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Volume 68, Issue 2
Displaying 1-33 of 33 articles from this issue
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—An Approach with In-Situ EC-AFM Observation—Nobumitsu Hirai, Horatiu Vermesan, Masashi Shiota, Toshihiro Tanaka2004 Volume 68 Issue 2 Pages 35-38
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSWe have investigated electrochemical reaction on a lead electrode, on which a small amount of BaSO4 or SrSO4 powder was fixed by pressing, in sulfuric acid solution by using in situ electrochemical atomic microscopy (EC-AFM) combined with cyclic voltammetry (CV). It was found that PbSO4 crystals precipitate on BaSO4 or SrSO4 powder during the anodic sweep of the CV, and the powder provides sites for the precipitation of PbSO4 crystals. It was also found during the cathodic sweep of the CV that PbSO4 crystals have dissolved more than 15 min after the cathodic current peak is observed. The PbSO4 crystals on SrSO4 precipitate at more negative potential than on BaSO4 during the anodic sweep, while dissolution of the crystals on SrSO4 needs more time than on BaSO4 during the cathodic sweep. From those results, it is concluded that BaSO4 is more suitable than SrSO4 for an additive in negative electrode of lead-acid batteries with higher charging ability.View full abstractDownload PDF (741K) -
Soong-Keun Hyun, Teruyuki Ikeda, Hideo Nakajima2004 Volume 68 Issue 2 Pages 39-42
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSLotus-type porous Ni3Al intermetallics (Ni-15 mol%Al, Ni-28 mol%Al and Ni-31 mol%Al) whose long cylindrical pores are aligned in one direction have been fabricated by unidirectional solidification of the melt in a pressurized hydrogen gas. The porosity and the pore size are decreased with increasing aluminum content. An increase of solidification velocity from 0.33 to 0.50 mms-1 leads to a decrease of pore diameter and an increase of pore number in lotus-type porous Ni-28 mol%Al.View full abstractDownload PDF (1919K) -
Norihiro Itsubo, Jaesung Noh, Atsushi Inaba2004 Volume 68 Issue 2 Pages 43-45
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSLCA (Life Cycle Assessment) has been attracted and been already spread to the public as a technique evaluating the environmental impacts of product life cycle. LCA case study for lead-free solder, which is expected as eco-material has already been performed, but most of these studies are focused on LCI (Life Cycle Inventory) and characterization in LCIA (Life Cycle Impact Assessment). In the case of the assessment of solder, the trade-off relationship between the human toxicity caused by the exposure of lead and global warming caused by the increase of energy use seems important. Conventional LCA case studies are difficult to solve this trade-off relationship, because LCI and characterization will not compare the seriousness of these environmental impacts.
Based on the above background, we conducted LCIA case study of lead-free solder using LIME (Life-cycle Impact assessment Method based on Endpoint modeling). We concentrated on the damage assessment for human health in order to solve the trade-off relationship between the impact categories. DALY (Disability Adjusted Life Year) is applied as the damage indicator in this study. It can be concluded that damage assessment enables to evaluate reasonably with comparing the several health impacts based on the scientific knowledge.View full abstractDownload PDF (629K) -
Masashi Wada, Jingtian Yin, Shigeo Tanase, Tetuo Sakai2004 Volume 68 Issue 2 Pages 46-49
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSWe have prepared Ag-Sb-Sn composite alloy powders as anode material for lithium-ion batteries using mechanical alloying method. These powders with a size of several micrometers are mainly composed of β-Sn, Ag3Sn and SnSb phases. The half-cell tests revealed that the cycling performance of the Ag-Sn alloy electrodes could be improved significantly by substituting part of Ag with Sb. The Ag36.4Sb15.6Sn48 electrode could maintain a rechargeable capacity of about 380 mAh/g even after 300 cycles. The analysis for the structural changes of the electrode during cycling suggested that the good electrode behavior was related to the presence of two structurally stable intermetallic-compounds of Ag3Sn and SnSb in the host structure, as well as the stepwise Li lithiation/delithiation mechanisms, which were considered to buffer the volumetric variations during cycling.View full abstractDownload PDF (1260K) -
Takakazu Suzuki, Natsuki Yoneyama, Hiroki Yoshizawa, Kouichi Murakami, ...2004 Volume 68 Issue 2 Pages 50-53
