巻号一覧
67 巻, 9 号
選択された号の論文の21件中1～21を表示しています
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多根 正和, 市坪 哲, 武田 亮, 平尾 雅彦, 池田 輝之, 中嶋 英雄2003 年 67 巻 9 号 p. 417-419
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーWe measured the anisotropic elastic constants of a lotus-type porous magnesium, which possesses cylindrical pores aligned unidirectionally. We used the combination of resonant ultrasound spectroscopy and electromagnetic acoustic resonance methods to determine a complete set of the elastic constants. The acoustic measurements revealed that lotus magnesium shows hexagonal elastic symmetry with the c-axis along the longitudinal direction of the pores. Young’s modulus E\varparallel parallel to the pore direction decreases linearly with porosity, while the normal Young’s modulus E⊥ drops rapidly.抄録全体を表示PDF形式でダウンロード (311K) -
池田 勝彦, 中村 祐一郎, 高濱 直哉2003 年 67 巻 9 号 p. 420-423
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーIn Ti-50 mass%Ta-0, 10 and 20 mass%Zr alloys, the effect of Zr content on phase constitution in solution-treated and quenched state (STQed state) and isochronal heat treatment behavior was investigated through electrical resistivity and Vickers hardness measurements and X-ray diffractometry. Orthorhombic martensite α″ phase was identified in STQed Ti-50Ta-0Zr alloy, β phase was identified in STQed Ti-50Ta-20Zr alloy and α″ and β phases were identified in STQed Ti-50Ta-10Zr alloy. On isochronal heat treatment, resistivity at liquid nitrogen temperature and resistivity ratio increased at 573 K and 423 K in Ti-50Ta-0Zr and -10Zr alloys, respectively. These increases are due to reverse-transformation of α″ to metastable β phase. In shape-recovery test, the bent Ti-50Ta-10Zr specimen started to recover toward original shape from 473 K heat treatment and shape-recovery ratio became about 90% by heat treatment at 573 K.抄録全体を表示PDF形式でダウンロード (365K) -
和田 仁, 尹 景田, 吉田 征治, 石原 公司, 棚瀬 繁雄, 境 哲男2003 年 67 巻 9 号 p. 424-427
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーWe have prepared Ag-Fe-Sn composite alloy powders as anode material for lithium-ion batteries using mechanical alloying method. These powers with a size of several micrometers are mainly composed of β-Sn, Ag3Sn, and Fe phases. The experimental results revealed that a rational substitution of Fe for Ag induced a significant improvement of the cycling performance of the ternary alloy electrodes. Some ternary alloy electrodes were found to be capable of keeping a reversible capacity of 270 Ah/kg over 300 cycles, which were better than that of the Fe-free binary alloy electrodes. The structural changes of the Ag26Fe26Sn48 electrode during charge-discharge cycling were examined by X-ray diffraction analyses. The results reveal that the composite alloy consisting of β-Sn and Ag3Sn phases transforms mostly into that of ternary lithiated phase during Li insertion, and recovers to one involving β-Sn, Ag3Sn and residual Ag2LiSn or AgLi2Sn phases after Li extraction. In this type of lithiation/delithiation process, the composite alloy electrode suffers from a moderate volumetric variation, which is beneficial for the improvement of the cycle life.抄録全体を表示PDF形式でダウンロード (487K) -
石川 恵子, 北城 弘樹, 井野 博満, 中島 謙一, 原田 幸明2003 年 67 巻 9 号 p. 428-431
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーCement industry accepts many kinds of wastes from other industries, and contributes to prolong the garbage dump life. It is one of the important roles of cement and concrete industry. From the aspect of circulation, however, it is questionable, because we postpone the problem of wastes. For finding a solution for this problem, it is essential to evaluate the environmental impacts of cement production. The aim of this study is to evaluate the effect of use of wastes and by-products to cement production. In this study, we used three methods for the evaluation: LCA (Life Cycle Assessment), exergy analysis, and TMR (Total Materials Requirement).
