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65 巻, 12 号
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山田 毅, 佐藤 広明, 都筑 隆之2001 年 65 巻 12 号 p. 1045-1052
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーSprayed preforms were fabricated with Ti-4.5Al-3V-2Mo-2Fe alloy (SP-700) powder of 23∼53 μm diameter instead of conventional powder of 23∼150 μm diameter to make the microstructure of the sprayed deposit fine. SCS-6/SP-700 composite made of the improved sprayed preforms (improved spray composite) showed superplasticity in the tensile direction perpendicular to the fiber with a maximum m-value of 0.58 at 1048 K. The tensile flow stress of the improved spray composite was a little lower than that of SCS-6/SP-700 composite made of woven preforms. Tensile strength at room temperature of the improved spray composite after deformation was comparable to that of the improved spray composite before deformation. Stringer- and blade-shaped TMC part models are demonstrated to be successfully superplastic-formed. No debonding defects at fiber/matrix interface were observed in the blade-shaped model using the improved spray composite.抄録全体を表示PDF形式でダウンロード (1323K) -
久保田 健, 岡崎 禎子, 古屋 泰文2001 年 65 巻 12 号 p. 1053-1056
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーFe-29.6 at%Pd ferromagnetic shape memory alloy (FSMA) ribbons formed by rapidly solidified, melt-spinning methods, is expected to be useful as a new type of material which shows giant magnetostriction as well as a quick response. The giant magnetostriction in the rolling direction, which is caused by movement and re-arrangement of martensite twin boundaries, depends strongly on applied field direction and has a maximum value of 8×10−4 when applied magnetic field is normal to the surface. Such a directional dependence is probably caused by fine columnar microstructure formed by rapid solidification methods. To confirm this hypothesis, we analyze magnetostriction, magnetic property and crystal structure of Fe-29.6 at%Pd bulk sample before rapid solidification and compare these properties with those of the ribbon sample.
The results show that (1) strength of bulk magnetostriction is 1/10 of that of the ribbon sample, (2) the coercive force of ribbon sample has strong directional dependency, while the coercive force of bulk sample is isotropic indicating isotropic distribution of twin boundaries, (3) X-ray diffraction of bulk sample shows that the diffraction peaks due to martensite phase with fct structure are weak and those due to bcc structure are strong. From these results, it can be concluded that remarkable anisotropy of giant magnetostriction of ribbon sample is caused by the fine structure formed by the melt-spinning method. It may be possible to apply this method successfully to other FSMA and Ni2MnGa, which is difficult to manufacture owing to its brittleness.抄録全体を表示PDF形式でダウンロード (339K) -
王 栄光, 竹田 睦, 向井弘 治, 木戸 光夫2001 年 65 巻 12 号 p. 1057-1065
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーThe morphologies of micro-drops of pure water on natural mica and SUS304 steel surfaces were observed with an AC non contact mode of the atomic force microscope. Shape changes of micro-drop pure water over time were also observed in situ. The surface elements before wetting were examined by X-ray photoelectron spectroscopy. The potential for accurate shape measurements and the stability of micro-drop pure water are discussed.
Micro-drop pure water observations carried out with the AC non contact mode of the atomic force microscope demonstrated that the morphologies on natural mica and SUS304 steel surfaces were different. Four morphological types of micro-drop pure water on mica were identified; they comprised semi-sphere, lump, film and assembly. Groups of semi-spheres were the most common. The morphology of micro-drop pure water on the SUS304 steel surface was fairly irregular. The difference might be related to the difference in surface roughness-smooth for natural mica and rough for SUS304 steel. Water droplets on both mica and SUS304 steel remained stable for more than six hours, whereas macro-drops evaporated in a few minutes. The authors speculate that the water vapor pressure is equilibrated near the surface of the micro-drop pure water and the mica or SUS304 steel specimen. To fully evaluate the micro-drop water wetting behavior on materials, a micro-order smooth surface and contact angle lower than 90° will be required.抄録全体を表示PDF形式でダウンロード (1425K) -
目黒 奨, 大橋 修2001 年 65 巻 12 号 p. 1066-1072
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーDiffusion joining processes of FZ silicon single crystals were carried out in order to study influence of oxide at joining surface. Relationship between joining conditions and mechanical properties, fracture morphologies, surface composition, cross section microstructure, and electric resistance were investigated.
