軽金属
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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51 巻, 8 号
選択された号の論文の8件中1～8を表示しています
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研究論文
  • AZ31マグネシウム合金の応力腐食割れ発生時の水素の挙動
    倉本 繁, 荒木 一郎, 菅野 幹宏
    2001 年 51 巻 8 号 p. 397-402
    発行日: 2001年
    公開日: 2007/03/30
    DOIhttps://doi.org/10.2464/jilm.51.397
    ジャーナル フリー
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    Hydrogen behavior during stress-corrosion cracking in an AZ31 magnesium alloy was studied by using hydrogen microprint technique (HMT), which is a method to visualize points of hydrogen emission from metals. Tensile test specimens were prepared from an extruded bar of the AZ31 magnesium alloy and deformed in tension at an initial strain rate of 8.3 × 10−3 s−1 or 8.3 × 10−6 s−1 under different environmental conditions. When the specimen was tested at a strain rate of 8.3 × 10−6 s−1 in a 4%NaCl solution, it exhibited brittle transgranular stress-corrosion with almost no macroscopic plastic deformation. HMT was applied to the specimen that was pre-strained in the NaCl solution, and it was revealed that hydrogen evolved from the surface of the specimen along slip lines after 5% plastic deformation. This result represents an evidence of accelerated diffusion of hydrogen by dislocation motion, which may be related to the brittle stress-corrosion cracking accompanied by plastic deformation in the localized area at a crack tip.
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  • 高純度Mg–9%Al合金鋳塊の結晶粒微細化機構と結晶粒径に及ぼす微量FeおよびMnの影響
    灰谷 直, 田村 洋介, 矢野 英治, 茂木 徹一, 河野 紀雄, 佐藤 英一郎
    2001 年 51 巻 8 号 p. 403-408
    発行日: 2001年
    公開日: 2007/06/01
    DOIhttps://doi.org/10.2464/jilm.51.403
    ジャーナル フリー
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    Grain refining mechanisms of Fe– and Mn–free high-purity Mg–Al alloy ingots and the influences of a small addition of Fe or Mn on their cast structures were investigated. In order to prepare the alloy, a distilled pure magnesium (< 99.99%) and a commercial high-purity aluminum (99.99%) were melted, and given amounts of Fe and Mn were added into the molten alloys. Microscopic observation shows that the grain structure of high-purity alloys refined naturally without the use of a grain-refiner or superheat treatment, and that the addition of Fe and Mn elements coarsened the grains. In the range of Fe or Mn where magnesium will never crystallize from the melt as a primary crystal, both the grain-coarsening and the effect of superheat treatment is more remarkable. EPMA and AES analyses made clear a dispersion of fine particles composed of Mg, O, Al and C elements in the high-purity alloy. Some combination of these elements seems to cause an effective nucleation substance for magnesium crystal, which similar to those whose presences have been confirmed in AZ91E magnesium alloys to which a proper amount of carbide was introduced. In coarse-grained alloys, Fe and Mn elements coexist with the above-mentioned nucleation substances , and thus disturb the grain refinement.
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  • 3004アルミニウム合金の伸びに及ぼす結晶粒径の影響
    古井 光明, 飯代 彰, 佐治 重興
    2001 年 51 巻 8 号 p. 409-413
    発行日: 2001年
    公開日: 2007/03/30
    DOIhttps://doi.org/10.2464/jilm.51.409
    ジャーナル フリー
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    In general, a fine grain structure may be produce an excellent elongation. However, the different tendency was observed with Al–Mg system alloys. In order to make clear a grain size dependence for elongation, a tensile test, a surface roughness measurement and a fractography were performed for 3004 aluminum alloy with various grain sizes from 18 to 121 μm. Then a total and a uniform elongation of 3004 aluminum alloy tensiled for a strain rate of 1.67 × 10−4 s−1 was plotted for grain size, a maximum elongation was obtained in 77 μm of mean grain size. The total and the uniform elongation was proportional to a reciprocal square root of grain size. There is no change a local elongation for the reciprocal square root of grain size. In fine grain region below the 77 μm of grain size, grain size dependence for elongation was indicated a inverse Hall-Petch type by the effects of a work hardening exponent and an amplitude of serration. In the meantime, coarse grain region over the 77 μm of grain size, the grain size dependence for elongation was indicated a Hall-Petch type by the effects of a three dimensional stress and a surface roughness on the tensile specimen. The same grain size dependence for elongation was observed in the strain rate of 1.67 × 10−3 and 1.67 × 10−5 s−1.
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  • 5000系アルミニウム合金板の機械的特性と角筒深絞り成形性の温度，ひずみ速度依存性
    大上 哲郎, 高田 健, 佐賀 誠, 菊池 正夫
    2001 年 51 巻 8 号 p. 414-418
    発行日: 2001年
    公開日: 2007/03/30
    DOIhttps://doi.org/10.2464/jilm.51.414
    ジャーナル フリー
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    Uniaxial tensile tests, square shell deep drawing tests of 5000 series aluminum alloy sheets from RT to 300°C temperatures were carried out in order to investigate temperature and strain rate dependence of mechanical properties and deep drawability. In these warm working temperatures, tensile strength (TS) decreases with the ambient temperatures, and these decrease of TS become smaller in high strain rate. Elongation (El) is nearly same from RT to 100°C, but it increases largely with the increase of temperature from 150 to 300°C, and these increase of El become larger in low strain rate. This change of El mainly depends on local elongation (LEl). Limiting drawing ratio (LDR) of square shell deep drawing in high speed forming becomes a little bigger than normal speed forming. The change of LDR is small in 100∼150°C, but it becomes larger from 200∼300°C, but LDR is smaller in high speed forming. ΔLDR shows the effect of working temperature from the LDR of RT. The effective experimental equation between ΔLDR and mechanical properties (TS, El, LEl) is developped.
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