日本金属学会誌
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
75 巻, 10 号
選択された号の論文の11件中1~11を表示しています
論文
  • 小橋 眞, 斎木 健蔵, 金武 直幸
    2011 年 75 巻 10 号 p. 525-531
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      The reactive infiltration of molten aluminum into a powder preform was investigated as a processing route for aluminum nitride (AlN) matrix composites. As the powder preform, titanium and boron nitride (BN) powders were blended and compacted, the infiltration occurred spontaneously at temperatures ranging from 1073 K to 1673 K. The conversion ratio of BN to TiB2 and AlN turned out to be insufficient (<0.8) at temperatures below 1273 K. The conversion ratio increased by increasing the processing temperatures, and it exceeded 0.95 at 1673 K. The conversion ratio at 1473 K was almost saturated with a 3.6 ks holding and the effect of extending the holding time was not confirmed. Decreasing the BN powder size was effective to promote the reaction between aluminum, titanium and BN. The effectiveness was particularly prominent at 1473 K in comparison with the specimen fabricated at 1673 K. The titanium powder size did not show a significant effect on the formation of AlN and TiB2. The volume fraction of AlN increased by changing the atmospheric gas from argon to nitrogen.
  • 森田 辰郎, 坂田 俊之, 加賀谷 忠治, 川嵜 一博
    2011 年 75 巻 10 号 p. 532-538
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      This study was conducted to investigate the effect of short-time heat-treatment and fine-particle bombarding (FPB) on the fatigue strength of Ti-6Al-4V alloy. The short-time heat-treatment was performed at 953~1203 K for 60 s. Then, the changes in hardness and mechanical properties were investigated. The yield strength was greatly decreased by the above heat-treatment conducted at 1103 K and the reduction in area was strikingly increased. On the other hand, the yield strength was increased by the heat-treatment conducted at 1203 K and the reduction in area was at a higher level than that of the untreated material. When the untreated material and the above heat-treated materials were further FPBed, the surface hardness was greatly increased and compressive residual stress was introduced. It was clearly observed on the fracture surfaces that the fatigue cracks of the FPBed materials were initiated from the substrates due to the existence of the hardened layers. This result showed that the fatigue strength of the FPBed materials were strongly controlled by the strength of the substrate. Actually, the highest fatigue strength was achieved by the heat-treatment at 1203 K and FPB because this heat-treatment remarkably improved the strength of the substrate.
  • 李木 経孝, 中村 格芳, 渡邊 真彦, 星河 浩介, 田渕 宏, 大園 洋仁
    2011 年 75 巻 10 号 p. 539-544
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      In order to improve the purity of 6N aluminum, it was melted in a vacuum of 3-6×10−6 Pa for 30 min and solidified gradually. The melted samples were cut into several pieces and the residual impurities of each part were analyzed by Glow Discharge Mass Spectrometry (GDMS). The Residual Resistivity Ratio (RRR) of each part was measured and the relationship of RRR with residual impurities is discussed. The purity of the melted sample was improved in comparison with that of the raw material, and the measured RRR almost doubled to 40000. GDMS analysis revealed that the amounts of elements of partition coefficient k<1 were reduced considerably, whereas those of elements of k>1 were not reduced. While each impurity concentration ratio in this study is about one-tenth of that in the previous report, the purification efficiency of each element in this study and that in the previous report matched well. Although the estimated RRR values from composition analyses were larger than the measured RRR values, both showed similar tendencies with regard to specimen position and also corresponded well with regard to impurity distribution.
  • 菊池 彰文, 石原 顕光, 大城 善郎, 松澤 幸一, 光島 重徳, 太田 健一郎, 松本 匡史, 今井 英人
    2011 年 75 巻 10 号 p. 545-551
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      Tantalum-based compounds prepared by reactive sputtering with heating were evaluated as non-platinum cathodes for polymer electrolyte fuel cells. Effects of species of target, TaC and TaN, and oxygen partial pressure on catalytic activity for oxygen reduction reaction (ORR) were investigated. We found that TaC target was more useful than TaN to prepare the specimen with high ORR activity. In addition, an existence of an appropriate amount of O2 was needed with the TaC target to obtain superior catalytic activity for the ORR. X-ray diffraction and Time-of-flight secondary ion mass spectrometry analysis suggested that crystalline structure of TaON (monoclinic) and carbon on the surface might affect the catalytic activity for the ORR.
