Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 52 , Issue 1
Showing 1-18 articles out of 18 articles from the selected issue
  • Yoshihiro Takahara, Norikazu Fujii, Hidehiko Matsuda
    1988 Volume 52 Issue 1 Pages 1-7
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The structural relaxation process of amorphous Fe78B7Si15 and Fe82B13Si5 alloys has been studied by electrical resistivity measurements and Mössbauer spectroscopy. The topological distribution of first-neighbor iron atoms at an iron atom was changed and the average number of first-neighbor iron atoms increased during the change in topological short range order (TSRO) with irreversible changes of resistivity. Reversible changes of resistivity due to chemical short range order (CSRO) were observed in Fe78B7Si15 alloy which contained one kind of metallic atom. The resistivity decreased with increasing CSRO. The kinetics of CSRO in this alloy can be described as a log-normal distribution of relaxation times. The activation energy for the CSRO was estimated to be 222.0 kJ/mol from the resistivity measurement. This value is nearly equal to that for diffusion of Fe and Si atoms in Fe-based amorphous alloys. It is therefore likely that Fe and Si atoms play an important role in the CSRO of this alloy.
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  • Tetsuya Katayama, Hiroshi Fujita
    1988 Volume 52 Issue 1 Pages 8-17
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The formation mechanism of strain-induced γ→α′ martensitic transformation in an Fe-Cr-Ni alloy with a low stacking fault energy has been investigated by in situ deformation with a 3 MV electron microscope. Results obtained are summarized as follows: (1) Formation of α′ martensite crystals always occurs by “double shear mechanism”. (2) α′ crystals are classified into the following two types; one is of “Schiebung” type which has a slow formation speed and the other is of “Umklapp” type which has a rapid formation speed. The former is observed in γ-grains of a single slip system, and the latter in those of multiple slip system or in work-hardened γ-grains. (3) In both cases, γ-twins are always well-formed prior to the formation of α′ crystals. (4) The secondary shear displacement of “double shear” is induced on the interface between γ-twins of the primary slip system and γ-matrix. (5) An α′ crystal grows easily along the primary shear plane.
    The nucleation and growth mechanisms of α′ crystals are discussed on the basis of the experimental results.
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  • Naotsugu Inakazu, Hirofumi Inoue
    1988 Volume 52 Issue 1 Pages 18-25
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The transformation texture in titanium cold-rolled and annealed at 1273 K was investigated by means of the orientation distribution function method and then the texture in β-phase at elevated temperature was predicted by Burgers’ relationship from the texture in α-phase which is possible to measure at room temperature.
    The deformation and recrystallization textures in α-phase of a 70% rolled sample were similar to those of a 90% rolled one. However, the textures in α-phase after sequential α to β and β to α transformations were different depending on the reduction. The predicted texture in β-phase was composed of the {112}⟨111⟩ and {001}⟨100⟩ orientations at 70% reduction and only of the {112}⟨111⟩ orientation at 90% reduction. This difference was related to the variant selection occurring during the α to β transformation on heating. The variants such that the [2\bar1\bar10] direction parallel to RD in recrystallization texture corresponds with the ⟨111⟩ directions may be selected only in the 90% rolled sample. The reasons for the occurrence of the variant selection have been discussed from the viewpoint of oriented strain.
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  • Toshiro Kobayashi, Mitsuo Niinomi, Makoto Adachi
    1988 Volume 52 Issue 1 Pages 26-33
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The relationship between triaxiality (σm⁄\barσ: hydrostatic stress, \barσ: equivalent stress) and ductile fracture morphology of Al-Zn-Mg-Cu alloys with varying Zr contents was investigated. The relationship between fracture toughness and microstructural characteristic distance, which was proposed by Ritchie and Thompson, was also investigated on these alloys.
    The size of dimple increased with the stress triaxiality. The ratio of the transgranular dimple fracture increased with increasing Zr content and decreased with increasing triaxiality. The microfracture mechanism of Al-Zn-Mg-Cu system alloys was discussed by using the critical strain-controlled microfracture model proposed by Ritchie and Thompson.
