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Volume 72, Issue 3
Displaying 1-20 of 20 articles from this issue
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Masaaki Imade, Takashi Iijima, Seiji Fukuyama, Kiyoshi Yokogawa2008 Volume 72 Issue 3 Pages 139-145
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSTesting equipment for materials under high-pressure hydrogen of 120 MPa at the temperature range of room temperature up to 393 K has been developed. The pressure vessel was designed to enable the measurement of actual tensile load on a specimen by an external load cell without the influence of axial load due to high pressure in the vessel and the friction between the O-rings and the pull rod. The hydrogen gas embrittlement (HGE) of austenitic stainless steels of SUS304, 316, 316L, 316LN and 310S was examined in 70 and 105 MPa hydrogen and argon by slow strain rate technique (SSRT) test at room temperature. Hydrogen showed a marked effect on the tensile properties of SUS304 and 316 stainless steel, a minimal effect on those of SUS316LN, and no effect on those of SUS316L and 310S. The HGE of sensitized SUS304, 316 and 316LN was larger than that of solution-annealed ones. It was observed that hydrogen caused brittle transgranular fracture along the strain-induced martensite in solution-annealed steels, and intergranular fracture in sensitized steels respectively.
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Noriyoshi Miwa, Mitsuru Hirano, Kazunori Tanaka, Yoshitake Nishi2008 Volume 72 Issue 3 Pages 146-151
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSCarbon fiber reinforced polymer (CFRP) had recently been applied to not only wing, but also fan blades of turbo fan engines. To prevent impact force, leading edge of titanium was often mounted on the CFRP fan blades by adhesive force. In order to enhance the joining strength, we suggested a joining method with carbon fiber reinforced interface. By using nickel-coated carbon fibers, we successfully developed a joining sample with carbon fiber-reinforced interface between CFRP and CFRM. The joining sample with nickel-coated carbon fiber exhibited the high tensile strength, which was approximately two times larger than that with non-coated one and was also more than 11 times higher than that with conventional adhesion.
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Naoki Okada, Yoshitaka Fujii, Yoshiki Ishikawa, Motonobu Onoda, Hee Yo ...2008 Volume 72 Issue 3 Pages 152-157
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSShape memory alloys with high transformation temperatures are required for being used in devices that operate at elevated temperatures. Ti-Ni-Zr alloys are regarded as most practical high temperature shape memory alloys due to the relative low price of raw materials compared with other high temperature shape memory alloys such as Ti-Ni-Hf, Ti-Ni-Pt, Ti-Ni-Pd and Ti-Ni-Au. In this study, the effect of Zr content on transformation temperatures, shape memory characteristics and cold workability in Ti-49.5Ni-(0-15)Zr alloys was investigated. The reverse transformation finish temperature increased monotonously with increasing Zr content, while the martensitic transformation temperatures decreased with increasing Zr content, reaching the minimum at 5 at%Zr and then increased by further increasing Zr content. The martensitic transformation temperatures above 373 K were obtained in Ti-49.5Ni-Zr alloys with a Zr content above 10 at%. The shape memory properties were investigated by thermal cycling tests under various constant stresses. The critical stress for slip increased with increasing Zr content. The maximum recovery strain of about 5% was obtained in the Ti-49.5Ni-(0-15)Zr alloys. The Ti-49.5Ni-(0-5)Zr alloys could be cold rolled up to 90% reduction in thickness without fracture. The cold workability became worse with increasing Zr content. The total thickness reduction prior to fracture was about 30% for the Ti-49.5Ni-15Zr alloy
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Ryo Sakuma, Ryuichi Tarumi, Masahiko Hirao, Tetsu Ichitsubo, Eiichiro ...2008 Volume 72 Issue 3 Pages 158-162
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSMicrostructure of glassy solids have been investigated by molecular dynamics (MD) simulation coupled with a Voronoi-Delaunay (VD) tessellation. NTP ensemble MD models are constructed from Ar atoms interacting via Lennard-Jones potential and glassy solids have been obtained by rapid quenches from an equilibrium liquid state. By utilizing the VD tessellation for a quenching process, we calculated statistical variables (expected value VE, variance σ2, deviation σ, skewness γ1, kurtosis γ2, probability density distribution function fj and Shannon's information entropy S) from volumes of Voronoi polyhedra Vi. The VE-T and S-T relationships show notable inflections around 55 K showing a glass transition phenomenon. During the quench process, fj continuously approaches to Gaussian form while γ1 and γ2 show significant inflections below Tg indicating that microstructure and local density fluctuation of the glassy solid suddenly freeze around Tg.
