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Volume 69, Issue 11
Displaying 1-17 of 17 articles from this issue
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Gen Sasaki2005 Volume 69 Issue 11 Pages 933
Published: 2005
Released on J-STAGE: November 25, 2005
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Tadanobu Inoue, Shiro Torizuka, Kotobu Nagai2005 Volume 69 Issue 11 Pages 934-942
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSThe caliber configuration design for creating ultrafine-grained steel bars through groove rolling is studied from the viewpoint of a large strain accumulation and cross-sectional shape variation in a bar. A three-dimensional explicit finite element analysis is employed for this purpose. The square-foval (flat-like-oval)-square rolling method is proposed to introduce a large strain in material. The relation between the foval configuration, a strain and cross-sectional shape is examined in the groove rolling. The influence of the equivalent strain distribution by 1st pass (foval rolling) is considered to clarify the strain distribution and a cross-sectional shape by 2nd pass, and then the foval configuration to accumulate a large strain efficiently is shown. The pass schedule to fabricate an ultrafine-grained steel of 13 mm square bar from a 24 mm square bar is proposed in warm groove rolling.
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Tadanobu Inoue, Fuxing Yin, Yuji Kimura, Kotobu Nagai2005 Volume 69 Issue 11 Pages 943-952
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSUltrafine-grained bars of a low carbon steel with a cross section of 12.9 mm and 7.9 mm square are fabricated through a multi-pass groove rolling at 773 K. A three-dimensional explicit finite element analysis is employed to evaluate inhomogeneous equivalent strain distribution and cross-sectional shape in the rolled bars. Microstructures at the center and on some edges of the cross section in the rolled bars are observed, and the cross-sectional hardness distribution is measured for each rolled bar. The microstructure and the hardness at the sites where a large strain is introduced are clearly different from those at the sites where a small strain is introduced. The variations on the microstructures and the hardness on the cross section in a warm groove rolled bar are discussed with respect to the strain distribution that is predicted from the numerical analysis.
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Shigeru Kuramoto, Tadahiko Furuta, Junghwan Hwang, Kazuaki Nishino, Ta ...2005 Volume 69 Issue 11 Pages 953-961
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSEBSP (electron backscattering pattern) analysis was performed on microstructure of three β titanium alloy specimens after cold working to study peculiar plastic behavior of the multifunctional alloy, Gum Metal. The specimens employed were Ti-36%Nb-2%Ta-3%Zr-0.3%O (mass%) alloy (Gum Metal) and two reference alloys having lower and higher bcc phase stability than that of Gum Metal. Deformation twinning of {332} <113> was observed in the specimen with lower bcc stability, and dislocation glide in the specimen with higher bcc stability. Orientation boundaries with rotation angle of 10-30 degrees were observed in Gum Metal specimen, and they are considered to be identical to the giant planar faults which were observed in TEM in the previous study. It seems that the giant faults act as grain boundaries and numerous subgrains are generated in the later stage of plastic deformation. Amount of crystallographic rotation in deformed Gum Metal specimens was very large, which implies that huge elastic energy was stored during plastic deformation.
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Daisuke Shindo, H. S. Park, Hirokazu Kanekiyo, Satoshi Hirosawa2005 Volume 69 Issue 11 Pages 962-966
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSMagnetic flux distribution in Nd-Fe-B based nanocomposite magnets was investigated at nanometer scale by electron holography. Both Nd4.5Fe77B18.5 and Nd-Fe-B-Ti-C, the latter of which was newly developed and commercialized under tradename of SPRAX, are found to consist of hard and soft magnetic grains of 10~30 nm in diameter. Through the comparison of reconstructed phase images of Nd4.5Fe77B18.5 and Nd-Fe-B-Ti-C, it is found that the lines of magnetic flux of Nd-Fe-B-Ti-C fluctuate more largely than Nd4.5Fe77B18.5 in both demagnetized and remanent states. The fluctuation in the distribution of lines of magnetic flux is considered to result from the randomness in the crystal orientation of the hard magnetic grains with high anisotropy. It is also pointed out that the fluctuated distribution of lines of magnetic flux is consistent with the high coercivity and high maximum energy product of Nd-Fe-B-Ti-C.
