Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 51, Issue 1
Displaying 1-10 of 10 articles from this issue
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RESEARCH REPORT
  • Two stage superplastic forming of 7475 aluminum alloy sheet into a hemispherical dome with uniform thickness
    Nobuyuki SUZUKI, Masahide KOHZU, Tohru JINISHI, Shigenori TANABE, Kenj ...
    2001 Volume 51 Issue 1 Pages 14-17
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.14
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    A new superplastic forming method for 7475 aluminum alloy sheets into a hemispherical dome, having uniform thickness, has been developed. The method consists of the preliminary forming into a truncated cone, and the final forming into a hemispherical dome from its bottom. The final thickness distribution of the hemispherical dome was determined by the thickness distribution of the bottom controlled by friction with die. The optimal configuration of the truncated cone was determined by a numerical calculation method. Finally 7475 aluminum alloy sheet was processed into a hemispherical dome by the two stage superplastic forming. The thickness distribution in both of the preliminary truncated cone and the final hemispherical dome were expected ones.
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  • Analysis of superplastic blowforming of 7475 aluminum alloy sheets into a truncated cone
    Nobuyuki SUZUKI, Masahide KOHZU, Shigenori TANABE, Kenji HIGASHI
    2001 Volume 51 Issue 1 Pages 18-22
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.18
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    A numerical analysis method of superplastic blowforming for axial symmetry cups has been developed. A relationship of stress-strain used in the analysis is taken into account the work hardening of material. Also this method is able to account an influence of friction forces with die caused by forming pressure. Ratio of stress for each direction of circumference and meridian on small elements in a blank sheet is determined by morphological functions which are supposed with the contacting condition of die and material. The ratio of stress are kept in conformity with the basic condition, plane stress in apex and plane strain in periphery. And its distribution along axial cross section is accommodated to them through the deformation process, from plane disk to hemispherical dome or truncated cone. To verify the validity of this analytical method, a superplastic forming experiment was carried out by using 7475 aluminum alloy sheets. The optimum pressurization schedule was determined for a truncated cone with the simulation of the deformation process. The deformation process and the thickness distribution on the formed sheet agreed well with calculated ones.
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  • Demagnesization of Mg2Ni by vacuum-heating
    Shotaro MOROZUMI, Hiroshi SAIKAWA, Kuniaki WATANABE
    2001 Volume 51 Issue 1 Pages 23-27
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.23
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    Cut pieces of cast Mg2Ni ingot were heated in a vacuum of about 10−2 Pa for 1.8∼14.4 ks at 773, 823 and 873 K, and then examined using X-ray diffraction, optical microscopy and electron probe X-ray microanalyzer with EDX. The vacuum heating resulted in the demagnesization of Mg2Ni phase by sublimation of magnesium from the surface, forming porous layer of MgNi2. Thickness of the layer increased with increasing temperature and/or heating time. Approximate estimation, using these kinetic data, showed that apparent activation energy of the growth of the layer was 210 kJ/mol. Based on the estimation, the whole Mg2Ni specimen with 0.7 × 10−3 m thickness was found to change into the porous MgNi2 after vacuum-heating for 14.4 ks at 923 K.
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  • Mechanical alloying process of Al95–xFexCr5 mixed powders by a high energy planetary ball mill
    Yong ZOU, Shigeoki SAJI, Kiyoshi KUSABIRAKI
    2001 Volume 51 Issue 1 Pages 28-33
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.28
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    Al95–xFexCr5 (X=10, 25, 35, 50) ternary powder mixtures and Al–(10, 25, 35, 50) at%Fe binary powder mixtures were mechanically alloyed by high-energy ball milling using a ball-to-powder weight ratio of 238: 10. The structural evolution during milling was investigated by X-ray diffraction techniques and transmission electron microscopy. The solid solutions of α–Al(Fe, Cr) and α–Fe(Cr) were formed in the early stage of milling for Al–Fe–Cr powder mixtures. In the case of Al–10 at%–5 at%Cr powder mixtures, the Al80Cr13.5Fe6.5 compound was formed and disappeared during milling, and Al5(Fe, Cr)2 and Al(Fe, Cr) were detected after longer time milling. In Al–25 at%–5 at%Cr powder mixtures, Al5(Fe, Cr)2, Al(Fe, Cr) and amorphous phases were consecutively formed during milling. In milling process of Al–35 at%–5 at%Cr and Al–50 at%–5 at%Cr powder mixtures, only the Al(Fe, Cr) compound was found and it finally became an amorphous phase. Retardation of amorphization was recognized in the Al–Fe–5 at%Cr ternary system, and the composition range of amorphous formation was almost in agreement with the results of enthalpy calculation for the solid solution and amorphous phase in the systems.
