軽金属
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
61 巻, 12 号
選択された号の論文の8件中1~8を表示しています
研究論文
  • 古井 光明, 江端 祐平, 池野 進, 榊原 勝弥, 才川 清二
    原稿種別: 研究論文
    2011 年 61 巻 12 号 p. 699-704
    発行日: 2011/12/30
    公開日: 2012/01/30
    ジャーナル フリー
    Aging characteristics of AM60 magnesium alloy cast into sand mold were investigated by means of hardness measurement and microstructure observation with optical microscopy. The microstructure of this alloy in the as cast condition with the cooling rate of 5.2 K/s was composed with a primary crystallized alpha magnesium phase and eutectic phase consisting of alpha magnesium and beta Mg17Al12 intermetallic compound. The eutectic phase was divided to none-equilibrium crystallized phase and precipitated phase. The hardness of cellular precipitation area in aged samples decreased with an increasing of the aging time. On the other hand, the hardness of intragranular precipitation area was constant against the aging time. Variation of hardness with aging was found to be caused mainly by the discontinuous precipitation along cell boundaries from the rule of mixture in hardness.
  • 赤堀 俊和, 新家 光雄, 仲井 正昭, 堤 晴美, 安芸 志郎, 逸見 義男, 村上 昌吾, 大山 英人
    原稿種別: 研究論文
    2011 年 61 巻 12 号 p. 705-710
    発行日: 2011/12/30
    公開日: 2012/01/30
    ジャーナル フリー
    The relationship between microstructures and mechanical properties such as tensile and fatigue properties were systematically investigated by conducting several heat treatments on Ti–4.5Al–4Cr–0.5Fe–0.2C (KS EL-F) and Ti–4.5Al–2Cr–1Fe–0.1C (KS EL-Fmod) for next-generation aircraft applications. TiC and TiCr2 are formed in KS EL-F and KS EL-Fmod annealed at temperatures higher than β-transus and aged at 773 K, respectively. However, the precipitation trends of TiC and TiCr2 are considerably higher in the case of KS EL-F because the amounts of both these precipitates are drastically suppressed in KS EL-Fmod even when the heat treatments are identical. As-received KS EL-F and KS EL-Fmod exhibit excellent fatigue strength as compared with annealed Ti–6Al–4V. Although the presence of TiCr2 tends to decrease the fatigue strength, the aged KS EL-Fmod exhibits higher fatigue strength than the as-received KS EL-Fmod with very low TiCr2 amounts. Therefore, the aging treatment for KS EL-Fmod can be effective in improving the fatigue strength.
  • 赤堀 俊和, 新家 光雄, 仲井 正昭, 堤 晴美, 安芸 志郎, 逸見 義男, 村上 昌吾, 大山 英人
    原稿種別: 研究論文
    2011 年 61 巻 12 号 p. 711-717
    発行日: 2011/12/30
    公開日: 2012/01/30
    ジャーナル フリー
    The effects of microstructures on the mechanical properties of Ti–4.5Al–2Mo–1.6V–0.5Fe–0.3Si–0.03C (KS Ti-9) were systematically investigated by conducting several heat treatments for next-generation aircraft applications. The mechanical strength of as-received KS Ti-9 exhibits high anisotropy that is derived from the intense texture (T-texture) of the primary α phase. Such high anisotropy is observed in KS Ti-9 annealed at temperatures slightly below β-transus, but it is drastically decreased in KS Ti-9 subjected to an anisotropy controlling treatment. The reduction in the anisotropy for KS Ti-9 is related to the differences in the orientations of the precipitated acicular α phase.
  • 箕田 正, 吉田 英雄
    原稿種別: 研究論文
    2011 年 61 巻 12 号 p. 718-723
    発行日: 2011/12/30
    公開日: 2012/01/30
    ジャーナル フリー
    The influence of the room temperature pre-aging (RTPA) conditions on the strength of 7N01 aluminum alloy in T6 temper was changed by the zinc and magnesium contents. When both the zinc and magnesium contents were the lowest and the RTPA was omitted, the strength became the lowest because the aging rate during artificial aging decreased and a non-homogeneous precipitation of the η′ phase occurred. On the other hand, the η′ phase became finer and the strength in T6 temper became higher as the RTPA was longer and higher. Also, the two-step artificial aging resulted in a higher strength. It was considered that the GP(I) zones, which formed during RTPA, dissolved and the GP(II) zones formed during heating process of the artificial aging. Because the GP(II) zones were the precursor to the h9 phase, the strength became higher by the RTPA and the two-step aging. Furthermore, the influence of RTPA on the strength in T6 temper decreased with the increasing zinc and magnesium contents, and it almost disappeared when both the zinc and magnesium contents were maximum values. It was considered that the aging rate increased, and the GP(I) and GP(II) zones adequately formed during the heating stage of the artificial aging process because the solute atoms of the zinc and magnesium were sufficiently present.
  • 矢吹 彰広, 奥野 弘尚
    原稿種別: 研究論文
    2011 年 61 巻 12 号 p. 724-728
    発行日: 2011/12/30
    公開日: 2012/01/30
    ジャーナル フリー
    The self-healing corrosion protective properties of polymer coatings for aluminum were investigated. Zirconium phosphate conversion coating and polymer coating, which are various primer and top coatings with a thickness of 5 and 11 μm, were applied to the surface of pure aluminum, and after creating a defect by means of a knife-edge, a corrosion test was carried out in 0.5 mass% NaCl solution at 40°C. The polarization resistance of each coating was measured using electrochemical impedance method to evaluate the self-healing capability of coatings. The polarization resistance of scratched specimen coated polymer containing pigment increased with increasing time, resulting in high resistance. Thus, the self-healing capability of the polymer coating was recognized. The healing film formed on the scratched surface contained carbon. Analyzing component eluted from the coating, diethyl phthalate was detected. Polarization measurement of aluminum substrate in corrosive solution with the organic compound was conducted, and it was confirmed that the organic compound has the inhibiting effect against corrosion. The results showed that the organic compound was related to the formation of healing film.
  • 中山 栄浩, 宮崎 徹也
    原稿種別: 研究論文
    2011 年 61 巻 12 号 p. 729-735
    発行日: 2011/12/30
    公開日: 2012/01/30
    ジャーナル フリー
    AC4CH casting alloys were subjected to the 2-step preheating and the ECAP processing at room temperature. Microstructure change was investigated in terms of size and globularity of the eutectic Si particles and hardness of the primary and the eutectic α-Al. The effects of 2-step preheating, ECAP processing and standard T6 heat treatment on the hardness and the tensile properties were also investigated. The results of this study are as follows. The ECAP formability was significantly improved by the optimum 2-step preheating (1st-step preheating at 560°C and 2nd-step preheating at 350°C). More than 12-times ECAP pressing (equivalent strain of about 5.6) could be made without cracking. The hardness distribution in the primary α-Al suggested that the accumulated plastic strain during the ECAP processing increased gradually toward the eutectic cell regions. The hardness measurement also showed that the accumulated plastic strain of the eutectic α-Al around less-globular Si particles was higher than that around globular Si particles. Concentration of the plastic strain may promote cracking in the eutectic cell regions and deteriorate the ECAP formability. Successive processing by the 2-step preheating, the ECAP processing and the standard T6 heat treatment brought about globularity and homogeneous distribution of the eutectic Si particles. During the tensile deformation, these microstructural features might lead to homogeneous distribution of the plastic strain, suppressions of the cracking of Si particles and the delamination between the Si particle and the matrix. As a result, the 0.2% proof stress and the fracture strain increased about 11% and 47% respectively compared with those of the standard T6 treated sample.
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