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  • Toshiro Kobayashi, Mitsuo Niinomi, Kimio Degawa
    1988 Volume 52 Issue 1 Pages 34-42
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effect of microstructures (aged-precipitates, dispersoid particles, grain boundaries, etc.) on the impact toughness of the aged Al-Li-Cu-Mg-Zr alloy was investigated. Consequently, the dynamic crack initiation toughness, JId and crack propagation toughness, Tmat were greater in the order of the underaged, full-aged and overaged specimens. Crack branching and deflections were observed in the underaged and peakaged alloys which exhibited greater toughness. Therefore, these factors are considered to be very important in improving the toughness of this alloy. The dynamic yield strength decreased with decreasing of dynamic fracture characteristics values in the overaged condition. The intergranular fracture caused by the stable acicular T1(Al2CuLi) phase predominantly precipitated on the grain boundary is considered to be the cause of this phenomenon.
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  • Kohmei Halada, Yuji Muramatsu
    1988 Volume 52 Issue 1 Pages 43-49
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    A method is described for measuring the surface tension and the contact angle by a new fitting method for experimental measurements of the contour of sessile drop. In the present method, more than one hundred of experimental points were read on the photographical contour in order to improve the accuracy. And an extension of the Newton-Raphson method was made for prevention of the increasing disconvergence with the number of data, and the uniqueness and the convergence of optimum values was discussed. The surface tension of molten Ag and the contact angle between Ag and graphite were measured by the use of this method. As a result, the surface tension of Ag in Ar atmosphere was γ=−1.97×10−4T+1.15 (N/m). It was found that the contact angle was 180° when the temperature attained the measuring point, and that the contact angle decreased with the holding time.
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  • Kazuo Yamanaka, Hiroo Nagano
    1988 Volume 52 Issue 1 Pages 50-56
    Published: 1988
    Released: April 04, 2008
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    The initial repassivation processes of anodic reaction on newly created surfaces of 75%Ni-0∼15%Cr-bal. Fe alloys were investigated by a rapid straining electrode technique in a 0.4%NaOH solution at 553 and 598 K at constant anodic potentials. The results obtained are as follows:
    (1) The decrease in current density with time after rapid straining was stopped follows the formula of itn (i: current density, t: time, n: constant) over a time range of about 20∼1000 ms.
    (2) The effects of chromium contents in the range of 0∼15 mass% on the repassivation rate is small at any potentials of −0.9 and 0 V. This suggests that the influence of chromium depleted zone on the caustic SCC of Alloy 600 should be small.
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  • Hiroshi Nakai, Mikiyuki Ichiba, Ken Okada
    1988 Volume 52 Issue 1 Pages 57-64
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The simultaneous attack of oxygen and sulphur on a range of Ni-Cr alloys containing 1-20(mass%)Cr has been investigated between 873 and 1173 K in PSO2=104 Pa atmosphere. Reaction kinetics was traced by using an automatic recording balance, and the scale structures were examined by metallography, scanning electron microscopy and microprobe analysis.
    The reaction kinetics was complex and classified into three groups of the temperature ranges. This complexity was owing to the sulphide formation and initial oxide properties. The corrosion kinetics followed more than two-step parabolic rate laws, but not followed by the simple single rate laws. Compared with pure nickel, the addition of up to 13%Cr at 918 K or below and at 1073 K or above, or 20%Cr at 918-1073 K has an effect on corrosion resistance.
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  • Hiroshi Nakai, Tomoyuki Sugino, Ken Okada
    1988 Volume 52 Issue 1 Pages 65-71
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The corrosion behavior of Fe-Cr alloys containing up to about 20 mass%Cr have been studied at 1123 K mainly in the Ar-SO2 atmospheres as a function of SO2 partial pressures in the range 103-105 Pa. Thermogravimetry, metallography, X-ray and electron probe microanalyses have been employed to clarify the oxysulfide scale growth on these alloys. The Fe-Cr alloys exhibited linear and or parabolic kinetics and are classified as follows; single parabolic kinetic (pure iron and Fe-1.9 mass%Cr alloy), two or more step parabolic kinetics (Fe-5.5 mass%Cr alloy), linear parabolic kinetics (Fe-11.8 mass%Cr alloy and more Cr containing Fe-Cr alloys). The parabolic reaction rates for pure Fe and Fe-Cr alloys are almost independent of SO2 partial pressures(1).
