巻号一覧
70 巻, 1 号
選択された号の論文の15件中1～15を表示しています
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木村 博, 北原 浩二, 奈賀 正明2006 年 70 巻 1 号 p. 1-6
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーThe solid state P/M processing that consists of rotating-arm reaction ball milling and pulse electric discharge consolidation provide a process control methodology to develop the hydroxyapatite (HA) with unique property inherent to the nanocrystalline (nc) structure. The mechanical alloying of the powder mixture is conducive to the solid state synthesis of HA{Ca10(PO4)6(OH)2} having the average crystallite size of 7 nm according to a reaction, 6CaHPO4•2H2O+4Ca(OH)2→nc-Ca10(PO4)6(OH)2+8H2O; this overall process is given by Johnson-Mehl-Avrami equation with the exponent of 1. The nc-Ca10(PO4)6(OH)2 powder compact can be consolidated at a full density; its rapid densification during heating is expressed by an Arrhenius-type equation of Newtonian viscous flow with the activation energy of 402 kJ•mol-1 under both pressure of 80 and 140 MPa. The average crystallite size of bulky Ca10(PO4)6(OH)2 increases from 10 to 50 nm with increasing temperature up to 1173 K. The high-speed superplastic forging is achieved having the strain rate of nearly 10-2 s-1 and the compressibility of 0.65 at a relatively low temperature of 1137 K, and characterized by the strain rate sensitivity exponent ranging from 0.7 to 1 and the activation energy of 75-113 kJ mol-1.
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吉岡 隆幸, 有川 秀行, 岡田 満利, 久松 暢, 児島 慶享2006 年 70 巻 1 号 p. 7-13
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーThis paper focuses on the oxide layer formed at bondcoat/topcoat interface of thermal barrier coatings (TBCs), which grows faster in comparison with the oxide layer formed on overlay coatings, although both bondcoat and overlay coating are made of MCrAlY alloy (M is Ni or Co, or combination of Ni and Co). The authors clarify the influence of ① the surface treatment (shot peening) of bondcoat and ② yttrium in bondcoat on the oxidation behavior of the thermal barrier coatings. Oxidation tests were carried out at 950°C in air by means of TBC specimens. The specimen consists of Ni-base superalloy (Inconel738LC), CoNiCrAlY bondcoat and ZrO2-Y2O3 topcoat. In the TBC specimen with as-sprayed bondcoat, the oxide layer consisted of “wart-like oxide” and “continuous alumina layer”. The wart-like oxide is caused due to un-melted particles of CoNiCrAlY alloy that remained at the bondcoat/topcoat interface in spraying process. The surface treatment of bondcoat prevented the formation of wart-like oxide because the unmelted particles were removed. In the TBC specimen with as-sprayed bondcoat, yttrium-rich oxide particles were included in the continuous alumina layer. The surface treatment of bondcoat and/or the removal of yttrium from the chemical composition of bondcoat in TBC specimen prevented the formation of the yttrium-rich oxide particles in the continuous oxide layer, and as a result, the growth of continuous alumina layer was decreased. There is a possibility that the application of the bondcoat without yttrium restrains the growth of the continuous oxide layer in TBC.
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梅田 和巳, 宮入 嘉夫, 牧原 義一2006 年 70 巻 1 号 p. 14-19
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーA new composite Mg-50 mass%ZrMn2 hydride with a cooperative hydrogen absorption/desorption mechanism has been elaborated by reactive mechanical milling in a hydrogen atmosphere. The structural and hydriding properties of the composite were investigated by XRD, SEM/EDS and TG/DTA measurements. The composite absorbs hydrogen at room temperature and forms the nanostructured composite hydride composed of ZrMn2Hx, MgH2 and Mg, which discharges hydrogen around 275°C without decomposition. It is concluded that the ZrMn2 fine particles uniformly distributed for the high density on the Mg matrix play an important role in the “cooperative mechanism” where the hydrogen in MgH2 and ZrMn2Hx are simultaneously discharged.
