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Volume 74, Issue 8
Displaying 1-10 of 10 articles from this issue
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Regular Articles
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Takashi Nozu, Masuo Koshi, Hiroshi Yamamoto, Junya Masuda, Tetsuro Nis ...Article type: Regular Article
2010 Volume 74 Issue 8 Pages 485-492
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSCorrosion is recognized as one of the potential drivers of whisker growth in regards to high-tin alloys. In this study, the growth of whiskers was observed for a period of 5000 hours on Sn3.0Ag0.5Cu (SAC305) as a function of soldering method under the environmental conditions of high temperature and humidity of 85°C/85%RH, 60°C/90%RH, and 40°C/95%RH. The soldering methods used were dip soldering, hand soldering with flux-cored wire, and reflow soldering with solder paste with all of the methods using commercially available flux formulations. The test pieces were examined at regular intervals for the onset of whisker growth, whisker density and maximum whisker length. In addition, samples were taken periodically for the measurement with the extent of corrosion and correlations between corrosion and whisker growth being explored.
Findings presented in this paper can be summarized as follows:
(1) Whiskers occurs at 85°C/85%RH and the growth rate, is two to four times greater than that at 60°C/90%RH and approximately ten times greater than that at 40°C/95%RH;
(2) There is a positive correlation between whisker density and maximum whisker length;
(3) For the dip soldering, a positive correlation between the average percentage of the corroded cross−sectioned region and the maximum whisker length suggests that corrosion is a driving force of whisker growth;
(4) Different soldering methods resulted in varying degrees of copper erosion along with different distribution of flux residues, and subsequently different rates and locations of corrosion.
It is concluded from these observations that the soldering method as well as the type of flux gives significant influence on the subsequent corrosion when exposed to high temperature and humidity conditions. Consequently, this also gives extensive effects on the onset time of whisker appearance and maximum whisker length.
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Shunji Kajikawa, Yasuaki Isobe, Masazumi OkidoArticle type: Regular Article
2010 Volume 74 Issue 8 Pages 493-500
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSAs the requirement for durability of automobile increase, the application of type 304 stainless steel is expanding because of its high workability and corrosion resistance. On the other hand, one of the main corrosion environments of automobile is chloride condition caused by deicing salt or sea salt particle, and it becomes more severe when added to the wet/dry cyclic condition that is specific to automobile. In this case, the corrosion resistance is not enough even if the stainless steel is applied.
In the case of stainless steel, crevice corrosion is mainly concerned in chloride environment. Pitting corrosion, however, can sometimes occur at non-crevice site.
The purpose of this study is to clarify how the corrosion factor such as salt composition or wet/dry condition affects to the corrosion behavior of type 304 stainless steel inside and outside of crevice.
The corrosion factors described above were evaluated by the corrosion test method developed in our previous work. Furthermore, electrochemical measurements were conducted. As a result, when NaCl is used for chloride addition, there is more severe corrosion at crevice than non-crevice site regardless of wet/dry condition. However, when sea salt particle or CaCl2 that is a major component of deicing salt are used, corrosion sites differ depending on wet/dry condition. That is, corrosion is severe at crevice site under high humidity condition of more than 60%RH, while pitting corrosion is prominent at non-crevice site under low humidity of less than 40%RH. Considering the corrosion behavior under various wet/dry conditions, main corrosion factor of sea salt particle is not NaCl but MgCl2 that is not major component.
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Keisuke Hayashi, Koji KakehiArticle type: Regular Article
2010 Volume 74 Issue 8 Pages 501-507
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSThe effect of γ″ (Ni3Nb) particle size on the mechanical properties and deformation mechanism of Inconel 718 was investigated. In this study, two kinds of aging heat treatment were used to obtain different γ″ particle size. The effect of γ″ size on the tensile/compressive-proof, creep and fatigue strengths at 24°C and 650°C were studied. When the average size of γ″ particle was 18 nm, they were considered to be sheared by the group of 1/2<110> dislocations during tensile deformation. When the average size of γ″ particle was 42 nm, the tensile deformation was occurred by the passage of deformation twins at 650°C. The creep and fatigue strengths were considered to be decreased as the deformation mechanism changed from dislocation's shearing of γ″ particle to deformation twins. The tension/compression anisotropy in single crystal Ni-base superalloys has been reported when the deformation twin is observed. However, in the polycrystalline Inconel 718, in spite of existence of the deformation twin, the anisotropy in yield strengths was not observed.