Joining surface of FZ silicon blocks were treated by hydrofluoric acid, RCA process, and thermal oxidation. Diffusion joining processes were held in air and vacuum atmosphere. Mechanical properties of joints were investigated by 4-point bending.
Joining at air atmosphere and oxide film at joining interface cause larger bending strength. Fracture morphologies observation of joints give suggestion that oxide film decreases interface fracture area. Auger electron spectroscopy of treated surfaces were carried out in order to study behavior of oxide. On RCA processed specimen, oxygen concentration decreases by heating over 1073 K. This result shows probability that thin oxide film disappears from joining interface. Scanning electron microscopy observation of fracture surfaces show that joints with thermal oxide film break at interface between silicon and oxide film. Transmission electron microscopy observation of cross sections shows that thermal oxide film is amorphous and interface between silicon and oxide is flat. Electric resistance of joints with thermal oxide film decreases at higher joining temperature.抄録全体を表示PDF形式でダウンロード (1138K) -
高木 周作, 井上 忠信, 津 兼彰, 南 二三吉2001 年 65 巻 12 号 p. 1073-1081
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーThe parameters for levels of the evaluation of hydrogen embrittlement susceptibility of high strength steel, which are independent of stress concentration and applied stress, are examined using circumferentially notched round-bar specimens with different notch root radius. The hydrogen embrittlement tests are performed for quenched and tempered JIS SCM440 steel with the tensile strength of 1403 MPa. The applied stress is changed from 0.33 to 0.72 times the tensile strength of the notched specimen and the stress concentration factor (Kt) ranges from 2.1 to 6.9. The initiation of hydrogen-induced crack is detected by acoustic emission measurement. Specimens are unloaded immediately after detecting the first acoustic emission and the crack initiation points are observed with SEM. The results are summarized as follows.
(1) The Weibull stress (σW) and diffusible hydrogen contents in fracture process zone (Hc*(ave.)) enable the hydrogen embrittlement susceptibility evaluation independently of stress concentration and applied stress levels of circumferentially notched round-bar specimens.
(2) Initiation points of hydrogen embrittlement fracture are located in the region where the maximum principal stress exceeds 0.8 times its peak value.
The significance of hydrogen embrittlement susceptibility evaluation using the σW-Hc*(ave.) relation is discussed in terms of the extent of fracture process zone ahead of the notch root.抄録全体を表示PDF形式でダウンロード (802K) -
高木 周作, 井上 忠信, 津 兼彰, 南 二三吉2001 年 65 巻 12 号 p. 1082-1090
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーAn experimental method to obtain the shape parameter m in the Weibull stress for evaluation of hydrogen embrittlement (HE) was examined in a commercial JIS SCM440 steel with the tensile strength of 1403 MPa. The stepwise HE tests were performed by using circumferentially notched round-bar specimens with the stress concentration factor of 4.9 after hydrogen pre-charging and homogenization treatments. The applied stress of the first step loading was set at 702 MPa and the stress increment from the second step was 14 MPa. The holding time was over 12 h for the first step and over 2 h for each step from the second step. It was conformed by acoustic emission measurement that the first cracking and final fracture occurred in the same step. The diffusible hydrogen content was measured by thermal desorption analysis immediately after fracture. The distribution of stress and hydrogen content near notch root was calculated by FE-analysis. By this procedure, it was able to obtain the distribution of critical Weibull stress under the condition that the local diffusible hydrogen content in fracture process zone was constant. The shape parameter m was determined to be 46 for the present steel. In the discussion part, it was confirmed that the evaluation of the HE susceptibility based on the local approach is appropriate and it was pointed out that the hydrogen content distribution in the fracture process zone must be taken into account for evaluating the HE.抄録全体を表示PDF形式でダウンロード (553K) -
李 景求, 姜 昌汐, 李 道宰2001 年 65 巻 12 号 p. 1091-1095
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーThis study examined the effects of 0.5 mass%Zn addition to a Sn-57 mass%Bi solder on the interfacial and mechanical properties of the solder joint with Cu substrate. The shear strength was measured by modified double lap shear joint model. Creep tests were performed at 10 MPa and 80°C.
