Transactions of the Japan Institute of Metals
Online ISSN : 2432-4701
Print ISSN : 0021-4434
ISSN-L : 0021-4434
Volume 27, Issue 5
Displaying 1-9 of 9 articles from this issue
  • T. Tanabe, K. Sawada, S. Imoto
    1986 Volume 27 Issue 5 Pages 321-327
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    In order to understand the hydrogen permeation phenomena in multiple metal layers, the time dependent permeation rates for duplex membranes of Cu–Ni and Cu–Fe have been systematically measured under hydrogen pressures from 103 to 105 Pa at temperatures from 500 to 1000 K, and the obtained results are compared with theoretical estimations calculated from the diffusion equation.
    In the case of the Cu–Ni duplex membrane, both injection and evolution transients are hardly influenced by the surface effect, and the permeation behavior is well described by the theory. In the case of the Cu–Fe one, the steady state permeation rate also agrees well with the theory, while the time transient seems to be influenced by the surface oxide or the bulk trapping effect.
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  • Kohei Kubota, Satoru Yamamoto
    1986 Volume 27 Issue 5 Pages 328-340
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    Dilatometric measurements were carried out during the first-stage graphitization of white cast irons. It has turned out that the data can not be analyzed consistently by the rate equations proposed by Johnson-Mehl or Austin-Rickett. A new type of rate equation, Y=1−exp{−(t⁄τ1)n1[1−e−(t⁄τ2)n2][1−e−(t⁄τ3)n3]−1} has been derived and proposed to interpret the data in terms of the following model: The rate of graphitization is controlled by the interfacial reaction by which cementite dissolves in the austenite, and the number of dissolving cementite particles increases with the increase of volume of voids in which graphite nodules are formed.
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  • Tokuzou Tsujimoto, Kenki Hashimoto, Minoru Nobuki, Hiroo Suga
    1986 Volume 27 Issue 5 Pages 341-350
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    By studying the effect of aluminium content on properties of an intermetallic compound TiAl, it has been found that the compound of composition near the stoichiometry possesses significant ductility. For further improvement of ductility, it has been intended to design TiAl-base alloys as a dual structure of the compound and any metal phases. Therefore, metals which are able to be equilibrated with TiAl have been explored, resulting in the fact that silver is only one element which satisfies the requirement in the present experimental scope. For the TiAl alloy of stoichiometric composition and those containing silver of 4–50 mass %, relations among heat-treatment, micro-structures and mechanical properties have been examined.
    Experimental results have shown that the TiAl alloys are promising as heat-resistant materials, because they possess excellent high temperature properties. Although the addition of silver improves the ductility of the alloys at room temperature, it lowers high temperature strength.
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  • Zenjiro Asaki, Takeshi Atsumi, Yoshio Kondo
    1986 Volume 27 Issue 5 Pages 351-360
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The oxidation of iron sulfide pellet was studied at 773 to 973 K in a mixed O2–N2 gas stream. The composition of iron sulfide was Fe0.90S to Fe1.00S. The oxygen partial pressure in the gas stream was between 5.05×103 and 2.02×104 Pa. The results were compared with those in the oxidation of dense plates of iron sulfide reported in a previous paper. In the oxidation of the pellet of higher sulfur activity, the pellet mass was decreased from the start of oxidation accompanied by the evolution of SO2 gas. The rate of oxidation was controlled by gas film mass transfer in the initial stage of oxidation and by gas diffusion through the outer oxide layer of the pellet in the subsequent stage. In the oxidation of the pellet of lower sulfur activity, on the other hand, the pellet mass was increased in the initial stage of oxidation, which was followed by a decrease of the mass. The evolution of SO2 gas was observed from the start of oxidation. This observation is different from that in the oxidation of dense plates of iron sulfide: no SO2 gas was evolved during the period of mass increase. It was found that the preferential oxidation of iron which resulted in a mass increase took place in the inner core of the pellet simultaneously with the oxidation of sulfide of higher sulfur activity in the outer layer of the pellet which was accompanied by the evolution of SO2 gas. It was also found that the preferential oxidation of iron in the sulfide particles of which the pellet consisted took place in a very short time. The overall rate of oxidation of the pellet was analysed by a simplified model.
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  • Zenjiro Asaki, Akihiro Ueguchi, Teruo Tanabe, Yoshio Kondo
    1986 Volume 27 Issue 5 Pages 361-371
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The oxidation of Cu2S pellet in a mixed O2–Ar gas stream was studied at 1023 to 1123 K. The oxygen partial pressure in the mixed gas stream was 5.05×103 to 2.02×104 Pa. In the initial 100 s of oxidation, the pellet temperature was raised due to the heat of oxidation, and the formation of CuO was hindered, which resulted in a rapid mass decrease due to the oxidation of Cu2S to form Cu2O. At 1123 K, the pellet was partly melted, and the oxidation was accelerated at the initial stage, where the rate was controlled by the gas film mass transfer especially when the oxygen partial pressure was lower. It was found at 1023 K that the basic sulfate was formed during the oxidation in addition to Cu2O and CuO. It was decomposed to form CuO at the later stage of oxidation. The oxidation rate at 1073 K was analysed by a two-interface model in which the formation of the Cu2S/Cu2O and Cu2O/CuO interfaces was taken into consideration.
