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 78, Issue 12
Displaying 1-5 of 5 articles from this issue
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Regular Article
  • Effect of Electrolysis Condition on the Lightness and Surface Morphology of Ni Deposited from Chloride Electro-Winning Solutions
    Ryo Takahashi, Yuki Sato, Satoshi Oue, Shinichi Heguri, Hiroaki Nakano
    2014 Volume 78 Issue 12 Pages 427-433
    Published: 2014
    Released on J-STAGE: December 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.J2014033
    JOURNAL FREE ACCESS
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      To investigate the effect of current density and pH in solution on the lightness and surface morphology of deposited Ni, Ni electrodeposition was performed at current density 100 to 500 A•m−2 and the amount of charge 7.2×105 C•m−2 in unagitated chloride solution of pH 1 to 3 at 333 K. The composition and structure of the surface of the deposits were analyzed by radio frequency glow discharge optical emission spectroscopy and three dimensional SEM. The lightness of deposited Ni decreased with increasing pH, and became to be minimum at 300 A•m−2. The concentration of the surface oxide of deposits increased with pH, and became high at 300 A•m−2, which shows that the surface oxide of the deposits causes the decrease in the lightness. On the other hand, the surface of the deposited Ni was composed of both the pyramid microcrystals of several micrometers and the hill formed by the aggregations of pyramid microcrystals. To separate the two structural units of the pyramid microcrystals and the hill, the deposits were cut every 200 nm from the top to the thickness direction in three dimensional SEM, and the number and area of deposits in the cutting plane were measured, as a result, it was found that the lightness of the deposited Ni depended on the surface structure. The lightness of deposited Ni seems to depend on both the surface oxide and the microstructure of deposits.
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  • Influence of Predeformation on Tempering Structure of Ti-5Al-2Fe-3Mo Alloy
    Yoshito Takemoto, Keita Wada, Kenta Asakura, Takehide Senuma, Tomonori ...
    2014 Volume 78 Issue 12 Pages 434-440
    Published: 2014
    Released on J-STAGE: December 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.J2014035
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      A near-β-type Ti-5Al-2Fe-3Mo alloy (Super-TIX®523AFM) was developed as a low-cost and high-strength material for automotive components such as intake valves. Its mechanical properties, such as strength, elongation and Young's modulus, are adjustable via the solution treatment temperature. Furthermore, a unique phenomenon different from the shape memory effect that appears after tempering has recently been discovered in the alloy. In this study, the influence of predeformation on the microstructural evolution attributed to the tempering of the alloy quenched from 900℃ (α+β) was investigated to clarify the cause of the unique phenomenon. Although the phase constitution of the quenched specimen was α+β, the effective Mo equivalency (6.5Moeffeq) of the β phase was lower than the minimum β composition (10Moeffeq) in common β alloys. Work-induced α″ martensite plates consisting of single α″ variant including nanosize β domains were formed in the β-phase by cold-rolling. Upon heating the rolled specimen to around 250℃, the plates vanished owing to the α″→β inverse transformation and the hardness decreased. However, when the rolled specimen was heated to 450℃, the hardness markedly increased as a result of the β→α″ transformation, and the plates were formed again. The plates consist of a single α″ variant, but the α″ lattice is not extensively continuous and is divided into nanosize domains by boundaries containing many faults. It is considered that the evolution of single-α″-variant plates generates a large distortion due to the transformation strain and leads to the unique shape change. Such plates were not formed in undeformed specimen by aging at 450℃, and the β-phase was transformed into a nanosize domain structure composed of multiple α″ variants. Consequently, these fine structure in the undeformed specimen led to its higher hardness than that of the rolled specimen.
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  • Effect of Iron Sulfide on Oxidation of Si-Bearing Steel Prior to Reducing Anneal during Galvanizing Process
    Yoichi Tobiyama, Masahiko Tada, Sakae Fujita, Masao Takeyama
    2014 Volume 78 Issue 12 Pages 441-448
    Published: 2014
    Released on J-STAGE: December 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.J2014030
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      Effect of pre-treatment by sulfate solution on the oxidation of Si-bearing steel prior to reducing anneal was investigated to improve the galvanizability of the steel in galvanizing. Ammonium sulfate and diluted sulfuric acid accelerate the oxidation of the Si-bearing steel: they produce the same amount of iron oxide as a steel without silicon. Silicate containing iron and manganese, which retards the outer diffusion of iron ions during oxidation, is continuously formed at the interface between an iron oxide film and the steel without ammonium sulfate. FeS, generated by the reaction of SO2 from (NH4)2SO4 and steel, is observed in the iron oxide film near the interface between the iron oxide film and the steel treated with ammonium sulfate. Iron ions diffuse through FeS after this reaction. Ammonium sulfate accelerates the oxidation of the Si-bearing steel not only because FeS acts as the outer diffusion path of iron ions but also because the formation of silicate is delayed due to the generation of SO2.
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  • Effects of Au-Addition on Plastic Deformation Ability of Zr-Cu-Ni-Al Bulk Metallic Glasses
    Masahiro Yamada, Tohru Yamasaki, Kazutaka Fujita, Yoshihiko Yokoyama, ...
    2014 Volume 78 Issue 12 Pages 449-458
    Published: 2014
    Released on J-STAGE: December 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.J2014042
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      Effects of Au-addition on plastic deformation ability of Zr-Cu-Ni-Al bulk metallic glasses (BMGs) during compression and tensile tests have been examined. Zr65Cu20Ni5Al10 BMG(Zr65) and Zr60+xCu22−xNi5Al10Au3(x=0, 5, 6.5, 8, 9 at%) BMGs(Zr60Au3-Zr69Au3) have been prepared by a tilt casting method. By the Au-addition on the BMGs containing Zr-content of 65 at% and more, precipitation of icosahedral quasicrystalline phase (I-phase) in supercooled liquids was observed, resulting in large increase of viscosity in the supercooled liquids. Compression and tensile tests were carried out in these BMGs under various strain rates of 1~5×10−4/s at room temperature. In the compression test of the Zr65 BMG, plastic strain at fracture was about 10% and only several localized shear bands were observed. In the Zr65Au3 and Zr66.5Au3 BMGs, plastic strains at fracture were largely increased to 20% and above. In these cases, initial plastic strains of about 5% with large number of shear band were observed as macroscopically homogeneous deformation, and successive plastic strains along main shear band was observed. In the tensile test, large plastic strain at fracture of about 0.5% was also observed for the Zr66.5Au3 BMG. By transmission electron microscopic observations of the Au-addition BMGs, precipitation of nano-crystallites having about 10 nm in diameter was observed near the fractured surfaces of the compressive and tensile test specimens. Viscosity of supercooled liquids in shear bands was estimated by the stress-drop of serrations in the compressive stress-strain curves. It is considered that the large increase of the plastic strain is due to the drastic increase of the viscosity of the supercooled liquids formed inside shear bands during plastic deformation.
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