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Volume 65, Issue 6
Displaying 1-12 of 12 articles from this issue
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Masahiro Yamamoto, Hideki Katayama, Toshiaki Kodama2001 Volume 65 Issue 6 Pages 465-469
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA new type of corrosion sensor was successfully applied for the monitoring of the atmospheric corrosion rate of steels. The sensor consisted of a steel ring and a pin located concentrically with a narrow gap of plastic insulator. Both high frequency (10 kHz) and low frequency (10 mHz) AC impedance data were retrieved to obtain solution resistance and polarization resistance, respectively. Corrosion rate was estimated from the polarization resistance data. The monitored data indicated that the corrosion rate of steel was higher at night and rainfall than in the sunny condition of daytime. The data suggested the corrosion rate of steel was strongly affected by dewing and relative humidity (RH). As for the effect of sea salt deposition, somewhat complicated corrosion tendency was obtained. In the case when the salt deposition was small, the corrosion rate increased with increasing amount of deposited salt. At higher deposition levels of the salt of 0.1 and 0.01 kg/m2, however, different trend in corrosion was observed. At low RH a steel sample with higher salt deposition (0.1 kg/m2) showed higher corrosion rate, while under higher RH conditions the sample with lower deposition (0.01 kg/m2) gave higher value. The contradictory phenomena can be interpreted on the bases that the water film thickness changes with the salt deposition density and that the corrosion rate is influenced by the water film thickness. By thermodynamical calculation, it is estimated that the film thickness having maximum corrosion rate ranges from several tens to one hundred μm.
The corrosion loss estimated by the surface roughness using a laser microscope was compared with the cumulative values of impedance measured on the sensors. A linear relationship was observed between two values. It indicates that the monitoring system by means of the concentric-ring sensor is effective in the estimation of atmospheric corrosion rate of steels.View full abstractDownload PDF (501K) -
Tomoyuki Nishida, Hidekazu Sueyoshi2001 Volume 65 Issue 6 Pages 470-476
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSGraphite was bonded to nickel in a vacuum using an RF-induction furnace by changing conditions of temperature, keeping time and joining compressive stress. The bending strength of graphite/nickel joints and the changes of microstructure and hardness near the joining interface of nickel were investigated. Thermal stress induced in the joints was estimated by means of finite element analysis. On the basis of these results, the influences of joining compressive stress on bonding were examined.
Joining compressive stress and temperature are important factors for close contact and strong bonding between joining surfaces of graphite and nickel. At high temperature, nickel is plastically deformed even under low joining compressive stress so that full contact and strong bonding are accomplished, while at low temperature, no strong bonding are attained when joining compressive stress is lower, because plastic deformation of nickel is restrained. Plastic deformation of nickel plays an important role in full contact and strong bonding.
The strength of the joints increased as joining compressive stress increases, because of the following reasons: The plastic deformation of nickel near the joining interface increases with joining compressive stress so that graphite is elastically deformed in radial direction during annealing. Therefore, longitudinal compressive stress is induced on the graphite surface near the joining interface. Thermal tensile stress induced on the graphite surface after cooling is relaxed by this compressive stress.View full abstractDownload PDF (976K) -
Keita Isogai, Shin-ichi Yamaura, Hisamichi Kimura, Akihisa Inoue2001 Volume 65 Issue 6 Pages 477-481
