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Volume 70, Issue 10
Displaying 1-12 of 12 articles from this issue
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Hisashi Mori, Takaya Tominaga, Motohide Matsui, Hai Qiu, Taro Tsujimur ...2006 Volume 70 Issue 10 Pages 785-789
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSIn order to origin of thermal cracks initiation to the brake disc in Ni-Cr-Mo alloy steel was investigate, crack initiation and propagation morphology was performed by brake test and observation of microstructure in this study. It was found that the propagation morphology of generated cracks were shell likes and half ellipse morphology for surface and through thickness. Driving force of crack initiation and propagation was caused by thermal fatigue.
The origin of thermal fatigue cracks was peculiar structure which were shown by effect of thermal activation during wear. It was considered that the thermal crack was generated by load of tensile stress to the carbide in peculiar structure.
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Atsushi Ikeda, Tetsuya Wada, Minoru Tagami, Tatsuya Okada, Fukuji Inok ...2006 Volume 70 Issue 10 Pages 790-796
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSAn aluminum bicrystal having a symmetric 90° tilt grain boundary was tensile-deformed at room temperature and subsequently annealed. In the component grains of the bicrystal, two slip systems with almost the same Schmid factor were activated on the primary slip plane. The grains were rotated in the opposite directions, which resulted in the decrease in the tilt angle by 20°. Two different types of deformation bands, i.e. band of secondary slip and kink band were formed in the grains. The deformation was not symmetric about the grain boundary. Recrystallization occurred through strain induced boundary migration predominantly from one of the grains towards the other.
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Tatsuro Morita, Wataru Takahashi, Kazuhiro Kawasaki, Takashi Maeda2006 Volume 70 Issue 10 Pages 797-803
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSThis study was conducted to examine the effect of aging treatment for a short time between 6 s and 1.8 ks after cold-rolling on the mechanical properties of the β titanium alloy Ti-20V-4Al-1Sn. Cold-rolling at between 30% and 70% reduction accelerated hardening with aging at 673 K. It was thought that the dislocations introduced during cold-rolling provided suitable places for α fine-phase precipitation. When the alloy was cold-rolled at 70% reduction and then aged at between 673 K and 823 K by induction heating, the α phase precipitation occurred from 6 s and its volume fraction increased with time. As the aging temperature was lower and the aging time was longer, the average distance between the particles of the precipitated α phase became small, so that hardness and tensile strength increase was remarkable. In particular, the tensile strength of the alloy was significantly improved to 1510 MPa by aging for 1.8 ks at 723 K after cold-rolling at 70% reduction although ductility was greatly decreased.
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Satoshi Oue, Hiroaki Nakano, Ryo Kuroda, Shigeo Kobayashi, Hisaaki Fuk ...2006 Volume 70 Issue 10 Pages 804-808
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSThe microstructure of Ni-Sn alloys electrodeposited at 65°C and in 50-5000 A/m2 from acidic aqueous solutions containing 1.25 mol/L NiCl2 and 0.03-0.41 mol/L SnCl2 were examined by TEM-EDX. In the Ni-Sn alloy deposition, Ni and Sn were codeposited at an atomic ratio of 1:1 under the wide ranges of solution compositions and current densities. EDX mapping images of a cross section of Ni-50 at%Sn alloy deposited at current densities more than 1000 A/m2 revealed a lamellar phase parallel to the interface between substrate and deposit. The lamellar phase were identified as Ni3Sn4 and Ni3Sn2 by EDX line analysis. It was concluded that the Ni-50 at%Sn alloys were not composed of the metastable-phase NiSn single alloy reported previously, but consisted of two Ni3Sn4 and Ni3Sn2 alloy phases in a thermodynamically stable instead.
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Properties of Sulfur-Contained Iron Powder Suitable for Degradation of Chlorinated Organic CompoundsHiroki Nakamaru, Tomoshige Ono, Yoshiei Kato, Kuniaki Ogura2006 Volume 70 Issue 10 Pages 809-815
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSBatch dechlorination experiments with a shaken electrolytic solution and soils were carried out to identify iron powders suitable for degradation of chlorinated organic compounds and investigate the effects of operational factors on the reaction rate. Reduced or water atomized iron powders with varying contents of sulfur, manganese, and silicon were used. 50 mL of the electrolytic solution and 5 g of iron powder were added to a 100 mL vial glass bottle for the degradation tests of water, and 40 g of dry sand and iron powder adjusted for the water content in soil were used in the dechlorination tests of soils contaminated by trichloroethylene (TCE). The TCE concentration was measured by the headspace GC/MS analysis method.