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSSusceptibility to stress-corrosion cracking (SCC) of type 316 (LC) stainless steel was investigated and discussed in this study in terms of microstructure. Five kinds of material with different microstructure such as as-cold-rolled, recovered, with grain size differing from 15 to 150 μm, were prepared by the combination of cold rolling and heat treatment. Seven specimens were examined for each material. The specimen was a flat plate with dimensions of 50 mm long, 10 mm wide and 2 mm thick. The creviced bent beam (CBB) test was performed to evaluate the susceptibility to SCC. The CBB test is a bend test with an artificial crevice under steady strain of approximately 1%, and one of the accelerated tests to evaluate the SCC susceptibility of a material. The specimens were fixed on CBB fixtures and set in an autoclave. The test was then performed for 3.6 Ms at 561 K in high-purity water containing dissolved oxygen of approximately 8 ppm under 8 MPa pressure. The specimens after the test were sectioned on the centerline. They were mounted, grinded and then polished. The polished cross-section was examined by an optical microscope. Crack depth was measured and the data were classified into a frequency distribution histogram with 50 μm width. The recovered specimens that were cold rolled and then heat-treated at 673 K for 3.6 ks, showed apparently high susceptibility to SCC. On the other hand, though the macro structure of as-cold-rolled specimens and the recovered specimens were very similar, a significant difference was observed in the susceptibility to SCC. Observed cracks initiated from the specimen surfaces, transverse in grains, and then propagated along grain boundaries. No obvious relationship between the susceptibility and the grain sizes was observed.View full abstractDownload PDF (1534K) -
Yutaka Koizumi, Hideo Koguchi, Tadaharu Yokokawa, Toshiharu Kobayashi, ...2004 Volume 68 Issue 2 Pages 54-57
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIn the ‘High Temperature Materials 21’ project, fourth generation single crystal (SC) superalloys have been developed adding Ru as a phase stabilizing element. A relationship between the amount of TCP-phase and the creep strength has been investigated for a series of Ni-base SC superalloys with 2 to 5 mass% Ru; these alloys were designed using an SC superalloy containing 5 mass% Re as a base alloy. The amount of TCP-phase decreased with increased Ru content from 2 to 5 mass%. and the amount of γ′ envelope, which normally forms on the TCP plate, decrease also with increase in Ru content. The creep strength increase with these structual changes but the main reason was considered to be the decrease in volume fraction of the γ′ envelope rather than the decrease in the amount of TCP-phase.View full abstractDownload PDF (3296K) -
Takamitsu Honjo, Haru-Hisa Uchida, Yoshihito Matsumura, Yoshitake Nish ...2004 Volume 68 Issue 2 Pages 58-61
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIn this study, the effect of the platinum surface treatment on mechanical response of LaNi5 thin film actuator deposited on polyimide substrates was investigated. Since this actuator could be reversibly driven by hydrogen pressure control, this actuator is expected as a sensor and/or controller of hydrogen gas flux in various hydrogen related devices.
In the experiments, initiating time of the actuation after hydrogen gas exposure is reduced from 100 to 10 s by platinum surface treatment. This significantly modified mechanical response is attributed to switching of the reaction rate determining steps. Dissociation of hydrogen gas molecules on the sample surface is considered to be changed to permeation/diffusion of hydrogen atoms in the film by the platinum treatment.View full abstractDownload PDF (976K) -
Seiji Fukuyama, Lin Zhang, Kiyoshi Yokogawa2004 Volume 68 Issue 2 Pages 62-65
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSTesting equipment for materials under high-pressure hydrogen of 70 MPa at the temperature range of room temperature up to 373 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 environment embrittlement (HEE) of austenitic stainless steels of type 304, 316, 316L and 316LN, was investigated at the room temperature. Hydrogen showed a marked effect on the tensile properties of types 304 and 316 stainless steels, and a minimal effect on those of types 316L and 316LN. The HEE of the austenitic stainless steels increased with increasing hydrogen pressure. It was observed that hydrogen caused brittle transgranular fracture along the strain-induced martensite lath in these steels.View full abstractDownload PDF (1126K) -
Michihisa Fukumoto, Motoi Hara2004 Volume 68 Issue 2 Pages 66-69
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe improvement in cyclic oxidation resistance of SUS304 stainless steel was tried by electrodeposition of Y in molten salt. Electrolysis of Y was conducted using potentiostatic polarization method in an equimolar NaCl-KCl melt containing 3.5 mol% YF3 at 1023 K. The mass of electrodeposited material increased with the passage of polarization time. The observation of specimen surface after polarization at −2.2 V (vs. Ag/Ag+ (0.1)) for 0.3 and 0.6 ks showed that Y particles were uniformly dispersed on the surface. The cyclic oxidation resistance of the electrodeposited stainless steel was remarkably improved as compared with untreated stainless steel. The scale formed on the untreated stainless steel after cyclic oxidation was thick, and had a alternate structure of Fe-oxide layer and Cr-oxide layer. On the other hand, the scale formed on the stainless steel electrodeposited at −2.2 V for 0.3 ks was extremely thin, and consisted mainly of Cr2O3.View full abstractDownload PDF (695K) -