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Eiji Oda, Horoshi Fujiwara, Kei Ameyama, Satoshi Yamaguchi2005 Volume 69 Issue 11 Pages 967-972
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSTungsten (W) is a useful material because of its high performances such as high melting temperature (Tm: 3653 K) and high strength (Young's modulus: 403 GPa). However, its high melting temperature requires high sintering temperature for producing a bulk W material, and it has a high Ductile-Brittle Transition Temperature which leads to brittleness at room temperature. To improve such negative properties, a nano grain structure formation is very effective. In the present study, a Mechanical Milling (MM) process is applied to W powder and W-Re powder mixtures. The MM process enables to produce a nano grain microstructure very easily and has been applied to many powder materials. Pure W powder or W-3 mass% or 10 mass% Re powder mixture is charged into steel vials with steel balls and rotated using a planetary ball milling at 200 rpm for 360 ks under Ar atmosphere. The MM powders are then sintered by spark plasma sintering (SPS) equipment at the temperature range of 1273 K to 1873 K under the compaction pressure of 50 MPa. The compacts and powders are examined by means of XRD, SEM and TEM/EDS. As a result, in the MM powder a nano grain structure, whose grain size is approximately 10 nm, is obtained after MM for 360 ks. The MM process enables sintering of the powders at 1273 K, while approximately 1673 K is necessary for non-MM powder to be sintered. Re addition prevents grain growth during sintering and thus increases hardness of the compacts.
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Makoto Hino, Minoru Hiramatsu, Koji Murakami, Teruto Kanadani2005 Volume 69 Issue 11 Pages 973-976
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSThis study was carried out to clarify the codeposition behavior of composite coatings, composed of Zn-Ni and SiO2 nanoparticles, for the purpose of the development of an alternative process to that using a chromating technique. The cross-sectional microstructure of the coating layer was studied by TEM observations together with element mapping technique. It was found that the silica nanoparticle has not uniformly dispersed in a coating film, but distributed only in the silica rich layer with about 50 nm in thickness formed beneath the surface. The silica rich layer can improve the corrosion resistance. Furthermore, this silica rich layer plays an important role for the fixation of the silane coupling agent to replace chromating process.
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Kenji Matsuda, Susumu Ikeno, Tomoaki Saeki, Katsuhiko Nishimura, Katsu ...2005 Volume 69 Issue 11 Pages 977-982
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSThe superconductive MgB2/Al composite material with low and high volume fractions of particles were fabricated by our special pre-packed technique. The composite material showed homogeneous distribution of MgB2 particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (Tc) was obtained via electrical resistivity and magnetization to be about 37~39 K. Specific heat measurements further supported these Tc findings. The Meissner effect was also verified in the liquid He, in which a piece of the composite floated above a permanent magnet. The thermal conductivity of the MgB2/Al composite material was about 25 W/K•m at 30 K, which value is much higher than those for the NbTi or Nb3Sn superconductive wires normally used in practice that are 0.5 and 0.2 W/K•m at 10 K, respectively.
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Kuang-chih Chang, Kazuhiro Matsugi, Gen Sasaki, Osamu Yanagisawa2005 Volume 69 Issue 11 Pages 983-988
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSInterfacial reaction between three types of carbon fiber (Cf) with different microstructure, which were vapor grown carbon nano fibers (VGCfs), graphitized and carbonized carbon fibers (polyacrylonitrile based carbon fibers), and pure aluminum (Al) in composites was studied in atomic scale by transmission electron microscopy (TEM). The composites were prepared by hot-pressing. On as-received VGCf and graphitized Cf surfaces, regular and liner graphitic lamellae of (002) lattice appeared. The irregular layer was formed on the interfaces of the VGCf/Al composite and graphitized Cf /Al composite. On those interfaces, aluminum carbide crystal was not found. When VGCf/Al composite was produced at 973 K for 1.8 ks or VGCf/Al composite was hot-treated at 873 K for 18 ks, an aluminum carbide crystal was precipitated in the irregular layers. On the other hand, an intense interfacial reaction of the aluminum carbide crystal occurred on the interfaces in the carbonized Cf was reinforced Al composites.
