Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 62, Issue 12
Displaying 1-4 of 4 articles from this issue
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RESEARCH ARTICLE
  • Effects of microstructures on age-hardening of Mg–Al binary alloys
    Seiji Saikawa, Katsumi Watanab, Kaname Fujii, Taiki Tsuchiya, Tokimasa ...
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 12 Pages 473-478
    Published: December 30, 2012
    Released on J-STAGE: January 30, 2013
    DOIhttps://doi.org/10.2464/jilm.62.473
    JOURNAL FREE ACCESS
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    Magnesium alloys of AM30, AM60 and AM90 containing 3, 6 and 9 % Al, respectively, were prepared. The ingots of the alloys were warm-rolled and then solution heat treated. Microstructures of the alloys at as cast condition and after solution heat treatment were observed. Only α solid solution was observed in the solution heat treated specimens. Discontinuous precipitation was observed and age hardening occurred during aging at 489 K in the alloys except the AM30 alloy. The area fraction of discontinuous precipitates increased with increasing aging time, which resulted in increasing hardness. Hardness on areas containing discontinuous precipitates and those containing continuous precipitates were separately measured. The former showed higher value at the early stage of aging and then decreased, while the latter increased with aging. Calculated hardness through the rule of mixtures using values of hardness for pure magnesium and β-Mg17Al12 phase is consistent with the experimental results. Spacing between lamellars in the discontinuous precipitation increased with increasing aging time, although the hardness in the area composed of discontinuous precipitates decreased.
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  • Nucleation and growth of GP (1) zones and growth of θ″ and θ′ phases in Al–4% Cu single crystal under applied stress
    Shoichi Okawara, Motoki Kurasawa, Chihiro Watanabe, Ryoichi Monzen
    Article type: RESEARCH ARTICLE
    2012 Volume 62 Issue 12 Pages 479-485
    Published: December 30, 2012
    Released on J-STAGE: January 30, 2013
    DOIhttps://doi.org/10.2464/jilm.62.479
    JOURNAL FREE ACCESS
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    The effects of an external stress on the nucleation and growth of disk-shaped GP (1) zones and growth of disk-shaped θ″ and θ′ precipitates have been examined for an Al–4 mass% Cu alloy single crystal. Application of a compressive stress along the[001]α direction of the aluminum matrix during aging promotes particularly the nucleation and growth of the GP (1) zones on (001) α and the growth of the θ″ and θ′ precipitates parallel to (001) α. However, a tensile stress does not have a significant effect on those of GP (1) zones and that of θ″ and θ′ precipitates. Using the single crystal that has only the disk-shaped GP (1) zones perpendicular to [001]α, the misfit strains, ε11 (=ε22) and ε33, along[100]α and[001]α for GP (1) zones, θ″ and θ′ precipitates have been successfully estimated from measurements of length change and lattice parameter during aging. The acceleration of the nucleation and growth of the specific GP (1) zones and the growth of the particular θ″ and θ′ variants can be well understood through the interaction energy between the stress acting on the GP (1) zones, θ″ and θ′ variants and the misfit strains of them.
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