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Volume 48, Issue 6
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RESEARCH REPORT
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Makoto INOUE, Masao IWAI, Kazuo MATUZAWA, Shigeharu KAMADO, Yo KOJIMA1998 Volume 48 Issue 6 Pages 257-262
Published: 1998
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSVarious amount of impurity element such as Fe, Ni and Cu were added to 99.99% purity magnesium, and the samples were remelted in a vacuum high frequency induction furnace. The corrosion behavior of the obtained magnesium were investigated by means of a 3%NaCl salt-water immersion test, a 5%NaCl salt-water spray test and an electrochemical method. The corrosion resistance of magnesium is unaffected by specimens containing 104 ppm, or less, of Fe in both the 3%NaCl salt-water immersion and the 5%NaCl salt-water spray environment. However, it is deteriorated by specimens containing more than 16 ppm of Ni in the 3%NaCl salt-water immersion and specimens containing more than 23 ppm of Ni in the 5%NaCl salt-water spray environment. While it is unaffected by specimens containing 1660 ppm, or less, of Cu in the 3%NaCl salt-water and specimens containing 250 ppm, or less, of Cu in the 5%NaCl salt-water spray environment. The current density of the anodic part of polarization curve does not vary significantly with the amount of impurities. But the current density of the cathodic part increases as the amount of the impurities increases.View full abstractDownload PDF (1166K) -
Hisamichi KIMURA, Akihisa INOUE, Kenichiro SASAMORI, Kazuhiko KITA1998 Volume 48 Issue 6 Pages 263-268
Published: 1998
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSAFCT–26P/M and AFCT–125P/M were prepared by extruding of Al–6.3 mass%Fe–3.8 mass%Cr–3.3 mass% Ti (AFCT) alloy powders at 673 K, of which the sizes were smaller than 26 μm and 125 μm, respectively. X-ray diffraction showed that the AFCT powder consists of three phases of icosahedral quasicrystal, fcc-Al and Al23Ti9. Both AFCT–P/M alloys have also the same structure as the powder. The ultimate tensile strength (&sima;UTS) , plastic elongation (εP), Young's modules (E), Vickers hardness (HV), Density (ρ) and specific strength (σUTS/ρ) at room temperature are 646 MPa, 4.4%, 86 GPa, 192, 2.951 Mg·m−3 and 2.19 × 105 Nm·kg−1 for AFCT–26P/M alloy and 541 MPa, 7.3%, 83 GPa, 165, 2.955 Mg·m−3 and 1.83 ×105 Nm·kg−1 for AFCT–125P/M alloy, respectively. After heating for 300 s at 573 K, σUTS, σ0.2 and εP are 361 MPa, 333 MPa, 1.5% for AFCT–26P/M alloy and 286 MPa, 270 MPa, 6.5% for AFCT–125P/M alloy, respectively. It is confirmed by a transmission electron microscope (TEM) that icosahedral quasicrystalline particles with a size of about 400 nm precipitate in both P/M alloys. It was found that the AFCT–26P/M alloy having elevated-temperature strength contains icosahedral quasicrystalline particles even after heat-treatment for 720 ks at 573 K.View full abstractDownload PDF (1359K) -
Hiromi NAGAUMI, Ken KOMATSU, Masaru UEMATSU, Nobuyasu HAGISAWA, Yasuhi ...1998 Volume 48 Issue 6 Pages 269-275
Published: 1998
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSPorosity generation situation was observed from surface to center in a DC slab of Al–4.4%Mg alloy. The quantities and area fractions of the porosity were measured quantitatively by using an image analysis apparatus (LUZEX). An explanation of this kind of the porosity generation mechanisms and distribution of the porosity was attempted by using a local equivalent pressure in dendritic solidification. The next conclusion was obtained, (1) The quantities of the porosity increase with decreasing the local equivalent pressure. (2) Distributions of the quantities of porosity correspond to the distribution of the area fractions in the slab, both increase to 180 mm, after that they decrease until the center (203 mm). (3) In the surface layer from surface to 60 mm, the porosity sizes are very small and almost exist between secondary dendrite arm. In the middle layer from 80 mm to 140 mm, the porosity sizes become large and the quantities of the porosity become much too. The most of the porosity exist between secondary dendrite arm and a part distributes along grain boundaries. In the center layer from 160 mm to 203 mm, the porosity sizes become more large and they exist not only between the dendrite arm but also the grain boundaries. The shapes of porosity are irregular and a typical shrinkage porosity.View full abstractDownload PDF (1245K) -
