軽金属
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
51 巻, 2 号
選択された号の論文の11件中1~11を表示しています
研究論文
  • 彦坂 武夫, 今井 恒道, 小林 俊郎, 戸田 裕之
    2001 年 51 巻 2 号 p. 86-92
    発行日: 2001年
    公開日: 2007/03/30
    ジャーナル フリー
    Effects of particle size and volume fraction of SiC particle on superplastic characteristics of SiCp/6061 aluminum alloy composites made by a vortex method before squeeze casting, extrusion and hot rolling were investigated in order to make clear the superplastic deformation mechanism. Flow stress of the SiCp (0.6 μm) /6061 aluminum alloy composite decreased with increasing the volume fraction in the case of the volume fraction of 0.13 and 0.20, and the m value became 0.30∼0.46 in the initial strain rate region of more than 2.4 × 10−1 s−1, and the maximum total elongation more than 200% was obtained at 853 K. And also, SiCp (1.2 μm) /6061 aluminum alloy composite exhibited m value of 0.32 at an initial strain rate of 7 × 10−2 s−1 and maximum total elongation of about 170%. However, 5 and 10 μmSiCp/6061 aluminum alloy composites did not produce superplasticity. It is thought that in SiCp/6061 aluminum alloy composite made by a vortex method, Vf=0.20 is optimum volume fraction for maximum total elongation. The threshold stress of the composites decreased with increasing SiC volume fraction. The stress exponent (n) indicated 3 for the creep deformation in the case of SiCp (5 and 10 μm)/6061 aluminum alloy composites, n showed 2 for the superplastic deformation in the case of SiCp (0.6 and 1.2 μm) /6061 aluminum alloy composites. On and near the fracture surface of the composite after superplastic deformation, filaments and striation bands were formed at sliding grain boundaries and interfacial sliding were observed and it is thought that high strain rate superplasticity of the composite could occur by grain boundary sliding and liquid phase accommodation mechanisms.
  • 中山 勝, 奥山 哲也, 美浦 康宏
    2001 年 51 巻 2 号 p. 93-97
    発行日: 2001年
    公開日: 2007/03/30
    ジャーナル フリー
    An Al–2.5 mass%Cu–0.23 mass%Sc alloy is strengthened by fine and uniform distribution of coherent spherical L12–Al3Sc phase and semicoherent plate-like θ′–Al2Cu phase, which precipitate during aging. These precipitates interact on growth and heterogeneous precipitation each other. In the present work, mechanisms of growth and heterogeneous precipitation between the two phases in the Al–2.5 mass%Cu–0.23 mass%Sc alloy aged at 623 K were investigated on the basis of TEM observation. On aging at 623 K, growth rate of θ′–Al2Cu phase in the Al–Cu–Sc alloy is much larger than that in the Al–Cu alloy. Growth rate of Al3Sc is almost same and very small in both of Al–Cu–Sc alloy and Al–Sc alloy and this is much smaller than that of θ′–Al2Cu phase. This is considered to be closely related to the high binding energy between scandium atoms and vacancies. Coarsening process of Al3SC and θ′–Al2 Cu phases obey the LSW theory of diffusion controlled particle coarsening. The migration of scandium or copper atoms to the strain fields of the interface dislocations formed at θ′–Al2Cu/matrix or Al3Sc/matrix interface have a significant effect on the heterogeneous precipitation of Al3Sc phase on θ′–Al2Cu phase or θ′–Al2Cu phase on Al3Sc phase.
  • 椿野 晴繁, 寺澤 倫孝, 三田村 徹, 野上 敦司, 杉本 公徳, 木野村 淳
    2001 年 51 巻 2 号 p. 98-102
    発行日: 2001年
    公開日: 2007/06/01
    ジャーナル フリー
    Surface segregation of Pb in the annealed Al-foils has been studied by Rutherford back scattering spectroscopy (RBS) and transmission electron microscopy (TEM). High-purity Al-foils containing 100 mass-ppm Pb were heat-treated for 1 h or 4 h at 540°C. Almost all of Pb segregate in a thin layer, 0.1 μm from the surface. Lead contents in the Pb-enriched surface layers were estimated to be 0.1∼0.14 at% Pb which were about 100–fold higher than the initial bulk concentration. TEM observations show that Pb-particles are formed at foil surfaces and their size increases from about 80 nm to 240 nm when final annealing time increases from 1 h to 4 h at 540°C. The Pb particles have a cube-cube orientation relationship with Al matrix and are bounded by {100} and {111} facets.
