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Volume 73, Issue 9
Displaying 1-17 of 17 articles from this issue
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Nobuya Banno, Takao Takeuchi2009 Volume 73 Issue 9 Pages 651-658
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSCarbon nanotube (CNT) has excellent lightweight properties, mechanical properties and electric conductivity, and therefore CNT is expected as the next generation conductive wires for the electric devices or as wire harnesses for the motor vehicles etc. However, the CNT is very small materials, for instance usually the diameter is about 0.7 to 100 nm and the length a few hundreds of micrometers, so that the application to the conductive wires needs combining with some another matrix material like copper or aluminum. Furthermore, because of the one-dimensional conductivity of CNT, high orientation of the CNT along with the wire axis is necessary in order to achieve the excellent electric property of the CNT composite. In this work, we tried to fabricate copper-CNT composite wires using the widely-used techniques, the mechanical alloying and the powder-in-tube method, with the industrialization in mind, and investigated their electricity and mechanical properties. For the wire fabrications, commercially available single-walled CNT (SWCNT) and multi-walled CNT (MWCNT) were used. As a result, it was found that addition of CNT enhances the hardness of the copper-CNT composite whether SWCNT or MWCNT, but the results of resistivity measurements apparently showed that the addition of the MWCNT increases the resistivity of the composite. Use of the SWCNT, on the other hand, sustained the conductivity to the level of the copper. This is a good indication as the first test to realize high electric conductive wires.
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Shigeru Sawada, Terutaka Tamai, Yasuhiro Hattori2009 Volume 73 Issue 9 Pages 659-665
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSTin plating is commonly applied for automotive connectors. To clarify the mechanism of fretting corrosion of tin plating, friction coefficient behavior of tin plating is needed to investigate in detail. In this study, the factors of the friction coefficient for tin plating contact were examined in the case of embossment-plane contact. As experimental results it was found that the friction coefficient is affected by contact force, plating thickness and contact radius. The force dependence of the real contact area estimated by FEM analysis shows that the real contact area occurred by elasto-plastic deformation. A larger contact radius and thicker plating thickness result in a larger friction coefficient, because the real contact area is larger. A heavier force results in a smaller friction coefficient, because the average of the contact pressure is larger. The shear stress, which is estimated from experimental results, is much higher than that of tin metal. This indicates that tin attrition of embossment-plane contact is not the shear of tin metal on tin metal but the shear of tin metal on tin oxide according to the hardness results of the tin oxide layer.
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Toshiyuki Sawada, Akihiko Yanagitani2009 Volume 73 Issue 9 Pages 666-669
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSShot peening is a surface treatment effective to obtain compressive residual stress on shot peened surface and to improve fatigue strength, and it is applied to automobile parts such as springs and gears. Based on recent trend for further reduction of automobile parts weight, higher hardness of automobile parts is required through various treatments such as carburizing. As hardness of shot peened surface is becoming higher, shot peening media with higher hardness is also desired.
In this study, life properties of Fe-8Cr-6.5B gas atomized powder (FeCrB powder) with hardness of about 1200 HV and density of 7.4 Mg/m3 developed for shot peening media was examined. Weight loss of FeCrB powder after shot peening on gas carburized JIS SCM420 target for 24 h was approximately a quarter of that of the high speed steel powder. High hardness of FeCrB powder is thought to suppress deformation at collision to the target and to prevent crack initiation. Furthermore, hardness change during shot peening operation is smaller than that of high speed steel powder.