A correlation was observed between the degradation rates of the electrolytic solution and the results of the soil tests.
The degradation rate of TCE in water was enhanced by higher concentrations of sulfur and silicon and lower concentrations of manganese. EPMA analysis of the iron powders with high concentrations of sulfur verified that FeS precipitates in iron powders with lower manganese concentrations, whereas MnS precipitates in powders with higher manganese concentrations. Because degradation of TCE takes place at the local electrode on the surface of the iron powder with FeS forming the cathode, the increase in the dechlorination reaction rate seen under the above-mentioned conditions was attributed to the fact that the electrical conductivity of FeS is higher that of MnS.
The dechlorination rates of TCE per unit mass of iron powder were constant and independent of the iron powder content in the soil. On the other hand, the overall degradation rate of TCE increased with the water content in the soil.
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Kazutaka Fujita, Tetsuro Hashimoto, Wei Zhang, Nobuyuki Nishiyama, Cha ...2006 Volume 70 Issue 10 Pages 816-823
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSFatigue tests were carried out on nanocrystalline Ti- and Cu-based bulk metallic glasses (BMGs) for which there are still no reports on fatigue strength. Test alloy rods with a diameter of 2 mm were prepared in nanocrystalline Ti41.5Zr2.5Hf5Cu42.5Ni7.5Si1 at% and Cu60Zr30Ti10 at% systems by copper mold casting. Nanocrystals were dispersed in the metallic glassy phase in both BMGs. The tensile strength (σB) in the nanocrystalline Ti- and Cu-based BMGs were 2.04 GPa and 2.00 GPa, and Young' s modulus were 95 GPa and 114 GPa, respectively. The test specimens were machined to hourglass shape type (the radius in axial direction; 4.45 mm, the minimum diameter; 0.9 mm), and after machining the specimen surfaces were electropolished by 50~100 μm. The specimens were tested at a stress ratio of 0.1 and a frequency of 5-8 Hz. The fatigue limit (σw) (half a total stress amplitude) and fatigue ratio (σw/σB) in the nanocrystalline Ti- and Cu-based BMGs showed very large values (Ti-based alloy; 806 MPa and 0.40, Cu-based alloy; 490 MPa and 0.25). This experimental result indicated a possibility that the nanocrystal dispersed BMGs have higher fatigue strength than the high strength crystalline alloys with high fatigue strength (e.g. Cr-Mo steel, σw≈500 MPa).
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Mitsuru Hirano, Hiroyuki Kobayashi, Yoshitake Nishi2006 Volume 70 Issue 10 Pages 824-827
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSInfluences of bending stress on an electrical resistivity of carbon fiber are studied as a basic research to develop high sensitive stress sensors. It is confirmed that an initial bending stress reversibly decreases the electrical resistivity, because the initial stress probably decreases the density of electron scattering sites. On the other hand, an excess stress increases the electrical resistivity.
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Tokimasa Kawabata, Kenji Matsuda, Shigeharu Kamado, Yo Kojima, Susumu ...2006 Volume 70 Issue 10 Pages 828-834
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSThe precipitation sequence in Mg-12.0 mass%Gd-1.9 mass%Y-0.69 mass%Zr alloy was investigated using high resolution transmission electron microscopy (HRTEM). The globular shaped contrast, which were probably composed of Gd and Y atoms were observed in a specimen quenched after solution heat treatment. Aging treatment was performed up to 64 hours at 473 K. The monoplanar precipitates were formed on plane (1100) of magnesium matrix of the specimen early in the aging stage at 473 K for 4 hours. In addition to the mono planar precipitates, a part of β″ phase with D019 structure and β′ phase with base centered orthorhombic structure were also observed in the same specimen. It was found that these precipitates coexisted in the specimen early at the aging stage. Based on the analysis of selected area diffraction patterns, it was revealed that β″ phase preferentially formed early in the aging stage. However, the β′ phase preferentially observed comparing to β″ phase in the specimen which had maximum hardness by aging at 473 K for 64 hours. Accordingly, the nucleation and growth of β′ phase dominates comparing to β″ in the stage of peak aging. These results suggest that coexistence of β′ phase and β″ phases, especially β′ phase attributes to the maximum hardness of aged alloy.