  • 石原 顕光, 菊池 彰文, 大城 善郎, 松澤 幸一, 光島 重徳, 太田 健一郎, 松本 匡史, 今井 英人
    2011 年 75 巻 10 号 p. 552-556
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      We analyzed TaCxNyOz and TaNxOy thin film catalysts prepared by reactive sputtering under Ar, N2 and O2 mixture with TaC or TaN target to reveal a correlation between oxygen reduction activity and physico-chemical properties of the films. XPS and Raman spectroscopy indicated that the graphite and amorphous carbon existed on the surface and grain boundary of the TaCxNyOz. Deposited carbon provides electrical condition paths that are necessary for oxygen reduction reaction (ORR) to be effectively occurred. X-ray absorption spectroscopy analysis revealed that both the TaCxNyOz and TaNxOy had some oxygen and/or nitrogen defects compared to the ideal TaON, providing oxygen adsorption sites. Because the TaCxNyOz had both oxygen and/or nitrogen defects as oxygen adsorption sites and deposited carbon as electrical condition paths, the TaCxNyOz showed higher ORR activity than the TaNxOy.
  • 金 成哲, 山浦 真一, 牧野 彰宏, 井上 明久
    2011 年 75 巻 10 号 p. 557-561
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      In this work, electro-less plating was adopted to produce a new metallic bipolar plate coated with amorphous alloy. The Ni-P amorphous alloy thin film was deposited on Al plate with a bipolar plate flow field and its corrosion resistance and contact electrical resistance were measured. As results, it was found that the electro-less plated Ni-P amorphous thin film showed much lower corrosion resistance than the Ni-Cr-P-B metallic glass because of its lack of Cr content and also found that the Ni-P film showed lower contact electrical resistance than the stainless steel SUS316L plate.
       The electricity generation tests with the single cell having the Ni-P amorphous alloy-coated bipolar plates produced in this study revealed that the single cell with the Ni-P amorphous alloy-coated bipolar plates showed excellent I-V performance as well as the cell with the carbon bipolar plates after 39th repetition. However, the I-V performance degraded gradually and was found to be much lower than that with the carbon bipolar plates after 50th repetition. Then the long time durability tests for 24 h were also conducted at the constant current density of 200 mA•cm−2. It was found that the cell voltage of the single cell with the Ni-P amorphous alloy-coated bipolar plates decreased gradually with time.
  • 徳永 仁夫, 藤田 和孝, 前原 啓人, 横山 嘉彦, 井上 明久
    2011 年 75 巻 10 号 p. 562-568
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      Zr50Cu40Al10 bulk metallic glass (BMG) matrix composite with crystalline B2 ZrCu was fabricated. Compressive test was carried out using the composite specimens with different volume fraction of B2 ZrCu. The effects of B2 ZrCu on plastic deformation behavior and mechanical properties of the composite were investigated. As the results, it was found that the ductility of the composite specimen was enhanced by increasing of volume fraction of B2 ZrCu. Also, it was found that the composite specimen exhibited work hardening behavior. On the other hand, yield stress and Young's modulus of the composite decrease with increasing of volume fraction of B2 ZrCu. Furthermore, it was confirmed that a stress-induced martensitic transformation in B2 ZrCu phase occurs during compressive test.
  • 徳永 仁夫, 小山 順平, 藤田 和孝, 横山 嘉彦, 山崎 徹, 井上 明久
    2011 年 75 巻 10 号 p. 569-574
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      Zr70Ni16Cu6Al8 bulk metallic glass (BMG) shows a clear tensile plastic deformation under high strain rate condition. In the present study, in order to investigate the tensile plastic deformation behavior of the BMG, the deformation behavior and fracture surface were observed by using high speed video camera and scanning electron microscope (SEM), respectively. As the results, it was found that the tensile plastic deformation of the BMG was induced by the specimen sliding deformation along one main shear band. Also, it was surmised that the main shear band completely penetrated the specimen, and there was viscous medium within main shear band. Furthermore, from a detailed analysis of SEM observation, it was confirmed that there were two distinct regions on the fracture surface. The first region was no-feature region and it corresponds to progressive siding of specimen along main shear band. The second region was covered with well-developed Vein pattern and it was caused as the result of a fast separation of specimen by an interaction of shear and normal force.