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Masaharu Menjo, Ting Hao, Motoaki Matsuo, Yuko Nakamori, Shin-ichi Ori ...2008 Volume 72 Issue 3 Pages 163-167
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSLi2NH (Li-imide) and LiNH2 (Li-amide) have been extensively investigated as solid-state hydrogen storage materials. We demonstrated the feasibility of an impregnation method for the synthesis of Li-imide/amide for the first time. A metallic Li foil placed on a sheet of porous Ni was heated under Ar atmosphere and then impregnated homogeneously into the porous Ni without changing the bulk morphology. The morphology of the porous Ni was retained after nitrogenation of the impregnated Li (formation of Li3N) as well as after ten repeated hydrogenation and dehydrogenation reactions (reversible formation of Li2NH and LiNH2). It was also noted that the hydrogenation reaction after the nitrogenation was drastically promoted by the addition of a small amount of Co powder on the metallic Li foil prior to the impregnation.
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Koji Murakami, Makoto Hino, Masao Takamizawa, Kiyomichi Nakai2008 Volume 72 Issue 3 Pages 168-175
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSGeneration and growth of whiskers on tin electroplating was studied by scanning electron microscopy and X-ray diffraction. When the surface of the plating whose thickness was 1 μm was etched by argon ion beam to remove oxide film and kept in a vacuum, whiskers were rarely observed but many nodules were formed. While residual stress of tin plating (1 μm) and the number of whiskers increased with the amount of Cu6Sn5 formed between the tin plating and the substrate of copper, that of the specimen whose thickness was 10 μm showed no meaningful change and no whiskers were found. The orientation of a whisker was shown to be identical throughout the crystal even in a kinked one by electron backscattering diffraction. The mechanism of generation and growth of whiskers is considered to be due to diffusion of tin atoms induced by inhomogeneous strain field, formation of vacancies, and its resulting increase in volume of the grain which received the tin atoms. Energy change in the growth of whisker was modelled and calculated, and the main factor which determines the growth was shown to be the formation enthalpy of a vacancy and the entropy of configuration.
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Atsushi Sawahata, Hiroyasu Tanigawa, Masato Enomoto2008 Volume 72 Issue 3 Pages 176-180
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSThe effects of the second refining process, Electro-Slag Remelting (ESR), were investigated on Ta rich inclusion formation in the Vacuum Induction Melted (VIM) Reduced Activation Ferritic/Martensitic steel (RAFM), F82H (Fe-8Cr-2W-V-Ta). The Ta rich oxides such as TaOx and TaOx-Al2O3 are major inclusion in VIMed F82H, and those were correlated with the reduction of the Charpy impact property, as those were found at the crack initiation points. It was revealed that the ESR process was effective on removing those Ta rich oxides. On the other hand, ESR process increased MnS and Al2O3 instead, and these inclusions were found at the crack initiation points. These could explain the little difference on Ductile-Brittle Transition Temperature (DBTT) of as-VIMed and ESRed F82H.
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Yuichi Oka, Ryosuke O. Suzuki2008 Volume 72 Issue 3 Pages 181-187
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSA new process is proposed to reduce V2O5 by using calcium in molten CaCl2 for vanadium production. It consists of the calcium reduction in molten CaCl2 and the electrochemical reaction for the recovery of Ca from CaO in the same bath. V2O5 pellet was placed on cathode in order to react with Ca electrochemically generated near the cathode. V2O5 exists as liquid at the experimental temperature (1123 K), because of the melting point of 963 K for V2O5. At the initial stage of the reduction, liquid sample is reduced to solid CaV2O4. As the supplied quantity of electricity increased, the oxygen concentration in the vanadium samples decreased exponentially. Vanadium containing only 1800 ppm oxygen was obtained after the electrolysis for 34.4 ks.