Ecocement production is evaluated as an example in this study. Besides, a presumed cement production process, in which the wastes used in cement industry are accepted in average, is evaluated. The treatment of disposal was insufficient in conventional LCA. It considered only the environmental load accompanied by energy consumption when the used products are transferred and wasted. In contrast, “zero emission” type system boundary is used in our LCA, in which disposal of materials is assumed to be in completely harmless substances. Moreover, the environmental impacts are evaluated by exergy analysis, in which a measure of the exergy of wasted materials is calculated as potential impact, and by TMR, in which the amounts of direct and indirect materials engaged by mining and discarding of the products are estimated.抄録全体を表示PDF形式でダウンロード (328K) -
西本 明生, 中尾 和祺, 赤松 勝也, 池内 建二2003 年 67 巻 9 号 p. 432-435
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーThe bonding of SiC (pressureless-sintered silicon carbide) and Cu (oxygen-free copper) with a Ti intermediate layer was carried out using pulsed electric-current sintering. The influences of the intermediate layer on the bond strength and the microstructure of the joint were then investigated by SEM and TEM observations. The bonding conditions were varied between 923-1173 K for 1.8-3.6 ks under a constant bonding pressure of 24 MPa. The bond strength of SiC to Cu with a Ti intermediate layer showed marked improvement, whereas the direct bonding without an intermediate layer resulted in the separation of SiC from the Cu specimen immediately after the bonding operation without any application of external load. TEM observations of the joint interface with the Ti intermediate layer revealed that a TiC layer ∼300 nm thick and a Cu solid-solution layer ∼70 nm thick had covered most of the interface, with the Cu layer formed between the TiC layer and the SiC matrix.抄録全体を表示PDF形式でダウンロード (688K) -
伊澤 寛之, 池田 祐哉, 青代 信, 太刀川 恭治, 竹内 孝夫2003 年 67 巻 9 号 p. 436-439
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーThick (Nb, Ta)3Sn layers with excellent high-field performance are synthesized through the reaction between Ta-Sn powder core and Nb (Nb-Ta) sheath. Preparation of fine and uniform size Ta powders plays a key role in the fabrication of filamentary (Nb, Ta)3Sn conductors. In this study, Ta hydride (TaH) is used as a starting material to prepare fine Ta powder. TaH flakes are crushed into powders by a ball mill (BM) in Ar atmosphere. Commercial −325 mesh Ta powders so far used contain large particles ∼20 μm in diameter, the average particle size being 1.7 μm. Meanwhile the TaH(BM) powder is much finer and more uniform, the average particle size being 0.46 μm. The TaH(BM) and −325 mesh Ta powder are mixed with −325 mesh Sn powder, and reacted at 950°C for 10 h in vacuum to synthesize Ta-Sn core powder. In this treatment the dehydrization of TaH(BM) may proceed simultaneously. These powders are encased in Nb-4 at%Ta tube and fabricated into a mono-core tape. A homogeneous Ta-Sn core is obtained after the fabrication when the TaH(BM) powder is used. Resulting tapes are heat-treated to form (Nb, Ta)3Sn layer. A small amount of Cu addition to the core is effective in reducing the heat-treatment temperature. Transition temperature of the tape does not degrade when the TaH(BM) powder is used. Nearly the same high-field performance is obtained in the TaH(BM) powder core tape as that of −325 mesh Ta powder core tape. The Ta hydride powder seems to be useful in the fabrication of fine filamentary (Nb, Ta)3Sn conductors.抄録全体を表示PDF形式でダウンロード (481K) -
源馬 龍太, 岡田 直樹, 西 義武, 内田 晴久2003 年 67 巻 9 号 p. 440-443
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーHydrogen reactivity of alkaline hydrogen storage materials prepared by ball milling was investigated. Effects of alkaline: Al ratio in starting material on the hydrogen reactivity and their formation of hydrogen reactive phase were also investigated. In Na-Li-Al-H system, reversible formation of Na2LiAlH6 phase is considered to be dominant to react with hydrogen regardless of the alkaline: Al ratio. Existence of LiH and Al in matrix phase possibly improves the reaction kinetics of Na-Li-Al-H system.抄録全体を表示PDF形式でダウンロード (355K) -
桑嶋 孝幸, 高橋 幾久雄, 富田 友樹, 大森 明2003 年 67 巻 9 号 p. 444-447
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーThe thermal spraying technique is used in many industries, for example, the automobile industry and the steel-making industry. However, the process suffers from several problems, because degree of cohesion between particles in the coating may be incomplete. It is very difficult to anneal the coating by heat treatment, because of deformation of the substrate and the hardness of the coatings is less than that of sintered coatings.
