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Volume 72, Issue 5
Displaying 1-13 of 13 articles from this issue
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Teruo Anraku, Iwao Sakaihara, Takeshi Hoshikawa, Masafumi Taniwaki2008 Volume 72 Issue 5 Pages 311-316
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSThermal expansion behavior in a stoichiometric AuCu alloy was investigated from a point of view of a phase transition. Thermal expansion measurement was carried out from room temperature to 873 K at various heating and cooling rate. The crystal structures and the phase transitions were analyzed by X-ray diffractmetry and differential scanning calorimetry, respectively. The structure of the casted alloy was a disordered face-centered cubic and changed to a face-centered tetragonal structure or mixed structure of fcc and AuCu I after thermal expansion measurement. In the thermal expansion curves, break points were corresponded to order-disorder transition. During the heating process, three break points corresponding to three different ordering stages were observed. The activation energy for each stage was obtained using Kissinger method. It was considered that first and second stages are ascribed to the migration of excess vacancies induced by quenching, and third stage is predominated by self-diffusion.
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Satoru Takahashi, Masayuki Yoshiba, Hirofumi Kimura, Yoshio Harada2008 Volume 72 Issue 5 Pages 317-322
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSIn order to clarify different manners of failure behavior for plasma sprayed thermal barrier coating (TBC) systems under the complicated modes of thermal-mechanical-chemical loadings, the stress rupture properties was evaluated in air and in high-temperature corrosive environment with relation to the failure analysis for two kinds of TBC systems produced by different bond-coat (BC) processing. CoNiCrAlY-BC was manufactured by a vacuum plasma spraying (VPS) or high velocity oxy-fuel (HVOF), and then the Y2O3-stabilized ZrO2 top-coat (TC) was made by an atmospheric plasma spraying (APS). After then, heat-treatment was adopted for the sprayed TBC specimens in pure argon atmosphere.
TBC system with HVOF-BC was found to result in the almost equivalent rupture life to that of VPS-BC, because the compositional and microstructural modification; equalization, of the HVOF-BC was attained by the heat-treatment. Furthermore, it was found that the strength properties of both TBC systems depend strongly on the loading condition. Namely, the static creep loading was found to cause the almost similar rupture life to the no-coated substrate superalloy for both TBC systems regardless of the environmental condition. On the contrary, the dynamic fatigue and creep-fatigue loadings tend to bring about a significant rupture life reduction, since the penetration crack induced by the heat-treatment in the TC provides directly the nucleation site of the fatigue main crack.
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Yasuhiro Asahi, Shinji Takayama2008 Volume 72 Issue 5 Pages 323-330
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSThe temperature dependent internal stresses distribution in depth for Al/Mo and Cu/Mo bilayer films were measured first time by using a grazing incidence X-ray scattering (GIXS) method. It was found that the residual internal stresses in each as-deposited layer film were tensile, and that there was a large stress gap at the interface between layers. These stress distribution profiles with depth in each layer were largely changed on annealing at an elevated temperature. Particularly, each internal stress at the interface between layers tended to change with each other so as to relieve a large stress gap at the boundary between layers. It was also revealed that there was a large difference in stress change at the interfaces on annealing between Al/Mo and Cu/Mo films.
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M. Taguchi, K. Itou, J. Nakayama, T. Hirasawa2008 Volume 72 Issue 5 Pages 331-336
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSA series of PbO2 nanoparticles prepared by hydrolysis of lead acetate in various mixtures of water and alcohol were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and BET adsorption measurement, and the properties of the lead acid battery using the nanoparticles as the active materials for positive electrode were examined by discharge-charge cycling. All the nanoparticles, which were identified as β-PbO2 single phase, ranged from about 9 to 13 nm in diameter. While (water/n-propylalcohol) mixture had little or no effect on refinement of the particles, the particles prepared in both (water/ethylalcohol) and (water/methylalcohol) mixtures were finer than those in pure water. In comparison with the PbO2 powder prepared by the conventional method in lead acid battery industry, namely the electrolytic oxidation of lead powder, the PbO2 nanoparticles had remarkably high performance in both utilization of the active materials for positive electrode and the current efficiency during discharge-charge cycling.