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Shunsuke Shimabayashi, Koji Kakehi, Hideyuki Murakami, Shinya UeharaArticle type: Regular Article
2010 Volume 74 Issue 8 Pages 508-514
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSThe detrimental effect of the diffusion zones between coating and the substrate had been investigated by performing creep tests on aluminized Ni-based single crystal superalloys. In present study, creep test-pieces that had two kinds of sub-surface crystallographic orientations, <100> and <110>, were aluminized by the pack-cementation process at 1000°C for 5 h. To exclude the influence of the coating heat treatment on the creep strength of the bulk material, a set of specimens without coating was heat treated in vacuum at 1000°C for 5 h, which was equivalent to the condition during aluminizing process, for comparisons the creep rupture test was carried out at 900°C and 392 MPa. The cross-sectional microstructures of the as-aluminized and creep rupture specimens were observed by SEM using the backscattered electron image mode (BSE) and TEM. Analysis indicated that creep strength of the aluminized samples was decreased by the formation of the inter-diffusion zone (IDZ) and the substrate diffusion zone (SDZ); both of them reduced the load bearing thickness, thus resulting an increase in the effective stress. Furthermore, it was found that the disappearance of the secondary precipitate during coating treatment also decreased the creep strength. The IDZ, which formed at the coating/substrate interface grew more rapidly on the {110} plane than that on the {100} plane because of the preferential growth of the Topological-Close Paced (TCP) phase. Ru addition on the substrate could enhance the creep strength and the SDZ formation between the IDZ/substrate interface.
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Takeshi Nagase, Takayoshi Nakano, Yukichi Umakoshi, Mitsuo NiinomiArticle type: Regular Article
2010 Volume 74 Issue 8 Pages 515-519
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSBeta-Ti-type Ti-30Nb-10Ta-5Zr (TNTZ) wires with high bending ductility were developed using the arc-melt-type melt-extraction method. The continuous melt-extracted wire with very smooth surface and small fluctuations in the diameter realizes high tensile strength and superior bending ductility of TNTZ alloy. The melt-extracted Beta-Ti wire shows the possibility for the use in biomedical applications. The arc-melt-type melt-extraction method is very effective for developing new Beta-Ti-based biomaterials.
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Koichi Takasawa, Yoru Wada, Ryoji Ishigaki, Rinzo KayanoArticle type: Regular Article
2010 Volume 74 Issue 8 Pages 520-526
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSThe effect of grain size on the susceptibility of high-strength low-alloy steels to hydrogen environment embrittlement in a 45 MPa gaseous hydrogen atmosphere was examined in term of the hydrogen content penetrating the specimen during the deformation. Notch tensile tests were performed in a 45 MPa hydrogen environment using specimens with different prior austenite grain size number varying from 2.5 to 5.4. The hydrogen content was measured by thermal desorption analysis with a quadrupole mass spectrometer before and after the tensile test. The fracture stress of the notch tensile test increased with decreasing grain size. This showed that grain refinement was effective in reducing the susceptibility of the specimens to hydrogen environment embrittlement in a high-pressure hydrogen atmosphere. Addition of nickel did not affect the fracture stress. A remarkable increase in the content of diffusive hydrogen was observed after the notch tensile test. Assuming that part of the diffusive hydrogen desorbed from grain boundaries, it can be inferred that grain refinement can reduce the mass of hydrogen in the unit grain boundary area, and the susceptibility to high-pressure hydrogen environment embrittlement.