An yttrium aluminum garnet (YAG) laser was used during high-velocity oxy-fuel (HVOF) spraying to improve the properties of the applied coating. The spray material was Cr3C2-Ni-Cr, and the substrate was stainless steel (SUS304). The YAG laser was combined with HVOF spraying by irradiating the spraying point on the substrate. The coatings obtained were compared with a coating sprayed by HVOF spraying without the YAG laser.
The hardness of coatings sprayed by HVOF with YAG laser treatment was higher, and the weight loss in a blast-erosion test was smaller, than for comparable coatings applied by HVOF spraying alone. The particles deposited in the coatings obtained by HVOF spraying combined with a YAG laser were shown to be very fine. Laser irradiation to the HVOF flame results in strong adhesion between particles, and the deposition of fine carbide particles in the coating.抄録全体を表示PDF形式でダウンロード (566K) -
古畑 肇, 大橋 修2003 年 67 巻 9 号 p. 448-451
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーThe pulse electric current bonding (PECB) process, also called plasma-activated sintering (PAS) or spark plasma sintering (SPS) by some researchers, has received much attention as one of the most advanced materials bonding processing in recent years.
To clarify the characteristics (bonded area, strength, inclusion ratio, electrical resistance and so forth) in the PECB process, the effects of surface roughness were investigated using SUS304 stainless steel with no interlayer materials.
The following results were obtained. When the surface was smooth, tensile strength of the joint was high and deformation of the joint was small. But focusing on the bonded area, when the surface was rough, the contact area was heated locally, and the temperature was higher than the average temperature of the joints. As a result, the amount of inclusion was small in the bonded area, and the bond quality was better.抄録全体を表示PDF形式でダウンロード (589K) -
小川 俊文, 春山 繁之, 貝田 博英, 上西 研, 関根 務, 森田 茂隆2003 年 67 巻 9 号 p. 452-455
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーAlthough many investigations on the mechanical properties of aluminum alloy castings have been performed, there have been few investigations that make positively good use of the effect of impurities-reduction. In this study, the influence of impurities on the tensile properties of aluminum alloy casting has been investigated by using aluminum alloy castings of different purity.
Al-Si-Mg alloy castings were melted by cold-crucible furnace using the commercial high-purity metals. The chemical composition of the melted aluminum alloy casting was same as that of JIS AC4CH. The melted aluminum alloy castings have no strontium modification. Solution treatment and age hardening treatment of the ingot was performed in atmosphere. After the heated treatment, the test pieces for tensile test ware made by machine. Quasi-static and impact tensile test were performed in atmosphere at room temperature. The usual AC4CH-T6 which has strontium modification was used for comparative material.
In both cases of quasi-static and impact tensile tests, the tensile strength of Al-Si-Mg alloy casting melted by cold-crucible furnace was lower than that of usual Al-Si-Mg alloy casting by about some percents and the elongation of Al-Si-Mg alloy casting melted by cold-crucible furnace was bigger than that of usual Al-Si-Mg alloy casting by more than one and half times. Because there was very little difference in dendrite arm spacing and size, shape, distribution of eutectic silicon between the Al-Si-Mg alloy castings used in this experiment, it is expected that the impurities-reduction is very effective to improve the tensile properties of aluminum alloy casting (AC4CH) from these results.抄録全体を表示PDF形式でダウンロード (582K) -
福山 誠司, 孫 東昇, 張 林, 文 矛, 横川 清志2003 年 67 巻 9 号 p. 456-459
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーHydrogen environment embrittlement (HEE) of type 316 series austenitic stainless steels was investigated in the temperature range from 300 to 80 K. Hydrogen showed a marked effect on the tensile properties of type 316, 316L and 316LN stainless steels. HEE increased with decreasing temperature, reached a maximum at around 200 K and decreased rapidly with decreasing temperature down to 80 K. Sensitization enhanced HEE and decreased a temperature immune to HEE. It was suggested that HEE of the type 316 series stainless steels from 300 K to the maximum HEE temperature depended on the transformation of strain-induced martensite and the behavior below the maximum HEE temperature depended on the diffusion of hydrogen.抄録全体を表示PDF形式でダウンロード (539K) -
張 林, 文 矛, 福山 誠司, 横川 清志2003 年 67 巻 9 号 p. 460-463
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーHydrogen environment embrittlement (HEE) of carbon steels (SUY, S15C and S35C) was investigated at the temperature range from 300 to 100 K with the strain rate of 4.2×10−5 s−1 by using specially designed equipment. The results obtained are as follows.