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Akihiro Sasaki, Nobuki Tezuka, Satoshi Sugimoto, Akinari Okubo, Rie Um ...2009 Volume 73 Issue 9 Pages 670-673
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSWe investigated the magnetoresistance effect for a magnetic tunnel junction(MTJ) using a Co2Ti0.5Mn0.5Al electrode on a Cr buffered MgO(001) single crystal substrate. The Co2Ti0.5Mn0.5Al formed an ordered L21 and B2 structures after post-annealing above 873 K and below 773 K, respectively. Maximum magnetization and minimum coercivity were exhibited in Co2Ti0.5Mn0.5Al annealed at 673 K. The MTJ using a Co2Ti0.5Mn0.5Al electrode with B2 structure exhibited tunnel magnetoresistance(TMR) ratio of 37% at room temperature and 60% at 5 K. The TMR ratio was larger than that of MTJ using a Co2Ti0.5Mn0.5Al electrode with L21 structure in this study.
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Masayuki Tojo, Hiroshi Ohtani, Mitsuhiro Hasebe2009 Volume 73 Issue 9 Pages 674-682
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSA thermodynamic analysis of the Fe-V-B ternary system has been carried out by estimating the unknown thermodynamic properties of binary and ternary borides using a first-principles method. The formation enthalpies for the (Fe, V)2B, (Fe, V)3B2, (Fe, V)3B4, (Fe, V)B2 phases were obtained from the calculations. For the compound phases of which crystal structures were unidentified, the thermodynamic properties were determined by analyzing the experimental data for the phase diagrams. The thermodynamic functions determined by using these theoretical values, as well as the available experimental information on the phase fields, successfully revealed the phase equilibria in the Fe-V-B ternary system over the entire composition and temperature ranges.
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Ryuichi Masumoto, Hiroshi Ohtani, Mitsuhiro Hasebe2009 Volume 73 Issue 9 Pages 683-690
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSA thermodynamic analysis of the Mg-Y-Zn ternary system has been carried out, mainly focusing on the phase separation of the Mg-based hcp phase. The thermodynamic properties such as the formation enthalpy for the metastable hcp phase were estimated by using a first-principles method, because the solubility of Y and Zn was very limited in the stable phase diagrams. The calculations showed that, at least in the ground state, the solid solution of hcp had a strong tendency to phase separate between the Mg-rich side and the Y-Zn binary side. The characteristic long period stacking ordered (LPSO) structures observed in some Mg alloys might originate in this thermodynamic properties of the hcp solid solution.
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Mikito Ueda, Hideki Hayashi, Toshiaki Ohtsuka2009 Volume 73 Issue 9 Pages 691-694
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSTo develop a sodium electrorefining process for the recycling of used sodium-sulfur secondary battery, a non-aqueous electrolytic melt was investigated to pursue an efficient solvent and electrolyte for the process. Propylene carbonate containing NaPF6 was selected, since it has a wide potential window for electrochemical stability and a weak reactivity with metallic sodium. From the impedance measurement of propylene carbonate containing NaPF6, the maximum electric conductivity of 75 mS cm-1 was found at concentration of 1 M NaPF6 at 338 K. The cathodic deposition of metallic sodium on a glassy carbon electrode and the anodic dissolution of metallic sodium occurred in the electrolytic melt. Sodium and a small amount of phosphorus were detected in the electrodeposit by ICP-AES analysis.
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Shuichi Arikawa, Seiichi Muneki, Hiroshi Okubo, Fujio Abe, Takao Yakou2009 Volume 73 Issue 9 Pages 695-702
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSThe formation process of a FeAl coating on carbon-nitrogen free Fe-12Ni-9Co-10W austenitic alloy by aluminizing treatment has been investigated. After heating to 1173 K, a pure Al foil on the base alloy surface changed to a FeAl3 surface layer and a FeAl thin layer. After that, in early stage of diffusion treatment at 1173 K, the surface layer changed to Fe2Al5. Thickness of the FeAl layer expanded from the boundary between the surface layer and the base alloy to the surface. The FeAl monolayer was formed after the diffusion treatment for 10.8 ks. The surface exhibited acicular morphology of the FeAl3 layer. This acicular structure changed to relatively flat as the diffusion process proceeds. After the diffusion treatment at 1173 K for 302 ks, the FeAl surface layer of 80 μm thickness was formed on the base alloy from the initial stage of the pure Al foil of 50 μm thickness. Hardness of the FeAl layer which was formed at 1173 K and 1373 K has been investigated. The FeAl layer with approximately 40 at%Al content which was formed at 1173 K was harder than that formed at 1373 K.