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Tomoaki Akabane, Yasushi Sasajima2005 Volume 69 Issue 11 Pages 989-996
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSComputer experiments on silicon nano indentation were performed. Conical shaped rigid indentor was pushed into silicon single crystal under constant load condition. The motion of silicon atoms was calculated using molecular dynamics method, where Stillinger-Weber potential was assumed as interaction between silicon atoms. The dynamic load-indentation depth curve was calculated and the universal hardness was evaluated from the maximum indentation depth. The obtained value of hardness was similar to the experimental value of silicon. The changes in the radial distribution function and bond angle distribution during the indentation process were calculated for the atoms in the neighborhood region of the indentor. It is suggested from the change in the radial distribution function and bond angle distribution that the structure of the atoms become meta stable structure similar to liquid rather than amorphous by the indentation.
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Yuichiro Koizumi, Masanori Ueyama, Nobuhiro Tsuji, Yoritoshi Minamino, ...2005 Volume 69 Issue 11 Pages 997-1003
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSInternal friction (Q-1) of nickel sheets highly deformed up to an equivalent strain (ε) of 4.8 by the Accumulative Roll-Bonding (ARB) process was investigated in order to clarify the damping mechanism of the ultrafine-grained materials produced by severe plastic deformation. Although the strength increased with increasing number of the ARB cycle (N), the maximum value of Q-1 was obtained at N=4 (ε=3.2). At relatively small ε about 1, where dislocation cell structure was formed, relatively small Q-1 below 5×10-3 was obtained. The dislocations within the cell walls appeared to be tightly pinned at high density of nodes or other dislocations. In the middle range of ε, where the ultrafine grains having diameter lager than 0.2 μm were formed, a high valued of Q-1 greater than 5×10-3 was obtained. In the ultrafine grains, dislocations without the pinning by nodes or other dislocations were observed. At the largest ε of 4.8, where the grain size was as small as 0.15 μm, the Q-1 was smaller than 4×10-3. The distance of the dislocation motion under vibration stress seemed to be small due to the fine grain size. The change in the Q-1 with number of the ARB cycles was attributed to the changes in the dislocation density and the distance of dislocation motion under vibrating stress which is controlled by the pinning points and the grain boundaries.
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Takahiro Ohno, Seiichiro Ii, Naoya Shibata, Katsuyuki Matsunaga, Yuich ...2005 Volume 69 Issue 11 Pages 1004-1009
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSThe grain boundary structure in a rutile-type TiO2 bicrystal with a [001] symmetric tilt boundary having a tilt angle of 66° was investigated. The tilt angle of this boundary deviates by 1.4° from an exact Σ13a to Σ17a relation. High-resolution transmission electron microscopy (HRTEM) has revealed that the grain boundary was free from any secondary phases, and the two adjoining crystals contacted each other perfectly at an atomic scale. The boundary showed almost straight feature without any step structures though a part of the boundary formed facet structures consisting of low index planes such as {310} and {110}. In addition, the weak-beam dark field observation revealed that the contrasts due to strong strain fields existed on the grain boundary plane with a spacing of 7.6 nm. As the result of atomic structural analysis using HRTEM, the strain field was found to result from a distorted Σ13a unit structure. This distorted unit structure was similar to Σ17a structure. Namely, the boundary consisted of a periodical array of major Σ13a unit structures and minor Σ17a-like unit structures. The deviation angle from the exact Σ13a relation in this boundary was not accommodated by DSC dislocations but by introducing different structural units.
