Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
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Volume 76, Issue 6
Displaying 1-8 of 8 articles from this issue
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  • The Effect of Anodizing on the Fatigue Life of Aluminum Alloy 7050
    Akiko Inoue, Tetsuya Tagawa, Takashi Ishikawa
    2012 Volume 76 Issue 6 Pages 365-374
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.365
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      High strength aluminum alloys of aerospace structural components are widely used with anti-corrosive coating. Typical anti-corrosive coating, anodic coating, can often impair the fatigue property. The deterioration in fatigue property due to anodizing is studied in this paper. Fatigue properties of high strength aluminum alloys 7050-T7451 with typical two types of anodizing, CAA (Chromic Acid Anodizing) and SAA (Sulfuric Acid Anodizing) were compared. The deterioration mechanisms in fatigue properties were investigated by fracture surface analyses and the numerical investigation of stress intensity factor. The deteriorated fatigue lives of CAA specimens were approximately 50% of AM (As-machined) condition and that of SAA specimens were 30% of AM. In CAA specimens, the fatigue fracture initiated from etched pits beneath the anodic coating. Although SAA specimens also have pits similar to those of CAA specimens, the fatigue cracks nucleated from micro cracking in the anodic coating and propagated into aluminum substrate. Stress intensity factor estimation revealed that the dominant initial flaw for fatigue crack initiation was the defect with the maximum stress intensity factor, in other words, etched pits for CAA and micro cracking in the anodic coating for SAA specimens. It was consequently suggested that the deterioration in fatigue lives due to anodizing resulted from the shortened crack propagation lives in the initial stage, which were determined by the geometric configuration of the initial flaw.
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  • TMR and Thermal Stability Improvement of FeCo-AlF Nano-Granular Thin Films
    Nobukiyo Kobayashi, Shigehiro Ohnuma, Hiroyasu Fujimori, Tsuyoshi Masu ...
    2012 Volume 76 Issue 6 Pages 375-379
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.375
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      We investigated tunnel magnetoresistance (TMR) properties to improve their thermal stability using FeCo-AlF, a new metal-insulator nano-granular thin film for GIGS® (granular in gap sensor), a highly efficient power-saving magnetic sensor. These system films exhibit granular type TMR properties, and Fe25Co19Al17F39 film has a 12% TMR ratio. The thermal stability of the TMR properties is greatly improved by adding of small amounts of Si to FeCo-AlF. Although the TMR ratio of Fe23Co17Al13F47 film deteriorates from 550K, Fe22Co18Si3Al16F41 film retains its TMR ratio up to 600 K.
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  • Rapid Solidification into Undercooled Melt of Ge by Means of Levitation Technique
    Yusuke Ishibashi, Katsuhisa Nagayama, Kazuhiko Kuribayashi
    2012 Volume 76 Issue 6 Pages 380-384
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.380
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      Using CO2 laser equipped electro-magnetic levitator, we carried out the containerless crystallization of Ge. From the point of the interface morphologies, the relationship between growth velocities and undercoolings was classified into two regions, I and II. In region I where the plate-like needle crystals were observed, the growth velocities are expressed by two dimensional (2D) nucleation-controlled growth model. In region II, where the morphology of growing crystals changed to massive dendrites, the growth velocities are approximately expressed by linear kinetics growth model. These results indicate that with increase of undercooling, the rate-determining factor changes from 2D nucleation on the faceted interface at the reentrant corer, which was formed at the edge of the multiple twin boundaries, to random attachment of atoms on the nonfaceted interface.
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  • Wear of Cemented Carbide Dies for Steel Cord Wire Drawing
    Masayuki Takada, Hideaki Matsubara, Yoshihiro Kawagishi
    2012 Volume 76 Issue 6 Pages 385-390
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.385
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      Cemented carbide dies with the five categories of composition, namely, WC-Co straight alloy, TaNbC-, Cr3C2- or VC-containing WC-Co alloys and WC-Ni alloy, were fabricated by sintering and HIP-treatment. The wear behavior of these cemented carbide dies for drawing steel cord wire is examined, and material properties such as hardness, transverse-rupture strength and corrosion resistance are evaluated. Through the above investigations, it is particularly noted that the TaNbC-containing alloy shows the longest life time of steel cord drawing die, which is followed by Cr3C2-containing alloy, WC-Co, VC-containing alloy and WC-Ni alloy. The results on strength and corrosion resistance have no relation with the drawing die life. The hardness has some degree of relation with the die life; for example, among the same category alloy, there is such a tendency that the longer die life is obtained for the higher hardness. However, it is not able to explain simply by the viewpoint of hardness the reason why TaNbC-containing alloy has the longest life although the VC-containing alloy has the finest grain size and the highest hardness. The wear mechanism of cemented carbide dies for steel cord wire drawing was discussed to consider WC/Co interface adhesion.
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  • Preparation of Compositionally Gradient Cr-Al-N-O Thin Films by Pulsed Laser Deposition
    Tsuneo Suzuki, Kazuya Fujinoki, Hiroki Asami, Makoto Hirai, Takashi Yu ...