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Fumio Kurosawa, Tomohiro Akimoto2009 Volume 73 Issue 9 Pages 703-707
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSIn order to understand an essential role of crystal lattice misfit on the critical size of coherent precipitates in metallic materials, the critical size were studied using a method newly developed by the author, which was tentatively called “Different Lattice Misfit Accumulating Method”.
The relationship critical size and lattice misfit of coherent precipitates were made clear by this method. In detail, the critical size of coherent precipitates was determined just before the accumulation value of difference (|ap-a0|) of lattice misfit had approached to be a half of the lattice size (1/2a0, just before the generation of the misfit dislocation) of the matrix.
The critical size of the coherent precipitates can be described as follows.
Y(Critical size of coherent phase) × (|ap-a0|)=1/2a0, and
Y(Critical size of coherent phase)=50/X(Lattice misfit ratio, %)
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Naoto Matsuo, Yasuyuki Takanashi, Akira Heya, Kazuhiro Kanda2009 Volume 73 Issue 9 Pages 708-712
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSWe investigated the characteristics of a-Si film with thicknesses of 1 and 50 nm those were irradiated by soft X-ray from the undulator source. The cohesion of Si atoms were observed after X-ray irradiation for 1 nm-thick a-Si, but it was not observed for 50 nm-thick a-Si. The average roughness Ra of 1 nm-thick-Si film were changed from 0.63 to 1.7 nm by soft X-ray irradiation. The electric resistivity of it also increased corresponding to the change of the surface roughness. Although the TO phonon peak was not observed for 1 nm-thick a-Si, it was observed for 50 nm-thick a-Si. For these phenomena, the mechanism that the electron excitation by photon becomes the trigger of the cohesion was discussed.
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Ryutaro Terakado, Kazue Ichino Takahashi, Ichiro Daigo, Yasunari Matsu ...2009 Volume 73 Issue 9 Pages 713-719
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSRecently, metal demands in the world, especially, in developing countries have rapidly risen. The recovery of metal scrap for recycling contributes to the conservation of natural resources and the construction of a sound material cycle society. A dynamic material (substance) flow analysis is a useful tool to estimate in-use stock of materials for investigating the potentials of metal scrap recovery in designated areas. However, it is a challenging task to estimate the in-use stock of materials, especially in developing countries, because of lack of data. There are two approaches, a top-down approach and a bottom-up approach, for estimating the in-use stock of materials. Top-down approach uses time-series data of consumption and trade of materials and products' life time distributions, whereas bottom-up approach uses the numbers of product units in the designated area and its material use intensities. In this paper, the copper stock in 7 end-uses in Japan was estimated with the bottom-up approach, and compared with the results obtained with top-down approach in our previous study. The results obtained by the two approaches fairly corresponded with each other. So, it is suggested that complementary use of these two approaches is helpful to estimate in-use stock of materials.
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Y. Ishimoto, M. Michiuchi, S. Nambu, K. Asakura, J. Inoue, T. Koseki2009 Volume 73 Issue 9 Pages 720-727
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSLocal deformation behavior of lath martensite was investigated in low-alloyed steel in the strain range of 0-10% under uniaxial tensile loading. Local strain measurement was in-situ conducted in SEM by digital image correlation method, and it was revealed that strain distribution was relatively uniform in the early stage of deformation less than 2% of strain and then strain localization arises along the lath as the strain increases. Schmid factor was evaluated for each block of martensite by EBSP analysis and was compared with the measured local stain distribution. It was clarified that the strain concentration occurs in blocks that have higher Schmid factor in in-lath-plane slip systems than in out-of-lath-plane slip systems. On the other hand, deformation was less significant than average in blocks that have higher Schmid factor in out-of-lath-plane slip systems. It was suggested by an estimation of dislocation glide distance that the anisotropy of deformation of lath martensite was caused by the interaction between dislocations and lath boundaries and consequent selection of preferable slip systems.
