巻号一覧
72 巻, 6 号
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中尾 佳史, 三浦 博己, 酒井 拓2008 年 72 巻 6 号 p. 397-406
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーA Cu-30 mass%Zn alloy was multi directionally forged (MDFed) at 300 K and 77 K. Dislocation walls, subboundaries and grain boundaries were gradually developed with increasing strain to form ultra fine grains (UFGs). Furthermore, the evolution of UFGs was drastically stimulated by mechanical twinning. Therefore, it was revealed that the grain refinement in a Cu-Zn alloy during MDF was induced by both mechanisms of mechanical twinning and continuous dynamic recrystallizatrion. When MDFed to a cumulative strain of ΣΔε=6, the grain size obtained was 18 nm at 77 K and 22 nm at 300 K. The MDFed alloy exhibited almost constant ductility irrespective of cumulative strain and MDF temperature, while the tensile strength increased monotonically with increasing cumulative strain. Thermal stability of the UFGed Cu-Zn alloy decreased with increasing cumulative strain and decreasing MDF temperature.
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Sung-Kyu Son, 竹田 真帆人, Kyu-Seop Park, 三留 正則, 板東 義雄, Ki-Woo Nam, Chang-Y ...2008 年 72 巻 6 号 p. 407-412
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーPrecipitation behavior of metastable phases in an Al-1.94at%Cu alloy during isothermal aging at 373 K was investigated by means of Vickers microhardness tests, DSC measurements and TEM observations. The size distribution of the precipitates was quantitatively investigated based on the TEM, HRTEM and HAADF-STEM images, and statistical parameters that fit the precipitate size distribution were determined under a log-normal distribution approximation. We have successfully estimated the volume fraction of copper in precipitates, and found that the G.P.(II) formation results in increases of volume fraction of metastable particles, mean size and hardness.
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岡本 尚樹, 藤井 祐子, 栗原 宏明, 近藤 和夫2008 年 72 巻 6 号 p. 413-419
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーIn this study, we studied how the structure of the Cu foil, which is used for a substrate, affects tin whisker formation and the structure of the deposited tin films. In particular, we considered the relation between the crystal grain size of Cu foils and the amount of intermetallic compound deposits that is formed at the interface between Sn deposited films with aging and Cu foils. We used two types of Cu foils for a substrate. One is “with gelatin additive” that has granular-shaped grains which are 0.5~1 μm in size and the other is “with Cl- ion additive” that has pillar-shaped grains and their nodules. And the crystal grain size of the Cu foil with gelatin additive is smaller than the Cu foil with Cl- ion additive. The structure of tin whiskers, tin films and Cu foils were investigated by TEM and SEM. The number of the whiskers that formed on the Sn deposited film increased after aging. And the number of the whiskers that formed on the Sn film deposited on the Cu foil with gelatin additive was larger than that with Cl- ion additives. The cross sectional morphologies of tin deposited films and Cu foils were observed from the TEM. From the analysis of TEM diffraction patterns that were obtained by after-aging sample, there was Cu6Sn5 intermetallic compound deposits at the interface between the Sn deposited film and the Cu foils. The amount of intermetallic compound deposits formed with gelatin additive was larger than that with the Cl- ion additive. The morphology of the intermetallic compound deposits was classified as nodular shaped or as layer shaped. We could observe the difference in the amount of nodular-shaped intermetallic compound deposits between the sample with gelatin additive and the samples with Cl- ion additive.
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角谷 英剛, 藤尾 和樹, 浄徳 昌宏, 山本 厚之, 椿野 晴繁2008 年 72 巻 6 号 p. 420-426
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーIt is generally recognized that impurity atoms affect the phenomena of corrosion. In the present study, we have prepared a low impurity magnesium alloy, and the corrosion behaviors of the alloy was compared with that of a commercial AZ31B magnesium alloy. The low impurity alloy was prepared with using 5N-Al, 4N-Zn and high purity magnesium, the last one was prepared by a vapor deposition technique. Chemical analyses showed that the composition of the alloy was about Mg-3% Al-1% Zn (in mass%). Slices with about 5 mm thickness were cut from an ingot of the alloy, and hot-rolled into 1 mm at 623 K, then solution heat treated at 673 K for 86.4 ks. Lowering the impurities resulted in improving a corrosion resistance. Corrosion test using a 1 mass% NaCl solution showed that the low impurity magnesium alloy had a superior corrosion resistance compared with those of the AZ31B and the AZ31PE alloys. In the AZ31B alloy, filiform corrosion occurred after a duration time of 0.6 ks. Heads of the filiform corrosion propagated with random walking, creating regular irtraces, while in the low impurity magnesium alloy, duration time for the filiform corrosion was prolonged to 7.2 ks. Moreover, morphology of tails were changed by lowering the impurity concentrations, into straightforward.
