Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 60, Issue 2
Displaying 1-8 of 8 articles from this issue
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RESEARCH REPORT
  • Effects of addition of SiO2 on fabrication of alumina filter bound by aluminum borate for molten aluminum
    Osamu Yamakawa, Hiroshi Shirakawa, Minoru Hashiba, Osamu Sakurada
    Article type: Research Report
    2010 Volume 60 Issue 2 Pages 55-60
    Published: February 28, 2010
    Released on J-STAGE: March 30, 2010
    DOIhttps://doi.org/10.2464/jilm.60.55
    JOURNAL FREE ACCESS
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    The quality of molten aluminum is dependent on the methods used for its treatment, and the rigid media tube filter (RMF) is the most reliable means of removing inclusions from molten aluminum. In the present study, we examined the effects of adding SiO2 to alumina filters bound by aluminum borate (9Al2O3·2B2O3 : 9A2B) to improve the penetration of molten aluminum into the filter. With the addition of SiO2, although the amount of 9A2B crystal was decreased by formation of borosilicate glass and 9A2B crystal shape became short and small, the penetration ratio for adding 10 mass% SiO2 was substantially improved and the amount of Si outflow and corrosion resistance were reduced. The degrees of thermal expansion of alumina filters with 10 mass% SiO2 were similar to those of non-SiO2-bound filters. In conclusion, alumina filters with bound 9A2B crystals including 10 mass% SiO2 showed improved penetration of molten aluminum and reduced both Si outflow and corrosion resistance. As the thermal expansion of the filter was similar to that of filters containing no SiO2, this material is suitable for bonding of RMF heated to 800°C under restriction.
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  • Slip deformation analysis based on full consistents model for α-type titanium alloy at low temperature
    Motoaki Morita, Osamu Umezawa
    Article type: Research Report
    2010 Volume 60 Issue 2 Pages 61-67
    Published: February 28, 2010
    Released on J-STAGE: March 30, 2010
    DOIhttps://doi.org/10.2464/jilm.60.61
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    Effects of restricted slip conditions on both Taylor factor and plastic strain energy under the condition of tensile yielding have been analyzed in α-titanium alloys at low temperature, using full constraints model. Role of secondary slip systems, i.e. ‹a› basal slip and ‹c+a› pyramidal slip, was clarified, when prismatic slip was dominant. Although no influence of secondary slip conditions on Taylor factor was detected, the plastic strain energy was sensitive to the operating secondary slip systems. When the basal system was chosen as secondary slip, the energy increased in all tensile axes, especially around ‹0001›. In addition, no basal slip operation decreased the plastic strain energy. In the tensile axis around ‹0001› , the plastic strain energy was the highest and the operation of ‹c+a› pyramidal slip was necessary. High elastic strain energy, therefore, must be accumulated to a high level around ‹0001›, since pyramidal slip can be hardly active because of its very high critical resolved shear stress.
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  • Lattice rotation and recrystallization due to cold-rolling and annealing treatment in Al–0.7%Mg–0.4%Si–0.2%Cr alloy
    Atsushi Yamamoto
    Article type: Research Report
    2010 Volume 60 Issue 2 Pages 68-74
    Published: February 28, 2010
    Released on J-STAGE: March 30, 2010
    DOIhttps://doi.org/10.2464/jilm.60.68
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    Recrystallization behaviors in an Al–Mg–Si alloy have been intermittently observed by means of SEM-EBSD in detail. A specimen of Al–0.73Mg–0.38Si–0.26Cr alloy was cold-rolled with reduction rate of 30%, then annealed at 673 K. Annealing, ion-polishing and EBSD measurement were repeated and changes in microstructures were observed on the same area in the specimen during annealing up to 4.8 ks. Cold-rolling resulted in lattice rotation along axes parallel to the specimen surface and about perpendicular to the rolling direction. Subgrains formed at a recovery stage have the rotated orientation. Subgrains with low lattice defect densities formed near prior grain boundaries were developed into recrystallized grains through the prior grain migration mechanism. Therefore, the recrystallized grains also have the rotated orientations. In some case, recrystallized grains were formed at interiors of prior grains, and in another case, new grains were formed without orientation relationships among the surrounding prior grains. The recrystallized grain with the prior grain migration mechanism invaded into neighboring prior grains, and the mother grain was invaded by other recrystallized grains. The original and/or rotated orientation of the mother grain was maintained at the outside of the original prior grain.
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  • Effects of alloy contents on strength and toughness in Al–Zn–Mg–Cu alloy
    Shingo Iwamura, Tadashi Minoda, Hideo Yoshida
    Article type: Research Report
    2010 Volume 60 Issue 2 Pages 75-80
    Published: February 28, 2010
    Released on J-STAGE: March 30, 2010
    DOIhttps://doi.org/10.2464/jilm.60.75
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    The effects of alloy contents on the strength and toughness of Al–Zn–Mg–Cu alloy T6 extrusion were studied by means of tensile test and Charpy impact test. In this study, the role of the main elements (zinc, magnesium, copper) on the strength and toughness of the Al–Zn–Mg–Cu alloy was systematized on the basis of experimental results. Fundamentally, large amounts of the main elements results in higher strength and lower toughness. Exceptionally, when the sum of magnesium and copper contents exceeds 4.0 mass%, undissolved S–Al2MgCu and/or η-MgZn2 dispersoids exist in the matrix and they cause lower toughness. The higher addition of magnesium and zinc, which compose strengthening η′ phase, has greater effect on strength. On the other hand, copper atoms, which seem to solute in the η′ phase, accelerate the precipitation of η′ phase and have smaller effect on strength compared with magnesium.
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  • Effects of alloying elements in aluminum alloys and activations on zincate treatment and electroless nickel-phosphorus plating
    Koji Murakami, Makoto Hino, Ryosuke Furukawa, Teruto Kanadani
    Article type: Research Report
    2010 Volume 60 Issue 2 Pages 81-87
    Published: February 28, 2010
    Released on J-STAGE: March 30, 2010
    DOIhttps://doi.org/10.2464/jilm.60.81
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    Zincate treatment and electroless nickel-phosphorus plating for aluminum alloys of A1100, A2017, A5052 and A7075 were researched from the viewpoints of alloying elements and activation conducted prior to zincate treatment. Adhesion strengths of the plated films were measured by 90° peeling test, which showed that double zincate treatment improved adhesion strength especially when ferric ion was added into the zincate solution. Temporal changes of electrode potential during zincate treatments and morphologies of the zincated surfaces showed that copper and zinc in the substrates promoted uniform precipitation of zinc. Excess zinc was shown to dissolve into the plating solution and cause formation of low-density areas or gaps between plated films and substrates. Activation for A1100 by various conditions showed that formation of oxide film remarkably affected the precipitation of zinc. When a mixture of nitric and hydrofluoric acid was used for activation, finer particles of zinc were formed near etch pits compared with the cases of hydrochloric or nitric acid. On the other hand, the surface was uniformly covered with fine zinc particles in the case of the activation with a solution of sodium hydroxide. This indicates that uniformity of oxide film on substrate before zincate treatment is thought to bring about uniform precipitation of zinc.
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