(1) HEE increased with decreasing temperature, reached a maximum at around 200 K, and then decreased rapidly with decreasing temperature. HEE of the materials increased in order of SUY, S15C and S35C at 200 K. The minimum HEE temperature of S35C was higher than that of S15C and SUY.
(2) Hydrogen induced cracking on the surface of the specimen enhanced cleavage fracture. It is considered that HEE of the carbon steels from 300 K to the maximum HEE temperature depended on the sensitivity of the cleavage fracture and the behavior below the maximum HEE temperature depended on the diffusion of hydrogen.抄録全体を表示PDF形式でダウンロード (429K) -
佐野 昌紀, 我山 武史, 井野 博満, 中島 謙一, 原田 幸明2003 年 67 巻 9 号 p. 464-467
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーAlthough Life Cycle Assessment (LCA) is used as an important method of evaluating environmental loads of a product or technology, it is difficult in conventional LCA to evaluate the effect of discarding appropriately. It is because there is a problem in setting of the system boundary of waste disposal. It is not taken into account that the waste which is reclaimed into land does influence to environment over many years by the reaction with the atmosphere or rain water. Recently, it is proposed to set the system boundary of a zero emission type that presumes the processing of harmlessness technologies of waste. In this study, we simulated the car disposal system as an example based on the system boundary of zero emission. As a result, the environmental loads for the vehicle system in this assessment are much larger than those in the conventional LCI. Besides, the environmental loads when the Pb-Sn plating steel board for the fuel tank was substituted for the Zn-Sn-Ni plating one were compared with the case by the old model. In the evaluation by old model, the effect of decrease in the environmental loads due to the heavy metal substitution was as low as 0.01 kg of CO2 in the disposal stage. On the other hand, it counted 0.38 kg in the evaluation based on virtual processes of harmlessness technology. It is concluded that the influence of a heavy metal on the environment was properly estimated by using the system boundary of a zero emission type.抄録全体を表示PDF形式でダウンロード (381K) -
小泉 裕, 張 建新, 小林 敏治, 横川 忠晴, 原田 広史, 青木 祥宏, 荒井 幹也2003 年 67 巻 9 号 p. 468-471
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーA single crystal superalloy with a superiority in creep strength to the fourth generation single crystal (SC) superalloys has been developed. Following the guideline given by our alloy design program, Mo was added to one of our fourth generation SC superalloy, TMS-138, to change its lattice misfit toward larger negative (aγ>aγ′). In a superalloy with larger negative lattice misfit, enhancement of rafting and formation of finer dislocation network at the γ⁄γ′ interface is expected. Ru was also added to suppress the formation of TCP phases which is expected with the Mo addition. The designed superalloy, TMS-162, was cast to SC bars, solution and aging heat-treated, and tested in terms of creep at 137 MPa and at 1100°C.