Mitsuhiro Yamaguchi, Manabu Ishimaru, Yoshihiko Hirotsu2004 Volume 68 Issue 2 Pages 70-73
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSAlthough extensive studies have been carried out on structural analyses of amorphous silicon-germanium (a-Si1-xGex) alloys, there are still controversies concerning short-range order in a-Si1-xGex alloys. In this study, we examined amorphous structures of Si1-xGex alloys by molecular-dynamics (MD) simulations using the Tersoff interatomic potential. Amorphous networks were prepared by rapid quenching from liquid Si1-xGex alloys. Computer-generated atomic configurations consisted of tetrahedral networks with complete chemical disorder in the first coordination shell. The bond lengths of Si-Si, Si-Ge and Ge-Ge pairs slightly increased with the Ge composition, and a weaker composition dependence was observed in the bond lengths of Si-Si and Si-Ge pairs than that for Ge-Ge pair. These results were in good agreement with those obtained experimentally, suggesting that the MD calculations based on the Tersoff potential is useful for the structural analysis of a-Si1-xGex alloys. It was confirmed that the Ge-Ge bond length and bond angle surrounding Ge atoms are more distorted. This is attributed to the difference between Si and Ge in the bond-stretching and in the bond-bending forces.View full abstractDownload PDF (709K) -
Hiroaki Sukegawa, Nobuki Tezuka, Koichiro Inomata, Satoshi Sugimoto2004 Volume 68 Issue 2 Pages 74-77
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSMagnetic double tunnel junctions (DTJs) have been investigated to achieve weak bias voltage dependence and to obtain large magnetoresistance (MR) ratio at several hundred mV. IrMn/Co90Fe10/AlOx/Co90Fe10/AlOx/Co90Fe10/IrMn structures were prepared as dual-spin-valve-type DTJs, which possess the middle ferromagnetic layers consisting of both continuous and discontinuous Co90Fe10 films. For the DTJs with continuous middle Co90Fe10 layers, the bias voltage value which MR ratio reduces by half (Vh) was about 880 mV, while that of single tunnel junctions (STJs) was about 450 mV. For the DTJs with discontinuous middle Co90Fe10 layers, it was found that the resistance increased remarkably and the magnetic field response decreased in MR curves. The discontinuous Co90Fe10 layers showed superparamagnetic behavior in magnetization curves.View full abstractDownload PDF (638K) -
Haruki Doi, Shigeru Suzuki, Kohji Mimura, Minoru Isshiki, Yoshio Wased ...2004 Volume 68 Issue 2 Pages 78-81
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe electrical resistivity and Vickers hardness of quenched and aged high-purity copper-titanium -aluminum alloys have been measured in order to study influences of aluminum addition on the electrical conductivity and hardness of copper-titanium alloys. The electrical resistivity of the quenched Cu-Ti-Al alloys showed that aluminum addition slightly increases the solid solubility limit in Cu-Ti alloys. The results of the present investigations samples showed that the hardness increases and the electrical resistivity decreases with aging, and the aluminum addition slightly decreases the precipitation rate. This result is considered to correspond to an increase in the solid solubility limit. In addition, the contribution of the aluminum addition to solution hardening is very small, although the precipitation hardening is observed in Cu-Ti-Al alloys.View full abstractDownload PDF (689K) -
Kazumasa Nishimura, Nobuki Tezuka, Satoshi Sugimoto, Koichiro Inomata2004 Volume 68 Issue 2 Pages 82-85
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSBoth magnetic and electric properties were investigated of Zn0.4Fe2.6O4 thin films grown on a MgO (110) single-crystal substrate with a TiN (110) buffer layer by using RF magnetron sputtering. X-ray diffraction patterns showed that the films grow with (110) orientation parallel to the MgO (110) surface. The saturation magnetization at room temperature was measured to be 0.59 Wbm-1 by vibrating sample magnetometer. Magnetic tunnel junction (MTJ), consisting of MgO (110)/TiN/Zn0.4Fe2.6O4/AlOx/Co9Fe/Ni8Fe2/Ta, were fabricated and showed a magnetoresistance (MR) ratio of about 6% at room temperature. The MR ratio increased up to 10% with decreasing temperature down to 75 K, while below 75 K, the MR ratio decreased with decreasing temperature.View full abstractDownload PDF (725K) -
Takashi Mizuguchi, Ken-ichi Ikeda, Fuyuki Yoshida, Hideharu Nakashima, ...2004 Volume 68 Issue 2 Pages 86-89
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSSilicon has been used as semiconductor devices. It is well known that silicon shows a sharp brittle-ductile transition and that silicon is a brittle material at the operative temperature of a device. Hence, it is important to understand fracture behavior to improve the reliability of a device.