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西嶋 文哉, 野村 幸矢, 渡邊 千尋, 門前 亮一2008 年 72 巻 6 号 p. 427-432
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーThe effects of alloying elements on the stress relaxation property of Cu-Ni-Sn-P alloys have been investigated using Cu, Cu-1.5 at% (1.4 mass%) Ni alloys, Cu-0.75 at% (0.7 mass%) Ni-0.75 at% (1.4 mass%) Sn alloys and Cu-1.5 at% (2.8 mass%) Sn alloys with and without 0.14 at% (0.07 mass%) P. Adding Sn to Cu enhances the resistance to stress relaxation by dragging atmospheres of Sn atoms behind dislocations. The Cu-Ni-P alloy exhibits better stress relaxation property than the Cu-Ni and Cu-P alloys, probably because atoms caused by pairs of P and Ni chemical binding are dragged by moving dislocations. Annealing of the Cu alloys with P at a low temperature of 300°C for a short time brings about higher stress-relaxation resistance. This is ascribed to the decrease in mobile dislocation density by segregation of P atoms on dislocations during the annealing. Adding 0.1 at% (0.04 mass%) Mg to the Cu-Ni-Sn-P alloy decreases the amounts of Ni and P dissolved in the Cu matrix, resulting in lower stress-relaxation resistance. The addition of 0.1 at% (0.09 mass%) Fe to the Cu-Ni-Sn-P alloy is effective for the improvement of stress relaxation property.
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長友 義幸, 北原 丈嗣, 長瀬 敏之, 黒光 祥郎, Harini Sosiati, 桑野 範之2008 年 72 巻 6 号 p. 433-439
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーFracture mechanism of the interface between an aluminum layer and an aluminum nitride plate during thermal cycling was studied. Observation of the interface with an ultrasonic flaw detector indicated that a crack was generated at an edge of the aluminum layer after approximately 2000 thermal cycles. Cross-section observation using SEM-ASB (Angle Selective Backscattered electron detector) revealed that the crack propagated into the aluminum layer and ran along the interface. The size of aluminum grains around the tip of the crack is 0.2-1.0 μm. This size is much smaller than that in the initial aluminum layer, which was approximately 500 μm. It is considered that the reduction in the size of aluminum grains was due to the accumulation of strains in the aluminum layer during the thermal cycling. Observations using SEM-ASB of higher magnification and TEM revealed that the crack was formed in the aluminum layer during thermal cycling, and propagated along the aluminum grain boundaries.
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宮内 喜子, 江阪 久雄, 田村 学, 篠塚 計2008 年 72 巻 6 号 p. 440-447
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーThe Sn-Cu Alloy is one of the candidate alloys for lead-free solder. It is important to understand the solidified structure of this alloy, but such reports are few. In order to make in-situ observation during solidification of this alloy, a laser confocal microscope has been used. Three alloys, hypo-eutectic, eutectic and hyper-eutectic alloys have been prepared.
In the case of hypo-eutectic alloy, primary β-Sn dendrite and interdendritic eutectic were observed. A large recalescence was observed when the primary β-Sn nucleated in thermal histories.
In the case of eutectic alloy, only eutectic structure was observed by the laser microscope. However, primary β-Sn dendrites were observed on the cross section. There was a large recalescence during solidification. This corresponded to the nucleation of β-Sn.
In the case of hyper-eutectic alloy, fibrous primary Cu6Sn5 grew and then β-Sn dendrite grew as halo. This followed by the formation of eutectic. It was observed that a large recalescence after growth of primary Cu6Sn5 precedes the nucleation of β-Sn as halo.