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Takashi Mizuguchi, Naoki Takata, Ken-ichi Ikeda, Hideharu Nakashima2005 Volume 69 Issue 11 Pages 1010-1015
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSIn this study, the energy and atomic structure of the <110> symmetric tilt boundaries in palladium were calculated using a molecular dynamics (MD) method and the electronic structures of hydrogen in the bulk and at the grain boundaries were calculated using discrete-variational Xα (DV-Xα) molecular orbital cluster calculaion by solving Hartree-Fock-Slater equation.
The result of MD simulation revealed that the energy of the <110> symmetric tilt boundary of palladium depended on the misorientation angle and that there were large energy cusps at the misorientation angles which correspond to the {111}Σ3 and {113}Σ11 symmetric tilt boundaries. The atomic structure of all <110> symmetric tilt boundaries could consist of the combination of the {331} Σ19, {111}Σ3 and {113}Σ11 structural units and {110}Σ1 and {001}Σ1 single crystal units.
The result of DV-Xα molecular orbital cluster calculation showed that the interstitial hydrogen atoms induced the palladium-hydrogen chemical bond which had a different energy level from the palladium-palladium bond. The component of the palladium-hydrogen bond at the grain boundaries was similar to those in the bulk palladium. It is clarified that electronic structure near the grain boundary is different from that in the perfect crystal.
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Keisuke Iwata, Hiroyuki Kobayashi, Yoshitake Nishi2005 Volume 69 Issue 11 Pages 1016-1020
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSInfluences of electron beam irradiation on impact fracture energy indicated by impact value were studied for alkali free glass. The irradiation, which was able to be one of short-time treatments reduced the brittleness and increased the impact value of alkali free glass. The impact value enhancement can be explained by stress relaxation induced by increase in density of dangling bonds.
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Hiroyuki Kobayashi, Yoshitake Nishi2005 Volume 69 Issue 11 Pages 1021-1025
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSA relation between implant depth of carbon fiber and its strength with a transparent adhesive polymer was studied. The fracture stress increases wit increasing the implant depth. Tensile fracture stress and Weibull coefficient showed high constant values at implant depth from 5 mm to 6 mm. Therefore, we concluded that the critical implant depth of carbon fiber in adhesive polymer was 5 mm.
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Tomomi Kobayashi, Kazuya Oguri, Mitsuo Iwase, Yoshitake Nishi2005 Volume 69 Issue 11 Pages 1026-1030
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSIn order to investigate sustainability of hydrophilicity in the dark, life of photo inductive wettability generated by ultraviolet ray irradiation for anatase-type titanium dioxide film was obtained. The films were prepared by using cylindrical magnetron gas flow sputtering (CM-GFS) source with pure titanium pipe target. Irradiation by ultraviolet ray tremendously enhanced wettability for short time. When the time decay of wettability was studied, the photo inductive wetting sufficiently kept the high wetting of anatase-type titanium dioxide (TiOx) film. The life of photo inductive wetting was a week. To discuss the change in surface condition, wettability change was applied for the extended Howkes theory analysis. Although the wettability decay was explained by decrease in the hydrogen bond strength, sustainability of hydrophilicity in the dark on the photo inductive wetting was explained by maintaining the increase of dipole interaction effect. Based on the results, difference between photo catalytic reaction and photo inductive effects were discussed for anatase-type titanium dioxide film.
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Yasuhiro Aoki, Masahiko Muro, Hitohisa Yamada2005 Volume 69 Issue 11 Pages 1031-1038
Published: 2005
Released on J-STAGE: November 25, 2005
JOURNAL FREE ACCESSLaves phase Ti-Mn-V type hydroden absorbing alloys are used for heat utilization systems such as refrigeration systems. Since the Ti-Mn-V alloys made by rapid solidification method show no segregation, the plateau becomes flat. However this effect is varied with the cooling rate. For this reason hydrogen absorption properties of hydrogend absorbing alloys made in various rapid solidification conditions were investigated. The measurements of pressure-composition isotherms, X-ray powder diffraction analyses and EPMA measurements were performed. As a result, it is found that the most suitable cooling rate exists for each alloy, and if cooling rate is too high, a peak width of X-ray powder diffraction broaden and the plateau becomes slope.
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