Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
Search
Advanced search
OR
Browse
Search
Volume 54, Issue 4
Displaying 1-7 of 7 articles from this issue
Show all abstracts
    • |<
    • <
    • 1
    • >
    • >|
RESEARCH REPORT
  • Increase in resistivity of Mg–Zn alloys by low temperature aging
    Shin-ya KOMATSU, Masahiko IKEDA, Umihiko MORI, Mutsumi ABE
    2004 Volume 54 Issue 4 Pages 131-136
    Published: 2004
    Released on J-STAGE: February 20, 2007
    DOIhttps://doi.org/10.2464/jilm.54.131
    JOURNAL FREE ACCESS
    Show abstractHide abstract
    Though G.P. zone formation had been widely recognized in Mg–Zn binary alloys, there still remained some ambiguity in resistivity increase by low temperature aging. Applying the previously improved method of reliable resistivity measurement, the increase in resistivity by low temperature aging of Mg–Zn binary and ZK60 alloys was quantitatively investigated. After solution treatment at 673 K for 86.4 ks, Mg–4~10mass%Zn alloy specimens sampled from ingots were aged at low temperatures below 373 K. The resistivity increase by aging at room temperature (R.T.: about 295 K) shows a clear and very long incubation period in all alloys and does not attain the peak until 40 Ms (1.25 year) aging. In the Mg–4mass%Zn alloy, the resistivity increase is not detected by the R.T. aging till 6 Ms. Because the ZK60 alloy containing 4.84%Zn shows a slight increase from 1 Ms, the incubation period of Mg–4mass%Zn alloy may be longer than 10 Ms. The highest aging temperature at which the resistivity increase due to G.P. zone formation is observed was 333 K. Very sharp resistivity peak on isothermal aging curve accompanying with a steep decrease is quite different from that of Al–10mass%Zn alloy. Up to the resistivity peak, a tendency is confirmed that the gradient of DMR corrected Matthiessen plot is smaller than that corresponding to precipitation of transition phases. Maximum increment in resistivity from as solution treated states is large in high alloys and low aging temperatures. Using these dependences of the maximum increment on solute concentration and aging temperature, a relation between composition and aging temperature is proposed for formation limit of G.P. zone which increases the resistivity.
    View full abstract
    Download PDF (645K)
  • Behavior of Mn added to 6082 aluminum alloys during homogenization of billets
    Shin-ya KOMATSU, Masahiko IKEDA, Minoru MORII
    2004 Volume 54 Issue 4 Pages 137-142
    Published: 2004
    Released on J-STAGE: February 20, 2007
    DOIhttps://doi.org/10.2464/jilm.54.137
    JOURNAL FREE ACCESS
    Show abstractHide abstract
    Behavior of Mn in billet of 6082 aluminum alloys was investigated by absolute value measurement of resistivity and direct analysis of solute Mn concentration. In as cast state, 57~75% of added Mn is found to be in solid solution. Heating up to the homogenization temperature, 823 K, was simulated by accumulative isochronal heat treatment with temperature and time interval 50 K/5.16 ks. Precipitation of Mg–Si compounds was detected from 473 K and attained maximum at 573 K, separated from the starting and maximum temperatures for precipitation of Al–Mn–Si compounds, 673 K and 773 K, respectively. Average diffusion distance of solutes, which was estimated from impurity diffusion data, ranged from 10 to 100 nm at the starting temperature of the each precipitation. Solute Mn concentration at 823 K is extremely lower than equilibrium solubility of Al–Mn binary system because of coexistence with Si. Above results suggest that the added Mn precipitates for most part during homogenization, therefore total amount of the insoluble particles containing Mn will be changed little by preheating and hot extrusion, except shape and dispersion of the particles. Thus, it can be predicted that resistivity and hardness changes during cooling after the homogenization or by various heat treatments after the extrusion are mainly caused by the change in Mg+Si concentration or amount of Mg–Si precipitates.
    View full abstract
    Download PDF (824K)
  • Superplastic forming of 5083 aluminum alloy sheet joined using friction stir welding
    Nobuyuki SUZUKI, Toru JINISHI
    2004 Volume 54 Issue 4 Pages 143-147
    Published: 2004
    Released on J-STAGE: February 20, 2007
    DOIhttps://doi.org/10.2464/jilm.54.143
    JOURNAL FREE ACCESS
    Show abstractHide abstract
    To develop a new SPF process using tailored blank technique, a series of forming experiments were carried out on 5083 SPF grade aluminum alloy sheets. Some rectangular blank sheets, with a butt joined line at each longitudinal center, were prepared using friction stir welding (FSW) under several conditions. The blank sheets were experimented to form into a slender pan with rectangular section, for intended reduction of thickness about in half, provided the forming is successful. Some blank sheets were formed successfully with decreased thickness on the joined line relative to the reduction on the base metal. Few defects or cavitations were observed in magnified views of cut section sampled from the joined line of the pan formed successfully. And it was found that the mechanical properties in that joined line kept the level of before forming. It means that a kind of superplastic deformation is happened in the joined line, if the conditions of FSW are suitable for SPF. As a result, the relationship between the superplastic formability in the joined line and the conditions of FSW was analyzed, and the possibility in the realization of the new process was verified.
    View full abstract
    Download PDF (2130K)
  • Effects of die structure on change of sectional dimensions in extrusion of aluminum alloys
    Noriatsu HARIYAMA, Shin-ichi MATSUOKA
    2004 Volume 54 Issue 4 Pages 148-152
    Published: 2004
    Released on J-STAGE: February 20, 2007
    DOIhttps://doi.org/10.2464/jilm.54.148
    JOURNAL FREE ACCESS
    Show abstractHide abstract
    In order to reduce the change of the flow velocity between the initial stage and the end stage of the aluminum extrusion process, the die structure were investigated by the extrusion experiments and finite-element method (FEM) simulation. As a result, it was confirmed that the change in the flow velocity reduced by setting the ring between a die and a container, and there were the most suitable dimensions of the ring, which became the smallest change in the flow velocity ratio. Furthermore, the change in the cross sectional dimension of the profile extruded from the die with this ring was the smallest.
    View full abstract
    Download PDF (783K)
REVIEW
LECTURE
Errata
    • |<
    • <
    • 1
    • >
    • >|
feedback
 Top