    The Fe-Cr alloys exhibit exponential decrease in the rates of reaction with the increase in the chromium content. The corrosion resistance of these alloys appears to be associated with the formation of a protective Cr2O3, the inner layers of which contain coarsely dispersed (Fe, Cr)3O4. The interpretation of the oxidation, and sulfidation of the Fe-Cr alloys are considered in some detail.
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  • Kiyoshi Nogi, Keiichiro Oishi, Kazumi Ogino
    1988 Volume 52 Issue 1 Pages 72-78
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    As wettability of solid oxides by liquid metals gives important information about the development of composite materials, metal-ceramics joinings, and a behaviour of deoxidation products, a considerable number of papers have been published. But there are large discrepancies among the values reported since the wetting properties are easily affected by the presence of a small amount of impurities such as oxygen and surface conditions of solid oxide.
    In this work, the wettabilities of solid oxides (Al2O3, MgO, CaO, ZrO2 and SiO2) by liquid pure metals (Sn, Ag, Au and Cu) have been measured over a wide temperature range by the sessile drop method.
    Main results obtained are as follows:
    (1) Surface tensions of pure liquid metals can be expressed by the following equations:
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    (2) Contact angles and work of adhesions between liquid pure metals and solid oxides were closely related to the standard free energy change of formation of oxides. Values of contact angle and work of adhesion change linearly with temperature and in some systems refracted points were observed at the temperatures which corresponded to the refracted points in the free energy-temperature diagram.
    (3) The wettability of solid oxides by liquid metals depends not only on the stability of solid oxides which can be expressed by the standard free energy change of oxide formation but also on ionic radii of metals which compose oxides.
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  • Shigeru Ando, Norio Kurose, Toshio Shimoo, Hiroshi Kimura
    1988 Volume 52 Issue 1 Pages 79-85
    Published: 1988
    Released: April 04, 2008
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    The behavior of carbon deposition on iron in CO-H2-H2S mixtures containing small amounts of H2S gas in the range without the formation of FeS has beem studied by means of metallography and thermogravimetry. Kinetic measurements show that carbon deposition is retarded or accelerated depending upon the ratio of partial pressure of H2S to H2, PH2SPH2. Particularly in 20%CO-H2-H2S mixtures, at PH2SPH2=0∼2×10−6, the rate of carbon deposition increases with the increase in the ratio of partial pressures because of the acceleration of filamentous carbon deposition, while at PH2SPH2≥5×10−6, the film of Fe3C forms on the substrate, so that carbon deposition is retarded. And it is found in the middle range of these ratios that the rate initially decreases but significantly increases later. This carbon deposition behavior may be ascribed to the acceleration or the retardation of formation and decomposition of Fe3C as well as the depression of laminar carbon deposition by the action of absorbed sulfur on the iron surface through the dissociation reaction of H2S gas. In particular, small amounts of sulfur may accelerate the decomposition of Fe3C and promote the deposition of filamentous carbon by the following reaction that removes atomic hydrogen, i.e. a Fe3C stabilizing element.
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  • Atsushi Sirasawa, Nobuyoshi Hara, Katsuhisa Sugimoto
    1988 Volume 52 Issue 1 Pages 86-94
    Published: 1988
    Released: April 04, 2008
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    Impedance diagrams of PTFE-bonded TiS2 electrodes on which lithium intercalation reactions were proceeding were measured at various cathodic potentials in LiBF4/tetrahydrofuran(THF), LiClO4/THF and LiClO4/propylenecarbonate(PC) solutions. It was found that the diagram was basically composed of a distorted capacitive semicircle at higher frequncies and two straight lines with different slopes at lower frequencies. The semicircle was ascribed to the combination of the double layer capacitance, the charge transfer resistance and an additional constant phase impedance due to the effect of electrode porosity, and the lines with slopes of π/4 and π/2 to the semi-infinite and finite diffusion effects of Li+ ions in LixTiS2, respectively. The charge transfer resistance, Rct, increased from 0.005 Ω·m2 at 2.5 V to 0.25 Ω·m2 at 1.8 V with decreasing potential in 2 kmol·m−3 LiBF4/THF, showing that the intercalation rate is controlled by the charge transfer process at lower potentials in this solution. In 1 kmol·m−3 LiClO4/THF and 1 kmol·m−3 LiClO4/PC, however, values of Rct were less than 0.01 Ω·m2 at all potentials examined. Diffusion coefficients of Li+ ions in LixTiS2, \ ildeD, were strongly dependent on the composition of electrolyte; their values in 2 kmol·m−3 LiBF4/THF, 1 kmol·m−3 LiClO4/THF and 1 kmol·m−3 LiClO4/PC were 2×10−15-1×10−14, 5×10−14-5×10−13 and 3×10−13-2×10−12 m2s−1, respectively. The increased value of \ ildeD in 1 kmol·m−3 LiClO4/PC seems to be attributed to the solvent-intercalation effects which leads to an increase in the basal plane spacing and the electrode porosity, and thus the effective electrode area for the intercalation.
