Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 62, Issue 8
Displaying 1-4 of 4 articles from this issue
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RESEARCH ARTICLE
  • Effects of plate thickness on microstructure and strength of high-speed solid-state joined 2024 aluminum alloy stud and 5052 aluminum alloy plate
    Shinji Kumai, Kento Takaya
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 8 Pages 293-299
    Published: August 30, 2012
    Released on J-STAGE: September 30, 2012
    DOIhttps://doi.org/10.2464/jilm.62.293
    JOURNAL FREE ACCESS
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    The advanced high-speed solid-state joining method was developed for stud welding of aluminum alloys. A double cylindrical copper tube, consisting of an inner tube and outer tube served as a pair of electrodes. A specially designed stud with a circular ridge projection at the bottom was mounted at the end of the inner tube. The stud was then pressed against the plate surface and a discharge current was introduced to the stud through the inner tube, whereupon current flew through the plate surface on to the outer tube, which acted as a ground. The circular ridge projection crushed and spread along the plate surface. High-density current running through the contact point acted to increase the local temperature, and this promoted plastic deformation and enhanced atomic diffusion at the contact point. The welding was normally completed within a few milliseconds and the temperature increase of the joint was negligible. In the present study, cylindrical 2024-T3 aluminum alloy studs were welded to 5052-H34 aluminum alloy plates with various plate thicknesses from 1 to 4 mm. The circular ridge projection crushed and spread along the plate surface. Deformation of the projection took place almost symmetrically about the projection tip, and the joining was achieved in the shape of double rings on the plate for the thick plates (e.g. 3 and 4 mm). This resulted in high strength of the joint. While, for the thin plate (e.g. 1 mm), asymmetrical deformation occurred on both the inner side and the outer side of the projection. Joining was made mainly at the outer-side of the projection and so the joining area exhibited the shape of a single ring on the plate surface. This resulted in the decreased joining area and the reduced joint strength. It was revealed that not only the position of electrodes but also the plate thickness controlled the current flow and the resultant microstructure and strength on the joint interface.
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  • Effects of magnesium addition on threshold stress of Al–Mn alloys
    Makoto Ando, Yoshikazu Suzuki, Goroh Itoh
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 8 Pages 300-305
    Published: August 30, 2012
    Released on J-STAGE: September 30, 2012
    DOIhttps://doi.org/10.2464/jilm.62.300
    JOURNAL FREE ACCESS
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    The effects of Mg addition on the threshold stress of Al–Mn alloys were investigated. A 3003 aluminum alloy and 0.2 mass% of Mg-added alloy were subjected to high-temperature tensile testing and creep testing at temperatures of 160, 200 and 240°C, and the threshold stress at each of these temperatures was evaluated. The Mg-added alloy showed higher threshold stress than the 3003 aluminum alloy at 160 and 200°C. This effect of Mg addition diminishes with temperature, however, and the threshold stress was approximately the same in both alloys at 240°C. Further, the threshold stress, which was normalized by elastic modulus at each temperature was higher than the Orowan stress that was calculated from the dispersion density. These results indicate that the solid solution of Mn enhances the threshold stress of the 3003 aluminum alloy, because the diffusion velocity of Mn is sufficiently small to limit the mobility of the dislocations. The solid solution of Mg may enhance such an effect of Mn; however, at higher temperatures, Mg does not have any effect.
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  • Effect of strain rate on hydrogen gas evolution behavior during tensile deformation in 6061 and 7075 aluminum alloys
    Keitaro Horikawa, Hiroyuki Yamada, Hidetoshi Kobayashi
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 8 Pages 306-312
    Published: August 30, 2012
    Released on J-STAGE: September 30, 2012
    DOIhttps://doi.org/10.2464/jilm.62.306
    JOURNAL FREE ACCESS
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    Effect of strain rate on hydrogen evolution behavior during tensile deformation and fracture in T6-tempered 6061 and 7075 aluminum alloys was studied by means of a testing machine equipped with a quadrupole mass spectrometer installed in an ultra-high vacuum chamber. The evolution of hydrogen atoms in the deformed microstructure was also visualized with a hydrogen microprint technique. It is revealed that the hydrogen gas evolution rate during the tensile deformation changes according to the testing strain rate. The highest hydrogen gas evolution was observed when the both alloys were tested at a strain rate of 2.5×10−2 s−1. Similar tendency was also identified when the sinusoidal stress was applied. The amount of hydrogen evolved at the early stage of plastic deformation in the 6061 alloy was much smaller than that in the 7075 alloys. This suggested that the hydrogen diffusion with the aid of hydrogen transportation by dislocations was retarded in the 6061 alloy because of the difference of the hydrogen trapping state in the microstructure, comparing with the 7075 alloy.
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