Because the surface energy, γs is considered to affect the fracture behavior of a brittle material, it is important to investigate the crystal orientation dependence of γs just after fracture in order to clarify the details of fracture mechanism. This study was carried out to clarify systematically the crystal orientation dependence of γs in silicon by molecular dynamics calculation. And it is also carried out to investigate the crystal orientation dependence of γs after 1098 K annealing and it was compared with γs just after fracture.
It is revealed that γs of (111) plane has the minimum value. This fact agrees with the experimental fact that cleavage plane of Si is {111}. It is also found that γs after 1098 K annealing is lower than that just after fracture. It is concluded that the decrease in γs was brought about by the reconstruction of the atoms.View full abstractDownload PDF (1029K) -
Tomohiro Suzuki, Takahiro Ishizaki, Satoru Mori, Akio Fuwa2004 Volume 68 Issue 2 Pages 90-93
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSGe10Sb67.5Te22.5 thin films were prepared by RF magnetron sputtering from a single high purity Ge10Sb67.5Te22.5 target under the following condition: RF power: 30 W, Ar pressure: 1.067 Pa, Ar flow: 9 ccm, substrate temperature: room temperature (water cooling), distance between target and substrate: 7 cm, and sputtering time: 10∼40 min. Although the as-deposited film was amorphous, annealing for 30 min at 573 K allowed it to be crystallized. The crystallization temperature and the activation energy of Ge10Sb67.5Te22.5 thin film were around 463 K and 2.50 eV, respectively, while those of Ge2Sb2Te5 thin film, prepared under the same conditions as stated above, were around 408 K and 2.04 eV, respectively. The difference of optical constants between crystalline and amorphous phases of Ge10Sb67.5Te22.5 and Ge2Sb2Te5 thin films were −0.9+i 0.93 and −0.77+i 0.67, respectively, in a blue laser area, i.e., wavelength 405 nm.View full abstractDownload PDF (686K) -
Toshiharu Kobayashi, Yutaka Koizumi, Tadaharu Yokokawa, Makoto Osawa, ...2004 Volume 68 Issue 2 Pages 94-97
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSNi-base directionally solidified (DS) superalloys have an advantage of production costs over single crystal (SC) superalloys because of better yield rate of casting and simpler heat treatment compared with SC superalloys. In this study, we designed a 4th generation DS superalloy, TMD-111, based on our 5th generation SC superalloy, TMS-162, containing 5 mass%Ru; we added C and B on TMS-162 to strengthen the grain boundaries. The alloy was directionally solidified and heat treated under four different conditions, i.e., as cast, as solution treated, solution treated and aged, and solution treated and two step aged. The solution treated and two step aged sample showed the highest creep strength, although the effect of heat treatment was found to be relatively small. All the samples except for as cast ones showed longer 1% creep strain under a 1100°C/137 MPa compared with that of CMSX-10, a typical third generation SC superalloy.View full abstractDownload PDF (704K) -
Xiujuan Zhao, De Xin Yang, Kohji Takazawa, Shuichi Kamota, Yasuki Miya ...2004 Volume 68 Issue 2 Pages 98-101
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe formation of complex carbides in the interface between hard metal and bead has been investigated in Tungsten Inert Gas welded joints of WC-Co hard metal and carbon steel. This welding process is expected to be a new bonding method of hard metals and steels. But, it is necessary to reveal the formation factor of complex carbides that decrease the strength of hard metal/steel joints. WC-30 mass%Co alloy as welding layer in functionally gradient hard metal and 0.48 mass%C steel were joined by TIG welding of direct current using a pure Ni and 57 mass%Ni-Fe alloy filler rod. These joints were also welded overlays in 1 and 4 times. In the case welded using pure Ni filler, the complex carbides are not formed. On the other hand, in the case welded using 57 mass%Ni-Fe alloy filler, the complex carbide particles, (M, W)6C; i.e., η carbide, are formed in the hard metal side of the interface between hard metal and bead. The thickness of region that the η carbide particles were formed in 1 and 4 overlays welding joints are approximately 50 and 150 μm in maximum value, respectively. In these regions, Fe concentration in hard metal becomes approximately 35 at% or more due to the diffusion from Ni-Fe bead to WC-Co hard metal during welding process. The amount of Fe atom diffusing from bead to hard metal side increase in accordance with the increase of Fe concentration of filler rod, melt-mixed steel and the number of overlay times, and the Fe atoms accelerate the formation of η carbide.View full abstractDownload PDF (1156K) -
Takashi Shirai, Koji Matsumaru, Chanel Ishizaki, Kozo Ishizaki2004 Volume 68 Issue 2 Pages 102-105