The temperature capability of the creep rupture strength in the TMS-162 was found to be about 20°C higher than that of our fourth generation SC alloy, TMS-138. It was confirmed by transmission electron microscope observation that the misfit dislocation network generated on the γ⁄γ′ interface in the rafted structure was finer in the new generation SC alloy, TMS-162, than in the fourth generation SC alloy, TMS-138, as designed. We concluded that the finer dislocation network increases the stress required to for dislocations to cut into γ′ phases and makes the creep strength higher.抄録全体を表示PDF形式でダウンロード (553K) -
水内 潔, 井上 漢龍, 杉岡 正美, 伊丹 正郎, 齋藤 守, 川原 正和2003 年 67 巻 9 号 p. 472-480
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーTi-aluminides reinforced Ti matrix composites were fabricated from 0.04 mm-thick Ti foils with 0.012 mm- and 0.024 mm-thick aluminum foils, using pulsed current hot pressing (PCHP) process, and the effect of holding temperature on the properties of the composites was investigated. The microstructure of the composite was an alternately laminated structure composed of Ti and reacted layers consisting of Ti-aluminides, and the reacted zones were composed of Ti-aluminides depending on the different holding temperatures. Tensile tests at room temperature revealed that the holding temperature is effective for the mechanical properties (yield stress, elongation and fracture mode) of the composites. The tensile strength and the elongation of the composite fabricated at 1273 K from 0.04-mm-thick Ti and 0.012-mm-thick Al foils showed 810 MPa and 3.64%, respectively, while they are 677 MPa and 3.44% for the composite fabricated at 1173 K. Microstructural observations of fractured specimens revealed that the Ti layers effectively bridged numerous cracks in the Ti-aluminides for the composites fabricated at 1173 K and 1273 K, which contributes to high ductility.抄録全体を表示PDF形式でダウンロード (2322K) -
水内 潔, 井上 漢龍, 杉岡 正美, 伊丹 正郎, 川原 正和2003 年 67 巻 9 号 p. 481-486
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーNi-aluminides reinforced Ni matrix composites were fabricated from 0.05 mm-thick Ni foils with 0.012 mm-thick aluminum foils, using pulsed current hot pressing (PCHP) process, and the effect of holding temperature on the properties of the composites was investigated. The microstructure of the composite was laminated structure composed of Ni and Ni-aluminides. With increasing holding temperature during PCHP, the thickness of Ni-rich Ni solid solution layer increased, while the thickness of Ni matrix layer decreased. Tensile tests at room temperature revealed that the mechanical properties of the composites depended on the holding temperature. The tensile strength and the elongation of the composite fabricated at 1373 K showed 500 MPa and 3.8%, respectively. These mechanical properties of the composite were higher than those by conventional vacuum hot pressing techniques. Microstructural observations of fractured specimens showed that the Ni layers effectively bridged numerous cracks formed in the Ni-aluminides in the composites.抄録全体を表示PDF形式でダウンロード (1146K) -
熊倉 浩明, 松本 明善, 山田 秀之, 平川 正澄2003 年 67 巻 9 号 p. 487-493
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーMgB2 tapes were fabricated using B fibers and Mg powder. B fibers and Mg powder were wrapped with Fe or Ta foils to form tapes and heat-treated at 700-900°C for 2 hours in a vacuum. MgB2 layers were formed around the B fibers for all the tapes, although the cores of the B fibers were remained un-reacted. For the heat treatment temperature of 900°C needle-like Fe2B compound was formed around MgB2 layers when used Fe foils. For the 700 and 800°C, however, no Fe-B compound was formed and only the MgB2 layers were obtained. Broad superconducting transitions with onset temperatures of 27-35 K were observed for Fe foils. In the MgB2/Ta tapes, on the other hand, only MgB2 layer was formed at 900°C and onset Tc of 36 K with sharper transition was obtained. Thus, the lower Tc and broader transitions of MgB2/Fe tapes can be explained by the inclusion of Fe in the MgB2 layers. Jc values at 4.2 K of the MgB2/Fe tapes were ∼109 A/m2 in a zero magnetic field and ∼108 A/m2 in 2 T. These Jc values of the MgB2 tape were comparable to those of MgB2 wires fabricated by heat-treating B fibers under Mg vapor atmosphere, but lower than those of the powder-in-tube processed MgB2 tapes.抄録全体を表示PDF形式でダウンロード (962K) -
由利 哲美, 小野 嘉則, 緒形 俊夫2003 年 67 巻 9 号 p. 494-498
