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Volume 70, Issue 12
Displaying 1-12 of 12 articles from this issue
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Masae Kanda, Keisuke Itou, Yoshitake Nishi2006 Volume 70 Issue 12 Pages 945-949
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSComposite polymers, which are Nylon6 matrix homogeneously dispersed with aluminum powders, are prepared. To evaluate the brittleness, Charpy impact values are obtained. Although an aluminum addition of 10 vol% tremendously decreases the impact value, excess aluminum additions from 30 to 40 vol% don't largely decrease the impact value. It is explained that cracks easily propagate through the interface between the aluminum powders and polymer matrix because of the weak interface.
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Nobuya Shinozaki, Naoya Satoh, Hiroshi Shinozaki, Kyoko Wasai, Hidenor ...2006 Volume 70 Issue 12 Pages 950-955
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSA new method to obtain experimentally the interfacial free energy between molten iron and graphite has been proposed. A high purity iron was melted on a graphite substrate, and the dissolution of carbon from the substrate to molten iron occurred. The interfacial free energy was measured from the morphological evaluation of the molten iron-graphite interface. This method is different from the conventional method using Young's equation in the point that the surface free energy value of graphite is not required. Moreover, it is possible to measure simultaneously, the graphite surface free energy. This method was confirmed to be useful for measuring the interfacial free energy, because the values obtained in the experiments almost agreed to each other.
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Rongguang Wang, Koji Mukai, Mitsuo Kido, Tarou Tokuda, Fumihiro Suzumu ...2006 Volume 70 Issue 12 Pages 956-961
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSTitanium is used as an implant material for dentures. However, the corrosion caused by fluoride and the low wettability of titanium by saliva are still problems. In this study, the corrosion behavior of pure titanium and its alloy was investigated in aqueous NaF solutions, and the macro-wettability change of pure water on these specimen surface after corrosion is discussed. The passive current density of pure titanium and its alloy tended to increase with increasing NaF concentration. The potential distribution nearby pure titanium surface slightly changed after immediate immersion in the solution, then the value soon became relatively stable. The contact angle ratio ψ, which is the ratio of the contact angle before immersion θ0 to that after immersion θi, decreased with increasing immersion time. Higher surface wettability was observed after more active corrosion, indicating that the progression of corrosion significantly influenced the wettability of these surfaces by pure water. The surface roughness Ra was larger after immersion in 2.0% NaF solution than in 0.1% solution, which might also have influenced its wettability by pure water.
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Mitsuo Kido, Fumihiro Suzumura, Koji Mukai, Tarou Tokuda, Rongguang Wa ...2006 Volume 70 Issue 12 Pages 962-967
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSWettability of a material surface plays a very important role in solid-liquid interaction phenomena used to analyze material surface treatments, soldering, and for the improvement of material properties with surfactant solutions and lubricants.
In this research, the shape of a liquid droplet on a solid surface was studied theoretically following the corrosion of pure titanium and the titanium alloy in NaF solution. In general, the wettability of a material surface is evaluated by the contact angle of the liquid droplet formed on the solid surface. The shape of the liquid droplet was solved with a nonlinear differential equation numerically derived from the Laplace equation. The contact angle of the numerically derived and experimentally measured shape of water droplets was compared.
As a result, the variation in the shape of the water droplet due to surface corrosion might greatly influence the contact angle.
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Akihiro Shibata, Mayumi Suzuki, Tadayoshi Tsukeda, Ken Saito, Kouichi ...2006 Volume 70 Issue 12 Pages 968-974
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSMg-Al-Ca based alloys consist of the α-Mg matrix and continuous eutectic compounds along grain boundaries. Higher coverage of grain boundaries with the eutectic compounds results in high creep resistance. Intragranular precipitation caused by the rare earth (RE) addition is expected to improve creep resistance of the alloy. However, the aging treatment to produce precipitates results in the decreased grain boundary coverage due to the fragmentation of the eutectic compounds. Creep properties of Mg-Al-Ca alloys with and without RE were investigated after several aging treatments to elucidate the optimum condition of the aging treatments. The Mg-Al-Ca-RE alloy was aged at 423, 473, 523 and 573 K for 24 h respectively, and then was subjected to creep tests at 473 K under 100 MPa. The creep strength of the Mg-Al-Ca-RE alloy was higher than that of Mg-Al-Ca alloy due to the precipitates within grains. On the other hand, the creep rate of the Mg-Al-Ca-RE alloy increases with increasing aging temperature due to the fragmentation and spheroidization of the eutectic compounds along grain boundaries. Further improvement of the creep resistance is expected by the distribution of fine precipitates, which is considered to be achieved by the addition of high RE content.
