Transactions of the Japan Institute of Metals
Online ISSN : 2432-4701
Print ISSN : 0021-4434
ISSN-L : 0021-4434
Volume 27, Issue 6
Displaying 1-9 of 9 articles from this issue
  • Yuh Yamada, Kazuhide Tanaka
    1986 Volume 27 Issue 6 Pages 409-415
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    To reveal the influence of hydrogenation on the electronic structure, structural modification and crystallization in Zr-based alloy glasses, electrical resistivity measurements are made on Zr50Ni50 and Zr67Ni33 glass ribbons during hydrogen charging in the gas phase and subsequent heating in vacuum. Both glasses manifest characteristic changes in the resistivity and TCR (the temperature-coefficient of resistivity) below 300 K depending on the hydrogen content. These changes are related to a modification of the d-band structures caused by the hydrogenation. The behavior of the resistivity at elevated temperatures is discussed in relation to hydrogen desorption, hydride precipitation and crystallization.
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  • Yoshimasa Takayama, Tatsumi Tozawa, Hajime Kato, Norio Furushiro, Shig ...
    1986 Volume 27 Issue 6 Pages 416-424
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    The influence of notch shape on the elongation has been investigated for a Sn-38.1 mass%Pb superplastic alloy using specimens with a couple of various V-type notches or a small hole type notch.
    The elongation of the notched specimen seemed to have a correspondence with the ratio of the cross-sectional area of the specimen, AnAs, where An was the minimum area appearing at the bottom of notch and As the original area in the smooth part. However, since the concept based on the ratio itself had no consideration on the significant difference due to the shape of notch, the analysis could not explain the variation in the elongation of specimens with different shapes of notch. Therefore, a simple model of superplastic deformation has been proposed in order to express the difference in notch shape more properly. The model is taking account for distributions of both the strain rate and the m-value (σ=K\dotεm, σ: flow stress, \dotε: strain rate and K: constant) over the gage length on the specimen, which correspond to the change in cross-sectional area in the gage section including the notch. Using the model, the elongation of the notched specimen has been calculated by the numerical analysis on the basis of the relation between the true stress and the true strain rate for the smooth specimen; a comparison between the experimental and the calculated values of the elongation has been carried out systematically. As a result, it is revealed that the two values are in a fairly good agreement. It is also considered that the flow stress during superplastic deformation is almost directly related to the true strain rate.
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  • Tadashi Hasegawa, Takao Yakou, U. F. Kocks
    1986 Volume 27 Issue 6 Pages 425-433
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    A model of the Bauschinger effect for cell-forming metals is summarized, in which a strain in the reversed direction is caused by “unpiling” of dislocations dynamically piled up in the cell interior during prestraining. The model suggests that, if both stress, σ, and strain, εr, in the reversed direction are normalized by the prestress, σp, σ⁄σp vs εr⁄σp curves become coincident with one another.
    Except after prestraining to small strains (<∼3%), the normalization by σp was found to be applicable to changes in prestrain and grain size in room-temperature deformation of aluminium and copper, the normalized curves for different prestrains and grain sizes becoming similar in shape. This indicates that the present model can explain the Bauschinger effect so far as the cell structure forms during prestraining. However, the normalization by σp⁄μ (μ: the shear modulus) failed for changes in deformation temperature and stacking-fault energy, namely for a change in the nature of dislocation structure (that is, for the conversion of cell structure to subgrain structure or to planar arrays of dislocations). For presenting a more widely applicable model, a quantitative change in a ratio of the number of dynamically stored dislocations during prestraining to that of total dislocations (namely, a fraction of reversely mobile dislocations) with dislocation structure must be taken into consideration.
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  • Masaaki Fukuchi, Katsuya Watanabe
    1986 Volume 27 Issue 6 Pages 434-440
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The plastic behaviours of a Ni3Nb single crystal are studied by tensile and compression tests. Three shear systems are found to operate. They are (010)[001] slip, (010)[100] slip and {211} ⟨‾10713⟩ twin systems, and the critical resolved shear stresses (CRSS) for these systems are obtained as 44, 51 and 56 MPa in tension, and 55, 64 and 380 MPa in compression, respectively. In case of tensile test, a brittle fracture occurs in almost all the stress orientations, since the CRSS for {211} twin in tension is comparatively low and the twin plane is easy to cleave. When the stress axis is parallel to [120], where the twin system is difficult to operate, a ductility can be expected under a tensile test. On the other hand, the CRSS for {211} twin in a compression test is considerably high, and the single crystal is plastically deformed up to strains more than 15% by the operation of the (010) slip systems. For the stress orientations parallel to [010] or parallel to the axes on the [100]-[001] great circle, however, the (010) slip systems can not be operated, and it is speculated to be brittle even in a compression test.
