Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 64, Issue 10
Displaying 1-6 of 6 articles from this issue
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RESEARCH ARTICLE
  • Effects of solid solute Mn and Fe contents on creep behavior of Al–Mn alloys
    Makoto Ando, Akio Niikura, Yoshikazu Suzuki, Goroh Itoh
    Article type: RESEARCH ARTICLE
    2014 Volume 64 Issue 10 Pages 451-456
    Published: October 30, 2014
    Released on J-STAGE: November 30, 2014
    DOIhttps://doi.org/10.2464/jilm.64.451
    JOURNAL FREE ACCESS
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    The creep behavior of an Al–0.6%Mn alloy at 200°C was investigated to obtain fundamental knowledge on the metallurgical factors associated with threshold stress generation. Before creep testing, the alloy was subjected to solution treatment at 620°C for 10 h. The creep testing results confirmed the presence of threshold stress. A plausible mechanism for the threshold stress caused Mn atoms in solid solution is as follows: the atmosphere of solute Mn atoms around the moving dislocations significantly restrict the mobility of the dislocations when the loaded stress is small enough that the dislocations remain in the atmosphere of the solute Mn, since the diffusivity of Mn in the Al matrix is far smaller than that of the Al self-diffusion. The effects of Fe content on the creep behavior at 200°C were investigated using Al–0.25%Si–1.0%Mn– (0.04, 0.6) Fe alloys from the viewpoint of industrial application. Higher Fe content resulted in a reduction in the threshold stress since the amount of solute Mn decreased with increasing amount of Al– (Fe, Mn) –Si constituent particles.
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  • Behavior of two-step aging of Al–10%Si–0.3%Mg system alloy cast into permanent mold
    Seiji Saikawa, Ryuichi Morioka, Kenji Matsuda, Kiyoshi Terayama, Susum ...
    Article type: RESEARCH ARTICLE
    2014 Volume 64 Issue 10 Pages 457-462
    Published: October 30, 2014
    Released on J-STAGE: November 30, 2014
    DOIhttps://doi.org/10.2464/jilm.64.457
    JOURNAL FREE ACCESS
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    Behavior of two-step aging in an as-cast to artificial aging process of Al–10%Si–0.3%Mg system alloy cast by permanent mold was investigated by TEM and micro-vickers hardness measurement. The final aging curves are similar after pre-aging at 348 K, 373 K and 423 K for a short time without significantly increasing hardness. On the other hands, the final aging has a positive effect on the hardness after pre-aging at 348 K, 373 K and 423 K for a relatively long time with significantly increasing hardness in the under-aging region. In the final-aged specimens have very ununiformity precipitation structure, the increasing hardness is caused by the not only rod-like precipitates but also granular precipitates.
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  • Evaluation of dislocation density for 1100 aluminum with different grain size during tensile deformation by using In-situ X-ray diffraction technique
    Hiroki Adachi, Yoji Miyajima, Masugu Sato, Nobuhiro Tsuji
    Article type: RESEARCH ARTICLE
    2014 Volume 64 Issue 10 Pages 463-469
    Published: October 30, 2014
    Released on J-STAGE: November 30, 2014
    DOIhttps://doi.org/10.2464/jilm.64.463
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    The ultra-fine grained (UFG) aluminum with the grain size of 260 nm was fabricated by annealing for the severely plastic deformed A1100 alloy. This UFG aluminum showed the 0.2% proof stress (σ0.2) of four times the stress that the conventional Hall–Petch relation showed. In this study, for the UFG aluminum, the fine-grained (FG) aluminum with the grain size of 960 nm and the coarse-grained (CG) aluminum with the grain size of 4.47 µm, dislocation density change during the tensile deformation was investigated by the In-situ XRD measurement using SPring-8. The dislocation density changed in four stages with increase in strain. The first stage was the elastic deformation region and the dislocation density hardly changed. Only in the CG aluminum, this stage was hardly observed and the stress in which the dislocation began to multiple (σI) was almost 0 MPa. In the second stage, the dislocation density rapidly increased to ρII in which plastic deformation became possible at constant strain rate. In the third stage, the change became moderately. In the fourth stage, the dislocation density rapidly decreased by the fracture of test pieces. Additionally, the σ0.2–σI were followed the conventional Hall–Petch relation regardless of grain size.
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  • Discontinuous precipitation behavior and microstructure in Mg–Al system alloys
    Satoshi Takeshita, Chihiro Watanabe, Ryoichi Monzen, Seiji Saikawa
    Article type: RESEARCH ARTICLE
    2014 Volume 64 Issue 10 Pages 470-475
    Published: October 30, 2014
    Released on J-STAGE: November 30, 2014
    DOIhttps://doi.org/10.2464/jilm.64.470
    JOURNAL FREE ACCESS
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    The effects of addition of Zn on the discontinuous precipitation (DP) behavior have been metallographically examined in AM90 (AM) and AZ91Mg (AZ) alloys aged at 423, 448 and 473 K. Prior to the occurrence of a significant age-hardening within grains, DP cells in the alloys nucleate at grain boundaries and grow into the grains ahead of reaction fronts. The boundaries migrate at a constant rate at the early stage of aging. For both alloys, the cell growth rate and average inter-lamellar spacing increase with aging temperature. The cell growth rates for the AM alloy are slightly faster than those for the AZ alloy. The incubation periods to initiate DP are identical for the alloys. Kinetics analyses of DP using the model of Turnbull, and that of Petermann and Hornbogen have yielded grain-boundary diffusion data. The activation energies of boundary diffusion are 76 to 98 kJ/mol, depending on the models and the alloys. The area fraction of DP cells in the AZ alloy at the over-aging stage is smaller than that in the AM alloy at the same stage. The smaller area fraction in the AZ alloy is ascribed to the higher number density of continuous β-Mg17Al12 precipitates which successively suppress the boundary migration.
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