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーTo evaluate material risk caused by human-error, the notch effects on the fatigue properties of forged Ti-5Al-2.5Sn ELI alloys have been investigated at cryogenic temperatures. Smooth and notched specimens with the Kt=1.5, 2 and 3 were prepared. High-cycle fatigue tests were carried out at 4 K (liquid helium), 77 K (liquid nitrogen) and 293 K (room temperature). The S-N curves of each specimen shifted to higher stress level with a decrease of the test temperature. At 4 K, the fatigue strength of the Kt=3 specimens were substantially lower than those of the smooth specimens. Although the notch effects on the fatigue properties of the Kt=1.5 and the Kt=2 notched specimens are not clear or significant. Fatigue crack initiation sites of the smooth and the Kt=1.5 notched specimens were in the specimen interior (internal type fracture) and those of the Kt=2 and the Kt=3 notched specimens were at the notch root (surface type fracture). The location of the fatigue crack initiation sites showed transition from the internal type fracture for the Kt=1.5 notched specimens to the surface type fracture for the Kt=2 notched specimens. Therefore, the Kt values of the internal fatigue crack initiation sites correspond between 1.5 and 2. The sizes of the internal fatigue crack initiation sites were calculated by the \sqrtarea. The \sqrtarea size of the Kt=1.5 notched specimens and smooth specimens were in a similar range and the fatigue strength of the two are not significant.抄録全体を表示PDF形式でダウンロード (828K) -
伊藤 清, 王 峰, 渡辺 徹2003 年 67 巻 9 号 p. 499-505
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーThe structures of Co-W binary alloy films electrodeposited at different bath concentrations and different electrodeposition conditions have been studied in detail by means of XRD and HRTEM. The crystallization sequences of deposited films under the heat-treatment were examined by XRD. The structures of Co-W deposited films were also compared with the Co-W thermal equilibrium phase diagram. The results indicated that the structures of Co-W deposited films gradually change from crystalline to amorphous phase with increasing W content in the deposited films. The deposited film exists as crystalline when the W if below 24.8 at%, whereas it exists as a homogenous amorphous phase when the W is from 25.4 at% to 26.0 at%. Accordingly, the composition of boundary between the crystalline and homogenous amorphous states can be determined at about 25.1 at%W.抄録全体を表示PDF形式でダウンロード (1290K) -
野上 敦嗣, 小関 敏彦, 福田 由佳2003 年 67 巻 9 号 p. 506-513
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーIn order to predict solidification morphology of multi component materials, hybrid computational modeling, which consist of deterministic finite difference method for the heat transfer and the solutes diffusions and stochastic Monte Carlo method for nucleation and crystal growth, was developed to be closely incorporated with computational thermodynamics. This model was found to be capable of simulating the columnar to equiaxed transition (CET) macrostructures of ternary ferritic stainless steels and predicting the solutes concentration dependency of the morphology vary accurately. By using very small finite difference meshes and Monte Carlo cells this model was also found to be capable of representing the development of the dendritic crystal growth of early stage of solidification. These results demonstrated the wide space scale applicability of this model to solidification phenomena. Furthermore, by incorporating stochastic models for solid state transformation, it was attempted to develop computational modeling for simulating more complex solidification morphology involving δ solidification, γ solidification and δ⁄γ transformation.抄録全体を表示PDF形式でダウンロード (1065K) -
林 哲郎, 丸山 俊夫2003 年 67 巻 9 号 p. 514-520
発行日: 2003年
公開日: 2008/04/24
ジャーナル フリーNbAl3 is expected as high temperature material. Industrial NbAl3 alloy is sure to contain the Nb2Al phase, which is severely oxidized, because NbAl3 has very narrow range of the homogeneity. Practical application of this alloy needs to improve the oxidation resistance of two-phase intermetallic alloy of Nb2Al-NbAl3. Six Nb2Al-NbAl3 alloys with 47∼74 mol%Al and identical activity of Al were prepared by arc-melting. The microstructures of these alloys were observed. Isothermal oxidation of them were carried out at 1473 K under Ar+O2(20%) atmosphere.
Four alloys with the composition between NbAl3 and eutectic point have the microstructures of NbAl3 and the eutectic structure, and the others with the composition between eutectic point and Nb2Al have the microstructures of the eutectic structure and Nb2Al. The sample with the higher content of Al exhibits the less areal fraction of Nb2Al. Six alloys show linear oxidation behavior, because the spallation of NbAlO4 occurs on Nb2Al and the eutectic structure from the early stage of oxidation. They had different oxidation rates, and the sample with the higher content of Al exhibits the less oxidation rate. Because Al2O3 is formed on NbAl3 and NbAlO4 is formed on Nb2Al in spite of identical activity of Al at the early stage of oxidation, and the mass gain of Nb2Al is much larger than that of NbAl3, the linear rate constant for the overall oxidation rate is proportional to the areal fraction of Nb2Al, the oxidation behavior of Nb2Al and NbAl3 is independent.抄録全体を表示PDF形式でダウンロード (1371K)
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