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張 世 勲, 南口 誠, 松丸 幸司, 石崎 幸三, 武田 雅敏2006 年 70 巻 1 号 p. 20-24
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーβ-FeSi2, which is one of the thermoelectric materials, has been more attractive in high-temperature range because of its low cost of raw materials. Oxidation resistance of sintered β-FeSi2 was investigated at temperatures ranging from 1073 to 1223 K in air. Fully densified and porous β-FeSi2 samples were fabricated by using the pulsed electric current sintering method. They were annealed at 1173 K for 5d to obtain β-FeSi2 phase. Microstructure of oxidized sample was observed by scanning electron microscopy with energy dispersion X-ray spectroscopy. Phase identification of samples oxidized was carried out by X-ray diffraction. Oxide layer, which is most likely an amorphous SiO2, was formed on β-FeSi2 samples after oxidation. Growth of the oxide layer obeyed a parabolic law. Growth rate of the oxide layer on sintered β-FeSi2 was comparable to that of Si. Granular ε-FeSi was developed below the oxide layer as a result of oxidation of β-FeSi2. Grain boundary oxidation was not observed. Formation of cracks in the SiO2 layer and β-FeSi2 was not observed even in on the porous samples. Oxidation resistance of sintered β-FeSi2 was excellent for high-temperature thermoelectric applications.
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小川 一行, 澤口 孝宏, 菊池 武丕児, 梶原 節夫2006 年 70 巻 1 号 p. 25-33
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーHigh resolution transmission electron microscopy revealed that the NbC carbides precipitating in Fe-Mn-Si-based shape memory alloys in the orientational relationship of [100]f//[100]NbC, (001)f//(001)NbC are partially coherent with the matrix showing the misfit dislocations on every five (002)f layers. It was also found that the pre-warm rolling prior to the aging refines the NbC carbides into as small as about 5 nm and makes their distribution homogeneous. It was statistically clarified that the deformation microstructures of the Fe-Mn-Si-based alloys containing finely dispersed NbC carbides exhibit the nano-sized mono-partial stacking martensite plates, similar to those of the conventional Fe-Mn-Si-based alloys subjected to the training treatment. These microstructural features are considered to improve the shape memory properties of the alloys.
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權 湧宰, 小橋 眞, 金武 直幸2006 年 70 巻 1 号 p. 34-42
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーTiB2 particle reinforced Cu matrix composites were fabricated by a combustion reaction between Ti and B in a Cu-Ti-B system. Addition to the fabrication of the composite, its bonding with 1050Al alloy were successfully carried out in a single-step process by using the high heat of the combustion reaction. When the combustion synthesis of Cu-50 vol%TiB2 was attempted, a minute quantity of unfavorable Cu3Ti was formed with TiB2 in the Cu matrix. However, for Cu-60 vol%TiB2, only fine TiB2 particles below 4 μm in diameter were formed in situ, and homogeneously distributed in the Cu matrix. Also for Cu-70 vol%TiB2, the combustion reaction occurred completely without forming any unfavorable phases, although some Cu was evaporated during synthesizing the composite. In a Ti-B binary system, any reaction was not generated in the temperature range from room temperature to 1473 K. However, in the Cu-Ti-B ternary system, the combustion reaction was generated near the melting point of Cu, suggesting that it was activated by molten Cu. Preheating before inducing the combustion reaction was effective in bonding with long Al rods and also in reducing bonding defects. Intermetallic compounds consisting of Al, Cu and Ti were observed with unreacted B in the bonded layer. For the bonded specimen with a Cu insert layer, a eutectic microstructure of Al and Cu was formed between the Al alloy and Cu insert, and unreacted B was observed with a compound of Cu and Ti between the composite and Cu insert. The bonding strength was improved by inserting the Cu layer and by preheating. The bonded specimen with no insert layer was fractured between the composite and the Al alloy. By inserting the Cu layer with preheating, the fracture occurred between the Al alloy and the Cu insert.
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三宅 正男, 平松 智明, 前田 正史2006 年 70 巻 1 号 p. 43-46
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーThe removal of phosphorus and antimony from molten silicon under low vacuum conditions has been investigated by using a glow discharge electron gun. The gun could generate electron beam and melt silicon at the low vacuum of 5-7 Pa. Phosphorus and antimony in silicon were evaporated and removed from silicon by the electron beam melting: the concentration of phosphorus decreased from about 200 ppm to about 1 ppm in one hour and that of antimony was reduced from about 300 ppm to below 0.1 ppm in 5 minutes. The removal rates obtained at the low vacuum were almost the same as those observed under high vacuum conditions.
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小林 敏治, 原田 広史, 張 建 新2006 年 70 巻 1 号 p. 47-50
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーNi-base superalloys require a multi-step heat-treatment to be used in practice, which includes solution heat-treatment and 2 step aging. The size and form of the γ′ precipitates, which strengthen the superalloys, strongly depend on the first step aging condition. A relationship exists between the sizes of the γ′ precipitates and creep strengths, which exhibits a creep condition dependence. In this paper, the effects of the first step aging condition on the size and the form of γ′ precipitates and creep strengths are examined for TMS-26, a first generation Ni-base single crystal superalloy. The results showed that, in 1100°C-137 MPa creep, the initial microstructure should be kept in coherency for increased creep strengths. On the other hand, in 900°C-392 MPa creep, a relatively high first step aging temperature was found to be effective for increasing creep strengths. It was concluded that increasing the first step aging temperature is effective for the improvement of creep strengths, given that coherency is kept in the initial microstructure.