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Osami Seri, Ryoma NakanoArticle type: Regular Article
2010 Volume 74 Issue 8 Pages 527-532
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSMagnesium has been dissolved by corrosion approach making use of anhydrous methanol as a solvent and titanium chloride as a catalyst for a period of 3.6 ks refluxing process. The XRD analysis showed that MgTiO3 powder was successfully obtained when the solution has been hydrated and sintered at 923 K-1523 K for 3.6 ks. The preparation of MgTiO3 was explained as double oxide mixed corrosion product of magnesium with TiO2 derived from addition of TiCl4.
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Tatsuya Ito, Shoichi Kikuchi, Yutaka Kameyama, Jun Komotori, Kengo Fuk ...Article type: Regular Article
2010 Volume 74 Issue 8 Pages 533-539
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSAn atmospheric controlled IH-FPP (Induction Heating and Fine Particle Peening) treatment system was developed. Using the system, the surface of ordinary structural steel was modified with Cr shot particle at room temperature, 500°C, 700°C and 900°C in atmosphere of either argon and air. The treated surfaces were characterized using a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX), an X-ray diffractometer (XRD) and an X-ray photoelectron spectroscope (XPS). In the case of the specimen treated in argon atmosphere, a relatively thick and uniform Cr rich layer was formed at the surface. The thickness of the layer was changed with an increase in temperature, the higher the temperature, the thicker the layer. In the case of the specimen treated in air, however, an oxidized scale was formed on the treated surface instead of a Cr rich layer. The results of the experiments prove that atmospheric controlled IH-FPP treatment successfully creates a Cr rich surface layer. The specimen treated by atmospheric controlled IH-FPP showed higher corrosion resistance compared to that of the untreated specimen, the higher the thickness of the Cr rich layer, the higher the corrosion resistance.
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Munekatsu Shimada, Takeo Chinen, Kazuyuki Kumabayashi, Masanori Yokoya ...Article type: Regular Article
2010 Volume 74 Issue 8 Pages 540-542
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSGalfenol (FeGaAlZrC) alloy ring was used for torque-sensing by detecting a leakage flux from the ring surface based on the inverse magnetostriction effect. This leakage flux changes depending on the magnetic parameter such as magnetostrictive strain(λ), residual magnetization (Mr), applied or residual stresses(σ) of the ring. Beside, the hoop stress (σh)which is one of the residual stress factor in the ring also has strong effect on torque-sensing because this affects those magnetic parameters. The fitting gap between ring and shaft was four kinds of 6, 10, 20 and 30 μm and hoop stress (σh) in each case can be estimated from the elastic formula of material-mechanics. As a result, torque sensitivity showed the maximum value in the case of 10 micrometers gap and it decreased toward the gaps of 10 and 20 μm and drastically decreased in the case of minimum gap of 6 μm. This change of torque sensitivity depending fitting gap is discussed based on the magnetic domain mobility and inelastic material effect at the interface of Galfenol ring and rotating shaft.
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Letters to the Editor
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Yusuke Sado, Chihiro Saito, Munekatsu Shimada, Minoru Matsumoto, Teiko ...Article type: Letters to the Editor
2010 Volume 74 Issue 8 Pages 543-545
Published: 2010
Released on J-STAGE: August 01, 2010
JOURNAL FREE ACCESSAn advanced multi-ferroic composite sensor designed by using two material elements of magneto-elasto-electric effect (MEE effect) combined mutual transformation of magnetic property and electric property. This sensor was made by PZT ceramics with high piezoelectric constant and magnetostriction thin film of Fe-20 at%Ga and Fe-50 at%Co with giant magnetostriction and large elastic property in Hirosaki University 2008. From the results of magnetic properties of Fe80Ga15Al5 and Fe50Co50, properties of magnetostriction materials affect output properties of this composite type sensor. Output voltage increased with decrease of thickness in magnetostriction materials.
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