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe surface of six different grades of commercial sub-micron high purity alpha alumina powders produced by two different processes, in-situ chemical vapor deposition (AA powders) and hydrolysis of aluminum alkoxide (AKP powders) methods are evaluated by Temperature Programmed Desorption Mass Spectrometry (TPDMS). All AA powders show almost the same quantities of H2O and CO2 desorbed molecules. On the other hand, the different grades of AKP powders show different quantities of H2O and CO2 desorbed molecules. The AKP-3000 powder quantity of desorbed H2O molecules is similar to that of the AA powders. However, the AKP-3000 powder quantity of desorbed CO2 molecules is about seven times larger than that of the AA powders. The maximum of the CO2 desorption peak is the range 230-270°C for all powders. The desorbed CO2 peak is considered to evolve from the adsorbed CO2 molecules forming hydrogen carbonyl groups by interaction with AlIV-OH groups on the α-alumina surfaces. The amount of hydrogen carbonyl groups on surface of the AKP powders is larger than for the AA powders, indicating that on AKP powder surfaces the amount of AlIV-OH groups is larger. These results show that on the surface of commercial high purity alpha alumina powder a complex hydrated layer exists by interaction between surface hydroxyl groups and CO2 adsorbed molecules, unlike commonly accepted stable alpha alumina structure.View full abstractDownload PDF (615K) -
Yoshikazu Mantani, Yoshito Takemoto, Moritaka Hida, Akira Sakakibara2004 Volume 68 Issue 2 Pages 106-109
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe purpose of this study is to investigate the textural changing process and the structural changing process of commensurate ω phase during tensile deformation in the metastable β-type Ti-14 mass%Mo alloy that is formed commensurate ω phase by quench. Optical microscopy, X-ray diffraction and transmission electron microscopy were performed for the specimens that were deformed until different tensile strain. In the 5%-strained specimen, many {332} ‹113› twins were formed, and commensurate ω phase of specific variant induced upon tensile deformation. In the 25%-strained specimen, secondary twins or slips which divided early formed {332} ‹113› twins into pieces were observed. Fine divided deformation texture was observed in the specimen after fracture, and it is considered that commensurate ω phase changed into incommensurate ω phase or transformed reversely to the β phase. The changing processes of deformation texture and commensurate ω phase were indicated from these results.View full abstractDownload PDF (673K) -
Naoki Okamoto, Tohru Watanabe2004 Volume 68 Issue 2 Pages 110-113
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIn the present study, the adhesive properties and interface microstructures of various electrodeposited films to various metallic substrates were investigated in detail. The adhesive strength of Cu, Ni and Ag thin films which were electrodeposited on the copper foils or the other metallic substrates deposited on copper foil were evaluated by adhesive tape test, while their interface structures were analyzed by using SEM, EDS, GD-OES and TEM. Cu deposited film on Ni or Ag film substrate, Ni deposited film on Ag film substrate as well as Ag deposited film on Ni or Cu film substrate are readily exfoliated from the substrate, showing a weak adhesion. It can be seen that there is a crystallographic coherency existing in the interface between Cu deposited films and Ni substrate. However, no crystallographic coherency can be observed in the interface between the Cu deposited film and Ag substrate. The results indicated that the adhesive properties of electrodeposited films closely correlate to the kind of metallic substrates, probably depending upon the different crystallographic coherency between the deposited films and various substrates.View full abstractDownload PDF (601K) -
Susumu Okamura, Ryota Goto, Nobuki Tezuka, Satoshi Sugimoto, Koichiro ...2004 Volume 68 Issue 2 Pages 114-117
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe structural, magnetic and transport properties are investigated for the full-Heusler alloy Co2(Cr1-xFex) Al (CCFA) thin films deposited on thermally oxidized Si substrates at room temperature (RT). X-ray diffraction reveals that the films possess the B2 structure for x=0, decrease the atomic site ordering by substituting Fe for Cr (x=0.4∼0.6) and form the A2 structure for x=1. Both the magnetic moment and the Currie temperature of the films increase with increasing Fe content (x), although the moment for x<1 is significantly smaller than that of the calculated value for the L21 structure. Spin-valve type tunneling junctions with CCFA films are also fabricated by using metal masks, which demonstrate tunneling magnetoresistance (TMR) of 19% for x=0.4 at RT and 27% at 5 K despite the atomic site disorder. This is the largest TMR observation at RT with half metallic ferromagnets.View full abstractDownload PDF (708K) -
Takayuki Kuwashima, Ikuo Takahashi, Tomoki Tomita, Akira Ohmori2004 Volume 68 Issue 2 Pages 118-121
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIn the thermal spraying technique, the process includes some problems such as insufficient cohesive strength between particles in the coating. It is considered that the laser treatment of thermal spray coating will be effective method to improve the coating properties. In this study, an yttrium aluminum garnet (YAG) laser treatment was carried out on the sprayed coating in order to examine the effect of laser beam on the coating properties.