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  • Yukimi Jyoko, Izumi Ohno, Shiro Haruyama
    1988 Volume 52 Issue 1 Pages 95-102
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Amorphous Co-Mo alloys have been electrodeposited with pulsating current from acid citrate baths, and their electrochemical properties in a sulfuric acid solution have been studied by means of electrochemical polarization and impedance measurements. The Co-Mo alloys pulse-plated at low duty cycles, namely at high activation overpotentials, exhibited an amorphous phase having a high degree of homogeneity, as well as high corrosion resistance, in spite of their very low molybdenum content compared with that of d.c.-plated alloys. The exchange current for cathodic hydrogen evolution on the amorphous alloys was two orders of magnitude larger than that on pure cobalt deposit and comparable to that on platinum electrode. This high activity for hydrogen evolution was ascribed to an increase in surface roughness caused by a selective dissolution of molybdenum from the amorphous alloy electrodes. On the basis of the partial polarization curves, it is highly probable that the induced codeposition of amorphous Co-Mo alloys proceeds via the formation of hydrated Co-Mo complex oxide as an adsorbed intermediate. The superiority of pulse plating over d.c. plating for producing amorphous alloys has been emphasized.
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  • Yutaka Shinata, Tsuneo Homma, Mitsuru Watanabe, Kokichi Hashiura
    1988 Volume 52 Issue 1 Pages 103-108
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    A new method for estimating the strain distribution of deformed metallic surface is proposed as an example of the technical applications of PSEE (photostimulated exoelectron emission) phenomena. PSEE from aluminum specimens placed in a gas-tight chamber under ultraviolet light irradiation was measured with a gas-flow type GM-counter. While a UV spot 0.3 mm in diameter was fixed in the chamber, a sample holder was scanned in the X-direction by a cum and Y-direction by a worm gear. The PSEE intensity was recorded as a function of position with an X-Y recorder. For tensile-deformed aluminum specimens, their nominal strains along their gauge lengths corresponded well to their line profiles of PSEE; i.e., their strain distribution was similar to the PSEE intensity distribution in the case of one-dimentional measurement. PSEE contour maps obtained by two-dimentional scanning also corresponded fairly well to the photographic patterns showing surface strains for both tensile- and fatigue-deformed specimens. The relative change in strain may be easily measured by this PSEE scanning technique, though the strain distribution obtained is not exact in a strict sense.
