Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 55, Issue 1
Displaying 1-9 of 9 articles from this issue
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RESEARCH REPORT
  • Dendrite growth simulation of Al-Zn alloys by the phase field method
    Yasushi SASAJIMA, Minoru ICHIMURA
    2005 Volume 55 Issue 1 Pages 2-8
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.2
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    Dendrite growth of Al-Zn binary alloy in one directional solidification process was simulated using the phase field method. The development of Zn composition profile and phase field were calculated and the effects of temperature gradient G and growth velocity V on the morphology of crystal growth were investigated. The obtained results dynamically showed that the curvature radius of the tip of the primary dendrite arm, R, became small and the number of the arms per unit length increased (i.e. the spacing between the primary dendrite arms, λ1, decreased) with increasing growth velocity V. The quantitative relationship between λ1 and V and that between the spacing of the secondary dendrite arm λ2 and the solidification time t were determined as λ1 α V-0.5 and λ23 α t, respectively. It was found that the values of R and the exponent of V for R agree well with the dendrite growth theory.
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  • Hot formability of 6000 series aluminum alloys
    Tsutomu ITO, Masayuki ISHIKAWA, Masahisa OTSUKA, Makoto SAGA, Masao KI ...
    2005 Volume 55 Issue 1 Pages 9-14
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.9
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    It has recently been clarified in a previous paper that 6XXX aluminum alloys of medium grain size exhibit a characteristic hot ductility behavior above 773 K, in which the elongation to fracture is minimum in medium strain rate range while it maintains high levels between 200% and 340% both in low and high strain rate. In this paper is discussed the relationship between such ductility behavior and rate controlling mechanisms of deformation and fracture at 803 K. The results are summarized as follows: (1) In spite of the fact that both strain rate sensitivity and ductility are high, hot working at low strain rate is not appropriate if not, for example, superimposing back-pressure because cavitation occurs remarkably at the grain boundaries. (2) Hot working at high strain rate is recommended, not only because productivity is high but also because, in spite of m-values as low as 0.2, the elongation up to 200% is obtained without remarkable cavitation.
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  • Effect of topography on glossiness and surface color for a 5052 aluminum alloy
    Makiko YONEHARA, Koichiro KIHARA, Yoshihito KAGAWA, Hiroaki ISONO, Tos ...
    2005 Volume 55 Issue 1 Pages 15-19
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.15
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    This paper is investigated experimentally about the effect of topography to the glossiness and surface color in order to characterize a surface texture of aluminum alloy 5052. The surfaces of specimens are machined by using a vertical milling machine, a horizontal milling machine and a shaping machine. Four kinds of specimens are machined by each machine so that the arithmetical mean roughness value, Ra, is less than 1 μm at four cutting conditions. From the results of experiments, the glossiness values of the vertical milling surface and the horizontal milling surface were about the same value, meanwhile the glossiness value of the shaping surface was less than half the value of the others. The surface color of specimens was gray. Especially, The lightness value of surface color, L*, of the horizontal milling surface was the highest value. The surface color was whitish gray of all machined surface. Based on those experimental results, it was summarized that the surface texture of specimen machined various machine could be characterized by the glossiness and surface color. These results could be an effective indicator in choosing the most proper machining method to add value to surface texture.
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  • Brazing of commercially pure titanium using silver-based filler metal containing nickel
    Takehiko WATANABE, Norihiko TAMAKI
    2005 Volume 55 Issue 1 Pages 20-26
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.20
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    In order to produce a brazed joint of commercially pure titanium having a sufficient tensile property at the lower temperature than the α-β transformation temperature (882°C) of the titanium and by holding for as short time as possible, the authors developed silver-based brazing filler metal to which a small amount of nickel was added and investigated the effect of nickel on the brazeability. The conclusions are summarized as follows. The tensile strength of a joint brazed using silver-based filler metal bearing nickel of about 3 mass percent was larger by approximately 20% than that of a brazed joint using conventional silver-based filler metal without nickel (JIS BAg-7). Using the nickel-bearing silver-based filler metal, the joint strength enough to be equivalent to that of the base metal was obtained by holding for just 7 min at the brazing temperature of 840°C. In addition, spread area of the nickel-bearing brazing filler metal increased about two times than that of nickel-free filler metal. Nickel in the filler metal has so large affinity for titanium that it predominantly segregates to the brazing interface and diffuses widely into the titanium bulk, resulting in leading to widely transformed β-titanium around the interface. Since the constituents of the filler metal are more easily diffuse in β-titanium than in α-titanium, they can diffuse a long distance in β-titanium for a short time. This seems to make it possible to shorten the holding time for achieving the joint with the tensile strength equivalent to that of titanium base metal.
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  • Mechanical and SCC properties of rheocast 7075 based aluminum alloys
    Shuhei OSAKI, Shingo HORIE, Katsuyuki KINOSHITA, Satoru SATO, Mitsuru ...
    2005 Volume 55 Issue 1 Pages 27-32
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.27
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    Effects of heat treatment and minor additional elements Cr or Zr on mechanical and SCC properties of 7075 based cast alloys fabricated with a newly developed rheocast method were investigated. SCC tests were conducted by SSRT (slow strain rate tensile) technique using a round bar tensile specimen under a constant strain rate 8.3×10-7/s in 3.5%NaCl aerated solution. Similarly with a rolled alloy 7075, the rheocast alloy with temper of underaging or peak-aging T6 showed a high susceptibility to SCC, while the alloy with temper of overaging, T73 or T77 exhibited a less elongation in tensile property, although together with an improved resistance to SCC. On the other hand, the alloy direct-quenched into an oil bath at 433 K from solution temperature, followed by aging for 86.4ks, represented a superior combination among strength, elongation and SCC resistance, and the alloy with 0.2mass% Cr addition showed a more improved combination. The improvement was attributed to a repression of hydrogen embrittlement caused by coarsening of precipitates in gain matrix and along grain boundary, and further by a relief for planar slip due to fine distribution of Cr dispersoides within grains.
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  • Improvements of the drawability of 6061 aluminum alloy sheets by the local solution treatment
    Takeshi NISHIWAKI, Naoyuki KANETAKE
    2005 Volume 55 Issue 1 Pages 33-36
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.33
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    Deep drawing method of peripherally softened blanks is one of the techniques to improve the deep drawability of aluminum alloy sheets. In the present work, the local solution process was investigated, which is enable to realize rapid process for the local softening and subsequent forming. The A6061-T6 sheets were clamped for only 0.6 seconds between heated dies at 500°C and the flange part of the sheets were locally solution treated and softened. Deep drawing tests of the blanks which were locally solution treated using various heated dies were examined. The limit drawing ratio of local solution treated blanks reached 2.58, which was increased in about 25% compared with that of the homogeneous T6 blank. The locally softened part remained in the cup wall and undrawn flange in the incomplete drawn cup. The remaining softened part in the undrawn flange was some hardened, but it is useful to improve subsequent bending formability. The hardness of the remaining softened part could be recovered more than that of a T6 sheet by artificial aging after forming.
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