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Tetsuya Ashino, Naofumi Ohtsu, Kazuaki Wagatsuma2009 Volume 73 Issue 9 Pages 728-731
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSFor characterization of corrosion resistance of metallic biomaterials, determination of trace amounts of metallic ions released from the materials in static immersion into simulated body fluids were investigated. In a pre-treatment method by sulfuric acid, sensitive, precise and accurate determination of the trace metallic elements in simulated body fluids could be performed by an inductively coupled plasma-optical emission spectrometry. For accurate analysis, it was necessary to employ a matrix-matched solution for the calibration. Moreover, usage of a vessel made of tetrafluoro ethylene-perfluoro alkylvinyl ether copolymer in the static immersion test was recommended for the prevention of contamination. Thus, it was possible to determine μg dm-3 order of elements in simulated body fluids and evaluate nano-gram order of the released metallic ions.
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Yoshiko Miyauchi, Hisao Esaka, Kei Shinozuka2009 Volume 73 Issue 9 Pages 732-741
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSRecently, lead-free solders have been used in electronic equipments. Sn-Ag-Cu system is an important alloy for lead-free solders. There have been so many reports for mechanical properties of bonding. It is important to understand the evolution of solidified structure of these alloys, though, such reports are few.
In order to understand the solidification process of Sn-Ag-Cu alloys, Sn-Ag alloys have been used in this study. Three alloys, hypo-eutectic, eutectic, and hyper-eutectic alloys have been prepared. The specimen was quenched during solidification and the solidified structure was interrupted and compared with thermal history.
In the case of hypo-eutectic alloy, the specimen was composed by primary Sn and eutectic. It was found that a small undercooling was necessary for nucleation of eutectic. Such undercooling was not observed in eutectic and hyper-eutectic alloys. This may be interpreted by the difference in the liquid composition when the eutectic solidification starts. In the case of eutectic and hyper-eutectic alloys, the eutectic as well as β-Sn may form at almost the same time of recalescence.
In the case of hyper-eutectic alloy, it was found that a large undercooling was not necessary for nucleation of Ag3Sn, even though it was facetted phase. Since the primary Ag3Sn was surrounded by the halo of β-Sn and eutectic, the Ag3Sn phase may be a site for nucleation of β-Sn and eutectic.
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Naoshi Watanabe, Hiroshi Yukawa, Tomonori Nambu, Yoshihisa Matsumoto, ...2009 Volume 73 Issue 9 Pages 742-746
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSPressure-Composition-Isotherm (PCT) measurements, in-situ small punch (SP) tests in hydrogen gas atmosphere and hydrogen permeation tests are conducted for Nb-W-Ta ternary alloys in order to investigate the alloying effects of tantalum on the hydrogen solubility, the mechanical properties and hydrogen permeability of Nb-5 mol%W alloy. It is found that the hydrogen solubilities of Nb-5 mol%W-Xmol%Ta (X=5, 10) alloys are very similar with that of Nb-5 mol%W alloy. Also, the mechanical properties in hydrogen gas atmosphere and hydrogen permeability of the alloys are comparable with Nb-5 mol%W alloy. Therefore, the addition of tantalum scarcely modifies the properties of Nb-5 mol%W alloys. Thus, it is not necessary to take into account the amount of tantalum in Nb-W alloys for hydrogen permeable membrane. In other words, it is not needed to remove tantalum impurity from niobium mineral ores in the course of the refinery process of niobium metal. This means that niobium mineral ore containing high tantalum impurity can be used to reduce the material cost of Nb-W-based hydrogen permeable membranes.