The Cr3C2-Ni-Cr powder was used as the spray material, and stainless steel (SUS304) was used as the substrate. Irradiation laser power conditions were 1.5 kW, 2.0 kW and 2.5 kW, and defocus distance conditions were ±0 mm, +30 mm, +60 mm, +90 mm, changing the energy density and the traverse speed conditions were 100 mm/s, 200 mm/s, 300 mm/s. The cross section of coating structure was observed by optical microscopy and was analyzed by EPMA and XRD. The hardness of the coatings was measured by micro vickers hardness tester.
The coating structure varied from the laser irradiation condition. In the conditions of defocus distance ±0 mm, traverses speed 100 mm/s, the sprayed coatings were melted. The coating structure was different even in the identical processing condition by the place. The micro vickers hardness of melted area of coatings was lower and heat affected area of coatings was higher than no laser treatment coating.View full abstractDownload PDF (663K) -
Yasuhiro Kamada, Lefu Zhang, Katsuyuki Ara, Hiroaki Kikuchi, Yousuke T ...2004 Volume 68 Issue 2 Pages 122-125
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSWe have investigated the magnetic properties of four model alloys (18Cr8Ni0.5Si, 16Cr10Ni1Si, 13Cr20Ni2Si, and 10Cr30Ni3Si) for simulating radiation induced segregation in SUS304 austenitic stainless steels. All alloys are paramagnetic at room temperature. With reduction of temperature, a structural transition was occurred for alloys with lower Ni content (18Cr8Ni0.5Si and 16Cr10Ni1Si), which produced ferromagnetic martensite. Alloys with higher Ni content (13Cr20Ni2Si, and 10Cr30Ni3Si) became ferromagnetic at low temperature without martensitic transformation. Different effects of stress on the structure and magnetism were found also. Martensitic transformations and magnetic properties of austenitic stainless steels depend strongly on its chemical composition and can be classified by the value of Ni equivalent. This study suggests the possibility of applying magnetic methods to the nondestructive detection of radiation induced segregation.View full abstractDownload PDF (778K) -
Atsushi Kadowaki, Mitsuaki Takeuchi, Yoshihito Matsumura, Yoshitake Ni ...2004 Volume 68 Issue 2 Pages 126-129
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSAn optical scanner consisting of a unimorph giant-magnetostrictive Tb-Fe alloy film was prepared by DC magnetron sputtering. The Tb-Fe alloy film was deposited onto a polyimide substrate and an Al thin film on the untreated surface of the polyimide substrate served as a reflecting mirror. Optical scanning characteristics of the device were examined by a bending cantilever method using a He-Ne LASER under a magnetic field. The device showed reflection angle displacement of 1.3 degrees of along the x axis and 1.6 degree along the y axis at 1100 kA/m. An applied magnetic field in range from 20 to 500 kA/m reproducibility produces a reversible linear displacement. Based on the results, the Tb-Fe alloy film device could be applied as an optical sensor.View full abstractDownload PDF (824K) -
Joint Strength and Microstructure of SUS304 Brazed with Nickel-base Filler Metal for Heat ExchangersSatoshi Takayama, Youhei Arikura, Ikuo Shohji, Takanori Nakazawa, Ken ...2004 Volume 68 Issue 2 Pages 130-133
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe influence of exposure to heat after brazing and the plate thickness on the mechanical properties and the microstructures of brazed joints of SUS304 with Ni-based filler (BNi-2 filler) has been investigated. Fine Cr-B compounds, with diameters of approximately 5 μm, formed in the brazed joint. The diffusion of Cr and B along the grain boundaries of SUS304 was observed at the joint interfaces. The Vickers hardness of the Cr-B compound and the diffusion layer were approximately double that of the BNi-2 filler. The Cr-B compounds disappeared after the exposure to heat of 980°C for 6 h. On the other hand, the growth of the diffusion layer into SUS304 was observed after the exposure to heat. The joint strength was found to be approximately 100 MPa when fracturing occurred in the filler layer with Cr-B compounds and at the joint interface between the filler layer and the diffusion layer. When the thin plates with BNi-2 filler were brazed and a stress below 100 MPa was applied to the brazed joint, fracturing occurred not at the brazed joint but in SUS304.View full abstractDownload PDF (1115K) -
Tadashi Fukuda2004 Volume 68 Issue 2 Pages 134-137
