Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 49, Issue 8
Displaying 1-17 of 17 articles from this issue
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REVIEW
TECHNICAL REPORT
RESEARCH REPORT
  • Development of aluminum alloy sandwich panel using roll bonding and superplastic buldge forming
    Tsutomu TAGATA, Yuji ABE, Kohtaro YOKOTA, Mamoru MATSUO, Masaaki MUNEK ...
    1999 Volume 49 Issue 8 Pages 353-357
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.353
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    The possibility of fabricating the metallic bonded truss structured aluminum board was studied by the combination of the roll bonding process and superplastic forming. Al–1.6%Mn alloy sheet was first pre-clad to the superplastic 5083 aluminum alloy sheet. These sheets were piled in three layers and then hot roll bonded. Here, the anti-bond coat was printed on both sides of the core sheet in striped pattern before hot roll bonding. These hot rolled bonded sheets were next subjected to cold rolling to obtain the superior superplasticity. The three layered roll bonded sheets were set between flat dies at superplastic temperature and the truss structured board was formed superplastically by applying the internal gas pressure to the un-bonded area with gradual opening of the flat dies. It was found that a higher pressure and a slower gap opening speed was desirable to obtain a flat surface board. As the results, the truss structured high rigidity board with flat surfaces was obtained.
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  • High strain superplastic forming into bead panels of particle reinforced 2124 aluminum alloy composite materials sheet
    Takashi NINOMIYA, Hirohito HIRA, Takao CHOH, Naoyuki KANETAKE
    1999 Volume 49 Issue 8 Pages 358-362
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.358
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    SiC particle reinforced 2124 aluminum alloy composite sheet was studied on high strain rate superplastic forming into three types of bead panels. The forming test was performed at 773 K using a 250 mm × 250 mm blank sheet by gas pressure, which was preset to achieve the average strain rate of 0.1/s. Three shapes were successfully formed in about 10 seconds and the formability into three-dimensional shapes were confirmed under high forming rate. In case of a box shape or a box shape with a shallow bead at the bottom, minimum thickness was seen at four corners of the box. For the multi narrow deep bead panel, however, it was seen at the side wall near the flange and the maximum thickness strain was 150 to 200%. The simple prediction method of gas pressure pattern used in this study is applicable to certain complex shapes.
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  • Superplastic formability of Ti–4.5 mass%Al–3 mass%V–2 mass%Fe–2 mass%Mo alloy
    Nobuyuki SUZUKI, Hiroshi IIZUMI, Atsushi OGAWA
    1999 Volume 49 Issue 8 Pages 363-367
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.363
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    Superplastic formability of Ti–4.5Al–3V–2Fe–2Mo (mass%) alloy and its mechanical properties after superplastic forming were investigated. The sheets of 0.8 mm thick were formed at strain rate of 2 × 10−4 to 1 × 10−3 s−1 into rectangular pans at temperatures ranging from 750 to 800°C. These superplastic forming temperatures for the alloy were lower by over 100°C than those for Ti–6Al–4V. Excellent superplastic formability was obtained in wide ranges of the above conditions. Due to mainly the lowered forming temperatures, grain growth during superplastic forming was limited, and subsequently drop in tensile strengths of the formed parts was marginal. Aeronautical structural components of this alloy was successfully formed by the established low-temperature superplastic forming process.
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  • Diffusion bonding properties of Ti–4.5 mass%Al–3 mass%V–2 mass%Fe–2 mass%Mo alloy
    Hiroshi IIZUMI, Atsushi OGAWA, Nobuyuki SUZUKI
    1999 Volume 49 Issue 8 Pages 368-372
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.368
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    Studies of diffusion bonding were made for Ti–4.5Al–3V–2Fe–2Mo alloy sheets. The process conditions of pressure, temperature and time required to produce a mechanically sound bond were investigated for several surface finishes. The integrity of the bonds was evaluated using optical metallography, shear strength measurements and fractography. Sound bonds were produced in the pickled sheets in 4 h with an applied stress of 2.0 MPa at 800°C. In the polished sheets, the time and the temperature required were reduced to 2 h and 775°C, respectively, at the same stress. It was revealed that diffusion bonding of Ti–4.5Al–3V–2Fe–2Mo is attained around the same temperatures as those for its superplastic forming. A cellular panel was successfully produced with this alloy, combining its low temperature superplastic forming and diffusion bonding processes.
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REVIEW
RESEARCH REPORT
  • Superplasticity and fractography over wide ranges of temperature and strain rate in a 5083 aluminum alloy
    Yoshimasa TAKAYAMA, Shinya SASAKI, Tatsumi TOZAWA, Hajime KATO, Hideo ...
    1999 Volume 49 Issue 8 Pages 378-382
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.378
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    Superplasticity over the wide ranges of both temperature and strain rate has been investigated for a 5083 aluminum-magnesium base alloy. Large elongations of more than 300% were obtained in a temperature range of over 200 K and in a strain-rate range of the two orders of magnitude. Such large elongations were attributed to both grain boundary sliding and solute-drag controlled creep mechanisms. Fractography has been performed systematically in the light of deformation mechanism and elongation to failure. In a low strain rate, granular feature was observed on fracture surfaces. The granular feature was coarsened with increasing temperature. As temperature approached to an apparent solidus, fracture surface was accompanied with typical filaments suggesting the presence of a liquid phase. Near the apparent solidus temperature, a small amount of filaments was found at a strain rate of 1.4 × 10−2 s−1, while distinct intergranular fracture was found at 2.8 × 10−1 s−1. Consequently, it is reconfirmed that the morphology of fracture surface is correspondent with deformation mechanisms and elongation to failure.