  • 山本 厚之, 塚本 雅章, 岡井 大祐
    2011 年 75 巻 10 号 p. 575-581
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      Microstructural changes in an Al-Mg-Si alloy during annealing at 673 K after cold-rolling with a 50% reduction rate were observed. An alloy specimen was repeatedly subjected to intermittent annealing using a salt bath, Ar ion-polishing, and observation with SEM (Scanning Electron Microscope)-EBSD (Electron BackScatter Diffraction) system. The observations were carried out in the same view field on a specimen. Large lattice rotation occurred due to cold-rolling, which lead to formation of dislocation cells having orientations with broad range of angles, and made existing grain boundaries unclear. Strain induced grain boundary migration was not observed in this case. After annealing, the dislocation cells changed into subgrains surrounded by high and low angle boundaries, and some of them grew into recrystallized grains without change in orientation. These recrystallized grains (“crystallites”) originated from the dislocation cells in the deformed microstructure. The orientations of the crystallites were different from those of the surrounding subgrains.
  • 山本 厚之, 塚本 雅章, 岡井 大祐
    2011 年 75 巻 10 号 p. 582-591
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      Changes in microstructures at recovery stage after cold-rolling at 50% reduction rate were observed in an Al-Mg-Si alloy by means of SEM-EBSD system. The same area in the specimen was observed before and after cold-rolling. Intermittent annealing at 673 K, Ar ion-polishing, and EBSD observation were repeated up to the annealing time of 3.6 ks. Dislocation cells formed by cold-rolling changed into subgrains with annealing. Low and high angle boundaries were formed with surrounding the subgrains depending on misorientations between the neighboring subgrains. The high angle boundaries migrated to form recovered microstructures. Original orientation of the dislocation cell was maintained in the recovered microstructure. Some of the recovered microstructures grew with invading others. Therefore, new discrete poles did not appear in a discrete pole figure during annealing but those in the invaded subgrains disappear, which made the pole figure of the annealed specimen different from that of the cold-rolled specimen. Secondary recovered microstructures were observed to be formed with invading primary formed recovered microstructures. The recovered microstructures were finally invaded by recrystallized grains to disappear. In a region where growth of recrystallized grains was delayed, coarse recovered microstructures composed of large subgrains were formed.
  • 塚本 雅章, 阪本 諭志, 山本 厚之
    2011 年 75 巻 10 号 p. 592-599
    発行日: 2011年
    公開日: 2011/10/01
    ジャーナル フリー
      Diffusion bonding requires loading relatively high pressures at elevated temperatures in order to advance an adhesion between surfaces. In the case of oxygen free copper, remarkable deformation occurs during the bonding process due to its poor mechanical strength at high temperatures. In the present study, the diffusion bonding of oxygen free copper under low pressures which enable the specimens to minimize deformation was attempted at 1073 K for 3.6 ks and 7.2 ks with other experimental factors. The process for increasing bonding areas consists of deformation and diffusion mechanisms. It was important to promote the latter because the former gets poorer under the low bonding pressures. Tensile strength of the specimens was increased with decreasing roughness on the bonding surfaces and comparable to that of the base metal in the specimens whose surfaces were polished with an emery paper #4000 and buffing. Furthermore, a fracture occurred at not the bonded interface but the base metal when contact between the bonding surfaces was delayed until a temperature was raised up to bonding condition. In the conventional procedure for diffusion bonding, the temperature has been generally raised with contact between the bonding surfaces so that copper oxides at the bonded interface are difficult to be decomposed due to depressed evacuation. The bonding surfaces were maintained as a free surface by the delayed contact procedure, which led to decomposing the copper oxides. Consequently, the tensile strength would be improved by reducing fracture origins. Grain boundary migration across the bonded interface was sufficiently generated only in the specimen prepared with buffing and prolonged for 7.2 ks in bonding time. In contrast, the fracture at the base metal was achieved in the specimens maintaining an original bonded interface. It was suggested that the grain boundary migration was not necessary to acquire superior joints.
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