Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 52, Issue 10
Displaying 1-10 of 10 articles from this issue
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RESEARCH REPORT
  • Mechanical properties and microstructure of semi-solid injection molded Mg–Al–Ca alloys
    Kazuo SAKAMOTO, Kenichi YAMAMOTO
    2002 Volume 52 Issue 10 Pages 437-441
    Published: 2002
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.52.437
    JOURNAL FREE ACCESS
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    Mg–Al–Ca alloy is relatively cost effective and has excellent creep resistance. Aluminum is one of the most important elements in this alloy system. In this study, effect of the amount of aluminum on mechanical properties and microstructures is investigated by using semi-solid injection molded Mg–Al–Ca alloy. The mechanical properties are hardly influenced by the amount of aluminum. This is different from the behavior of common Mg–Al alloys. In the case of Mg–3Al–3Ca, intermetallic compound on grain boundary is (Mg, Al)2Ca that some magnesium sites of Mg2Ca occupied by aluminum atoms. As the amount of aluminum increases, (Mg, Al)2Ca changes to (Mg, Al)2 (Ca, Al) that some calcium sites of Mg2Ca occupied by aluminum, too. Mg2Ca structure of the intermetallic compound on grain boundary is stable and crystallization of Al2Ca or Al4Ca does not occur even if the amount of Al in the compound increases to 50 at%. This may be the reason why the amount of aluminum does not affect the mechanical properties.
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  • Formation of the TiO2-boehmite composite film on aluminum plates by the hydrothermal method
    Takayoshi FUJINO, Masataka SHIMOKADO, Hayao NOGUCHI
    2002 Volume 52 Issue 10 Pages 442-447
    Published: 2002
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.52.442
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    In recent years, investigations of techniques for fabricating films having various functions have been actively conducted, and investigation taking in the powder which has function inside film attracts attention. In this study, we investigate the functionalization of aluminum plates. We attempted to fix titanium oxide (anatase-type) powder in crystalline boehmite film by the hydrothermal method. By the hydrothermal treatment for 30 minutes at 200°C, a 10 μm thick TiO2-boehmite composite film was formed on an aluminum plate. The composite film had superior adhesivity, hardness, and anticorrosive and photocatalytic activities. In particular, the TiO2-boehmite composite film showed higher photocatalytic activity than other crystalline boehmite films and SOL–GEL thin films. Furthermore the addition of aluminum nitrate increased the crystalline boehmite film thickness by three fold. Anatase-type TiO2 and AlO(OH) in the composite film were identified by XRD, and the surface of the film was observed to have globular [macroinstruction] and fibrous structures [microcosm] by SEM. In conclusion, the hydrothermal method was useful for improving the function of the aluminum plate: as well as for increasing film thickness and photocatalytic activity by the addition of aluminum nitrate.
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  • Effect of second phase particles on the bendability of an Al–Mg–Si alloy
    Mineo ASANO, Hidetoshi UCHIDA, Hideo YOSHIDA
    2002 Volume 52 Issue 10 Pages 448-452
    Published: 2002
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.52.448
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    The effect of second phase particles on the bendability of Al–Mg–Si alloy for outer panels in autobodies was investigated by changing solution heat treatment condition and quenching rate. Slow quenching rate made inferior bendability. Because the number of second phase particles on the grain boundaries increased. Crack by bending test was not observed with short solution heat treatment time. However, in the case of long solution heat treatment time, the crack was observed. Depth of the crack increased with solution heat treatment time to maximum value and then decreased. The number of second phase particles decreased and the formation of shear bands by deformation increased with solution heat treatment time. When the formation of shear bands is observed significantly and the number of second phase particles is many, the crack occurs easily along the shear bands and the second phase particles.