Kaku UEHARA, Kiyoshi MIZUTANI, Tadakazu OHNISHI1998 Volume 48 Issue 6 Pages 276-281
Published: 1998
Released on J-STAGE: June 01, 2007
JOURNAL FREE ACCESSThe unsaturated polyester resin concretes using the aluminum dross wastes as aggregate were prepared and their mechanical properties and water resistance were examined. Four types of dross wastes were used; the waste pre-treated with water, the non-treated waste, the dust waste and the chloric waste. When the mixing between the resin and the waste was satisfactorily achieved, the resin concretes with the strength and the water resistance equal to or above the commercially available products could be obtained. The aluminum-nitride contained in the waste is seemed to contribute to strengthening of the resin concrete owing to the formation of aluminum hydroperoxide acting as an initiator of polymerization, although an excessive content damages the water resistance. The dust waste could be also used to prepare a resin concrete, but the chloric waste could not be used.View full abstractDownload PDF (1115K) -
Shuu KURODA, Ken TOHMA1998 Volume 48 Issue 6 Pages 282-287
Published: 1998
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSTo investigate the effect of SO42- ion on pitting corrosion behavior of aluminum and aluminum alloy brazing sheets immersion corrosion test and electrochemical measurements were carried out in the solution of lower chloride concentration containing SO42- ion. As the SO42- ion reduced the anodic and cathodic reaction rate, the pitting corrosion resistance of aluminum increased. The pitting corrosion occurred even in solution containing SO42- when the cathodic reaction was high enough. In that case the pitting corrosion rate was much higher than that in the SO42- ion free solution. Higher pitting corrosion rate induced by SO42- ion was due to the lower pitting corrosion density which was closely related with the thicker oxide film formed on aluminum surface. The probability of pitting corrosion was estimated with the relation between Ecorr and Erep value in anodic polarization measurement in the solution.View full abstractDownload PDF (891K) -
Shuu KURODA, Ken TOHMA1998 Volume 48 Issue 6 Pages 288-293
Published: 1998
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSTo investigate the pitting corrosion growth rate of aluminum alloys in the solution containing SO42- ion, the immersion corrosion test and electrochemical measurements were carried out on aluminum and Al–0.4%Cu alloy clad with the liner containing Zn. In the solution containing SO42- ion the pitting corrosion could grow deeply even in the alloy having gradient of Zn concentration. While Cl- and SO42- ions concentrated into the pit, SO42- ion had little effect on electrochemical characteristics in acidified higher chloride solution. The pitting potential of aluminum became much less noble with as a little addition of Zn as 0.2%, but that of Al–Cu alloy scarcely varied in acidified higher chloride solution. As the SO42- ion had the controlling effect of pitting corrosion density, which introduced higher chloride ion concentration in a pit. Therefore, for the control of pitting corrosion growth rate the potential slope had to be sharper in the solution containing SO42- ion. Enough Zn content at surface was required to obtain better pitting corrosion resistance, especially in Al–Cu alloy.View full abstractDownload PDF (997K) -
Shin-ya KOMATSU, Masahiko IKEDA, Tomohiro KOHMOTO, Yoshiaki TABATA, Ta ...1998 Volume 48 Issue 6 Pages 294-298
Published: 1998
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSAl–0 to 8.1 mass (0 to 8.9 at)% Mg solid solution alloys were annealed at 623 K for 3.6 ks and then water quenched. Resistivity at 77 and 300 K (ρ77 and ρ300) was measured. According to a corrected Nordheim's law, the relations between resistivity and atomic fraction of solute Mg, X, are obtained as follows;
ρ300/nΩm=27.66+550.6X(1−1.72X)
ρ77/nΩm=2.319+527.5X(1−1.72X)
The factor before the X (1 − 1.72 X) term becomes larger at elevated temperature of resistivity measurement. This fact shows that the solute Mg atom in aluminum has a positive deviation from Matthiessen's Rule, giving η=Δρ300/Δρ77= 1.044. The best fit relation between resistivity ratio R= ρ300/ρ77 and ρ77 is ρ77/nΩm=25.26/(R−1.043) +0.0019. Using most reliable relation between temperature and equilibrium solid solubility of magnesium to aluminum, the temperature-concentration-resistivity chart has been obtained. Utilisation of the chart is introduced.View full abstractDownload PDF (803K)
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