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have examined electrode properties and thermal stability of the melt-spun amorphous Mg67Ni28Pd5 alloy subjected to electrochemical hydrogen charge. The maximum discharge capacity obtained at 308 K reaches 411 Ah/kg. The result shows that the melt-spun amorphous Mg-Ni based alloy has good hydrogen discharge characteristics even at room temperature. In the cycle test of the electrochemical measurement, the discharge capacity increases significantly with increasing cycle number in contrast to the significant degradation of the discharge capacity with cycle number for mechanically alloyed Mg-Ni based amorphous alloys. The present electrochemical data also indicate the existence of the plateau-like stage with very small gradient in the discharge hydrogen-composition isotherm curve. Furthermore, the hydrogen-absorbed amorphous alloy crystallizes through two stages consisting of the first-stage precipitation of Mg2Ni, followed by the second-stage precipitation of Mg2NiH4. The completed temperature of crystallization for the hydrogen-absorbed alloy increases by 65 K as compared with the as-spun amorphous single phase alloy. It is thus concluded that the stability of the Mg-Ni based amorphous alloy against crystallization increases by absorbing hydrogen.View full abstractDownload PDF (378K) -
Chang Seog Kang, Kenji Wakashima2001 Volume 65 Issue 6 Pages 482-489
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA mechanical spectroscopy study has been made on fine-grained Ni-TZP (ZrO2-3 mol%Y2O3) composites in an attempt to assess the following micromechanical prediction in a previous paper: a dual-phase material with two different fine-grained constituents, each deforming by Coble-type boundary-diffusion creep, exhibits viscoelastic (anelastic plus viscous) behavior in consequence of differential creep between the phases. Two composites with 10 and 20 vol% TZP, fabricated by powder processing, are examined. Despite the metal-rich compositions, either “metal-matrix” or “ceramic-matrix” microstructure is produced, which is characterized by essentially equiaxed, mostly single-grained, domains of one constituent in a fine-grained matrix of the other. Dynamic Young’s modulus, Eω, and internal friction, tanφ, are measured over a temperature range of 25 to 800°C at frequencies of 0.01, 0.05 and 0.1 Hz using a specially designed tension-compression apparatus; the data obtained are analyzed in terms of loss compliance, J2≅tanφ⁄Eω. Two relaxation peaks are observed in both composites; also, an exponential rise with temperature is a trend characterizing the background profile especially for the metal-matrix composite. The activation energies and pre-exponentials involved in the peak and background components are determined and, by making a further analysis based on the previous micromechanical formulation and also taking the well-known relaxation due to viscous grain-boundary sliding into account, the implications of these quantities are discussed in terms of constituent material parameters (boundary diffusivity, grain size, etc.).View full abstractDownload PDF (982K) -
Yoshinobu Saito, Akinori Sato, Masakatsu Hinai2001 Volume 65 Issue 6 Pages 490-494
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe vibrational damping capacity and magnetoelastic effect were investigated for an Fe-49 mass%Co-2 mass%V alloy. The alloy was water-quenched and air-quenched, and cooled slowly with and without a magnetic field of 16 kA/m after heating at 1123 K for 2 h, respectively. Measurements of the logarithmic decrement (δ) and ΔE effect (ΔE⁄E0) were carried out using a cantilever method, and the magnetic hysteresis curve was measured using a direct current BH tracer. The δ and ΔE⁄E0 of alloy showed the maxima with the strain amplitude, and the maximum values became higher with decreasing cooling rate. The X-ray diffraction patterns showed the bcc lattice structure; only the reflection of the basic lattice in the water-quenched sample and additionally the reflection of the orded lattice in the slow-cooled samples.
The coercive force (Hc) value became smaller with decreasing cooling rate. By cooling in a magnetic field, the δ and ΔE⁄E0 values became higher and the Hc value became smaller. These results suggest that the alloy is able to use as the high vibrational damping material.View full abstractDownload PDF (398K) -
Kiyoshi Itoh, Feng Wang, Tohru Watanabe2001 Volume 65 Issue 6 Pages 495-501
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe electrodeposited Ni-P alloy films were obtained from Watts baths containing H3PO3. The crystallographic structure and morphology of electrodeposited Ni-P films were studied by using XRD, HRTEM, SEM and heat-treatment technique. The crystallographic structures of electrodeposited Ni-P alloy films was also compared with the Ni-P thermal equilibrium diagram.