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Kenichi Numazaki, Haru-Hisa Uchida, Yoshitake Nishi2006 Volume 70 Issue 10 Pages 835-839
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSTo obtain the high power mover device with high responsiveness, mover devices driven by hydrogen storage alloy film have been successfully developed. The effect of load on bending movement of LaNi5 hydrogen storage alloy film deposited on thin copper substrate has been studied. The thin copper sheets, 10 μm in thickness, have been prepared by cold-rolling. As a result, the power of the mover device is higher than that of the Ni-Ti shape memory alloy commercially used.
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Keisuke Iwata, Akira Tonegawa, Yoshitake Nishi2006 Volume 70 Issue 10 Pages 840-844
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSInfluences of electron beam (EB) irradiation on the impact value for silica glass were studied by using a standard Charpy impact test. EB irradiation below 0.216 MGy, which was one of short-time treatments of dry process at low temperature, increased impact values of the glass. As the EB irradiation generated dangling bonds of the E′ center at the silicon-oxygen atomic pairs in the silica glass, partial relaxation occurred at points of residual strain near dangling bonds in the network structure mainly constructed with silicon-oxygen pairs. If the inter-atomic distance of the silicon-oxygen pairs became to be optimum potential curves of the silica glass, the relaxation should increase the bonding energy of the network structure. Evidently, the increased impact value was mainly due to an increase in the bonding energy for the silicon-oxygen atomic pairs in the atomic network structure, as well as a relaxation of the network structure.
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Katsuya Ishii, Ryota Ozaki, Kenji Kaneko, Masataka Masuda2006 Volume 70 Issue 10 Pages 845-848
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSWhen aluminum is immersed in pure water, hydrogen evolves at the cathode in pure water where there is no oxygen, although hydrogen dose not evolve in pure water with oxygen present. Based upon the fact, the effect of hydrogen evolved at the cathode on aluminum corrosion was investigated in relation to oxygen concentration in pure water in the present study. The length of incubation period, which is the time from the beginning of the corrosion test to a sharp increase in the corrosion amount, is almost constant regardless of the oxygen concentration. However, the corrosion period which begins right after the incubation period and continues until the saturation point is reached varies depending on the oxygen concentration. When the oxygen concentration is low, the amount of hydrogen at the cathode is large and small pits through the barrier layer spread rapidly over the entire surface, resulting in increase in the corrosion amount. From these results, it is thought that the hydrogen evolved by the cathode reaction greatly affects the deterioration of barrier layer and the aluminum corrosion.
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Takuro Kushima, Koichi Tsuchiya, Yasukazu Murakami, Daisuke Shindo, Yo ...2006 Volume 70 Issue 10 Pages 849-855
Published: 2006
Released on J-STAGE: October 20, 2006
JOURNAL FREE ACCESSPhase transformation, microstructure and magnetic properties of Cu-(11-14)mol%Mn-20 mol%Ga alloy were investigated. Magnetic domain structures were also investigated by the Lorentz microscopy and electron holography. Plate-like martensite phase(ζM, ordered hcp) was observed in as-quenched Cu-12 mol%Mn-20 mol%Ga. Phase transformation from ζM martensite to ζ phase(hcp) occurred at around 540 K on heating. The ζ phase decomposed into ζ″ (ordered hcp) and β(bcc) phase at around 700 K, then became the single β phase at around 840 K. By subsequent slow cooling, ζ phase was observed at room temperature. Results of the Lorentz microscopy and electron holography revealed that the twin plates of ζM martensite and magnetic domains have one-to-one correspondence, suggesting high magneto-crystalline anisotropy energy of the martensite phase. Saturation magnetization and Curie temperature increased with Mn content.
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