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe effect of titanium on the ductility of 30% chromium ferritic steels was investigated by a tensile test at low temperatures. Carbon content is 0.023±0.002 mass%, and titanium content varies from 0.051 to 0.26 mass%. The ratio of titanium content to carbon content, Ti/C, ranges from 2.1 to 12.4. Ductility was evaluated by ductile-brittle transition temperature (DBTT) in reduction of area and fracture modes. The results obtained are summarized as follows: (1) Aging after solution-treatment gives rise to grain boundary precipitation of coarse Cr carbides and numerous fine Ti carbides depending on Ti/C ratio, while annealing without solution-treatment produces coarse globular carbide particles within grains. (2) The DBTTs for the specimens containing grain boundary carbides are higher than those for the specimens containing carbide particles within the grains independently of Ti/C ratio. The Effect of Ti/C ratio on the DBTT determined by the tensile test is not as remarkable as that on the DBTT determined by a Charpy impact test. (3) The effect of Ti/C ratio on fracture modes of the specimens containing grain boundary carbides is more remarkable than that on fracture modes of the specimens containing carbide particles within the grains. In case of the specimens containing grain boundary carbides, the amount of intergranular fracture first decreases with increasing Ti/C ratio up to 8 and then increases with the ratio at testing temperatures above 200 K, while at 153 K it first increases with increasing Ti/C ratio up to 8 and then decreases with the ratio.View full abstractDownload PDF (954K) -
Tadaharu Yokokawa, Makoto Osawa, Kenji Nishida, Yutaka Koizumi, Toshih ...2004 Volume 68 Issue 2 Pages 138-141
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIn this study, the partitioning behavior of alloying elements into γ matrix and γ′ precipitates in Ruthenium (Ru)-bearing γ′ precipitation hardening Ni-base superalloys has been investigated using electron probe X-ray micro-analyzer (EPMA). The third generation single crystal (SC) superalloy TMS-121 (Ni-16Co-3Cr-3Mo-6W-6Al-6Ta-5Re-0.1Hf: mass%) and three alloys with the addition of Ru in the range of 2 to 6 mass% into TMS-121 alloy were used. It is shown that Ru addition into Ni-base superalloys is effective in suppressing the topologically close packed (TCP) phase formation. Ru is preferentially partitioned into the γ matrix with the partitioning ratio of about 3:1 at 900°C, and 1.5:1 at 1200°C. Furthermore, it seems that the partitioning behavior of alloying elements is not affected by the Ru addition. For example, Re is preferentially partitioned into the γ matrix in any of the superalloys investigated, and the partitioning ratio of Re at 900°C in TMS-121 alloy is 13.5:1, and 9.5:1 for the alloy with 6 mass%Ru addition. The effect of Ru addition to suppress the TCP formation should not be attributed to a ‘Reverse partition’, which was reported by O'hara, et al.View full abstractDownload PDF (1488K) -
Mitsuaki Takeuchi, Yoshihito Matsumura, Hirohisa Uchida2004 Volume 68 Issue 2 Pages 142-144
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe magnetostrictive properties of Fe-Ga (Ga: 8 at%-21 at%) alloy films prepared by DC magnetron sputtering system were investigated. Base pressure was less than 1.0×10-4 Pa and Fe-Ga films were deposited onto Single crystal Si(100) and polyimide substrate at room temperature with DC 200 W in an Ar atmosphere of 2.5×10-1 Pa. The lattice parameter of Fe-Ga films with a bcc structure increased with the increasing Ga concentration. The Fe-Ga films showed columnar grains with a crystalline orientation for ‹110› perpendicular to the film plane. The magnetostriction of Fe-Ga films increased with the increasing Ga concentration. Fe-21 at%Ga film showed a maximum magnetostriction of 180 ppm at an applied magnetic field of 1200 kA/m.View full abstractDownload PDF (2732K) -
Etsuo Hamada, Masayasu Nagoshi, Kaoru Sato, Kotaro Kuroda2004 Volume 68 Issue 2 Pages 145-151
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSUsing electron back-scattering pattern (EBSP), phase identification of iron oxides, tin oxides and Fe-Zn intermetallics was tried. Even in the case of samples having rough surface or of insulators, enough quality of EBSPs for phase identification was obtained with submicron spatial resolution by modifying the measurement and data processing procedure, and with easy sample preparation. Crystalline phases were identified comparing the experimentally obtained pattern and the calculated pattern using the crystal parameters. The samples were successfully identified, except for crystals giving similar diffraction patterns each other or not having enough crystallographic data. EBSP was shown to be a useful tool for phase identification of submicron sized area.View full abstractDownload PDF (1300K) -
Hiroshi Sato2004 Volume 68 Issue 2 Pages 152-157