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Izumi Muto, Hidenori Yoshida, Hiroshi Ogawa, Nobuyoshi Hara2008 Volume 72 Issue 5 Pages 337-346
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSThe effect of alloying elements on the atmospheric corrosion behavior of zinc die-casting alloys was investigated using the cyclic wet and dry test which simulated a diurnal change in specimen temperature and relative humidity in an actual outdoor environment. The deposition amount of chloride ions on the specimen surface was adjusted to 1.0×10-3 and 1.0 g•m-2 by forming of a uniform layer of diluted synthetic seawater. The addition of aluminum and mischmetal (MM) improved the corrosion resistance of zinc die-casting alloys, while that of Cu degraded the corrosion resistance. Polarization measurements indicated that Cu addition promotes the reduction reaction of dissolved oxygen. Corrosion products formed on Cu-containing specimens also promoted the cathodic reaction. On the contrary, the corrosion products on Al-containing and MM-containing alloys had the ability to suppress the anodic reaction. The value of average corrosion depth and the composition of corrosion products in the accelerated corrosion test were compared to those obtained by atmospheric exposure tests. It was concluded that the cyclic wet and dry test, in which diluted synthetic seawater is used as a test solution, is appropriate for an accelerated atmospheric corrosion test for zinc alloys.
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Atsushi Sasago, Shoichi Kikuchi, Yutaka Kameyama, Jun Komotori, Kengo ...2008 Volume 72 Issue 5 Pages 347-352
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSA new surface treatment system (IH-FPPsystem) combined with an induction heating and a fine particle peening machine were developed. FPP treatments were carried out on structural steel discs by using Cr shot particle at room temperature, 400°C, 600°C and 900°C. After characterizing the surfaces by SEM, EDX and XRD, corrosion tests were performed by a three electrode method using a computer driven potentiostat. No noticeable differences were observed on the specimen treated at RT, 400°C and 600°C. In the case of the specimen treated at 900°C, however, higher corrosion resistance which is almost the same as FPP treated stainless steel (SUS316L) was observed. This was because Cr diffused layer covered with relatively smooth oxidized surface prevented a corrosion reaction in 3%NaCl environment.
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In-Joon Son, Hiroaki Nakano, Satoshi Oue, Shigeo Kobayashi, Hisaaki Fu ...2008 Volume 72 Issue 5 Pages 353-359
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSThe effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L of AlCl3 and also by surface analysis. The time required before initiating pitting corrosion of anodized Al-Cu alloy was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. Second phase precipitates were present in Al-Cu alloy matrix and the size of these precipitates was greatly decreased by application of ECAP. The precipitates composed of Si and Al-Cu-Si-Fe-Mn were not oxidized during anodization, and the anodic oxide film were absent at the boundary between the normal oxide films and these impurity precipitates. The pitting corrosion of anodized Al-Cu alloy occurred preferentially around these precipitates, the improvement of pitting corrosion resistance of anodized Al-Cu alloy by ECAP appears to be attributable to a decrease in the size of precipitates, which act as origins of pitting corrosion.
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Yoko Ohnishi, Kazuki Fujio, Eigo Kakutani, Atsushi Yamamoto, Harushige ...2008 Volume 72 Issue 5 Pages 360-365
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSChanges in residual stress and precipitation phenomena were studied, during aging for an austenitic stainless steel, SUS316L, cold-rolled with various degrees of reduction and surface ground by transmission electron microscopy and synchrotron radiation (SR) diffractmetry. After aging at 573 K, two kinds of precipitates were observed in the cold-rolled specimens. They were identified as M7C3 and M23C6 by SR diffraction and electron diffraction measurements. The precipitate M7C3 was formed both in grain interiors and at grain boundaries, while the precipitate M23C6 was formed in grain interiors. Precipitation was promoted with increasing cold-rolling reduction. Additionally, segregation of phosphorous was expected along grain boundaries. Residual stresses measured at a synchrotron radiation facility, SPring-8, showed that the compressive stress detected in cold-rolled specimens was changed into tensile stress with proceeding of aging. On the other hand, the tensile stress induced by surface grinding was decreased.
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Hironori Sato, Keisuke Iwata, Masae Kanda, Akira Tonegawa, Yoshitake N ...2008 Volume 72 Issue 5 Pages 366-370
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSTo investigate the influence of electron beam (EB) irradiation on water absorption of acryl resin, the acryl resin samples before and after the irradiation were dipped in the water at 353 K. The water absorption increased the mass (1.81 mass% at 105 s) of irradiated acryl resin, which mass was larger than that (1.75 mass% at 105 s) before irradiation. When the absorption time was less than 104 s, the EB irradiation tremendously increased the mass (0.054 mass%) of absorbed water. Based on surface energy and extended Fowkes theory, the influence of EB irradiation on the water absorption was evaluated to discuss the mass increase induced by EB irradiation. It strongly enhanced the acryl solid-liquid interfacial energy (interfacial energy) of water, which was higher than those of n-hexadecane and 1-bromonaphtalen. EB irradiation increased the interfacial energy of hydrogen bond strength. Based on ESR results, EB irradiation broke the weakly bonded pairs and formed the dangling bonds in acryl resin, whereas water absorption annihilated the dangling bonds. The influence of electron beam (EB) irradiation on water absorption of acryl resin was mainly explained by the dangling bond formation in acryl resin.
