Transactions of the Japan Institute of Metals
Online ISSN : 2432-4701
Print ISSN : 0021-4434
ISSN-L : 0021-4434
Volume 21, Issue 6
Displaying 1-8 of 8 articles from this issue
  • Hiroshi Nagai, Makoto Okabayashi, Hiroyasu Mitani
    1980 Volume 21 Issue 6 Pages 341-348
    Published: 1980
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    The isothermal oxidation behavior of Ni–20Cr alloys with 0.7 mass% of various reactive elements (Y, La, Al, Zr, Ti and Si) was investigated in air at 1273 and 1373 K.
    It was found that the alloying elements except for Ti reduced the oxidation rate of the Ni–20Cr alloy at 1273 and 1373 K . There was a tendency that the parabolic rate constants obtained during the first 36 ks oxidation at both temperatures for the alloys with the alloying elements except for Ti were closely related to the affinity for oxygen of the alloying elements. The larger the standard free energy for the oxide formation of the alloying element, the smaller was the parabolic rate constant for the oxidation of the alloy with the alloying element. The oxidation behavior after 36 ks oxidation at 1373 K was rather complex compared to that at 1273 K . The highest oxidation resistance was obtained by a Ni–20Cr–0.7Y alloy at a lower temperature (1273 K) and during the early stage of oxidation at a higher temperature (1373 K). Whereas, a Ni–20Cr–0.7Al alloy showed the highest oxidation resistance after 72 ks at 1373 K with the formation of the internal oxide layer α-Al2O3. The addition of 0.7%Ti considerably reduced the oxidation resistance of the Ni–20Cr alloy.
    The spallation of the scale was also reduced by the addition of the reactive alloying elements, especially Al and Si, which formed their internal oxides beneath the scales.
    The difference between the improving effects of the alloying elements observed in the Ni–20Cr and Fe–20Cr alloys were discussed from the difference in the diffusivities of oxygen and the alloying elements in both alloys.
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  • Masanori Kiyoshige, Shoichi Ryusuke, Kiyoshi Kita, Toshimi Yamane
    1980 Volume 21 Issue 6 Pages 349-358
    Published: 1980
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    The effect of working temperatures on the recrystallization behavior of Ni-30%Cu alloy was investigated by Vickers hardness measurements, light microscopy and transmission electron microscopy. As the working temperature raised, the beginning of recrystallization was retarded and the grain size of a recrystallized structure became finer. However, the activation energy for recrystallization was not affected so much by the working temperature, except for a somewhat high activation energy in the specimen annealed from the cold worked state.
    Transmission electron microscopy revealed that the dislocation cell structures were developed by working at a higher temperature and they seemed more stable compared with uniform dislocation structures in the cold worked specimens. These results suggest that the fine grain structure obtained by isothermal annealing after warm working can be attributed to the dislocation structures which consisted of stable cells.
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  • Noriyuki Kuwano, Toshihiro Doi, Tetsuo Eguchi
    1980 Volume 21 Issue 6 Pages 359-365
    Published: 1980
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The stacking disorder in the filed α2 phase af Cu–Al alloys was investigated by means of X-ray powder diffraction. The theoretical line profiles were calculated so as to reproduce the observed ones by using the diffraction theory of Kakinoki and Komura developed for one-dimensionally disordered structure. The values of the parameters in the diffraction equation, thus determined, indicate that the stacking mode in the filed α2 phase can be characterized by a statistical mixing of 3R, 9R in a negative sequence, and 2H. The annealing behavior of the filed α2 was examined and it was found that the filed α2 decomposes to (α+γ2), although the final stable state is the α2 phase. The annealing behavior observed is quite similar to that of the filed β1′ martensite of Cu–Al alloys.