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三浦 永理, 田原 竜夫, 劉 杰, 田中 康弘, 白石 孝信, 久恒 邦博2006 年 70 巻 1 号 p. 51-58
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーCross-sectional microstructure observation of the titanium firing porcelain inserted ion-coated gold layer was performed by SEM-EDS that can analyze light elements from boron. Two gold-coated samples applied to mirror finished titanium surface were prepared; one was applied only degassing treatment, and the other was applied firing after degassing treatment. Effect of gold coating on interfacial layer formation was investigated and discussed by the comparison with titanium/porcelain interface without gold coating. From SEM-EDS observation of the specimen, approximately 2.5 μm thickness titanium oxide layer appeared across the gold film in the degassed sample. In the titanium firing porcelain after degassing treatment, two obvious reaction layers appeared across the gold coating. One included mainly titanium and oxygen, and another included titanium, oxygen, gold and aluminum. A firing process and gold layer affected thickness of the reaction layers. Titanium/porcelain without gold coating had two reaction layers at the interface, however, many cracks and crevices appeared in the layer and between the layers. Thickness of the reaction layers decreased by gold coating, and cracks and crevices in the layer disappeared. The results suggested that titanium diffusion became lower due to gold coating, and titanium-gold reaction changed layer's microstructure. Subsequently it was suggested gold coating on titanium contributes to improvement of adhesion between titanium and porcelain due to these mechanism.
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淡路 英夫, 松永 拓也, Seong-Min Choi2006 年 70 巻 1 号 p. 59-66
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーIn order to improve the fracture toughness of ceramics, we need to develop a new material design concept. One of the suitable concepts is to utilize dislocation activities even in brittle ceramics. Intra-type nanocomposites use dislocation activities to enhance the strength and fracture toughness. The dislocations are caused by sintering residual stresses around the second-phase nano-particles dispersed within the matrix grains. In this research, first, we clarified the relation between the strength, fracture toughness, and critical frontal process zone (CFPZ) size using alumina ceramics. The fracture toughness of ceramics is related closely to the CFPZ size, because ceramics with larger CFPZ size consume higher fracture energy during crack extension and indicate larger fracture toughness. Second, we fabricated toughened alumina-nickel nanocomposites using a soaking method which we developed recently to create an intra-type nano-structure, and found that the suitable annealing after sintering could achieve toughened nanocomposites. Finally, we discussed the relation between the fracture toughness and CFPZ sizes of the monolithic alumina, as-sintered nanocomposites, and annealed nanocomposites. The results revealed that the annealed nanocomposites had the highest CFPZ size and fracture toughness, because it was conceivable that the sessile dislocations in the CFPZ became nuclei of nano-cracks, created many nano-cracks, and expanded the CFPZ size.
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木村 隆, 粟根 徹, Ke Wai Gao, Lijie Qiao, 橋本 健紀2006 年 70 巻 1 号 p. 67-72
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーThe surface of an L10-type TiAl base alloy has been modified by coating it with an L12-phase (AlMn)3Ti(V) using a pack-cementation method in a temperature range of 1273-1473 K and with a treatment time of 18-72 ks. The structural morphology and composition distribution in the coat and substrate were analyzed by EPMA and XRD to examine the factors that control the thickness of the coat. Two-phase equilibrium was confirmed between the L10-phase substrate and the L12-phase coat at each temperature tested. Aluminum particulates, 1-2 μm in diameter, were observed inside the coat and were confirmed to be related to the experimental condition and to the increase in coat thickness. The coat is 35 μm thick at temperature range of 1373-1473 K, while at the temperature range of 1273-1323 K the thickness is 11-12 μm. The temperature dependence of coating layer is different from that was reported previously. The results are then discussed from facts basically revealed in this experiment and/or based on information about the phase equilibrium between L10 and L12.
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町田 純一, 江阪 久雄, 田村 学, 篠塚 計2006 年 70 巻 1 号 p. 73-79
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーThe Sn-Cu binary eutectic alloy is one of candidate alloys for lead-free solder. In order to investigate the evolution of solidified structure of Sn-Cu binary eutectic alloy, the unidirectional solidification technique has been applied using a Bridgman type furnace.