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  • Shigeru Ando, Yasukazu Okamoto, Toshio Shimoo, Hiroshi Kimura
    1986 Volume 27 Issue 6 Pages 441-448
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The carbon deposition behavior by pyrolysis reactions of CH4–H2 mixtures on iron at 1133 to 1323 K has been studied. Kinetic measurements and chemical analyses showed that the carbon deposition started when the carbon concentration in iron reached the solubility limit of graphite in austenite. Two types of carbons, filmy carbon and filamentous carbon, were observed on iron. The deposition of filmy carbon proceeded at an early stage, and particularly at temperatures above 1273 K filmy carbon spread on iron so fast that the iron surface was completely covered with it in a very short time. After some induction period filamentous carbon deposited on the iron substrate which had been covered with filmy carbon, so that it brought the film to the local break. Mechanisms are suggested for the deposition of these two types of carbons.
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  • M. Isshiki, Y. Fukuda, K. Igaki
    1986 Volume 27 Issue 6 Pages 449-453
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    Activation analyses of carbon and nitrogen in pure iron, cobalt and chromium have been developed using nuclear reactions, 12C(γ, n)11C and 14N(p, α)11C. Activated carbon was separated in the form of CO2 by fusing the specimen at 1573 K in oxygen atmosphere. It was found that the contents of carbon and nitrogen are reliably determined in the level of 50 and 10 ppb, respectively. The effect of the hydrogen treatment is also confirmed on the removal of carbon and nitrogen contained in iron, chromium and cobalt.
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  • Kunimasa Takeshita, Paul Hideo Shingu
    1986 Volume 27 Issue 6 Pages 454-462
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    The thermal contact during the cooling of a Ni-19 at%P alloy by the single roller chill block casting has been investigated by best fitting of experimentally measured actual temperatures of solidifying ribbons to calculations performed on the basis of heat transfer analysis. The effects of process variables on the thermal contact have been discussed in conjunction with contact patterns at the roller-side surface of the ribbons cast.
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  • O. E. Okorafor
    1986 Volume 27 Issue 6 Pages 463-468
    Published: 1986
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The effects of casting conditions and of varying amounts of silicon on volume shrinkage have been determined on the full mould cast AlSi binary alloys. The constitution of the AlSi alloys leads to two stages in which either shrinkage or expansion is occurring during their solidification. The behaviour of the associated volume changes leads to the occurrence of shrinkage defects. In these castings, the overall amount of volume shrinkage that occurs during solidification is associated with both volumetric contraction and the formation of macrocavities, surface sinks and internal porosity. The amount of silicon affects the contraction and soundness of casting by influencing the eutectic silicon amount. An important finding is that increasing the silicon content leads to a decrease of the overall volume shrinkage. This is a common foundry variable which can be measured, and is amenable to some control. The results are discussed with relation to the inherent behaviour of various alloy systems and foundry processes.
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  • Takafumi Nakayama, Hakaru Masumoto, Michio Kikuchi
    1986 Volume 27 Issue 6 Pages 469-475
    Published: 1986
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    The thermal expansion, magnetic properties, hardness and workability were investigated in Mn-22%Ge based ternary ε phase alloys containing noble metals in groups VIIA, VIII and IB of the periodic table. In the thermal expansion curves of the ternary alloys there appears a minimum corresponding to the Néel point of the ε phase, showing the Invar characteristics below this temperature. The thermal expansion coefficient of the ternary alloys in the vicinity of room temperature shows the zero or a negative value. The spontaneous volume magnetostriction of Mn-22%Ge-0.9%Ir, −1.7%Ag and −0.9%Au alloys at 77 K is about 1.3×10−2. The value is hardly affected by the additions and is nearly equal to those of a Mn-22%Ge binary alloy and Invar-type Fe–Ni or Fe–Pt alloys. The magnetization of the ternary alloys shows almost the same temperature dependence as that of the Mn-22%Ge binary alloy which shows a parasitic ferromagnetism. The magnetization at TTN=0.65 decreases with increase of the additions except Ag. The Néel point of the ε phase is scarcely affected by the additions except Ir, Pt and Re.
    The Vickers hardness of almost all ternary alloys containing the noble metals less than 2% shows a value lower than that of Mn–Ge alloys, and they are superior in workabilities such as cutting and forging to the binary alloys.
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