The shear stength of the solder/Cu joint was found to decrease with aging treatment. Rapid decrease in shear strength of the Sn-57 mass%Bi/Cu joint was noticed in the aged specimen. This seems to be caused by crack growth between a reaction layer and a Cu substrate. At the tension test after aging treatment, the failure of joint was dependent upon existence of crack in the intermetallic compound layer. When the crack existed in the intermetellic compound layer, fracture occurred at the interface of Cu and intermetallic compound. By Zn addition in the Sn-Bi system, the fracture occurred at the interface of the solder and the inermetallic compound. In the Sn-Bi system, however, the crack under creep test was popagated in the solder with regardless existence of crack in the intermetallic compound. In the Sn-Bi-Zn system, the crack was popagated through the interface of the solder and the reaction layer.抄録全体を表示PDF形式でダウンロード (1078K) -
中東 潤, 吉村 博文2001 年 65 巻 12 号 p. 1096-1103
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーTo study the structural characteristics and superplasticity of ultra-fine grained α+β type Ti-6Al-4V titanium alloys obtained through protium treatment (protium absorption-quenching-hot rolling-protium desorption), observation of the structure and each grain orientation using a scanning (SEM) and a transmission electron microscope (TEM), and superplastic tensile tests in vacuum were carried out. The temperature and initial strain rate dependences of flow stress and elongation in ultra-fine grained Ti-6Al-4V alloy were investigated. The structural changes after testing were also observed using an optical microscope. Experimental results are as follows: according to the observation of ultra-fine grained materials using TEM, most grains were between 0.3 and 0.5 μm with high angle boundaries. When the superplastic properties of the materials with each grain size were investigated, the temperature at which ultra-fine grained materials showed maximum elongation was lower than those of coarse- and fine-grained materials. The ultra-fine grained material exhibits a huge elongation more than 9000%, the higher value than any metallic material, at the temperature of 1123 K and a strain rate of 1×10−3 s−1. Observation of microstructure in the coarse-grained material after tensile testing revealed that many voids appeared at the early stages of deformation. In the case of ultra-fine grained materials, voids don’t appear until growing into coarse grain. This is considered to be one of the factors explaining the huge superplastic elongation.抄録全体を表示PDF形式でダウンロード (1010K) -
河野 亮, 山田 毅, 藤原 力, 福島 明, 廣田 雅, 河内 幸雄2001 年 65 巻 12 号 p. 1104-1107
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーContinuous fiber reinforced titanium matrix composites (TMCs) are attractive for aerospace structures because of their high specific properties and a high temperature capability. Particularly, when a fan rotor ring is circumferencially reinforced with the unidirectional TMCs, much of weight saving is expected, because the ring is able to carry the high hoop stress. In this paper, manufacturing process and properties of TMC ring are investigated.
The TMC ring was produced by the following process: A fiber was wound onto a core ring, and then matrix metal was sprayed onto the fiber by low pressure plasma spraying. The surface of the sprayed preform was smoothed by grinding. The fiber winding, plasma spraying and machining were repeated to produce a five-layered TMC ring preform. The preform was consolidated to obtain a full dense ring by hot isostatic pressing. The ring was finished to the designated dimension by machining.
To examine the quality of TMC ring, the matrix of the TMC ring was dissolved chemically and fibers were extracted. A lot of fiber breakage was observed on the etched TMC ring surface, and a possible cause of this breakage is indicated.抄録全体を表示PDF形式でダウンロード (681K) -
伊藤 義康, 安藤 秀泰, 須山 章子, 新藤 尊彦2001 年 65 巻 12 号 p. 1108-1112
発行日: 2001年
公開日: 2008/04/24
ジャーナル フリーTungsten/copper coatings were developed by using plasma spraying for electric arc resistant coatings. However, the thermal and electrical properties of thermal sprayed coatings were not clarified. Two kinds of free-standing tungsten/copper coatings, which were sprayed by an atmospheric plasma spraying (APS) and a low pressure plasma spraying (LPPS), were machined from the thick coatings. The thermal conductivity, electric resistivity and specific heat were measured at room temperature. The experimental results suggested that the volume fraction of tungsten or copper, porosity and oxide content had important effects on the thermal and electrical properties. Namely, the high thermal conductivity and the low electric resistivity could be obtained from the tungsten/copper coatings sprayed by LPPS process, because of the low porosity and the low oxide content.抄録全体を表示PDF形式でダウンロード (512K)
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