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe liquidus surfaces and the isothermal section at 1073 K of the pseudo-ternary CaO-Fe2O3-B2O3 system were determined in a composition range of less than 50 mol%B2O3 using the thermal analysis and X-ray diffraction. The liquidus surface which is in equilibrium with Fe3O4 spreads over a wide composition range and that in equilibrium with Fe2O3 extends long and narrow toward CaO·B2O3 and then toward B2O3 apex. Temperature of the liquidus surface in equilibrium with Fe3O4 remains above 1473 K in the composition range of less than 20 mol%B2O3 but decreases when the B2O3 content exceeds 40 mol%. The liquidus surface in equilibrium with 2CaO·Fe2O3 extends widely and its slope is steep in the region of less than 10 mol% B2O3 but gentle when the B2O3 content exceeds 15 mol%. Pseudo-ternary CaO-Fe2O3-B2O3 compounds were not found in the composition range investigated.View full abstractDownload PDF (822K) -
Akihiro Mizutani, Nobuhiro Uchida, Kazuya Oguri, Yoshitake Nishi2004 Volume 68 Issue 2 Pages 158-161
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSPercussion welding has been applied to the joining of carbon fiber (Torayca M30SC) to pure iron. The joining potential employed ranged from 160 to 210 V at a condenser capacity of 100 μF. Using a tensile test for fine fibers, fracture load from 0.01 to 0.075 N were obtained for optimum joining potential. Fracture occurred at the welding heat-affected zone of the carbon fiber near joining part.View full abstractDownload PDF (1035K) -
Kenya Nagahisa, Kazuteru Iwamoto, Kenji Shinozaki, Hideharu Fukunaga, ...2004 Volume 68 Issue 2 Pages 162-171
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe sintered SiC fiber reinforced SiO2-mullite composites, which have three levels of added Al2O3 in the matrix, i.e., SiO2-3.7, 30, 50 mol%Al2O3, were synthesized by liquid state hot-pressing. Variation in the thermal residual stress fields in the composites caused by the difference in the thermo-mechanical mismatch between the fiber and matrices were investigated. The effects of the Al2O3 content in the matrix on the mechanical properties of the composites were then examined.
The obtained composites had a very dense structure, and both the mullite and glassy SiO2 phases were found in the matrices. A higher Al2O3 content in the matrix lead to a higher mullite volume fraction. No chemical reaction among the constituents due to the fabrication process was observed.
It was confirmed that the thermal residual stress field in the composites changed with an increase in the coefficient of thermal expansion of the matrix accompanied by an increasing Al2O3 content in the matrices.
The network structure of the mullite crystals found in the SiC fiber/SiO2-30 mol%Al2O3 and SiC fiber/SiO2-50 mol%Al2O3 composites seemed to effectively prevent plastic deformation of the matrices during the flexural test at 1573 K.
The SiC fiber/SiO2-30 mol%Al2O3 composite showed excellent mechanical properties up to 1573 K compared with previously reported ceramic matrix composites such as the SiC fiber/LAS composite or SiC fiber bonded ceramics in an inert atmosphere.View full abstractDownload PDF (1773K) -
Kenya Nagahisa, Kazuteru Iwamoto, Kenji Shinozaki, Gen Sasaki, Manabu ...2004 Volume 68 Issue 2 Pages 172-180
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe sintered SiC fiber reinforced SiO2-mullite composites with matrix compositions, i.e., SiO2-3.7, 30, and 50 mol%Al2O3, had already been developed. In these composites, the thermal residual stress field changed with an increase in the coefficient of thermal expansion of the matrix accompanied by an increasing Al2O3 content (mullite volume fraction) in the matrices. A three-point flexural test was conducted for the composites at room temperature. The strain gauge method and AE monitoring were used to detect the matrix cracking strain during the test. The effect of the thermal residual stress on the matrix cracking strain and fracture behavior were investigated. The results are as follows.
The matrix cracking strain observed in the composites with a higher tensile thermal residual stress in the matrix region parallel to the fiber axis was well predicted by the BHE theory. For the SiC fiber/SiO2-50 mol%Al2O3 composite, the first acoustic emission signal was detected just after the initial proportional limit of the stress-strain curve. For the other composites, the signals were detected below this limit. When the residual stress in the matrix region parallel to the fiber axis was compressive, the linear fracture behavior was found. On the contrary, the bi-linear fracture behavior was enhanced by the tensile residual stress in the matrix. This tendency agreed with the prediction method by Luh and Evans. The magnitude of the fracture energy obtained in each composite was qualitatively explained by the conventional theoretical formula.View full abstractDownload PDF (1762K)
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