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  • Thermo-inelastic simulation of butt curl phenomena during DC casting of aluminum
    Nobuhito ISHIKAWA
    2002 Volume 52 Issue 10 Pages 453-459
    Published: 2002
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.52.453
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    In an aluminum DC casting slab, butt curl phenomena are recognized at the short side of its bottom region and they are prone to decrease the productivity through fatal defects such as hot cracking or metal bleeding. In order to evaluate the mechanism of butt curl growth, a thermo-mechanical finite element model has been developed, in which thermally induced strains and stresses associated with phase transformation (solidification phenomena) are simulated using an elasto-plastic constitutive equation based on an isotropic hardening rule and the Mises yield condition. Comparison of butt curls shows a good agreement between calculations and measurements within tolerance of ±20%. As a driving force of butt curl, it is found that a torque moment due to tensile stresses distributing along a mushy region makes the solidified bottom shell bent rapidly when the whole slab surface is covered with secondary coolant. The study on influence of casting condition on butt curl growth reveals that resultant variations of butt curl are almost consistent with practical experiences in the cast house.
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  • Effects of solution treatment temperature on serration in 6061 aluminum alloy sheets
    Yoshihiro NAKAYAMA, Koichiro NARUKE, Masanobu FURUTA
    2002 Volume 52 Issue 10 Pages 460-464
    Published: 2002
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.52.460
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    The effects of solution treatment temperature on the serration in 6061 aluminum alloy sheets were investigated by tensile test carried out at 303 K. In order to examine the microstructure change with solution treatment temperature, measurements of the electrical resistivity and grain size were performed. Serrations were quantitatively evaluated using the critical strain, mean amplitude and frequency of stress drops. The amplitude of stress drops increased with higher solution treatment temperature due to the increase of solute atoms, whereas the amplitude and the frequency of stress drops vanished rapidly at coarsening of grain size. The critical strain of A–type serration decreased slightly with the rise of solution treatment temperature, whereas it of B–type increased markedly due to the increase of solute atoms. Grain size had, furthermore, no effect on the critical strain for each serration.
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  • Origin of the initial rapid hardening in a 2024 aluminum alloy aged at 423 K
    Shinji KUMAI, Masato OKUTSU, Natsuki YONEYAMA, Akikazu SATO
    2002 Volume 52 Issue 10 Pages 465-470
    Published: 2002
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.52.465
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    In order to reveal the origin of the initial rapid hardening of Al–Cu–Mg alloys, stress-strain response under various tensile loading conditions was investigated in a 2024 aluminum alloy aged at 423 K (15O°C). Cyclic tensile loading at 77 K resulted in no significant change in stress-strain response. On the other hand, yield-point phenomena evidently appeared in the specimen tested at room temperature. In addition, reduced flow stress was obtained at a higher strain rate in the room-temperature strain-dip test. These experimental findings supported the idea proposed by Ringer et al. that the interaction between dislocations and solute atoms (or co-clusters) was responsible for the initial rapid hardening. However, the idea cannot explain the large stress gain during the initial hardening. Microstructural change at the early stage of aging was examined using TEM. A uniform dispersion of dislocation loops was evident from the very early stage of aging and it remained during the initial hardening stage. Simple calculation based on Orowan mechanism indicated that the existence of dislocation loops resulting from quenched-in excess vacancies was the predominant reason for the initial hardening.
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  • Fabrication of functionally graded Al/Al2O3 materials using pulse current pressure sintering process
    Takekazu NAGAE, Mai MIZUBAYASHI, Masaru YOKOTA, Masateru NOSE, Tomoaki ...
    2002 Volume 52 Issue 10 Pages 471-476
    Published: 2002
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.52.471
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    To fabricate densified Al/Al2O3 functionally graded materials (FGM) on hardness and thermal expansion, a pulse current pressure sintering process was employed. This FGM consists of an aluminum layer, an (α–Al2O3 layer and 7 inter layers between them. As a starting material, aluminum and Al(OH)3 powders were used. Results obtained were as follows, (1) Temperature of an upper punch which directly contact with Al2O3 layer reached about 1800 K when the mold temperature reached about 870 K of holding temperature. (2) Mechanical grinding of powder mixture of Al(OH)3 and 20 mass% α–Al2O3 reduced the transformation temperature of Al(OH)3 to α–Al2O3 by 300 K. (3) The hardness of inter layers gradually increased as the volume fraction of γ–Al2O3 increased. Top layer which consists of α–Al2O3 was about 1000 HV in average and the surface of this layer reached 1500 HV.
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RESEARCH NOTE
REVIEW—5th JILM PRIZE & AWARDS
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