    2012 Volume 76 Issue 6 Pages 391-396
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.391
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      Compositionally gradient chromium aluminum oxynitride (Cr-Al-N-O) thin films have been prepared through the pulsed laser deposition method. The aluminum content in metallic elements (x) ranging from 30 to 95 at% were successfully changed with position of one thin film sample. The X-ray diffraction revealed the crystal structure of the main phase to be NaCl type. The Cr-Al-N-O thin film with x=35 at% exhibited the highest Vickers hardness HV of 4300.
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  • Mechanical Strength and Biocompatibility of Meta-Stable β Type Ti-5Fe-3Nb-3Zr for Biomedical Applications
    Keisuke Ushida, Kenta Tsuge, Toshikazu Akahori, Tomokazu Hattori, Mits ...
    2012 Volume 76 Issue 6 Pages 397-401
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.397
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      Ti-29Nb-13Ta-4.6Zr (TNTZ) is a very attractive material for biomedical applications because of its low Young's modulus. However, this alloy contains a certain amount of rare-metals elements. In this study, Ti-Fe-Nb-Zr system alloys were developed by substituting Fe for Ta as the low cost β stabilizer, and the mechanical properties and biocompatibility of these alloys were investigated for five different compositions through thermo-mechanical treatments.
       The micro-Vickers hardness of the Ti-Fe-Nb-Zr system alloy decreases with Fe addition up to 7 mol% because of the suppression of the ω-phase precipitate. Subsequently, it increases by further Fe addition due to solid-solution strengthening. Ti-5Fe-3Nb-3Zr (Ti-5-3-3) subjected to solution treatment (ST) shows the lowest Young's modulus among the other composition. In addition, the tensile strength of Ti-5-3-3 subjected to ST is higher than those of the annealed Ti-6Al-4V ELI and TNTZ subjected to ST. The specimens of the alloy implanted in the femoral epicondyle of rabbit are surrounded by new bone tissue formed with direct contact after 24 and 48 weeks from the implantation. It is considered that Ti-5-3-3 has relatively good biocompatibility with contact osteo-genesis as compared with those of Ti-6Al-4V ELI and SUS316L stainless steel.
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  • Effect of Thermal History on Microstructural Changes in Aluminized Nickel-Based Single-Crystal Superalloy
    Kazuki Kasai, Hideyuki Murakami, Kazuhiko Noda
    2012 Volume 76 Issue 6 Pages 402-406
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.402
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      The effect of thermal history on microstructural changes in the aluminized and Pt-aluminized Ni-based single-crystal superalloy was investigated. The substrate superalloys were firstly electro-polished in order to get rid of the surface residual strain. Then the electrodeposition of Pt followed by vacuum annealing was conducted for some of the substrates, and the aluminized and Pt-aluminized specimens were prepared by the conventional aluminizing process.
       It was found that in the case of the aluminized specimens, voids were formed in the vicinity of substrate/coating interfaces, by thermal cyclic heating, whereas secondary diffusion zones (SDZ) were formed by isothermal heating. These differences in microstructural changes of the aluminized specimens can be explained by the diffusion kinetics between the coating layer and the substrate during heating/cooling processes. In the case of the Pt-aluminized specimen, on the other hand, secondary reaction zone (SRZ) formation was observed by both the thermal cyclic and isothermal treatments. These results can be explained by the poly-crystallization of the substrate surface by the annealing process that could promote the interdiffusion, resulting in the formation of SRZ.
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  • Same Area Observation on Recrystallization in A1050 Aluminum after Cold-Rolling at 50%
    Takuya Kajiura, Masaaki Tsukamoto, Atsushi Yamamoto
    2012 Volume 76 Issue 6 Pages 407-413
    Published: 2012
    Released on J-STAGE: June 01, 2012
    DOIhttps://doi.org/10.2320/jinstmet.76.407
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      Recrystallization behaviors in A1050 aluminum was observed on the same area in a specimen with SEM (Scanning Electron Microscope)-EBSD (Electron Back Scatter Diffraction) system. Specimen were solution heat-treated at 823 K for 10.8 ks. The specimen was cold-rolled at a reduction rate of 50% and then annealed at 623 K. Intermittent annealing using a salt bath, Ar ion-polishing and EBSD measurement were repeated. Cold-rolling induced many subgrains surrounded with low and high angle boundaries depending on lattice rotation, which made prior grain boundaries unclear. Strain induced grain boundary migration was not observed. Subgrains surrounded with high angle boundaries grew into recrystallized grains without changing orientation. Origins of recrystallized grains, crystallite, already exist in microstructures before annealing. Orientations of prior grains were spread into a relatively broad range in angle due to cold-rolling. Although orientations of crystallites were of course observed within the range in angle, the orientation was different from those of surrounding subgrains. Subgrains having similar orientations formed recovered regions composed of subgrains surrounded with low angle boundaries. The recovered regions were invaded by recrystallized grains and consumed to recrystallized microstructures.
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