The X-ray diffraction patterns of Ni-P electrodeposited films with various P contents gradually changed from sharp peaks to broad peaks with increasing P contents in electrodeposited films. HRTEM observation revealed that the crystallographic structure of electrodeposited Ni-P film with 18.5 at%P content was crystalline and its crystal size was about 10 nm. Moreover, the crystalline structure was observed and the crystal size was about 3 nm in the electrodeposited Ni-P alloy film with 21.5 at%P content. However, when the film with 21.5 at%P content was heat treated, the crystalline phase did not grow and Ni3P existed alone under 300°C heat-treatment. From this result, it was clear that the crystallographic structure of Ni-P film with 21.5 at%P content was amorphous.
Therefore, it can be concluded that the microcrystalline phase existed up to 19 at%P in electrodeposited Ni-P alloy film and the amorphous phase existed from 19 at% to 32 at%P.View full abstractDownload PDF (1201K) -
Yukio Ide, Hidenori Era, Katsuhiko Kishitake2001 Volume 65 Issue 6 Pages 502-508
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCr-N films were deposited using a dc reactive sputtering apparatus equipped with an optical emission spectroscope(OES) and the behavior of some species excited in the plasma was monitored by OES during sputtering. The films deposited were characterized with respect to the chemical composition, crystal structure and wear resistance. The results are summarized as follows.
(1) The N/Cr ratio monitored by OES increased proportionally with the nitrogen partial pressure.
(2) The N/Cr ratio in the deposited films was nearly proportional to the N/Cr ratio measured by OES during sputtering. Therefore, it may be possible to control the chemical composition of Cr-N films during sputtering.
(3) The N/Cr ratio in the Cr-N films increased continuously , and the structure of the films changed from Cr2N through Cr2N+CrN to CrN with increasing nitrogen partial pressure.
(4) Cr2O3 oxide surface layer was observed on the Cr-N films after heating at 800°C for 60 min in air.
(5) The crystal structure of CrN films hardly affected the friction coefficient at room temperature. The wear resistance of CrN single-phase film was superior to Cr2N single-phase film and Cr2N+CrN dual-phase film at 100°C.View full abstractDownload PDF (714K) -
Tomonobu Owa, Takeshi Shinoda, Yoshihisa Katoh2001 Volume 65 Issue 6 Pages 509-516
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn this work, a feasibility study has been conducted on the formation of NiTi intermetallic compound coating by plasma transferred arc (PTA) surfacing process. The filler materials used were alloyed powder of NiTi and physically mixed powder of nickel and titanium. Wear characteristics of the coatings were evaluated by a modified Okoshi-type wear tester.
It was found that it is possible to produce intermetallic compound coatings from the mixed powder as well as alloyed powder by PTA surfacing process. The wear resistance of the coatings formed from alloyed powder (the NiTi coating) is superior to the resistance of Stellite #6 coatings. The coatings formed from mixed powder (the Ni+Ti coating) have wear resistance similar to that of Stellite #6 coatings. X-ray diffraction result indicates that the NiTi coatings mainly consist of NiTi phase, whereas the Ni+Ti coatings principally consist of NiTi and FeTi phases. Hardness values of both NiTi and Ni+Ti coatings reached to 800HV or more, and then minute cracks were observed in both coatings.View full abstractDownload PDF (1641K) -
Minoru Tagami, Keizo Kashihara, Tatsuya Okada, Fukuji Inoko2001 Volume 65 Issue 6 Pages 517-523
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to clarify the relationship between deformation-induced structure and formation of recrystallized grains in multipled slip regions, ⟨112⟩ aluminum single crystal was deformed in tension to a strain of 22% at room temperature and then annealed at certain condition. The results obtained were compared with the previous ones of ⟨111⟩ and ⟨001⟩ single crystals. No deformation band was observed in ⟨112⟩ specimen in addition to ⟨001⟩ and ⟨111⟩ ones. The misorientations in the whole area of the deformed ⟨112⟩ specimens were within 5°. More than sixty percent of recrystallized grains had the ⟨111⟩ rotation recrystallized relationship with the deformed matrix. The stress value at 22% strain and the number of the recrystallized grains in ⟨112⟩ specimen were relatively smaller than those in ⟨111⟩ one and larger than those of ⟨001⟩ one. The behaviors of deformation and recrystallization are discussed to be affected strongly by the operation of cross slip.View full abstractDownload PDF (1427K) -
Shintaro Ishiyama, Yasushi Muto, Takashi Nishii, Michihiro Kasaba2001 Volume 65 Issue 6 Pages 524-533
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSFeasibility study on a HTGR-GT (High Temperature Gas cooled Reactor-Gas Turbine) system is examining the application of the high strength/high thermal conductivity alumina dispersed copper (AL-25) in the ultra-fine rectangle plate fin of the recuperator for the system.