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高井 健一, 村上 耕太, 矢部 宣明, 鈴木 啓史, 萩原 行人2008 年 72 巻 6 号 p. 448-456
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーThe fundamental properties of thermal hydrogen desorption for Inconel 625 and SUS 316L for face-centered-cubic(FCC) metals have been analyzed. Then, the high-pressure-gas charging of hydrogen has been substituted by electrolysis charging. Hydrogen was charged into Inconel 625 and SUS 316L in H2SO4 with or without NH4SCN as a catalyst at current densities in the range from 0 to 90(A/m2) and in gaseous hydrogen at the pressure of 0.3, 10, 20 and 45 MPa at 90°C. The states of hydrogen existing trapping sites were compared using thermal desorption analysis(TDA). The diffusion activation energy is 46.5(kJ/mol) and the trap activation energy is 46.3(kJ/mol) for Inconel 625. These close values indicate that the hydrogen released from FCC metals is determined not by desorption from trapping sites but by diffusion in lattice. The hydrogen content of Inconel 625 increased upon the quenching and cold-working. This increase in hydrogen content corresponds to the increase in the densities of vacancies and dislocations. The hydrogen peak consists of solution hydrogen and trapped hydrogen at vacancies and dislocations. The peak temperatures in the hydrogen evolution curves of Inconel 625 and SUS 316L charged by electrolysis and high-pressure gas at 90°C are the same after hydrogen saturation. In addition, hydrogen contents obtained upon charging by electrolysis exceed those obtained by high-pressure gas of 45 MPa. This means that higher-pressure gas environments of at least 45 MPa can be substituted by electrolysis charging. The hydrogen-saturated contents of the metals increase with current density and catalyst content. Sievert's law describes the relationship among hydrogen content, hydrogen gas pressure, and temperature. Therefore, the gas pressures corresponding to electrolysis charging conditions can be obtained. When hydrogen is charged by electrolysis using 0.1 mass% NH4SCN at 50(A/m2), the hydrogen gas pressure of 1200 MPa is actualized by electrolysis charging.
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新野邊 幸市, 澄 郁夫, 竹下 直也2008 年 72 巻 6 号 p. 457-463
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーIn order to improve the oxidation resistances of Mo and Nb alloys, aluminide coatings were developed by lamination cladding. Mo, Nb, and Al sheets with a purity of 99.99 wt% and dimensions of 15 mm×10 mm×0.5 mm were prepared by cutting, followed by the development of a specimen piece by holding the Al sheet between two sheets of Mo or Nb. The specimen wrapped with a Ta foil to prevent oxidation was heated at temperatures of the order of the melting point of Al in a pure Ar atmosphere. On the basis of the elemental analysis by characteristic X-rays, the laminated layers formed on the Mo substrates were found to be composed of MoAl5, MoAl4, and Mo3Al8. It was also found that the main phase constituting the laminated layers changed from MoAl5 to Mo3Al8 on increasing the temperature from 973 K to 1473 K. In contrast, NbAl3 was singly formed on the Nb substrate, irrespective of the heating temperatures. However, since NbAl3 grains have a spherical shape, the NbAl3 layer was not formed on the Nb substrate.
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岩瀬 啓吾, 西野 洋一, 宮崎 秀俊, 曽田 一雄2008 年 72 巻 6 号 p. 464-469
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーWe report on the temperature dependence of the electrical resistivity and the Seebeck coefficient for the Heusler-type (Fe1-xCox)2TiAl alloys with compositions 0.25≤x≤0.70. A small deviation from stoichiometry (x=0.50) causes a decrease in the electrical resistivity and an enhancement in the Seebeck coefficient with positive and negative sign for x<0.45 and x≥0.45, respectively. This compositional variation of the Seebeck coefficient is in line with a pseudogap scenario where the off-stoichiometry causes a rigid-band-like shift of the Fermi level from the central region in the pseudogap. The measured Seebeck coefficient is found to be lower than that evaluated from the theoretical density of states, which may be attributed to an atomic disorder between Fe and Co.
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倉田 有司, 二川 正敏2008 年 72 巻 6 号 p. 470-476
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーCorrosion tests of CrN-coated steels for nuclear reactors were conducted in liquid lead-bismuth (Pb-Bi) at 450°C and 550°C for 3000 h to investigate the applicability of CrN coating to a liquid Pb-Bi environment. CrN coatings on F82H (Fe-8Cr-2W-0.3V-0.04Ta-0.1C) and 316SS exhibited good compatibility in liquid Pb-Bi during corrosion test at 450°C. The CrN coating layer suffered heavy damage such as cracking and spalling, and showed no effectiveness as a protective layer in corrosion test at 550°C. Nickel and chromium in 316SS dissolved into Pb-Bi through the damaged coating layer at 550°C. The cracking and spalling were not found after heating CrN-coated steels in Ar gas at 550°C. It is considered that stresses caused by the difference of thermal expansion coefficients between CrN and steels led to cracking and spalling of the CrN coating through corrosion attack by liquid Pb-Bi at 550°C.
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平野 充, 松尾 敦, 広中 直人, 西 義武2008 年 72 巻 6 号 p. 477-482
発行日: 2008年
公開日: 2008/06/01
ジャーナル フリーIn order to strengthen carbon fiber reinforced polymer (CFRP), effects of a pre-stressing on Charpy impact value have been investigated. The pre-stressing remarkably enhances the impact value. It probably depends on the residual compressive stress induced by the pre-stressing in CFRP.
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