Papers by Author: Goroh Itoh

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Authors: Masatoshi Mori, Nguyen Loc The, Goroh Itoh, Nobuhide Itoh, Yasuhiro Shimada
Abstract: In automobiles, a suspension bush, a set of aluminum parts connected to each other via rubber, is mounted into the suspension members to link the body to the wheels, and realizes hard and soft mounts contributing both to the stabilization during high speed driving and to absorbing the shock from the road. However, decohesion of the aluminum part from the rubber occurs occasionally, arising from the interface corrosion of aluminum, which deteriorates the performance of the vehicle directly. In this study, effects of alloy composition and processing route on this kind of corrosion will be investigated. Also, development of a new corrosion test that shortens the time for the test will be attempted.
Authors: Iya I. Tashlykova-Bushkevich, Takahiro Shikagawa, Takayoshi Suzuki, Vasiliy G. Shepelevich, Goroh Itoh
Abstract: Hydrogen (H) behaviour in materials was investigated in rapidly solidified (RS) foils of pure aluminium (Al), Al-0.4 Cr and Al-0.25 Zr alloys (at %) by means of thermal desorption spectroscopy (TDS). In addition, Al-0.25; 0.3 Zr alloys were examined with respect to microstructure and its instability during the thermal process using SEM and microhardness measurements. The effect of dopes and heating rate on H desorption was summarized. The lowest energy desorption is attributed with significant thermal desorption peak which temperature was found is correlated with sample composition.
Authors: Hidetoshi Umeda, Goroh Itoh, Yoshinori Kato
Abstract: The effect of heat treatment conditions such as atmosphere, temperature, annealing time and alloying elements on the hydrogen content in Al-Mg based alloys was investigated. The hydrogen content after annealing depends on the annealing atmospheres and alloying elements. When annealed in a wet atmosphere, the release of the hydrogen in the Al-Mg alloys to outside and the absorption of hydrogen from atmosphere into Al-Mg alloys are presumed to occur at the same time. The oxide layer on the surface is revealed to prevent the hydrogen from being released to outside. The spheroidal MgO particles can be seen on the surface of Al-Mg alloys after annealing at 550°C. The number of the MgO particles increases with increasing impurity elements such as Si and Fe, reducing the shielding effect against hydrogen permeration. Therefore, the condensation of hydrogen near the surface after annealing occurs more easily in an Al-Mg alloy of a high-purity than that of an ordinary purity.
Authors: Katsumi Koyama, Goroh Itoh, Hiroshi Okada, Motohiro Kanno
Authors: Iya I. Tashlykova-Bushkevich, Goroh Itoh
Abstract: Microstructure of rapidly solidified (RS) pure Al and Al-0.8; 1.0 Cr alloys (at %) foils was examined with reference to near surface composition, solute/microstructure interactions, and surface topography. The hydrogen desorption from Al-Cr alloys was investigated in order to clarify effect of rapid solidification processing (RSP) on hydrogen trapping in specimens. It is suggested that hydrogen occupancy for vacancy traps in the alloys is decreased in contrast to that reported for pure Al foils and is related to the formation of vacancy-alloying element atom complexes.
Authors: Iya I. Tashlykova-Bushkevich, Takahiro Shikagawa, Vasiliy G. Shepelevich, Goroh Itoh
Abstract: Thermal desorption spectroscopy (TDS) technique has been used to study hydrogen behaviour in rapidly solidified (RS) aluminium (Al) both as-cast and exposed to humid air (HA). The surface morphology of the foils was studied through atomic force microscopy (AFM). Analysis was made of the effect of rapid solidification processing (RSP) on H/microstructure interactions, including investigation of alloying element (0.05 at % Ti) influence on H trapping in Al.
Authors: Takahiro Shikagawa, Goroh Itoh, Shunsuke Suzuki, Hiromitsu Kuroda, Toshiyuki Horikoshi
Abstract: Although low-alloyed aluminum has been used as electric line and cable materials to date, there still is a great demand for higher strength with retaining the good electrical conductivity and ductility. In the study, iron has been chosen as an additive element and the addition effect on the strength and electrical has been investigated since iron is reported to have a marked solution-strengthening effect at a given addition amount. Aluminum with 99.99mass% purity and Al-Fe alloys with iron up to 0.9mass% were induction-melted, continuously cast into a rod with 8mm diameter, and cold-drawn into a wire with 0.3mm diameter. Tensile test and electrical resistivity measurement were carried out on the rod and wire after each pass. It was found that, in the rod, the strength increased while the ductility and electrical conductivity decreased as the addition iron amount was increased. Work hardening occurred clearly at an early stage of cold drawing, while it became sluggish as the cold reduction increased in each material. At the early stage, the strengths increased as the iron amount was increased, and at the later stage, the alloy with iron addition of 0.9mass% had higher strengths and larger elongation to failure.
Authors: Qing Zhou, Goroh Itoh, Hisashi Hasegawa, Yoshinobu Motohashi, Mitsuo Niinomi
Abstract: The deformation characteristics of a beta-type Ti-29%Nb-13%Ta-5%Zr alloy, developed for biomedical application, and their relation with the microstructure are investigated. The cold-rolled specimen is subjected to a tensile test at high temperatures ranging from 700 to 800°C under a constant cross-head speed ranging from 1×10-4 to 1×10-2s-1. The elongations tested at different temperatures are compared with that of Ti-15%V-3%Cr-3%Sn-3%Al, a typical beta titanium alloy. The deformation mechanism is characterized from the parameter of the strain rate sensitivity. The microstructures before and after the tensile test are observed with optical microscope and the correspondent grain sizes are measured. The grain growth during the deformation is also described.
Authors: T. Izumi, Goroh Itoh, Nobuhide Itoh, Y. Sasaki
Abstract: Aluminum alloy is one of the candidates for the liners of compressed hydrogen tank mounted to fuel cell vehicles. It is crucial to elucidate the behavior of hydrogen in the alloy sheet with one side being exposed to hydrogen gas. In the present work, using the hydrogen microprint technique, in 6061 and 7075 aluminum alloy sheets, relationship between hydrogen pressure and the molar quantity of hydrogen emitted from the inside has been investigated. Under any pressure, the quantity of emitted hydrogen is about 10 times smaller in the 7075 alloy than in the 6061 alloy. This indicates that the amount of hydrogen atoms accumulating in the 7075 alloy may be much larger than that in the 6061 alloy.
Authors: S. Nakano, Yoshinobu Motohashi, Goroh Itoh
Abstract: A Zn-Al eutectoid alloy known as a fine-grained superplastic material is tested both in tension and compression under superplastic conditions, and the influence of the stress state on superplastic deformation behavior, such as flow stress, is investigated. In the compression test, deformation is interrupted and turning is performed to remove a barreled portion so that the gauge section becomes uniform, and then the deformation is continued. Microstructural change during the deformation is also investigated. As a result, flow stress in the compression becomes higher than that in tension even after the barreled portion is removed. After deformation, grain growth is observed both in the tension and compression, and growth rate in the compression is larger than in the tension.
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