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Kazue Ichino Takahashi, Jiro Nakamura, Kazumi Otabe, Masaaki Tsuruoka, ...2009 Volume 73 Issue 9 Pages 747-751
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSMobile phones contain many useful metals, such as gold, silver, copper and tungsten, etc. The contained metals in each mobile phone are relatively little, however, the total number of mobile phones used in Japan has become very large. Therefore, mobile phones are paid attention as a stock-in-use of various metals. In contrast, these metals have not been well recycled because of low collecting rate of end-of-life mobile phones. Moreover, the lifecycle of the mobile phone is very short because they have been changed many times for offering new functions, such as cameras, electronic organizers, music players, and televisions. So many materials are considered to be added to obtain these multi functions, and the compositions of materials in mobile phones have changed. In this paper, we collected more than two hundred used mobile phones made between 1996 and 2008 and dismantled them to analyze their metal content. Concentrations of more than 20 metals in mobile phones were measured. It was found that their net amounts of these metals increased year by year. However, the tendency was different for each element. For example, the copper content increases as the number of the functions of a mobile phone was increased. Lead was mostly used as solder and its content decreased. This can be explained with the influence of the environmental regulations. To improve the recycling of mobile phones, the useful data base that including environmental and economic information is essential. Therefore, we also investigated CO2 emissions and the economic effects of mobile phones based on the results of elemental analyses. CO2 emissions generated by the incineration of plastics were estimated to be nearly equal to the avoided CO2 emissions by recovering the metals. The economic impact assessment result showed that the manpower cost exceeds the recovered cost of metals. Therefore it is suggested that the eco-design for recycling is needed.
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Yoshito Takemoto, Yukiyoshi Miyake, Takehide Senuma2009 Volume 73 Issue 9 Pages 752-757
Published: 2009
Released on J-STAGE: September 01, 2009
JOURNAL FREE ACCESSIn this study, we investigated the microstructure, hardness, Young's modulus, and tensile behavior of binary Ti-4~9 mass% Mo alloys, quenched from a temperature of 1223 K. Among the solution-treated binary Ti-Mo alloys, the lowest Young's modulus was observed in the case of the Ti-6Mo alloy, which was the border composition of α′/α″. When the rolling deformation of 2% reduction was carried out, the Young's modulus of Ti-Mo alloys having less than 6 mass% Mo increased, whereas that of higher than 6 mass% Mo reduced. The Young's modulus of the 6Mo alloy hardly changed with the rolling deformation. Ti-6Mo-X-(Y) alloys, where X and Y are 1 mass% of Al, Sn, Cr, and Fe, were prepared in order to investigate the influence of additional elements on the microstructure and mechanical properties of the 6Mo alloy. The phase constitution of quenched Ti-6Mo-X-Y alloys mostly corresponded with the value of the Mo equivalency (Moeq); however, Ti-6Mo-1Al-1Fe (MAF) and Ti-6Mo-1Fe (MF) exhibited slightly more β-rich structures for their respective Moeq values. The lattice parameters “a” and “b” of the α″-structure in the Ti-6Mo-X-Y alloys changed with Moeq in a manner similar to that in the Ti-Mo alloy; however, “c” exhibited a different behavior. The mechanical properties of Ti-6Mo-X-Y alloys except for the MF alloy were similar to those of Ti-Mo alloys corresponding Moeq. However, the Young's modulus of the Ti-6Mo-X-Y alloys was greater than that of the 6Mo alloy. The tensile properties of the MF alloy having β+ω structure were extremely unstable with respect to the fracture elongation. This peculiar behavior is attributed to the occurrence of deformation-induced β+ω→α″ transformation. The formation of the α″ structure caused significant softening and local intense deformation in the α″ phase resulted in a brittle fracture. On the other hand, a successive α″ formation induced by work hardening would result in good ductility. It was suggested that the unstable elongation in the MF alloy resulted from competition between the reverse effects.
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