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Hiroki Hatayama, Hiroyuki Yamada, Ichiro Daigo, Yasunari Matsuno, Yosh ...2006 Volume 70 Issue 12 Pages 975-980
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSAluminum demand has faced a significant growth in the last few decades in Japan. For most uses, small amounts of other metals are added to primary aluminum to make harder alloys, which are classified by the alloying elements and their concentrations. Aluminum scraps from end-of-life products, which are used as raw materials for secondary aluminum, are often mixtures of several alloys. Therefore, not only the amount of obsolete scrap generation but also their concentrations of alloying elements must be taken into account for assessing the maximum recycle ratio of aluminum scraps.
In this paper, a dynamic substance flow analysis of aluminum and its alloying elements in Japan was conducted. Focused alloying elements were Si, Fe, Cu and Mn. We categorized aluminum end-uses in 8 categories and aluminum alloys in 16 types. Each amount of alloy used in each end-use category was estimated from statistical data. Then we estimated amounts of the future aluminum scrap generation in 8 categories by population balance model. At the same time, the concentrations of alloying elements in each end-use were calculated.
It was estimated that the amount of aluminum scrap recovery in Japan would be about 1800 kt in 2050, which was 2.12 times as large as that in 1990. Calculated concentrations of alloying elements in scraps were compared with those of measured data, which showed fair correspondence.
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Yusuke Nakagawa, Toshio Itami2006 Volume 70 Issue 12 Pages 981-986
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSThe electrical resistivity of compound forming Bi-Te system in the liquid state was studied by the dc-four probe method. Anomalous behavior around the intermetallic compound Bi2Te3, which was reported in the previous study, was not found. In the present study, anomalous behaviors of the temperature coefficient of the electrical resistivity were found at both two eutectic compositions present in this system. These behaviors were discussed based on the effective medium theory of electrical conduction. It is concluded that the concentration fluctuation at the eutectic composition(90 at%Te) grows in the homogeneous liquid phase with the approach to the eutectic temperature.
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Tutomu Murakawa, A. Toshimitsu Yokobori, Takenao Nemoto, Hideo Miura2006 Volume 70 Issue 12 Pages 987-994
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSThe effect of residual stress on vacancy transportation in Cu interconnection due to electromigration was investigated. An equation of vacancy transportation caused by electromigration coupled with residual stress was proposed. The distribution of vacancy concentration was derived using the computer aided simulation. The hydrostatic stress was calculated by an elastic-plastic finite elemental method. Behavior of vacancy transportation was found to be dominated by the competitive relationship between residual stress and electrical stress in interconnection.
When the residual stress dominantes, vacancy concentrates around the maximum hydrostatic stress region, such as elastic-plastic boundary. On the other hand, when electrical stress is dominant, vacancy do not concentrate around the maximum hydrostatic stress region, but moves from the cathode end to the anode end. These results are in good agreement with the in-situ experimental results conducted in our previous paper.
Based on the result mentioned above, various failure modes in LSI interconnection cased by electromigration are predictable by using the proposed equation.
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Hiroyuki Yamada, Hiroki Hatayama, Ichiro Daigo, Yasunari Matsuno, Yosh ...2006 Volume 70 Issue 12 Pages 995-1001
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSIn this paper an optimization method for metal recycling flow has been developed. The method adopts a linear programming to optimize the recycling of material, in which the concentrations of two or more tramp elements in the scraps are considered.
The method was applied to analyze the aluminum recycle flow in Japan in 2003. It was found that the 65% of virgin material could be substituted by recycled material.
When the use of casting from end-of-life vehicles (ELV) is expanded, Cu included in the aluminum casting will be predominant restriction for the reduction of virgin material. The other side, when the use of aluminum scrap from construction is expanded, the maximum recyclable amount of aluminum scrap is dominated by Mn concentration in the scrap.
