Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 53, Issue 4
Displaying 1-8 of 8 articles from this issue
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RESEARCH REPORT
  • Dragging of liquid Bi particles induced by grain boundary migration in Al–Bi alloys
    Ryosuke KAINUMA, Ikuo OHNUMA, Kiyohito ISHIDA
    2003 Volume 53 Issue 4 Pages 141-146
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.141
    JOURNAL FREE ACCESS
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    Microstructure and grain growth characteristics of the pre-deformed Al–Bi alloys annealed at 773 K are investigated mainly by scanning electron microscopic (SEM) observation. It was shown that while there are a small amount of very fine liquid Bi particles in the grains, the Bi particles on the grain boundaries grow dragged by the moving grain boundaries. The grain growth is significantly restricted by the dragging effect. Origin of this dragging phenomenon can be explained with mixture effects of the grain boundary curvature and the surface energy of the intragranular Bi particles. By a quantitative analysis it was confirmed that the diffusion of Al atoms in the liquid Bi particles on the grain boundaries rate-controls this dragging effect.
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  • AE signals caused by environmental embrittlement of an Al–Mg–Si alloy deformed at slow strain rates in laboratory air
    Keitaro HORIKAWA, Kenichi YOSHIDA, Akihiro OHMORI, Kiyoshi SAKAMAKI
    2003 Volume 53 Issue 4 Pages 147-151
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.147
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    Acoustic emission (AE) accompanied by environmental embrittlement was examined for a coarse-grained Al–Mg–Si alloy tensile tested at slow strain rates in laboratory air with a relative humidity of 70%. Elongation was slightly decreased with a decrease in the initial strain rate from 1.7× 10−4s−1 to 1.7× 10−6s−1. Fracture morphology under the strain rate of 1.7× 10−4s−1 was completely transgranular, while those of 1.7× 10−5s−1 and 1.7× 10−6s−1 were a mixture of transgranular and intergranular. Occurrence of the intergranular cracks near the specimen surface due to the environmental embrittlement could be discerned by the variation in root mean square (RMS) voltage at the moment of fracture. Propagation of the intergranular cracks was also detectable by the variation of AE signals with high amplitude ranges up to 100 dB at the final stage of plastic deformation. In addition, hydrogen microprint technique (HMT) revealed a trace of hydrogen accumulation at grain boundaries in the Al–Mg–Si alloy slowly strained by 15%.
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  • Effects of tool radius on formability during deep drawing of AZ31 magnesium alloy sheets
    Ratchanee PAISARN, Shougo TAGAWA, Nobuhiro KOGA
    2003 Volume 53 Issue 4 Pages 152-156
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.152
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    In previous studies, it is known that forming products with practical depth made of AZ31 magnesium alloy sheets can be obtained by applying the warm-deep drawing, where a heated die, blank holder and water-cooled punch are used. However, influence of tool radius, which is one of significant factors on deep drawing formability, has not been examined systematically under the practical forming speed condition in which hydraulic or mechanical press machine forming are assumed. In this study, we systematically examined effects of tool radius and forming speed on the forming limit of warm-deep drawing for the cylinder and square cups. Furthermore, we studied the possibility of the reform of a square cup with small shoulder and corner radii by sizing, as it is difficult to form by only deep drawing.
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  • Intergranular corrosion and SCC properties of Al–Mg–Si alloy sheets
    Shuhei OSAKI, Katsuyuki KINOSHITA, Daisuke NAGANUMA
    2003 Volume 53 Issue 4 Pages 157-162
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.157
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    Properties on intergranular corrosion (IC) and stress corrosion cracking (SCC) of three Al–Mg–Si alloys with a fixed Mg content were studied. IC test samples and tensile specimens were prepared from cold rolled sheets of alloy No. 2 (Al–0.7%Mg–0.45%Si), alloy No. 5 (Al–0.7%Mg–1.1%Si) and alloy No. 7 (Al–0.7%Mg–0.45%Si–0.34%Cu), subjected to solution treatment and then aging at 448 K. When immersed in an acid NaCl aqueous solution based on ISO11846–B method, alloys No. 2 and No. 5 were immune to IC, while alloy No. 7 showed a high sensitivity to IC under a wide range from underaging to overaging. Tensile tests by SSRT (slow strain rate technique) in the solution of IC tests were carried out to evaluate the index I of susceptibility to embrittlement as the ratio of reduction in elongation, compared to that in laboratory air. The index I of peak-aged specimens was ranked on the order of alloy No. 5 > No. 2 > No. 7, which disagreed with the tendency of IC susceptibility. Intergranular stresscorrosion cracks occurred in the SSRT tests were attributed to strain-induced APC (active path corrosion) for alloys No. 5 and No. 2, accompanied with preferential breakdown of surface film along grain boundary zones, while for alloy No. 7 to pre-existing APC caused by solute-depleted zone along grain boundaries.
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  • Effect of surface roughness on glossiness of a 5052 aluminum alloy
    Makiko YONEHARA, Keisuke SUZUKI, Koichiro KIHARA, Akira KIJIMA, Hiroak ...
    2003 Volume 53 Issue 4 Pages 163-168
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.163
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    In this paper, the effects of topography with different rough surfaces on glossiness are investigated experimentally in order to characterize a surface texture of an aluminum alloy A5052–H34. The surface texture of aluminum alloy is determined by the glossiness and the three factors of surface roughness: arithmetical mean Ra, period of roughness profile and slopes of the roughness. The surface of sample used in the experiment has different rough surfaces due to different cutting process. The topography of sample was measured by using a mechanical stylus profilometry. The periodic of roughness was evaluated by mean width of the profile elements RSm. The experimental results showed that the glossiness slightly increased as Ra decreased. As glossiness increased, RSm decreased. These means that the surface with low amplitudes and short wavelengths of the roughness results in high glossiness values. Moreover, histogram of the reflection angle calculated roughness profile showed that the specular reflection values of glossiness decreased as the diffuse reflection values increased. Thus the local slopes of the roughness correlate strongly with the glossiness. These results clearly verified that the proposed method for evaluating the surface texture of aluminum alloy was effective.
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  • Strengthening of aluminum alloy pipes by back-torsion working
    Hiroshi ANADA, Masaki SHIBATA, Mai MIZUBAYASHI, Mitsuaki FURUI, Shigeo ...
    2003 Volume 53 Issue 4 Pages 169-175
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.169
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    The application of the back-torsion process to the strengthening of aluminum alloy pipes was examined in this study. The results showed that this process was useful for both alloy pipes for working and those for aging. The most outstanding characteristic of this method is that the strengthening of the materials can be adjusted by simply adjusting the number of twists without the use of dies or core bars, which are necessary for the conventional drawing process. Also, it was determined that the cross-section hardness of pipes with back-torsion treatment gradually increased from the inside toward the outside of the pipe, while the pipes treated by the drawing process had an M-shape distribution.
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