limit of the theoretical value.
Bending Damage Evolution and Its Influence on Critical Current and N-Value of Bi2223/Ag Superconducting Composite Tape
Authors: Doko D. , Miyazaki N. , Ochiai Shojiro , Okuda Hiroshi , Oh Sang Soo , Tanaka Masashi , Hojo M. , Osamura Kozo
Published: March 2009

Bending behavior of Bi2223/Ag superconducting composite tapes, and the influence of the bending damages on critical superconducting current Ic and n-value that is a measure for the sharpness of the transition from super- to normal conduction, were studied. Following damages, responsible to the reduction in critical current at high bending strains, were observed. (i) Transverse and (ii) longitudinal crackings of the filaments, (iii) interfacial debonding between filaments and silver, and (iv) buckling in compression side. The damage of the filaments arose first locally,
resulting in a reduction of the Ic and n-value in the corresponding local portion. The overall Ic and n-values were determined by such a local portion. With increasing strain, the damage of the other portions arose successively, resulting in loss of superconductivity in all portions.
Processing and Microstructures of Tungsten/Copper Composites Produced by Plasma Spray and Cold Spray
Authors: Kang Suk Bong , Kang Hyun-Ki , Euh Kwang Jun
Published: March 2009

Tungsten/copper composites were produced using an agglomerated feedstock powder by plasma spray and cold spray. In the case of the plasma spray, the external feedstock injection (EFI) and the internal feedstock injection (IFI) were adopted to compare oxidation, microstructure, porosity, and tungsten recovery in the deposits. The IFI deposit had less oxidation, denser microstructure, and more tungsten retention compared to the EFI. Especially, more tungsten particles were melted from the IFI than from the EFI at input power of 25kW. Thermal expansion coefficient of plasma sprayed composite (72W/28Cu vol.%) was approximately 5.2x10-6/K. In the cold spray, no oxidation and more dense microstructures were observed with porosity of less than 1.0 vol.%. However lots of tungsten was lost due to insufficient plastic deformation.
Strengthening and Toughening Mechanisms of the Microalloying Non-Quenching and Tempering Steel
Authors: Huang Yun Hua , Zhang Yue , Zhai Hao , Zhou Cheng , He Jian
Published: March 2009

The microstructure of a microalloying non-quenching and tempering steel developed
recently was analyzed through OM, SEM and TEM, in order to find the strengthening and toughening mechanisms of the steel. All of the dislocations and subgrain boundaries in the grains, the martensite in the martensite-austenite islands of the grainy bainite structure, the dispersed phases in the grains and at the grain boundaries, and the grain size were observed and studied in our experiments. The results indicate that the strengthening results from phase transition, dislocation,
subgrain structure, dispersion phase and fined grain, and the toughness relates with the ferrite matrix consisting of the grainy bainite and the grain size of the steel. The mechanisms between the hot-rolled-and-cooled and the tempered steel are slightly different.
Numerical Estimation of Thermal Conductivity in Copper and Superalloy Matrix Composites
Authors: Alcaraz Diego , Alhama F.
Published: March 2009

Using a steady-state 2-D network model to simulate the thermal behaviour of copper and superalloy matrix composites, reinforced with different types of randomly distributed continuous fibers, the limit values of thermal conductivity are established for the analysed composites. A large number of random distributions for each matrix-fiber combination is tested to assess the accuracy of the numerical results. The influence of the type of fiber, its distribution and its proportion is shown graphically. Examples of continuous fiber metal matrix composites (continuous MMCs), such as those of copper and Incoloy 907 matrices, are studied.
Manganese Oxide Photodeposited onto Titanium Dioxide as a New Environmental Catalyst
Authors: Tateoka Ayumu , Sekine Yoshika , Tsuda Takamasa , Ohashi Takanobu
Published: March 2009

Authors have successfully synthesized a new environmental catalysis which reacted with harmful formaldehyde in air at room temperature. Although manganese oxide is practically used for a major ingredient of formaldehyde removing materials, intermediates such as formate formed on the surface reduced the removal efficiency. Then, manganese oxide was photodeposited onto the surface of titanium dioxide particles which could decompose certain organic compounds with UV irradiation. It was confirmed that the complex oxide decomposed formaldehyde into carbon dioxide at room temperature. Moreover, UV irradiation enhanced the production of the carbon dioxide.
Characteristics of Corona-Charged PET Sandwich Electrets
Authors: Tai L.S. , Wong Y.W. , Poon Y.M. , Shin F.G.
Published: March 2009

Polyethylene terephthalate (PET) is one of the major electret materials which has been studied and widely used in charge storage applications for a long time. The homo-charge and hetero-charge formation responsible for the electret effect of PET can be explained by the dipolar polarization, space charge separation and charge injection respectively as a result of contact poling or corona charging. These processes are also verifiable from studies of surface charges and thermally stimulated depolarization current (TSDC) of the PET films. Now consider a stack of PET films charged under the same condition as a single film. It would be intuitively expected that the electret effects of the individual films of the stack should be different due to their different positions in the stack. However, in a recent study on charged PET stacks, it was found that the electret effects of the individual films are quite similar. The surface charges of the individual films are about the same and they sum to make same total as a single charged PET film. On the other hand, the TSDC thermograms of individual films show similar characteristics in the thermal relaxation processes where homo- and hetero- charge effects are still observed. From the TSDC results, especially for the film in the middle of a triple layer sandwich, it shows clearly dipolar polarization and charge injection related peaks. These findings agree with the results of surface charge studies of the individual films.
A Comparative Study of Radon Retention Ability of Crystalline Apatite and Amorphous Oxide Materials
Authors: Boujrhal F.Z. , Hlil El Kebir , El Moursli R.Cherkaoui , El Khoukhi T. , Sghir B.
Published: March 2009