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Koji Tanaka, Nobuhiko Takeichi, Hideaki Tanaka, Nobuhiro Kuriyama, Tam ...2008 Volume 72 Issue 3 Pages 188-194
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSMg/Cu super-laminates prepared by repetitive fold and roll method using conventional two-high roll mill was investigated on changes of micro/nano-structures and hydrogen absorption properties during initial activation.
The results of in-situ XRD analyses suggested that the hydrogen absorption/desorption mechanism of Mg/Cu super-laminates was as follows. In the hydrogenation process at 573 K, intermetallic phase Mg2Cu is formed through interdiffusion between Mg and Cu layers, and then the Mg2Cu decomposes into MgH2 and MgCu2 through disproportionation. In the subsequent dehydrogenation process at 573 K, the MgH2 dessociates H2 and metallic Mg. The Mg reacts with MgCu2, and then Mg2Cu is formed again. Therefore, Mg2Cu phase absorbs and desorbs hydrogen reversibly through this sequence.
The results of TEM observations revealed structure changes of Mg/Cu super-laminates during initial activation. Interesting points of micro/nano-structures are summarized as follows: In as-rolled Mg/Cu super-laminates, (1) laminated structures in size of sub-micrometer thickness are constructed of Mg and Cu layers, (2) lattice defects are dense. In initial activated super-laminates, (1) laminated structures are preserved, (2) pores with a diameter of sub-micrometer distribute uniformly between Mg2Cu layers, which leads to large surface area. In Mg/Cu super-laminates during initial activation, (1) laminated structures are preserved, (2) spongiform structures composed of MgH2 and MgCu2 are formed. The spongiform structures at the first hydrogenation are coarse and become fine at the second hydrogenation, i.e. the diffusion distance for hydrogen absorption reaction becomes shorter after initial activation.
Hydrogen absorption test reveled that Mg/Cu super-laminates absorb hydrogen much faster than Mg2Cu powder and initial activation improve kinetics of both super-laminates and powder, although super-laminates absorb hydrogen much faster than powder, again.
Micro/nano-structures of Mg/Cu super-laminates such as large surface area, dense defects and short diffusion distance for the reaction enhances kinetics and enable Mg/Cu super-laminates to absorb hydrogen very fast, which would contribute to achieve high performance hydrogen storage materials.
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Nobuaki Kunikyo, Mitsuru Hirano, Masae Kanda, Yoshihide Ebihara, Yoshi ...2008 Volume 72 Issue 3 Pages 195-200
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSCu-powders dispersed ABS polymers were prepared by solution-cast, which could easily control the dispersion ratio. The Cu addition gradually enhanced the electrical conductivity at less and more less than the critical volume fraction (19.0±1.0 vol%Cu) in ABS polymer. The jump of electrical conductivity was observed by the Cu addition at the critical volume fraction. The result was explained by the percolation theory.
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Analysis of Grain Boundary Segregation in Al Alloy Thin Films by Using Molecular Orbital CalculationKoutarou Urayama, Rie Mori, Shinji Takayama2008 Volume 72 Issue 3 Pages 201-205
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSGreat attention has been directed toward the suppression of the formation of thermal defects such as hillocks and voids in interconnect lines during the thermal process of TFT-LCD or VLSI devices in order to improve their reliability and to get a high product yielding. It was revealed that these thermal defects can be suppressed largely by the segregation of adding impurities to form an intermetallic compound on the grain boundaries. The grain boundary segregation in dilute Al alloy thin films was investigated by employing an ab-initio molecular orbital calculation and the McLean- Guttmann theory. It was found that the calculated bond overlap population between like atoms was related closely to their reported bond energy values of diatomic molecules, while the calculated Homo level between unlike atoms also correlated linearly with the reported bond energy values. By using these correlations, we obtained the binding energies between constituent atoms in Al thin films. The trend of the grain boundary segregation of impurities in Al alloys was then assessed by a binary interaction coefficient energy calculated from the binding energies. We demonstrated that the calculated binary interaction coefficient energies showed fairly good agreement with the grain boundary segregation phenomenon of impurities in Al alloy thin films.
