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 6
Displaying 1-5 of 5 articles from this issue
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RESEARCH ARTICLE
  • TiC coating on titanium by carbonization reaction using spark plasma sintering
    Tomohiro Hayashi, Kiyotaka Matsuura, Munekazu Ohno
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 6 Pages 233-236
    Published: June 30, 2012
    Released on J-STAGE: July 30, 2012
    DOIhttps://doi.org/10.2464/jilm.62.233
    JOURNAL FREE ACCESS
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    Hard TiC coating layer is formed on commercially pure titanium by heat treatment in a Spark Plasma Sintering (SPS) mold filled with graphite powder. The thickness of the TiC coating layer is about 10 μm in case of heat treatment for 3600 s at 1243 K and the thickness of this layer is almost uniform. This coating consists of TiC and graphite, and titanium oxide is not detected by X-ray diffractometer (XRD). Vickers hardness test revealed that the hardness of TiC coating was 1600 HV, which was much higher than that of titanium substrate (130 HV). The hard TiC coating on titanium is considered to have advantage in the applications to load-bearing parts of hard tissue replacements. The growth behavior of TiC is conformed to be parabolic, and the activation energy of growth of TiC is 218.6 kJ/mol. This value is close to the activation energy of carbon diffusion in TiC. Therefore, the rate of growth of TiC is controlled by carbon diffusion in TiC phase.
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  • Joining strength of AM50 magnesium alloy sheet jointed by in-situ heating self pierce riveting process
    Naritoshi Aoyagi, Toshiki Karasawa, Yukio Miyashita, Shigeharu Kamado
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 6 Pages 237-243
    Published: June 30, 2012
    Released on J-STAGE: July 30, 2012
    DOIhttps://doi.org/10.2464/jilm.62.237
    JOURNAL FREE ACCESS
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    Self pierce riveting (SPR) as mechanical joining is widely used for aluminum alloy, high strength steel or dissimilar materials such as polymer and metal in vehicle structures. The purpose of this study is to evaluate the tensile-shear strength of AM50 magnesium sheets jointed by a newly developed in-situ heating SPR joining system. It is difficult to joint magnesium sheets by riveting due to less ductility from a limitation of slip at room temperature, although there are few studies. In-situ heating SPR joining process has been developed to improve reliability of the joining sheet of magnesium, and to prevent occurrence of cracks which are initiated at beginning of riveting process. AM50 magnesium alloy sheet has 0.8 mm in thickness, and commercial aluminum rivet with 3.3 mm in diameter of the leg and 4 mm in height was used in this process. Cracks occurred in a lower sheet in both as-rolled and annealed AM50 sheet when conventional SPR joining process was applied at room temperature. No cracks are observed during in-situ heating SPR joining process at 250°C. The tensile-shear test was carried out at room temperature in order to estimate an effect of in-situ heating on reliability of the joint. The tensile-shear strength of AM50 joint heated at 250°C is higher than that of the joint from 5052 aluminum alloy with the conventional equipment.
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  • Effects of acetic acid on pitting corrosion acceleration in corrosion tests of aluminum alloys
    Yoshiyuki Oya, Yoichi Kojima
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 6 Pages 244-248
    Published: June 30, 2012
    Released on J-STAGE: July 30, 2012
    DOIhttps://doi.org/10.2464/jilm.62.244
    JOURNAL FREE ACCESS
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    Effects of CH3COOH on the corrosion behavior for aluminum alloys during accelerated corrosion tests were investigated. Based upon polarization curves, the dominant cathodic reaction for pitting corrosion of Al–Zn alloys was reduction of hydrogen ion because their pitting potentials were less noble, while that of Al–1mass%Mn alloys, whose pitting potentials were relatively noble, was reduction of dissolved O2. While the corrosion rate for the Al–Zn alloys were also increased with the concentration of CH3COOH, that for Al–1mass%Mn alloys were independent of the concentration of CH3COOH. It is indicated that corrosion rate for Al–Zn alloys is related to the concentration of CH3COOH added in the solutions. The relation between the corrosion rate and concentration of CH3COOH was confirmed from immersion tests. The reason for increase in the corrosion rate for the Al–Zn alloys is due to that CH3COOH acts as a hydrogen ion carrier rather than agent of lowering pH. The concentration of CH3COOH is should be standardized but not the pH to increase the reproducibility of the corrosion tests.
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