Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
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Volume 79, Issue 8
Displaying 1-6 of 6 articles from this issue
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Regular Article
  • Refining Crystal Grain of Inconel 718 by δ Process
    Tomohiro Nishimaki, Koji Kakehi, Yusuke Kawakami
    2015 Volume 79 Issue 8 Pages 385-390
    Published: 2015
    Released on J-STAGE: August 01, 2015
    DOIhttps://doi.org/10.2320/jinstmet.J2015018
    JOURNAL FREE ACCESS
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      The Ni-based superalloy Inconel 718 is used for aero-engine disks and is processed by forging and subsequent machine work. This study aimed to achieve uniformly fine crystal grain of Inconel 718 by the δ process, which prevents grain growth by applying a pinning force that intentionally precipitates any δ phase products. We observed the morphology of the δ phase, which changes according to the process of δ-phase precipitation heat treatment, and then prepared δ-processed Inconel 718 (DP718) by a small-size compression test that simulated the precision forging process. It was found that δ-processed specimens had finer and more uniform microstructures than the traditional processed Inconel 718.
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  • Improvement of Strength and Elongation Balance of Al-Mg-Si Alloy Utilizing Mg-Si Cluster and Its Mechanism
    Ken Takata, Kohsaku Ushioda, Ryutaro Akiyoshi, Ken-ichi Ikeda, Jun Tak ...
    2015 Volume 79 Issue 8 Pages 391-397
    Published: 2015
    Released on J-STAGE: August 01, 2015
    DOIhttps://doi.org/10.2320/jinstmet.J2015026
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      Tensile properties of Al-Mg-Si alloy with Mg-Si clusters was compared with that with β″ precipitate with the same strength. It was found that the elongation of the alloy with Mg-Si cluster was greater than the alloy with β″ precipitate because of high work hardening rate, in particular at large strain region. Decomposition of Mg-Si cluster into solute Mg and Si atoms during the tensile deformation test were also shown by differential scanning calorimetry (DSC). Three types of dislocation characteristics were observed from these alloys by transmission electron microscopy (TEM), homogeneous distribution of dislocation with β″ precipitate, cell structure with Mg and Si in solid solution, and combination of them with Mg-Si cluster. For the case of alloy with Mg-Si cluster, the yield strength was significantly increased due to the cutting mechanism. Simultaneously, the elongation was greatly improved due to the presences of decomposed solute Mg and Si atoms with plastic strain, which are inferred to prevent dynamic recovery in the later stage of tensile test. Consequently, the alloy with clusters has advantages from both alloys with precipitates and solutes, in terms of strength and elongation balance among the conventional 6000 series and 7000 series Al alloys.
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    Best Paper Award 2016

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  • Electrodeposition Behavior of Zn-Ni Alloys Produced from Sulfate Solutions at High Current Densities
    Satoru Ando
    2015 Volume 79 Issue 8 Pages 398-403
    Published: 2015
    Released on J-STAGE: August 01, 2015
    DOIhttps://doi.org/10.2320/jinstmet.J2015024
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      The electrodeposition behavior of Zn-Ni alloys produced from acidic sulfate solution were investigated via the partial polarization curves produced during alloy electrodeposition. The current density at which the co-deposition of Zn-Ni alloy produced anomalous results, we found that the Zn deposition is polarized and affected by the bath Zn concentration and flow rate. This indicates that at high current densities the Zn deposition is controlled by diffusion. Under the conditions to increase Zn deposition we found that Ni deposition was not suppressed, even in the region of anomalous co-deposition. At low pH bath condition Ni concentration in deposit was not increase under high current density, because of strong suppression of Ni deposition under low pH condition.
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  • Microstructure of Surface Contaminant Layer of Joint Stucco between Stone Walls of Takamtsuzuka Tumulus
    Masahiro Kitada, Yohsei Kohzuma, Toru Tateishi
    2015 Volume 79 Issue 8 Pages 404-412
    Published: 2015
    Released on J-STAGE: August 01, 2015
    DOIhttps://doi.org/10.2320/jinstmet.J2015033
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      The Takamatsuzuka tumulus was constructed in the 7th to 8th centuries at Asuka in Nara prefecture. The mural and wall surfaces are soiled and deteriorated by rainwater, mold, and other causes. The mural is painted on the stone wall that is coated with stucco. The stone walls are jointed with masonry joint stucco. The purpose of this investigation is to clarify the composition, crystal structure, and other material factors of the surface contaminant layer on the joint stucco. An X-ray computer tomography, an X-ray diffractometer, a scanning electron microscope, and a transmission electron microscope are utilized to examine the microstructure. The contaminant layer thickness is 0.2-0.3 mm. Kaolinite, muscovite, montmorillonite, hematite and a few silicates are detected from the contaminant layer. The compounds detected are constituents of soil-like clay, and most of them contain Fe. By transmission electron microscopy observation, the contaminant layer is found to consist of fine mineral grains, as mentioned above, most of which are acicular. The acicular grain size is approximately 0.2-1 μm in length and 0.015-0.2 μm in width. The grains are in a row parallel to the layer surface. The hematite grains are circular with diameters of 15-250 nm. In addition, iron titanate is observed. The yellowish brown color of the stucco surface is mainly due to iron ions contained in the above-mentioned compounds. It is thought that the grains deposited on the stucco surface from colloidal-like water containing the above-mentioned fine grains.
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  • Molecular Dynamics Simulation of Dislocation Behavior in TiAl Intermetallic Compound
    Shunichi Takeuchi, Takahiro Kawamura, Yasuyuki Suzuki, Tomonori Kitash ...
    2015 Volume 79 Issue 8 Pages 413-418
    Published: 2015
    Released on J-STAGE: August 01, 2015
    DOIhttps://doi.org/10.2320/jinstmet.J2015025
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      TiAl intermetallic compound has received much attention as a lightweight heat resistant material. Because mechanical property is affected by dislocation behavior, it is important to understand dislocation behavior in microscopic viewpoint. In this study, we simulated dislocation behavior in single phase γ-TiAl and α2-Ti3Al using molecular dynamics method. From the results, we confirmed that perfect dislocation was divided into partial dislocations and stacking faults. We also investigated temperature dependence of dislocation behavior. We found that the dislocations at 1000 K moved less than those at 300 K.
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