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  • Kiyoshi Ichikawa, Satoshi Ishizuka
    1988 Volume 52 Issue 1 Pages 109-115
    Published: 1988
    Released: April 04, 2008
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    An investigation is made on the homogenization of microstructure and the improvement of mechanical properties in Cu-Al binary alloys containing 8, 9, 9.5 and 10 mass% aluminum and Cu-7 mass%Si alloy produced by the vacuum rheocasting in which solidifying alloys are vigorously agitated at high rotation speeds from 16 to 60 rev/s of a stirrer immersed in the alloys. The results are as follows. The torque values in Cu-8%Al and Cu-7%Si alloys with rotation of stirrer at a speed of 50 s−1 are higher than those at a speed of 25 s−1. Homogeneous microstructures are formed by fragmentation of columnar dendritic crystals by the rotation of stirrer at high speeds during the solidification of Cu-8%Al, Cu-9%Al and Cu-9.5%Al alloys. Oval primary solid particles coexisting with eutectoid are observed in the rheocast Cu-Al alloys. The elongation values for a strain rate of 1.85×10−4 s−1 at 973 K are 162% in Cu-8%Al alloy rheocast at a rotation speed of 50 s−1, 178% in Cu-9.5%Al alloy rheocast at 60 s−1, 174% in Cu-10%Al alloy rheocast at 40 s−1 and 141% in Cu-7%Si alloy rheocast at 25 s−1. The elongation values for a strain rate of 1.85×10−4 s−1 at 1073 K are 176% in Cu-8%Al alloy rheocast at rotation speed of 25 s−1, 148% in Cu-9%Al alloy rheocast at 40 s−1 and 192% in Cu-7%Si alloy rheocast at 25 s−1. It is also found that the ductility in Cu-Al and Cu-Si alloys at elevated temperatures is strongly improved only by the high-speed rheocasting in comparison with the mechanical properties in their rheocast alloy ingots with those in the conventionally cast ones.
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  • Osamu Odawara, Kazuhiro Nagata, Kazuhiro S. Goto, Yasumasa Ishii, ...
    1988 Volume 52 Issue 1 Pages 116-120
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The ceramic layer produced by a centrifugal-thermit process consists of corundum (α-Al2O3) and hercynite (FeO-Al2O3 spinel) when inducing the thermit reaction with aluminum and iron oxide powders. Although the hercynite in the ceramic layer plays some role in improving mechanical properties of ceramic layer such as toughness and thermal shock resistance, it is not desirable for improving the corrosion resistance, because FeO component included in hercynite would be attacked in highly acidic conditions.
    In the present work, in order to make clear the mechanism of FeO remaining in the ceramic products and to reduce its content, the centrifugal-thermit process is performed with Al and Fe2O3 powder mixtures of the mole ratios (Fe2O3/2Al) of 1.1, 1.0, and 0.9 under the environments of nitrogen gas and air flow. It is also performed by adding some amounts of Mg and Si powders to the stoichiometric mixture of Al and Fe2O3 powders.
    Thus, it is confirmed that the content of FeO decreases with the increase of the amount of Al. The FeO content in the stoichiometric mixture under nitrogen gas flow is about 11 mass% and almost the same with that under air. Therefore, the predominant factor affecting on the FeO residue is not considered due to the lack of Al caused from its reaction with atmospheric oxygen but to the incomplete reaction. As the ratio of thermit mixtures deviates from the stoichiometric one, the amount of FeO obtained under air flow becomes larger than that under nitrogen gas flow. The incomplete reaction caused from the interaction between atmospheric oxygen and nonstoichiometric mixtures is also discussed. On the addition of Mg or Si powders, the FeO content decreases in the reactant condition of 1800 g in total amount and of 0.1 in mole ratio of 3Mg/Fe2O3 or 3Si/2Fe2O3. When Mg powder is added, most of Mg powders react to produce MgO in the ceramic layer. On the other hand, when Si powder is added, it melts into the metal layer and therefore the amount of produced SiO2 is not so large as that of MgO.
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  • Koji Hayashi, Dai-Whan Lim, Masao Itabashi
    1988 Volume 52 Issue 1 Pages 121-125
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The relative density (Ds) of the sintered compact from water-atomized Cu powder of 5-11 μm was investigated in relation to the relative density (Dg) of the green compact and the addition of iron powder. The green compact was sintered in flowing H2 gas at 773-1253 K for 3.6-72 ks.
    It was found that Ds tended to show a maximum of 93-96% and did not become 100%, irrespective of the value of Dg and also sintering conditions. This finding was considered to be due to H2O gas probably produced by the reaction of a minute amount of retained copper oxide or dissolved oxygen with H2 gas. Therefore, the powder of iron which is able to reduce the copper oxide and to form a oxide having low H2O/H2 equilibrium pressure ratio was added to the compact, and then the sintered compact of Ds\simeq100% was obtained.
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  • Yoshinobu Sato, Takeshi Takeyama
    1988 Volume 52 Issue 1 Pages 126-127
    Published: 1988
    Released: April 04, 2008
    JOURNALS FREE ACCESS
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