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Kenji Kako, Yuuichi Miyahara, Koichiro Hide, Masami Mayuzumi2008 Volume 72 Issue 3 Pages 206-210
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSThe dynamic strain aging phenomenon is believed to be one of the most important mechanisms that harden the weld-heat-affected zone of low-carbon austenitic stainless steels. Hence, we investigated the effects of the test temperature and strain rate during tensile tests on the dynamic strain aging of type 316L stainless steel (SS) in this study. The results obtained are as follows; (1) Two types of stress-strain curves were obtained with serrations caused by the dynamic strain aging in the tensile tests at different test temperatures and strain rates, one with a high-frequency serration and the other with a low-frequency serration. (2) The area where the serration was observed was determined by two lines, showing that the temperature dependence of the strain rate was in the form of ε=A exp {-Q/(RT)}, where A: constant, Q: apparent activation energy (150 kJ/mol or 300 kJ/mol), R: gas constant, T: absolute temperature. (3) The increase in the micro-Vickers hardness of type 316L SS after being strained to certain strains showed maximum values determined by both the test temperature and the strain rate. The largest increase in the hardness was obtained at the combination of the lowest temperature and the lowest strain rate among the test conditions.
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Hiroki Takao, Hidekazu Miyajima, Kengo Mouri, Toru Miyoshi, Makoto Ari ...2008 Volume 72 Issue 3 Pages 211-215
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSTitanium dioxide (TiO2) has been known as a photocatalyst. It is generally said the photocatalytic activity of anatase phase is superior to that of rutile phase despite the difference in the conditions of preparation for these two phases. We prepared anatase and rutile thin films under the same deposition conditions by reactive magnetron sputtering with Quasi-Epitaxial Growth (QEG) and discussed the relationship between the photocatalitic activity and the conditions of film deposition.
An excellent photocatalytic performance was obtained for the rutile thin film prepared with QEG. With UV light illumination, QEG rutile exhibited a 0° contact angle with water as well as anatase and had better photo-decomposition activity than anatase. The photocatalytic activity of TiO2 thin films is strongly affected by deposition conditions.
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Takahito Kawamura, Satoshi Sunada, Hisakimi Notoya, Katsuyoshi Kondo, ...2008 Volume 72 Issue 3 Pages 216-223
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSThough Mg alloys are the outstanding candidates for the use in automotive, aerospace and electronic industries because of their low density and excellent strength to weight ratio, they have a great disadvantage in corrosion resistance. In this study, their corrosion behavior has been investigated by the polarization test and electrochemical impedance spectroscopy test for their practical use. AZ series Mg alloy samples produced by conventional ingot metallurgy showed a little slight decrease Ecorr with an increase of Al content, while they indicated a remarkable decrement of Icorr with increasing amount of Al content.
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Atsushi Uemura, Kaori Kuga, Hideki Wakana, Yoshitake Nishi, Haru-Hisa ...2008 Volume 72 Issue 3 Pages 224-228
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSAlkali-earth element of magnesium has been expected as a large capacity of hydrogen storage materials. However, low hydrogen reactivity even at higher temperature under higher pressure of hydrogen is a significant problem for the practical utilization. Recently, we reported improvements of hydrogen reactivity of alkali metals such as an ion bonding hydrogen storage materials by means of rare earth oxide mixing. Because a similar effect has been expected for magnesium, in this study, we report an interesting result of rare earth oxide doping into magnesium by mechanical mixing for the higher hydrogen reactivity, where the rare earth oxide may enlarge the diffusion path in the sample powder particles. As a result, Mg+26.1 mass%CeO2 absorbs and desorbs more than 4 mass% H2 (including weight of catalyst) at 573-673 K within 10 min, while the sample without rare earth oxide exhibits drastically small hydrogen reactivity.
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Masao Takamizawa, Toshihide Naka, Makoto Hino, Koji Murakami, Yutaka M ...2008 Volume 72 Issue 3 Pages 229-235
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSThis study investigated the effect of Pb co-deposition on the whisker growth on electrodeposited tin film onto phosphor bronze substrate by using XRD, FE-SEM, FE-EPMA and GD-OES.