Comparative radon investigations of two natural materials, crystalline apatite and amorphous oxide, are presented here. The radon retention in the apatite (sedimentary apatite) is more than 70% of the total radon formed in the solid matrix. The amorphous oxide (gel hydrothermal alteration) retains only 7% of radon. The nature of the material which plays an important role in the radon diffusion is confirmed by heat treatment. The major and interesting result of this heat treatment is increasing of crystallite size. This phenomenon induces improvement on radon retention ability. To study these properties one uses a structure band calculations based on the Linear Combinations of Orbital Atomic (LCAO) method convenient numerically for the ionic systems.
Effect of Heat Treatment on TiNx Film Structure
Authors: Zerkout S. , Benkahoul M. , Sahraoui H. , Achour S. , Mosser A.
Published: March 2009

TiN films with different nitrogen contents were deposited on glass and Si (100) substrates by d. c. magnetron reactive sputtering. The structure of the films was determined by Xray diffraction. It was found that heat treatment at 773 decreased the lattice parameter. A considerable thermal instability of over-stoichiometric films was observed after annealing films in air. This instability enhanced with increasing nitrogen content and is characterized by an abundant appearance of clear and dark disks in Scanning Electron Microscopy (SEM). Also, it was shown that the film instability does not come from an interfacial reaction but was observed when the TiNx layers present a (200) preferred orientation together with high nitrogen content.
Effect of Laser Process Parameters on the Surface Absorbtivity
Authors: Demian Gabriela , Taca Mihaela , Gutu Iulian , Demian Mihai
Published: March 2009

Hardening laser surface offers new possibilities for the enhancement of the mechanical resistance of superficial layers. Essential for the laser treatment processes is the efficiency at which the incident laser power is coupled into the work piece. The aim of the work was to study the effect of some factors such as spot shape, beam angle of incidence and surface coating on the steel surface absorptivity. Samples made of carbon steel were laser processed using a CW CO2 - 1,2 kW laser unit. Different process parameters (beam power, spot dimension and traverse speed), were used. The microstructure of laser hardened layers which have been investigated by optical microscopy. The mechanical characterization of the layers has been done by hardness measurements. Correlation has been established between the structure of the laser-processed layers and the
process parameters.
Estimation of Selenium Consumption during Selenization of Cu-In Metallic Layer in a Quazi-Closed System
Authors: Kurdesau F. , Kaelin M.
Published: March 2009

Selenium vapour distribution and consumption during selenization process of Cu-In metallic layers provided in a quasi-closed system with inert gas environment at atmospheric pressure were studied. A model taking into account the four most important mechanisms of Se consumption, namely the creation and maintenance of Se vapour over-pressure, the out-diffusion through open boundaries of quasi-closed system, the drift transport by constant nitrogen flux and chemical reactions with Cu-In metallic layers, is developed to estimate the total amount of selenium required for selenization process. The diffusion mechanism was found to be dominating the selenium consumption for the used reactor design. Calculated values find a good agreement with experimental results from weighing of the Se source material before and after selenization.
Modification of Faceplates by Selective Chemical Etchings
Authors: González M. , Domenech M. , Lifante G.
Published: March 2009

The structuring of the inner surface of photocathode windows is of great interest with regard to the efficiency of photomultipliers. A way of increasing the number of photons absorbed by a given surface is to define periodic structures with a period lower or greater than the wavelength of light. Tailoring the structure of the surface to drastically reduce the reflectance, and thus increasing the effective absorption, is possible. Experiments have been conducted with fibre-optic faceplates of
imaging tubes. In this work, these structures have been developed by chemical etchants, which selectively react with the transmission fibres or matrix glasses.
Electric Charge Trapping and Transport at Medium Fields in Low-Density Polyethylene
Authors: Marat-Mendes José N. , Neagu Eugen R. , Neagu Rodica M.
Published: March 2009

The transient conductivity in low-density polyethylene is studied. Isochronal currentvoltage measurements for 1800 s and 1 day time intervals are carried out under dry N2 atmosphere. When after every measurement the sample is fully discharged at high temperature the isochronal current - voltage characteristic reveals an ohmic behavior. When the next field increase is applied without sample discharging the current-voltage characteristic is super-quadratic. We explain this increase of the current assuming that a fraction of the previous injected charge is detrapped by the field and it contributes to current increase. Consequently the current – voltage characteristic is strongly dependent on the time lag between two successive rises in the field. Neither the Poole-Frenkel mechanism nor the Richardson – Schottky mechanism can by used to explain the experimental results. The isothermal charging and discharging currents are explained assuming the movement of injected/ejected charge in the resultant local field. The values obtained for the adjustable parameters of the model are in good agreement with the values in the literature.