Primary β-Sn exhibits dendrite morphology, on the other hand, a primary Cu6Sn5 indicates a faceted crystal, the cross section of which is typically H-shaped and eutectic structure is rod-like. Coupled growth zone of this alloy system is found to be extended to Cu-rich side and to be rather symmetric. This may be due to the difference in undercooling for growth of Cu6Sn5, β-Sn and eutectic phases. Jackson parameter of Cu6Sn5 is deduced to be high comparing with β-Sn.
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南部 智憲, 清水 信恵, 江崎 尚和, 湯川 宏, 森永 正彦2006 年 70 巻 1 号 p. 80-88
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーThe deformation and fracture modes of pure niobium metal membrane were investigated by a series of hydrogen permeation tests in a highly soluble hydrogen state. The membrane underwent a large plastic deformation due to the lattice expansion and contraction during hydrogenation and dehydrogenation. A crack initiated on the membrane surface under the tensile stress condition, but not under the compressive stress condition. All the fractured sections in the membrane showed the characteristics of quasi-cleavage fracture. However, even in the case of a large amount of hydrogen dissolved into the membrane, it never fractured as far as hydrogen keeps permeating through the membrane at a constant temperature and a constant hydrogen pressure difference between inlet and outlet surfaces. In other words, brittle fracture of pure niobium metal membrane was not caused by the amount of dissolved hydrogen, but by either a rapid change in the hydrogen density in the membrane or a continuous hydrogen dissolution reaction in progress into it.
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坂口 信人, 新家 光雄, 赤堀 俊和, 戸田 裕之2006 年 70 巻 1 号 p. 89-95
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーTi-30Nb-10Ta-XZr alloys were fabricated based on Ti-30Nb-10Ta-5Zr alloy, which was the composition simplified that of Ti-29Nb-13Ta-4.6Zr alloy for biomedical applications. The tensile deformation mechanisms of Ti-30Nb-10Ta-XZr alloys (X: 0, 3, 5, 7 and 10%) were then investigated.
The plastic deformation mechanisms of Ti-30Nb-10Ta-XZr alloys during tensile loading change with changing Zr content. Microstructure of Ti-30Nb-10Ta alloy without Zr after tensile test shows a stress-induced transformation of β phase. In Ti-30Nb-10Ta alloy, the plastic deformation mechanism is mainly dominated by the stress-induced transformation of β phase. Microstructure of Ti-30Nb-10Ta-3Zr alloy after tensile test shows a stress-induced transformation of β phase and many dislocations in β phase. In Ti-30Nb-10Ta-3Zr alloy, the plastic deformation mechanism is mainly dominated by the stress-induced transformation of β phase and slip. Microstructures of Ti-30Nb-10Ta-XZr alloys (X: 5, 7 or 10%) after tensile test show many dislocations in β phase. In these alloys, the plastic deformation mechanisms are mainly dominated by slip. The elastic deformations of Ti-30Nb-10Ta-XZr alloys (X: 3, 5 or 7%) do not depend on Hooke's law. The maximum recovery strains of these alloys increase with increasing the total strain.
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雲 暁勇, 本橋 嘉信, 伊藤 勉, 浅野 俊之, 平野 聡2006 年 70 巻 1 号 p. 96-105
発行日: 2006年
公開日: 2006/01/25
ジャーナル フリーA cyclic neutral-salt spray test, CCT, has been applied to friction-stir-welded A7075 and A6N01 aluminum alloys and corrosion behavior in each region of stirred-zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM) in the joints are studied. Weight loss, appearance of corroded regions, depth of corrosion and so forth were examined by means of optical and scanning electron microscopies and violet laser color 3D profile microscope. Energy dispersive X ray spectroscopy, EDS, analysis was made on SZ, TMAZ, HAZ and BM regions of the joints. It was found that the region of the TMAZ/HAZ boundary and around it was most susceptible to corrosion among the four regions in both of the FSWed A7075-T6 and A7075-O alloys. The EDS result showed that Cu might be enriched in the TMAZ/HAZ region. It seemed that a main cause of the susceptibility to corrosion in the TMAZ/HAZ region was due to the formation of the second phase particles containing Cu in them in the region. We presumed that the Cu atoms migrated from SZ to TMAZ/HAZ during FSW process that brought about sharp temperature and internal stress gradient in the alloy, which would lead to the enrichment of Cu in the TMAZ/HAZ region. Meanwhile, the FSWed A6N01-T5 alloy showed excellent corrosion resistance under CCT for 1000 h.
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