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 12
Displaying 1-8 of 8 articles from this issue
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RESEARCH REPORT
  • Effects of contact pressure and surface roughness on fretting fatigue characteristics of a high workable Ti–4.5%Al–3%V–2%Mo–2%Fe alloy
    Junji TAKEDA, Mitsuo NIINOMI, Toshikazu AKAHORI, Yoshiki SUZUKI
    2003 Volume 53 Issue 12 Pages 563-569
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.563
    JOURNAL FREE ACCESS
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    The effects of contact pressure and surface roughness on fretting fatigue strength of Ti–4.5Al–3V–2Mo–2Fe conducted with annealing at 1123K were investigated in this study. Fretting fatigue tests in the low and high cycle fatigue life region of the alloy annealed at 1123K were carried out at each contact pressure of 10, 15, 30, 45, 75, 105 and 153 MPa. The fretting fatigue crack initiation mechanism is changed by contact pressure. At a contact pressure of 15 MPa, fretting fatigue life tends to be very low in each fatigue life region. The tangential force tends to increase with increasing contact pressure in each fatigue life region. Contrary to this trend, the tangential force coefficient tends to decrease with increasing contact pressure in each fatigue life region. The fretting fatigue life of the alloy buff-polished to produce mirror surface tends to increase about 20% and 10% in the low and high cycle fatigue life region, respectively as compared with the alloy wet-polished by water-proof emery paper up to #1000.
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  • Grain refinement of 5083 based aluminum alloy sheets by warm rolling
    Hiroki TANAKA, Yasunori NAGAI, Hideo YOSHIDA
    2003 Volume 53 Issue 12 Pages 570-574
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.570
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    An attempt was made to refine the grain structure of the 5083 based aluminum alloy containing Zn, Cu and Zr, by employing a new warm rolling method under the control of both roll temperature and material temperature. Samples were rolled at temperature ranging from 200°C to 400°C with re-heating after each rolling pass in order to keep sample temperature. As rolling temperature gets higher, the subgrain structure becomes more stable. In the case of rolling at 400°C, fine grains with diameter less than 3 μm are observed after final annealing. It is also found that the sheet rolled at 400°C has a high ratio of low angle boundaries, less than 15°, after final annealing. On the other hand, the sheets rolled at below 250°C show a fully recrystallized structure. The warm-rolled sheets have strong β-fiber orientations. There is no apparent change caused by the subsequent annealing in the orientation density of the β-fiber in the sheet rolled at 400°C. The yield strength of a sheet in O-temper rolled at 400°C is 40% higher than that of a cold rolled sheet.
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  • Behavior of Hydrogen in Al–Mg Alloys Investigated by Means of Hydrogen Microprint Technique
    Tomoaki IHARA, Goroh ITOH
    2003 Volume 53 Issue 12 Pages 575-581
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.575
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    In recent years, hydrogen has been attracting attention as a clean energy. For its transport, a tank for liquid hydrogen is necessary, and 5083 aluminum alloy has been chosen as a candidate of the tank material. On the other hand, hydrogen is thought to permeate most metallic materials from a corrosive environment, resulting in hydrogen embrittlement. In the actual liquid hydrogen tank, only one side of the inner sheet material is exposed to hydrogen gas. Although serious environmental embrittlement of aluminum alloys by molecular hydrogen has not been reported so far, the behavior of hydrogen has not been investigated in detail in this condition.
    In the present study, analysis on the permeation and migration behavior of hydrogen atoms in the above condition has been made by means of hydrogen microprint technique on a sheet of 5083 aluminum alloy, together with Al–4.5mass%Mg binary alloy which is a base material of the 5083 alloy. It was revealed that hydrogen atoms can invade and permeate aluminum alloys from the gaseous hydrogen atmosphere. The entrance site was thought to be the second phase particle and the fresh surface produced by the plastic deformation. Once hydrogen atoms entered the alloys, they were deduced to act in the same manner as impurity hydrogen atoms: migrate with gliding dislocations or by a short-circuit diffusion along dislocation lines, be transferred to grain boundaries or interphase boundaries and finally be evolved at slip lines, grain boundaries, and second phase particles on the surface.
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  • Recovery, recrystallization and grain growth of TD-rotated cube grains in aluminum
    Takeshi MURAKAMI
    2003 Volume 53 Issue 12 Pages 582-587
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.582
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    Mechanism of formation of sharp cube texture was investigated by transmission X-ray diffraction at the same point of specimens after various thermal and mechanical treatments. In cube oriented grains formed by partial annealing after heavy cold rolling, lattice rotation occurs mainly around transverse direction during light rolling. Upon slow heating from room temperature, polygonization was observed in deformed cube grains. Polygonization was attributed to recovery in TD rotated cube regions. Cube grains grow by bulging out of those boundaries to unrecrystallized region. After formation of cube texture with orientational spread of around TD, grain growth begin on final annealing at high temperature among TD-rotated cube grains, resulting of formation of sharp cube texture.
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  • Precipitate microstructures and thermo-mechanical fatigue life of Cu added AC4C aluminum cast alloys
    Ken MOIZUMI, Hiroyasu TEZUKA, Tatsuo SATO
    2003 Volume 53 Issue 12 Pages 588-594
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.588
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    The influence of ultimate tensile strength, 0.2% proof stress and elongation on the thermo-mechanical fatigue life has been studied for Cu added AC4C aluminum cast alloys. Hardness changes have been also investigated during isothermal aging at 180°C together with the detailed TEM observation of precipitate microstructures. The thermo-mechanical fatigue life decreased with increasing 0.2% proof stress. In the Cu added AC4C alloys, high density of needle shaped precipitates of the Q′ phase were observed in the over-aged condition. Furthermore, it was found that Cu retarded both the coarsening of the precipitates and resultantly softening of the matrix. This is because that the misfit of the Q′ phase with the matrix is smaller than that of the β′ phase founded in AC4C aluminum alloys. The retarded softening of the matrix causes the decrease in the thermo-mechanical fatigue life due to the preferential crack propagation through the fractured eutectic Si particles during thermo-mechanical fatigue loading. The optimized over-aging conditions, however, resulted in the decreased 0.2% proof stress and are extremely effective to improve the thermo-mechanical fatigue life of the Cu added AC4C aluminum alloy.
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  • Tribological properties of Mg(OH)2 coating on Magnesium alloys by anodic treatment
    Hiroshi SEKIGUCHI, Chikashi OTANI, Yukihiro SAKAMOTO, Matsufumi TAKAYA
    2003 Volume 53 Issue 12 Pages 595-600
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.595
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    Magnesium is given anodic oxidation coatings to improve corrosion and wear resistance and for decorative purposes and so on. Representative anodic treatments for magnesium, H.A.E. and Dow17 have useful corrosion resistance to the atmosphere, wear resistance and heat resistance. But these treatments require high voltage with break down when coatings are formed. On the other hand, it is known that magnesium hydroxide coatings can be formed at low voltage 0.3 V to 3 V in 1 M NaOH solutions by alternating electrolysis. Magnesium hydroxide has the same lamella structure as the representative solid lubricants graphite and molybdenum disulfide. This paper describes the friction characteristics of magnesium hydroxide coatings by periodic reverse electrolysis in NaOH solution on pure magnesium 3N (99.9%), magnesium alloy AZ31 and magnesium alloy AZ91D. Magnesium hydroxide coatings on magnesium by anodic treatment provide superior friction characteristics and specific wear resistance than untreated magnesium.
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REVIEW — 6th JILM PRIZE & AWARDS
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