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  • Yoshiaki Iijima, Osamu Taguchi, Ken-ichi Hirano
    1980 Volume 21 Issue 6 Pages 366-374
    Published: 1980
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    Interdiffusion coefficients (\ ildeD) in cobalt-platinum alloys have been determined by Matano’s method in the temperature range between 1271 and 1673 K using couples of pure cobalt and platinum. It was found that at all temperatures, \ ildeD increases with platinum content up to about 40 at% and decreases gradually with a further increase of platinum. However, both the activation energy (\ ildeQ) and the frequency factor (\ ildeD0) have a maximum value at about 10 at%Pt. The logarithm of the ratio of the interdiffusion coefficient at the melting temperature to the thermodynamic factor for interdiffusion, ln(\ ildeDTmm), has been found to be proportional to the concentration of platinum. This relationship is found to be valid for other cobalt alloy as well as nickel alloy systems. The shift of Kirkendall markers toward the cobalt-rich side and the formation of voids in the diffusion zone corresponding to the concentration range of 5 to 10 at%Pt have been observed. From the interdiffusion coefficient and the velocity of markers, the following equations have been obtained for the intrinsic diffusion coefficients, DCo and DPt, in Co–21 at%Pt alloy:
    DCo=2.25×10−4exp(−278kJ mol−1RT)m2⁄s
    and
    DPt=8.09×10−4exp(−291kJ mol−1RT)m2⁄s.
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  • Hiroaki Nakamura, K\={o}ki Gunji
    1980 Volume 21 Issue 6 Pages 375-382
    Published: 1980
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    Calcium sulfide disks have been carefully prepared to avoid any contamination by means of a newly-developed sintering method. The electrical conductivity has been measured at temperatures from 923 to 1173 K and in the PH2SPH2 range from 0 to 102 with the aid of an alternating current bridge. Because the conductivity was independent of sulfur partial pressure, it was concluded that pure calcium sulfide is a perfect ionic conductor. The specific conductivity can be expressed as follows:
    log(σ⁄S·m−1)=−8.64×103T+3.390 (993∼1173 K)
    and the apparent activation energy for the conduction is 165.3 kJ/mol.
    The tracer diffusivity of Ca2+ was estimated from electrical conductivity measured by using Nernst-Einstein relation. Comparing with the activation energies of self-diffusion of anions in similar crystals, it seems that the divalent calcium cation is the main charge carrier of the electrical conduction.
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  • Yoshifusa Shoji, Sosuke Uchida, Tadashi Ariga
    1980 Volume 21 Issue 6 Pages 383-389
    Published: 1980
    Released on J-STAGE: May 22, 2007
    JOURNAL FREE ACCESS
    The effect of copper position on the dissolution has been studied between 613 and 781 K under static conditions using a reaction couple method. The dissolution of copper under the copper lower position was governed by diffusion, and the diffusion coefficient of copper in molten tin was expressed as follows: DL=4.20×10−9exp(−11kJ mol−1RT) (m2/s). Whereas the dissolution under the copper upper position was governed by natural convection resulted hydrodynamic instability from density differences in the melt. In this case the calculated concentration boundary layer thickness in molten tin increased with increasing temperature. The dissolution rates of copper into molten tin-copper alloys were proportional to the difference between saturation and initial concentration of copper in the melt.
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  • Kazuo Kawamura, Toshio Watanabe, Kôichi Nishizaka, Masaaki Onode ...
    1980 Volume 21 Issue 6 Pages 390-400
    Published: 1980
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    Based on Claisse’s model and considering the effects of the particle size and mixing rate, a theoretical formula expressing the intensity of the fluorescent X-rays emitted from heterogeneous systems has been established, by which the degree of homogeneity can be determined. The formula indicates that the effect of cobalt on the internal standard analysis of Fe content increases when the specimen and the element added thereto are pulverized to 2–3 μm or finer and thoroughly mixed. Insufficient mixing results in an apparent increase in the particle size. As microscopically confirmed, an iron ore sample, added with a briquetting binder and an internal standard, can be pulverized to 5 μm or finer by wet crushing for 3–5 min. This crushing also assures good mixing. This method almost fully cancels the influence of the matrix, and permits accurate determination of Fe content in various grades of iron and manganese ores and slags. The calibration curve is not necessarily linear over the wide Fe content range, probably because of the slight difference between the absorption coefficients of Fe and Co.
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  • 1980 Volume 21 Issue 6 Pages 400
    Published: 1980
    Released on J-STAGE: May 31, 2007
    JOURNAL FREE ACCESS
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