FE-SEM observation revealed that the whisker growth was suppressed with the increase in the amount of Pb in deposits and the increase in the thickness of Sn deposit. The diffusion layer consisting of intermetallic compounds (Cu6Sn5) was formed at the interface between the Sn deposits and substrate as Cu diffused from the substrate to the Sn deposits. This diffusion layer grew, and the compressive stresses in Sn deposits increased correspondingly. On the other hand, diffusion layer and compressive stresses in Sn-10 mass% Pb alloy deposits were smaller than these in Sn deposits. The depression efficiency of the whisker growth by Pb co-deposition is attributed to the depression of the diffusion layer and the reduction of the compressive stresses.
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Tohru Nobuki, Toshiro Kuji2008 Volume 72 Issue 3 Pages 236-243
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSThis study aims to discuss the morphology of TiAl alloys prepared by mechanical alloying (MA) techinique. The alloy composition varied from 45 to 75 at% of Ti with MA time from 0 to 60 hours under Ar atmoshere. The vial and the balls were stainless steel.
From the SEM observation, the diameter of MA particle is becoming smaller with increasing MA time. The diameter of Ti50Al50 powder indicates a size of 15 μm after 40 hours of ball milling. From the XRD measurements, the microstructure of MA alloy indicates an amorphous structure in the case of 20 hours of MA.
We tried to synthesis TiAl or Ti3Al intermetallic alloy phase by heat treatment. DSC measurements shows crystallization started around 600°C for each alloy, Although we could not synthesis the single phase, from the TEM bright image observation, we have confirmed that the alloy is composed by nano-size particles more and less 10 nm of diameter of crystalline particles.
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Tomotake Tohei, Ikuo Shohji, Keisuke Yoshizawa, Masaharu Nishimoto, Ta ...2008 Volume 72 Issue 3 Pages 244-248
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSThe effect of filler content in an underfill material on thermal fatigue life of a lead-free solder joint of a chip size package (CSP) has been investigated. Three types of bisphenol-F-type epoxy-based underfill material, which filler content was changed from 0 to 60 mass%, were prepared. The thermal cycle test in a temperature range from -40 to 125°C was conducted to investigate thermal fatigue lives of solder joints encapsulated with underfill materials. Plastic strain range loaded in the solder joint under thermal cycle conditions was investigated by a finite element analysis method. From the thermal cycle test results, it was clarified that the thermal fatigue life of the solder joint increases with increasing filler content in the underfill material investigated. Moreover, a Coffin-Manson-type of relation was obtained between the plastic strain range and the thermal fatigue life. n value in the Coffin-Manson's equation was estimated to be 1.8.
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Hiroyuki Kobayashi, Naoto Hironaka, Keisuke Iwata, Mitsuru Hirano, Mic ...2008 Volume 72 Issue 3 Pages 249-253
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSEffects of electron beam irradiation on stress-strain curves of glass fiber reinforced polymer (GFRP) have been studied. Electron beam (EB) irradiation decreases the resistivity (dσ/dε) of bending deformation of the GFRP. Although EB irradiation slightly decreases the maximum resistive stress on bending deformation (maximum bending stress), it also enhances the strain at the maximum bending stress. EB irradiation enhances the deformation energy to the maximum bending stress of GFRP. This energy mainly depends on not only the strain improvement at the maximum bending stress of epoxy resin and glass fiber, but also interfacial friction force.
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Nobuyuki Takahira, Takeshi Yoshikawa, Toshihiro Tanaka2008 Volume 72 Issue 3 Pages 254-260
Published: 2008
Released on J-STAGE: March 01, 2008
JOURNAL FREE ACCESSDecomposition morphologies of wüstite in scale layer formed on iron substrate were investigated, and a porous layer was fabricated at the surface of the iron substrate by a reduction of the decomposed layer. The pre-oxidized iron substrates were held at various temperatures less than 843 K for different lengths of time to decompose wüstite in the scale layer to Fe and magnetite. When the scale layer was treated with two steps of thermal processes, the proeutectoid magnetite precipitated vertically in near-surface areas of the scale and the lamellar structure was observed in other areas. When the decomposed sample was reduced in H2, a porous layer was formed at the surface of the iron substrate. By unusual wetting phenomenon of liquid indium, it is confirmed that pores in the porous layer was 3-dimentionally interconnected.
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