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  • Dynamic evolution of fine grained structure and superplasticity in an unrecrystallized 7075 aluminum alloy
    Xuyue YANG, Taku SAKAI, Hiromi MIURA
    1999 Volume 49 Issue 8 Pages 383-388
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.383
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    Dynamic evolution of fine grains and superplasticity of an unrecrystallized 7075 aluminum alloy were studied by means of two-step tensile testing as well as optical, SEM and TEM metallographic observation. Typical superplasticity takes place accompanied by the evolution of new fine grains in the medium region of strain rate at 798 K. Newly evolved grain size decreases with increase in the reduction of prior cold-rolling, i.e. with decrease in the thickness of layered initial grains (DST). Strain rate dependence of flow stress and total elongation to fracture is sensitively affected by cold-rolling reduction because of changes in DST. Grain boundary sliding (GBS) frequently takes place just after yielding even in the layered pre-existing grain boundaries parallel to tensile axis. With further straining, GBS brings about subgrain rotation, followed by transformation of low angle boundaries to high angle ones. Repitition of this process can result in the evolution of new fine grains with high angle boundaries at high strains. It is concluded from the mechanical and metallographic results that GBS can play a key role in the dynamic evolution of fine grains as well as the appearance of superplasticity.
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  • Microstructure refinement and high strain rate superplasticity of Al–Zn–Mg–Cu P/M alloy extrusions
    Tetsuo AIDA, Kenji MATSUKI, Hiroki ADACHI, Kozo OSAMURA, Jun KUSUI, Ka ...
    1999 Volume 49 Issue 8 Pages 389-394
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.389
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    The effects of thermo-mechanical treatment (TMT) on grain refining and high temperature deformation properties have been investigated for the alloy with chemical composition of Al–9.6Zn–3.0Mg–1.4Cu–0.04Ag–0.4Zr in mass% fabricated by hot-extrusion from rapidly solidified powders The present TMT consisted of aging at 498 K for precipitation of T phase (Mg32(Zn, Al)49) and subsequent warm rolling at the same temperature. Due to aging up to 7.2 ks at 498 K, extremely fine T phase precipitated homogeneously in the matrix. At the next warm rolling step, those fine precipitates contributed to form the uniform dislocation cell structure with high number density. The microstructure analysis by means of XRD and TEM made clear that their dislocation cell structure recrystallized continuously and transformed to very fine (sub-) grain structure with average size of 0.45 μm at the tensile testing temperature of 718 K. The fine grain structure was stabilized by the distribution of fine Al3Zr particles. Thus the high strain rate superplastic behavior realized for the warm rolled specimens after aging at 498 K for about 7.2 ks. On the other hand, the warm rolled specimens after aging at 498 K for the longer time than 18 ks formed a very coarse grain structure and resulted in a poor superplasticity. The reason has been discussed on the basis of discontinuous recrystallization theorem.
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  • Production of Al–Cu superplastic sheets by means of the melt direct rolling
    Nobuhiro TSUJI, Takashi NAKAMURA, Yoshihiro SAITO
    1999 Volume 49 Issue 8 Pages 395-400
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.395
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    In order to clarify the possibility of simple and novel process to produce superplastic thin sheet, melt direct rolling of Al–Cu alloys was investigated. Sound strips of Al–6%∼20%Cu alloys were successfully produced from molten state by the melt direct rolling process. 47%∼64% of rolling reduction was applied to the materials during melt direct rolling. Fine θ (Al2Cu) particles were distributed in the deformed matrix, though the distribution of θ phase was quite inhomogeneous through thickness location in the melt direct-rolled strips: θ (Cu) concentrated near the surface to show inverse segregation. The Al–Cu melt direct-rolled strips were provided for tensile tests at 520°C. Although elongation of the Al–6%–15%Cu melt direct-rolled strips was not large and hardly depended on strain rate, elongation of the Al–20%Cu strip largely depended on strain rate and showed the maximum value of 354% at a strain rate of 4.2 × 10−3s−1. At the strain rates where large elongation appeared, the strain rate sensitivity (m-value) reached up to 0.32. It could be concluded that it is possible to produce the supelplastic sheets of Al–20%Cu directly from molten state by means of the melt direct rolling.
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  • Superplastic characteristics in an extruded AZ31 magnesium alloy
    Hiroyuki WATANABE, Toshiji MUKAI, Koichi ISHIKAWA, Yoshihira OKANDA, M ...
    1999 Volume 49 Issue 8 Pages 401-404
    Published: 1999
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.49.401
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    Deformation characteristics at elevated temperatures were examined in an AZ31 magnesium alloy. The asreceived bar was extruded for refineing its microstructure. The extruded alloy had equiaxed grains with an average grain size of ∼5 μm. Tensile test revealed that the material exhibited superplasticity. The maximum elongation of 608% was obtained at a temperature of 598 K and at a strain rate of 1 × 10−4 s−1. Microstructural observations indicated that the dominant deformation process was grain boundary sliding. The strain rate sensitivity exponent in the superplastic region was 0.5 and the activation energy was close to that for grain boundary diffusion in magnesium. Experimental results suggested that the dominant deformation mechanism in AZ31 was grain boundary sliding accommodated by dislocation glide controlled by grain boundary diffusion.
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