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  • Leaching reactions of aluminum dross in various aqueous solutions
    Shinji FUKUMOTO, Tomoko HOOKABE, Harushige TSUBAKINO
    2001 Volume 51 Issue 1 Pages 34-39
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.34
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    Chemical reactions between aluminum dross with deionized water, various basic and acid solutions were investigated. The dross were evolved from the aluminum scraps that were recovered individually from each kind of aluminum alloy. Aluminum dross were composed of aluminum, Al2O3, AlN, and other oxides. The NH3 gas evolved owing to hydrolysis of AlN, resulting in the increment of pH of the solutions. The change behavior in pH of the water with AlN was quite different from that with aluminum dross. The pH of AlN powder solution increased by one step, on the other hand, that of the dross solution increased by two steps. The pH increment in the 1st stage was due to the hydrolysis of MgO that was included in dross and the 2nd stage was due to the hydrolysis of AlN. The hydrolysis of AlN included in dross was promoted in the basic and acid solutions. In particular, AlN included in dross was quickly hydrolyzed in NaOH solution at high temperature.
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  • Tensile properties of Al–Fe alloys prepared by mechanical alloying with C60
    Kunio ITO, Toru KUZUMAKI, Yuji KAWAZOE, Junichi KANEKO
    2001 Volume 51 Issue 1 Pages 40-44
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.40
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    The aluminum, of which the recovery was retarded by the addition of solute iron, was mechanically alloyed with C60 or graphite, hot pressed at 400°C or 500°C, extruded at 400°C, and then tensile tested at the room temperature. The added amount of C60 or graphite is 5% at the volume fraction, and the iron concentration is 0.5 mass%. In the case of C60, the tensile strength rises from 120 MN/m2 to 170 MN/m2, while the elongation decreases from 44% to 5%. When the graphite is added, the tensile strength hardly changes and the elongation decreases to 4%. The main cause of the increase in strength by addition of C60 is discussed to be the dispersion-hardening brought about by Al4C3 particles which were formed by decomposition of C60.
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  • Microstructure and tensile property of an Al–Si–Cu–Mg alloy produced by thixocasting process
    Shigeru IWASAWA, Seiji SAIKAWA, Taketoshi TOMITA, Katsuzo HAYASHI, Shi ...
    2001 Volume 51 Issue 1 Pages 45-50
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.45
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    Thixocasting is focused as a suitable casting process for near net shaping, weight reduction of a product and obtaining good mechanical properties. In the present study, the microstructures and tensile properties of the Al–6 mass%Si–3 mass%Cu–0.3 mass%Mg alloy produced by the thixocasting process were investigated and compared with those of the permanent mold castings. Microstructure of the thixocast parts basically consists of spherical primary α–Al phase particles, fine eutectic Si phases and acicular compounds containing iron. The average size of α–Al phase particles was about 60 μm in diameter. After solution treatment, the average size of Si particle for the thixocast alloy was about 2.6 μm and was smaller than that of the permanent mold castings. At aging temperature between 433 and 473 K, the hardness of thixocast alloy was higher than that of the permanent mold casting and the maximum hardness of thixocast and permanent mold cast specimens aged at 433 K were HB 118 and HB 108. The ultimate tensile strength, 0.2% proof stress and elongation of T6–treated thixocast alloy were 394 MPa, 331 MPa and 7.5% respectively. These value are far superior to those of the permanent mold casting. Such the high tensile properties of thixocast alloy might be caused by this extremely high solidification rate in thixocasting process made eutectic Si phase and Al–Fe system intermetallic compound to be fine, increase in Cu and Mg concentration in α–Al matrix compared with the permanent mold castings.
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  • Interfacial structure of β–silicon nitride whisker reinforced 7075 aluminum alloy composite
    Masahiro TOKUSE, Toru MATUBARA, Katsuaki SUGANUMA, Ichiro NAKABAYASHI
    2001 Volume 51 Issue 1 Pages 51-55
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.51
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    The interfacial structure of β–Si3N4 whisker reinforced 7075 aluminum alloy composite was examined using a high-resolution transmission electron microscope. As-cast and T6 materials have almost the same surface structures, and (100) facet of each whisker was considered to be covered with a continuous layer of M–Si–Al–O–N (M: Mg, Zn) with a lattice plane spacing of approximately 0.26 nm. This layer is considered to prevent the reaction between whiskers and aluminum. In contract, (110) whisker facets without such layers react in a different manner from (100) facets. A MgZn2 phase or its solid solution containing aluminum was identified on the whisker surface of the as-cast material as a precipitate phase. Heat treatment was performed at temperatures of 823 K, 933 K, and 1073 K to confirm the reaction between whiskers and 7075 aluminum. With the formation of the liquid phase of 7075 aluminum, the reaction progressed rapidly and AlN particles were produced on the surfaces of the whiskers with the heat treatment at 1073 K.
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