Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 56, Issue 4
Displaying 1-9 of 9 articles from this issue
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RESEARCH REPORT
  • Formation of titanium dioxide as photocatalyst coating on aluminum by chemical conversion method
    Takayoshi FUJINO, Teppei MATZUDA
    2006 Volume 56 Issue 4 Pages 191-196
    Published: 2006
    Released on J-STAGE: June 06, 2006
    DOIhttps://doi.org/10.2464/jilm.56.191
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    Titanium dioxide (TiO2) coatings were prepared by chemical conversion treatment of aluminum in (NH4)2TiF6 with H2O2, to followed by sintering of the coating to immobilize the photocatalyst on aluminum. In the conversion treatment in (NH3)2TiF6 and H2O2, the F− ions in the bath reacts with the aluminum, to form AlF3 brought to the aluminum surface. Simultaneously, reduction of hydrogen ions take place over the aluminum surface, which in turn, leads to the increase in pH of the interface. The hydrolysis of the titanium peroxo fluoride was deposited on aluminum because pH increased on the surface. The coating sintered at 473 K was found to have the highest catalytic activity. The photocatalytic activity of the coating sintered at 673 K was lower than the coating heated at 473 K, which is attributed to the aggregation of TiO2. This forming process of the coating is low cost because of the useless of electrolytic decomposition process. Furthermore, practical uses are expected because immobilized substances on aluminum can easily, be to decompose at low temperatures.
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  • Activation of photocatalytic coatings applied on aluminum oxidation film
    Takayoshi FUJINO, Takanori HATTORI
    2006 Volume 56 Issue 4 Pages 197-202
    Published: 2006
    Released on J-STAGE: June 06, 2006
    DOIhttps://doi.org/10.2464/jilm.56.197
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    Aluminum was anodized in a H2SO4 solution, and then platinum and tin were electrodeposited into nano-pores of anodic oxidation film in H2PtCl6 and SnSO4 solutions. Titanium(IV) oxide (TiO2) thin film was immobilized on electrolytically colored anodic oxide coating of aluminum. The photocatalytic activity of prepared films was analyzed for photolysis of the malachite green. In the results, the photocatalytic activity of Pt loaded TiO2 (TiO2/Pt/Al2O3) film was highest in all films, and the relation between the amount of metallic colloid and photocatalytic activity was confirmed. Photocatalytic activity improved with electrodeposition increases, and activity was highest when the amount of platinum was about 3.1 µgcm−2. But photocatalytic activity began to decline when the amount of platinum exceeded 3.1 µgcm−2 because the platinum had a recombination center and decreasing surface area by electrodeposition. The photocatalytic activity of Sn loaded TiO2 (TiO2/Sn/Al2O3) film didn't reach the TiO2/Pt/Al2O3 film, indicating photocatalytic activity of about 1.8 times compared with TiO2/Al2O3 film. SnO2 manifested photocatalysis as well as TiO2, confirming that sintered tin was SnO2 in the results of ESCA. Therefore, anodic oxidation film and electrolytically colored anodic oxide coating were effective substrates of photocatalyst films.
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  • Effect of heat treatment condition on the hydrogen content in Al–4%Mg alloys
    Hidetoshi UMEDA, Goroh ITOH, Yoshinori KATO
    2006 Volume 56 Issue 4 Pages 203-209
    Published: 2006
    Released on J-STAGE: June 06, 2006
    DOIhttps://doi.org/10.2464/jilm.56.203
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    Effect of heat treatment conditions such as atmosphere, temperature and time on the hydrogen content in two Al–4%Mg alloys was investigated. The hydrogen content in the as-cast slab is dispersed uniformly, while the hydrogen content in the annealed slab tends to be increased in the area near the surface. Such a condensation of hydrogen near the surface can be seen when it is annealed in a wet atmosphere. When annealed in a dry atmosphere, the hydrogen content near the surface becomes lower than that of the center of the specimen. Although the hydrogen in Al–Mg alloy tends to be released to outside at temperatures higher than 400°C, the absorption of hydrogen existing in the atmosphere is also presumed to occur at the same time when annealed in the wet atmosphere.
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  • Visualization of hydrogen during fatigue fracture in an Al–Mg–Si alloy
    Keitaro HORIKAWA, Yusuke TAKEUCHI, Kenichi YOSHIDA, Hidetoshi KOBAYASH ...
    2006 Volume 56 Issue 4 Pages 210-213
    Published: 2006
    Released on J-STAGE: June 06, 2006
    DOIhttps://doi.org/10.2464/jilm.56.210
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    Hydrogen accumulation during fatigue of a bake-hardened Al–Mg–Si alloy was investigated by means of hydrogen microprint technique. As a result of S–N curve relation as a function of testing frequency, effect of environmental hydrogen on fatigue properties was not clearly identified. Based on the low cycle fatigue test with 60 MPa stress amplitude, it was revealed that hydrogen was accumulated on slip bands and that distribution of hydrogen emission was changed in the crack propagation direction. Hydrogen was preferentially accumulated at the coarse slip bands near the fatigue crack where the separation of slip planes was observed in the fracture surface. On the other hand, hydrogen was observed on the slip lines arranged like steps where the fatigue striations were formed in the fracture surface. At near the final fracture area where the fine slip bands were formed on specimen surface, hydrogen was arranged on each slip bands formed by multiple slips.