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  • Takehiro Dan, Noriyoshi Aritomi, Kazuyuki Ogawa, Yoshisuke Nakamura
    1986 Volume 27 Issue 5 Pages 372-381
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The purpose of the present work is to investigate the contamination of molten iron with crucible materials during the melting process.
    High purity iron was melted at 1873 K for 900 s in an alumina crucible by use of a tungsten-mesh heater furnace, and the ingot was sectioned for chemical analysis. The cross section of the ingot was deep-etched electrolytically and was observed with a scanning electron microscope. From the deep-etched cross section, inclusions were extracted onto a carbon film and their chemical composition was determined with an analytical electron microscope.
    The results are as follows:
    (1) Iron was contaminated with silicon during the melting process. The silicon content of the iron in-got depended on the silica content of the crucible.
    (2) By use of an alumina crucible which contained less amount of silica, 0.005 mass%, the silicon contamination of melt was suppressed.
    (3) The silicon content of inclusions depended on both the silicon and oxygen contents of ingots. It can be estimated by both the postulated equilibria which were obtained in terms of Turpin and Elliott’s treatment and the change in melt composition during solidification.
    (4) The composition of inclusions can be also presumed from a predicted Fe–Si–O system phase diagram.
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  • Kazuhisa Azumi, Toshiaki Ohtsuka, Norio Sato
    1986 Volume 27 Issue 5 Pages 382-392
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The semiconductive properties of the passive film on iron were investigated by measuring the impedance of iron electrode in borate and phosphate solutions at various pH values. The impedance data were compared with the thickness data previously obtained from 3-parameter reflectometry. From the effect of frequency and potential on the impedance an equivalent circuit is postulated for the passivated iron electrode, which consists of a series connection of two parallel RC circuits. One component RLCL of the two parallel circuits which predominates over frequencies lower than 100 Hz, characterizes the dielectric property of the passive film, whereas the other component RHCH, which appeares at higher frequencies corresponds to the oxide/solution interface. From comparison of CL with the film thickness, the passive film is found to consist of an inner electron-conductive layer where no potential drop occurs and an outer carrier depletion layer where the electric field is of the order of 1×108 Vm−1. The dielectric constant of the outer layer is also evaluated at about 40. The component RHCH is sensitive to the anionic species present in the solution and is thus likely to be assosiated with an ionic adsorption-desorption process taking place across the electric double layer at the oxide/solution interface.
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  • Michio Kikuchi, Hakaru Masumoto, Takafumi Nakayama
    1986 Volume 27 Issue 5 Pages 393-400
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The magnetization, Young’s modulus and thermal expansion at 150–600 K and crystal structures at room temperature were investigated in the Mn–Ge based ternary alloys containing Ti, V or Cr less than 14%, which had various crystal structures i.e., γ (14% Ge), γ+ε(16–20% Ge) and ε(22% Ge) phases.
    Magnetization values of the ternary alloys attainable are 0.4−0.5×10−6Wb·m·kg−1 in the range of temperatures measured. The temperature dependence of magnetization of the ternary alloys shows a tendency similar to that of the basal binary alloys and distinct variations at Tt, corresponding to the β\ ightleftarrowsγ or the β\ ightleftarrowsε reversible phase transformation and at TN(ε) and/or TN(γ) corresponding to the antiferromagnetic Néel points of the ε phase and the γ phase, respectively. At each point of Tt, TN(ε) and TN(γ), both Young’s modulus and thermal expansion show remarkable variations. The Elinvar properties are observed in the temperature range between Tt and TN(ε) or in the range below TN(γ), and a small thermal expansion coefficient is obtained in a temperature range below TN(ε) in the alloys having the ε or ε-rich phase. A very small temperature coefficient of Young’s modulus in the neighborhood of room temperature is obtained over a wider composition range in the Mn–Ge–Ti system than in the alloys containing V or Cr. Unlike the case of elasticity, Mn–Ge–Cr alloys show a small thermal expansion coefficient over a wider composition range than in the other alloys. In the case of the Mn–Ge–V alloys, there is a certain composition range where both the thermal expansion coefficient and the temperature coefficient of Young’s modulus become very small at room temperature. Therefore, the temperature coefficient of the ultrasonic delay time shows a relatively small value.
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  • Hakaru Masumoto, Masakatsu Hinai, Showhachi Sawaya
    1986 Volume 27 Issue 5 Pages 401-407
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    The damping capacity, magnetic properties, anodic polarization behavior and mechanical properties have been investigated for ternary Fe–Co–Cr alloys with Co less than 30% and Cr less than 40%. Measurements of the internal friction Q−1, the coercive forc Hc, the pitting potential EP and the tensile strength σt were carried out using an inverted torsion pendulum, an automatic recording fluxmeter, a potentiostat and an Instron-type machine, respectively.
    Upon furnace cooling, the alloys have fairly high Q−1 over two composition ranges of Fe-3–5% Co-17–22% Cr and Fe-5–25% Co-0–5% Cr. Upon water quenching, the Q−1 of the alloys with higher Cr concentration shows a fairly high value.
    The alloys in the state of α solid solution have very high Q−1 because of the low Hc. The alloys, in which the γ→α transformation strain partially remains and the σ, γ or ε phase is precipitated in the α phase matrix have lower Q−1 because of the high Hc.
    In all cases the Fe–Cr binary alloys become higher in EP with increasing Cr concentration, and the addition of Co results in an increase of EP. The EP of the water-quenched alloys is generally higher than that of the furnace-cooled alloys.
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