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Saburo Matsuoka, Nobuhiro Homma, Hiroyuki Tanaka, Yoshihiro Fukushima, ...2006 Volume 70 Issue 12 Pages 1002-1011
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSWe investigated the effect of hydrogen on the tensile properties of a quench-tempered low-alloy steel, SCM435, with the tensile strength of 930 MPa used for hydrogen storage cylinders. Tensile specimens were machined from a cylinder with the inside and outside diameters of 245 and 315 mm. The specimens were immersed in a 20 mass% aqueous solution of ammonium thiocyanate (NH4SCN) at 313 K for 48 hours and then charged with hydrogen. Tensile tests were performed in the air at room temperature. The cross head speed was ranged from 0.01 to 100 mm/min. Hydrogen-charged specimens were hold in the air for a period of 1 and 300 hours. The 0.2% proof stress and tensile strength for the hydrogen-charged specimens were similar to those for the uncharged specimens, whereas the reduction of area was lower in the hydrogen-charged specimens than in the uncharged specimens. Thermal desorption spectroscopy showed that the residual hydrogen contents in the hydrogen-charged specimens fractured by tensile tests were between 0.14 and 0.93 mass ppm. The reduction of area of the hydrogen-charged specimens decreased linearly with increasing residual hydrogen content. Scanning electron microscopy showed that the cup-corn fracture occurred in the hydrogen-charged and the uncharged specimens and that the fracture surfaces were covered with dimples. The normal stress fracture area in the center of the hydrogen-charged and uncharged specimens was almost the same. The shear stress fracture area near the specimen surface was wider in the hydrogen-charged specimens than in the uncharged specimens. This means that hydrogen enhances slip deformation near the specimen surface and resulted in the lower reduction of area in the hydrogen-charged specimen. We therefore concluded that the hydrogen embrittlement behavior of the 900-MPa-class SCM435 steel was explained by the hydrogen enhanced localized plasticity model rather than by the lattice decohesion model.
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Hitoshi Hayashibara, Masami Mayuzumi, Yoshihiro Mizutani, Jun-ichi Tan ...2006 Volume 70 Issue 12 Pages 1012-1015
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSAustenitic stainless steels (SS) are widely used in various components of chemical plants, nuclear power plants, etc, because of the superior mechanical property and general corrosion resistance. However, it is also well known that austenitic stainless steels are susceptible to localized corrosion in the environments containing chloride ions, and several equipment in the plants built in coastal area has been suffering from chloride induced external stress corrosion cracking (ESCC). Hence, for the establishment of the countermeasures it is very important to clarify the factors governing ESCC process from the view points of stress, material and environmental conditions. The purpose of this study is to investigate the effect of applied stress on ESCC of type 304 stainless steel. ESCC tests were conducted on type 304 SS specimens, which were fabricated from a cold rolled plate, by a uniaxial constant load method using springs. After loading, droplets of synthetic sea water were put on the gage section of specimen and dried, and then the specimens were placed in a chamber with a constant temperature of 353 K and a relative humidity of 35%. The test specimens after the test were observed by a scanning electron microscope to measure the crack length and depth. No clear difference was found in the maximum values of the average crack propagation rate (crack depth divided by test time) among the applied stress conditions. In addition, most of ESCC were initiated from the bottom or periphery of pits under the low applied stress condition (0.5σ0.2).
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Tomoyuki Nishida2006 Volume 70 Issue 12 Pages 1016-1021
Published: 2006
Released on J-STAGE: December 20, 2006
JOURNAL FREE ACCESSCarbon heat-treated at different temperatures was bonded to nickel in a vacuum using an RF-induction furnace. On the basis of the results of these experiments, the effects of the heat treatment of carbon on the interface strength of a joint were examined. With increasing heat treatment temperature, the graphitization progresses and the crystallite grows; in addition, in the joining surface, the region almost perpendicular to the basal plane, which contributes to strong bonding, increases in size. Therefore, the joinability of carbon to nickel is improved. Utilizing this property effectively, the heat treatment of carbon can adjust the interface strength of a joint. Moreover, by selecting carbon materials with a specific crystal structure and adequate joining and exfoliating temperatures, bonding with the exfoliation process becomes feasible.
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