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  • Formation behavior of acoustic cavitation in molten aluminum alloys under ultrasonic vibration
    Tadashi MATSUNAGA, Kenji OGATA, Tomei HATAYAMA, Kenji SHINOZAKI, Makot ...
    2006 Volume 56 Issue 4 Pages 214-220
    Published: 2006
    Released on J-STAGE: June 06, 2006
    DOIhttps://doi.org/10.2464/jilm.56.214
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    In order to investigate behavior of acoustic cavitation in molten aluminum alloys when ultrasonic vibration was applied, we measured sound pressure in molten aluminum alloys by means of acoustic emission (AE). The frequency analysis was performed to the obtained sound pressure. As a result, the characteristic frequency of acoustic cavitation would be 5, 10 and 260 kHz. The maximum intensity at 260 kHz was increased by addition of magnesium in molten aluminum at the ultrasonic power of more than 200 W drastically. The reason why the addition of magnesium led to promote the generation of the cavitation would be caused by its relatively low surface tension and high vapor pressure. From the viewpoint of the cavitation threshold, both the decrease in the surface tension of the molten aluminum alloy and the increase in the vapor pressure will lead to generate the acoustic cavitation. Therefore, addition of zinc of 8.7 mass% and bismuth of 0.5 mass% also caused to generate acoustic cavitation.
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  • Restoration process of bulge-formed aluminum sheet
    Nobuo HATANAKA, Consorcio S. NAMOCO Jr., Norio TAKAKURA, Takashi IIZUK ...
    2006 Volume 56 Issue 4 Pages 221-225
    Published: 2006
    Released on J-STAGE: June 06, 2006
    DOIhttps://doi.org/10.2464/jilm.56.221
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    When a sheet metal product is subjected to local damages like as hollows or bends, the appearance, in many cases the quality, of that product would largely decrease. To regain the original shape and quality, the product should be restored. However, there are many difficulties in the restoration process because the flow stress and thickness of the sheet have already changed at site by site. So far, such a restoration process has not been investigated so much. However, in taking the problems of environmental conservation into consideration, the importance of that process would get larger and larger from now on. In this paper, such a restoration process on bulged sheets of soft aluminum is investigated. Various restoration processes are examined to restore bulged sheets to the original flat shape with uniform thickness. In case that the flat tool without lubrication was pressed to a bulged sheet, the central part of the bulged region was not restored to the original thickness. On the other hand, using the tool with lubrication, the peripheral region of the bulged shape was not restored to the original thickness. In combination of lubrication tool and lubrication-less tool, a bulged sheet could be successfully restored to the original flat shape. It was also confirmed that, by pressing ring tools in turn from outer region of bulged shape, the sheet was restored to original thickness and flat shape.
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  • Infiltration mechanism of molten aluminum alloys into bundle of carbon fibers using ultrasonic infiltration method
    Tadashi MATSUNAGA, Kenji OGATA, Tomei HATAYAMA, Kenji SHINOZAKI, Makot ...
    2006 Volume 56 Issue 4 Pages 226-232
    Published: 2006
    Released on J-STAGE: June 06, 2006
    DOIhttps://doi.org/10.2464/jilm.56.226
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    As the fabricating process of continuous M40J carbon fiber reinforced aluminum alloys composite wires by using ultrasonic infiltration method, the mechanism of the infiltration of molten alloys into the bundle of the carbon fibers was examined especially from the viewpoints of wettability, acoustic cavitation and threshold pressure for infiltration. It was found that the infiltratability of the alloys was proportional to the maximum intensity of the acoustic cavitation. Both the infiltratability and the intensity were enhanced by the addition of surfactant elements for molten aluminum. Thus, decrease in surface tension will cause the generation of acoustic cavitation to increase. When the ultrasonic vibration is applied to molten aluminum alloys, acoustic cavitation would be formed on/in the bundle of carbon fibers. Then the shock wave, which was caused by the cavitation collapsed, would lead to leave the distance between fibers in the bundle. From the results of the direct observation of the bundle in the aqueous solution using high speed camera during applied ultrasonic vibration, the diameter of the bundle was increased by generating the cavitation. Thus, this phenomenon will also cause the decrease in the threshold pressure for infiltration. Therefore, both the generation of the acoustic cavitation and increase in the interval between fibers will be the controlling factors of the infiltration in the fabricating process of this kind of composites by using ultrasonic vibration.
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