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Ryo Nakano, Yoshihito Matsumura, Yoshitake Nishi2008 Volume 72 Issue 5 Pages 371-375
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSThickness dependence of aluminum substrate on magnetic field induced bending motion of Fe2.4Sm alloy thin film prepared by direct current magnetron sputtering process was investigated. The residual gas pressure before argon sputtering and the sputtering pressure of argon gas (5 N) were less than 3.3×10-4 Pa and 2.0×10-1 Pa, respectively. The thickness of the Fe2.4Sm films deposited was about 2.1 μm. Bending motion of Fe2.4Sm alloy film largely depended on substrate thickness. The large bending motion induced by magnetic field and its high susceptibility were found in the compressive magnetostrictive Fe2.4Sm alloy film on aluminum thin sheet.
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Kensuke Kuroda, Hironobu Shidu, Ryoichi Ichino, Masazumi Okido2008 Volume 72 Issue 5 Pages 376-382
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSThe aim of this study was to examine the formation of titania (TiO2)/hydroxyapatite (HAp) composite films on a titanium substrate using anodic-cathodic pulse electrolysis. The TiO2/HAp composites were coated on commercial pure titanium plates (surface area: 1.0 cm2) using pulse electrolysis in an autoclave in an aqueous solution that consisted of 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2 and pH=5.5 at 120°C. The pulse potentials were applied at +8.7 V vs. Ag/AgCl sat. KCl as anodic potential and -9.3 V as cathodic. The total electrolysis time was 1800 s. We examined the effects of the electrolysis cycle (60~600 s) and duty ratio on such properties of the coatings as the surface morphology, the amount of precipitated HAp, and the size of the HAp crystals. Prior to the pulse electrolysis, cathodic and anodic electrolysis experiments were also conducted. With pulse electrolysis, we could obtain TiO2/ HAp composite films with fine HAp particles dispersed uniformly on a thin TiO2 coating.
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Kensuke Kuroda, Hironobu Shidu, Ryoichi Ichino, Masazumi Okido, Azusa ...2008 Volume 72 Issue 5 Pages 383-387
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSTitania (TiO2)/hydroxyapatite (HAp) composite films were prepared on commercial pure titanium rods (2 mm in diameter, 5 mm in length) by anodic-cathodic pulse electrolysis in an aqueous solution consisting of 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2 and pH=5.5. The electrolysis was carried out in an autoclave at 120°C for 30 min. using +8.7 V vs. Ag/AgCl sat. KCl as the anodic potential and -9.3 V as the cathodic potential, and changing the electrolysis cycle (60~600 s) and duty ratio. We obtained TiO2/HAp composite films in which fine HAp particles were uniformly dispersed on a thin TiO2 layer. The coated rods were implanted in the tibiae of 10-week-old male rats. The constructs were retrieved 14 d postimplantation and examined for new bone formation and tissue response in the cancellous and cortical bone. They were compared with HAp-coated titanium rods, TiO2-coated rods (anodizing in an aqueous solution), TiO2/HAp-coated rods formed by the high temperature oxidization of specimens coated with HAp by cathodic electrolysis, and uncoated titanium rods. Fourteen days after implantation, new bone had formed on all the coated samples (HAp, TiO2, and TiO2/HAp) and noncoated titanium rods in the cancellous bone and cortical bone. In particular, TiO2/HAp composite films prepared by pulse electrolysis had very high osteoconductivity in the part of cortical bone, which resulted from a synergistic effect of HAp and TiO2 on the bioactivity.
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Noriaki Sakurai, Junjiro Takekawa2008 Volume 72 Issue 5 Pages 388-395
Published: 2008
Released on J-STAGE: May 01, 2008
JOURNAL FREE ACCESSTo obtain stronger metal foams, a heat treatment was done to strengthen the matrix of the foams. A powder of SUS440C stainless steel, the strongest of all stainless steels, was used as the starting material.
The green foams of the SUS440C steel powders with various porosities made by vacuum process using slurry were debound at 450°C and sintered at 1200°C in H2 into SUS440C steel foams. Some of the foams were heat-treated under a specified condition. The compressive test was done on both the heat-treated and non-heat-treated specimens.
Non-heat-treated SUS440C steel foams, even at a porosity as low as 53%, showed plateau regions with a stress of 168 MPa and a strain of 60%. These results suggest that these foams have potential for use as a good shock absorber. On the other hand, the plateau stress of the heat-treated SUS440C steel foams were twice as high as the non-heat-treated foams. The two heat-treated SUS440C steel foams, having densities of 2.7 and 4.5 g/cm3, showed almost the same yield stress as the wrought Al and Ti alloys, respectively. This demonstrates that the SUS440C steel foams could be inexpensive alternatives for those alloys. The maximum weight-lightening achieved with the SUS440C steel by making porosity inside was one-third of the guideline of the minimum weight design.
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