  • 北澤 君義, 西林 保, 藤野 博文
    2001 年 51 巻 2 号 p. 103-107
    発行日: 2001年
    公開日: 2007/03/30
    ジャーナル フリー
    An incremental stretching process with a single tool-path for sheet metals is useful for reduction of the tool-path schedule. However, the forming limit has not been revealed sufficiently for the single-tool-path process. In order to clarify the forming limit in the incremental stretching with a single tool-path, aluminum and aluminum alloy blanks are stretched to truncated conical shells with several values of half-apex angle, and the deformation behavior is examined. Experimental results show that forming limit is determined by the onset of cracking which propagates to circumferential direction in the early stage of the process. It is found that velocity of tool, V, and thickness of blank have major influences on the forming limit. The forming limit increases with decreasing V, and attains a maximum value at Vm; for V below Vm, a decrease in forming limit is caused by the low-cycle fatigue effect. Although the chemical composition of blank materials has a significant influence on the forming limit, the temper condition of blank materials has no influence on the forming limit. From considering of Sine law, experimental results show that the value of limiting strain is 2 to 30 times as high as that of work-hardening exponent of the blank. It is concluded that the forming limit of the incremental stretching is higher than that of press forming.
  • 藤田 誠
    2001 年 51 巻 2 号 p. 108-112
    発行日: 2001年
    公開日: 2007/03/30
    ジャーナル フリー
    TiO2 particles are available as reinforcements of aluminum alloy, because of their relatively low cost. But it is very difficult to make the composite with low volume fraction of TiO2, because of their fine spherical shape. Therefore, many researches had been done on TiO2–aluminum alloy composite in which the volume fraction of TiO2 was high. On the other hand, we had developed the process to make the preform with low volume fraction of TiO2 particles. Using this preform and AC8A aluminum alloy, TiO2–aluminum alloy composite in which the volume fraction of TiO2 reinforcement was relatively low was fabricated by pressure casting. Mechanical properties of this composite and the reaction between TiO2 and some elements in AC8A aluminum alloy occurred at casting and at T6 heat treating process were investigated. The results are as follows: (1) As cast state, the mechanical properties were affected only by the reinforcing effect of TiO2. Hardness and tensile strength increased with the amount of TiO2. (2) After T6 heat treating, mechanical properties were affected by the intermetallic compound that was formed by the reaction between TiO2 and some elements in AC8A aluminum alloy such as Mg or Si and this reaction occurred not only at T6 heat treating process but also at casting process. Consequently, hardness could be raised. Tensile strength at room temperature was below that of matrix, because there was no Mg that lead to the aging phenomenon. But at high temperature it was above matrix.
  • 戸田 裕之, 小林 俊郎, 星山 中, 高橋 明宏
    2001 年 51 巻 2 号 p. 113-118
    発行日: 2001年
    公開日: 2007/03/30
    ジャーナル フリー
    In-situ SEM observations of fracture toughness tests have been used to characterize microscopic damage evolution at coarse particles around a main crack in a 6061 aluminum alloy. About 13% of the particles coarser than 1 μm in diameter is identified as Mg2Si and the remaining is α–AlFeSi. All of the coarse Mg2Si particles suffer from damage within several hundred micrometers from a crack-tip. Meanwhile, some of the α–AlFeSi particles remain intact. The coarser the particles, the more considerably they are damaged. Fracture of the particles is predominantly observed for the coarser particles, while the tendency of interfacial debonding increases with decreases in the particle size. In addition, in-situ fracture strength values of the two kinds of particles are estimated as a function of particle size. Stronger dependency of the strength on the size is shown in the α–AlFeSi particles than in the Mg2Si particles. It is concluded that the fracture toughness of the alloy is scarcely affected by the damage at the coarse particles. However, much more considerable effects on strength and ductility are predicted due to the very low strengths of the particles.
  • 池田 賢一, 津曲 兼一郎, 吉田 冬樹, 中島 英治, 阿部 弘
    2001 年 51 巻 2 号 p. 119-124
    発行日: 2001年
    公開日: 2007/03/30
    ジャーナル フリー
    In this study, to clarify the formation process for electrolytic capacitor, crystal orientations and residual strains in a cold rolled foil, a partially annealed foil and an additionally rolled foil were evaluated by EBSP method. The partially annealed foil and the additionally rolled foil were heat treated at 300°C and the crystal orientation and the grain boundary character were analyzed. The main results are summarized as follows, (1) Additional rolling preferentially introduces strains in off-cube grains. (2) Most of the grain boundaries of cube grains are high angle boundaries. (3) The cube grains in high purity aluminum foils grow by the migration of high angle boundaries due to the lower strain energy.
解説:小山田記念賞
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