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 12
Displaying 1-9 of 9 articles from this issue
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RESEARCH REPORT
  • Effects of cold rolling and heat treatment on Fe precipitation in aluminum by Mössbauer spectrometry
    Satoru KUBOTA, Masahiko KAWAI, Masaki YAMAMOTO, Masayuki SHIGA
    2001 Volume 51 Issue 12 Pages 635-639
    Published: 2001
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.2464/jilm.51.635
    JOURNAL FREE ACCESS
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    Effects of cold reduction and heat-treatments on the Fe precipitation behavior in high purity aluminum with 55 ppm Fe were investigated by Mössbauer spectrometry using 90% enriched 57Fe. It has been revealed that the precipitated fraction of Fe becomes maximum by a heat treatment at 310°C in supersaturated solid solutions with high density dislocation introduced by 97% cold reduction. The precipitates in the 310°C aging sample are probably metastable Al6Fe compound. Moreover, it was found that the precipitation starts even at 120°C and by 200°C aging, the precipitated fraction reaches more than a half of the maximum value. However, these precipitates observed in low temperature aging seem not to be the definite Al6Fe compound but something like precarious phase leading to Al6Fe because they easily disappear by additional cold-rolling and Mössbauer spectrum is slightly different from those of high temperature aging samples. Scarcely any precipitates were found in supersaturated solid solution without cold rolling for any aging temperatures below 300°C, indicating the crucial role of dislocations for precipitation process.
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  • Al–Ti–Cr ternary phase diagram and solidification structure of (Al, Cr)3Ti alloys
    Motoyuki ICHIMARU, Nobuyuki MORI, Yasuhiro MIURA
    2001 Volume 51 Issue 12 Pages 640-645
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.640
    JOURNAL FREE ACCESS
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    The Al-rich region of the Al–Ti–Cr ternary phase diagram was determined on the basis of the experimental results of differential thermal analysis, high temperature isothermal heating, and X-ray micro analysis. The solidification passes of alloys with primary L12–(Al, Cr)3Ti phase were analyzed by using the diagram. The L12 solidus and liquidus at 1250∼1350°C were measured, and solute distribution coefficients for Ti or Cr (kTi, kCr) were derived as functions of liquid composition (CLTi, CLCr). Further, boundaries of liquidus surfaces between L12 phase and the surrounding phases (Cr(Cr2Al), Al17Cr9, Al3Ti, Al7Ti3, TiAl, TiAlCr) were established. Changes of liquid and solid concentrations during solidification of various Al–Ti–Cr alloys were calculated by the progressive solidification equation using the above Al–Ti–Cr diagram and kTi, kCr. The calculated structures agreed well with the experimental results.
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  • Tensile and low-cycle fatigue properties of heat treated ultra-fine grain 5056 aluminum alloy
    Kenichi HIGASHI, Vsevolod PATLAN, Kazuo KITAGAWA, Masataka KAWAZOE
    2001 Volume 51 Issue 12 Pages 646-650
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.646
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    Mechanical properties and fatigue performance of ultra-fine grained 5056 aluminum alloy produced by severe plastic deformation by means of Equal-Channel Angular Pressing (ECAP) have been assessed in tensile and plastic strain controlled cyclic experiments. One part of the specimens was shortly annealed at moderate temperatures to obtain partial recovery around grain boundaries that have been most heavily distorted. Compared to its conventional O-temper counterpart, the ECAP material exhibits fairly high tensile strength, but lower ductility. Deviation from Hall-Petch relations in fine grain material may be caused by decreasing of dislocation pile-up due to accelerated grain boundary diffusion and higher dislocation density within the grains. Low-cycle fatigue properties of fine grained materials investigated in the series of strain controlled experiments are worse than those of coarse grained materials, as shown by Coffin-Manson plot. The susceptibility of ECAP materials to strain localization can be the main factor which limits tensile and fatigue ductility and determines fatigue weakness compared with conventional materials. Short time annealing at moderate temperature (425 K) shows the improving of their ductility of ECAP material due to partial recovery of grain boundaries. This results in increase of tensile elongation up to 30% without a notable loss in strength, and a remarkably prolonged low-cycle fatigue life in comparison with as-received ECAP material.
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  • Grain refinement of 7475 based aluminum alloy sheet by warm rolling
    Tadashi MINODA, Hiroki TANAKA, Kazuhisa SHIBUE, Hideo YOSHIDA
    2001 Volume 51 Issue 12 Pages 651-655
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.651
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    The effect of transition element on grain refinement of 7475 aluminum alloy sheet produced by warm rolling was investigated. The alloy which contains zirconium instead of chromium showed ultra fine structure with stable subgrain structure after warm rolling at 350°C, followed by solution heat treatment at 480°C. The average size of subgrains was about 2 μm in diameter. Furthermore, it became clear that zirconium in solution has the effect of stabilizing subgrains. That is, fine Al3Zr compounds precipitate during warm rolling, inhibit recrystallization and stabilize subgrains. While, in the case of the 7475 alloy with only chromium, recrystallization occurs during warm rolling, because chromium-bearing compounds precipitate in relatively large size and they have less effect of inhibiting recrystallization. Moreover, the alloy containing both chromium and zirconium showed a duplex structure with recrystallized grains and subgrains.
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  • Effect of aging temperature on precipitation behavior in Al–7%Mg alloys containing additional element of chromium or manganese
    Masanobu FURUTA, Yoshihiro NAKAYAMA
    2001 Volume 51 Issue 12 Pages 656-661
    Published: 2001
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.51.656
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    The effects of the chromium or manganese addition on the precipitation behavior of the Al–7%Mg alloy were experimentally investigated. The aging treatment was conducted at temperatures between 453 and 553 K in order to examine the influence of aging temperature on the precipitaion of both the metastable and stable phases. According to the differential scanning calorimetry analysis, the metastable phase was formed at temperatures below 493 K and the stable phase was formed above 493 K, and the chromium or manganese addition had no influence on the formation of these phases. In the early stage of aging, the precipitation of the metastable and stable phases in the chromium and manganese added specimens was accelerated due to the preferential precipitation at grain boundaries and interfacies between the second phases (Mg3Cr2Al18 or Al6Mn) and matrix.
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RESEARCH NOTE
REVIEW—4th JILM PRIZE & AWARDS
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