However, it is very difficult to manufacture a ultra-fine fin by large-scale plastic deformation from the hard and brittle Al-25 foil.
Therefor, in present study, to establish the fine fin manufacturing technology of the AL-25 foil, it did the processing simulation of the fine fin first by the large-scale elasto-plastic finite element analysis(FEM) and it estimated a forming limit.
Next, it experimentally made the manufacturing equipment where it is possible to do new processing using these analytical results, and it implemented a manufacturing experiment on the AL-25 foil.
With these results, the following conclusion was obtained.
(1) It did the processing simulation to manufacture a fine rectangle fin (fin height×pitch×thickness, 3 mm×4 mm×0.156 mm) from AL-25 foil (Thickness=0.156 mm) by the large-scale elasto-plastic FEM using the double action processing method. As a result, the manufacturing of a fine rectangle fin found a possible thing in the following condition by the double action processing method. It made that 0.8 mm and 0.25 mm were a best value respectively in the R part and the clearance between dies by making double action processing examination equipment experimentally and implementing a manufacturing examination using this equipment.
(2) It succeeded in the manufacturing of the fine fin that the height×pitch×thickness is 3 mm×4 mm×(0.156 mm±0.001 mm) after implementing a fine rectangle fin manufacturing examination from the AL-25 foil.
(3) The change of the process of the deformation and the thickness by the processing of the AL-25 foil which was estimated by the large-scale elasto-plastic FEM showed the result of the processing experiment and good agreement.
This way of analyzing made an effective thing clear as the processing estimation of the manufacturing practicalizing of the fine fin of the difficulty process-ability material by the double action processing method from this study.View full abstractDownload PDF (988K) -
Yuji Fukaya, Shunichi Sato2001 Volume 65 Issue 6 Pages 534-538
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA simple control method for the velocity distribution of cesium atoms is demonstrated using a frequency modulated diode laser with a wider spectrum. Current to the diode laser was modulated and the laser spectrum was broadened to overlap the Doppler broadening of the atomic beam. The reduction of the atom velocity was achieved on the basis of the laser cooling technique and a single narrow peak at approximately 45 m/s was observed. From a view point of a novel purification process, the possibility to deflect this cooled cesium atomic beam was discussed to spatially separate the beam from impurities.View full abstractDownload PDF (430K) -
Masakazu Kobayashi, Yoshimasa Takayama, Hajime Kato2001 Volume 65 Issue 6 Pages 539-545
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSGrain-boundary mobility, which plays a significant role during grain growth in polycrystalline materials, is related to activation energy for grain-boundary migration. From this aspect, the authors simulated grain growth considering mobility into an activated state accompanying reorientation. The mobility is affected by impurities in the activation process and is represented as a function of interaction factor between grain boundary and impurities. The authors confirmed that grain boundary migration is slower for a larger interaction factor. Assuming a constant driving pressure of the grain boundary, the mobility suggests Arrhenius type dependence of temperature. The direction of grain-boundary migration at a triple junction depends on not only the grain boundary energy but also the interaction factor. Therefore, equilibrium at the triple junction of grain boundaries should be established based on the grain-boundary energy compensated by the mobility.View full abstractDownload PDF (490K)
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