MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 49 , Issue 3
Showing 1-50 articles out of 53 articles from the selected issue
  • Yasumasa Chino, Katsuya Kimura, Mamoru Mabuchi
    2008 Volume 49 Issue 3 Pages 393-397
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: December 19, 2007
    JOURNALS FREE ACCESS
    Pure Mg consisting of elongated grains was fabricated by the directional solidification process, and its compressive properties were investigated at room temperature, 473 and 773 K under the conditions where the angle between the long axis direction of the elongated grains and the compression direction was 0, 45 and 90 degree. At room temperature, the specimen at the angle of 45 degree was fractured prior to ε=0.3, although the specimens at the angles of 0 and 90 degree were not fractured even at ε=0.3. In addition, the yield stress at the angle of 45 degree was higher than those at the angles of 0 and 90 degree. The (0002) basal planes were distributed at a tilt of 30–50 degree to the solidification direction. This was responsible for the higher yield stress at the angle of 45 degree. Also, the yield stress at the angle of 0 degree was lower than that at the angle of 90 degree. The lower yield stress at the angle of 0 degree was attributed to twinning. At 473 K, the yield stress at the angle of 45 degree decreased significantly. The large decrease in yield stress at the angle of 45 degree resulted from grain boundary sliding. At 773 K, the yield stresses were almost the same, irrespectively of the loading direction. Thus, compressive properties of the directionally solidified Mg were affected by the loading direction.
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  • Kohsuke Mori, Sayoko Shironita, Toshiaki Shimizu, Takao Sakata, Hirota ...
    2008 Volume 49 Issue 3 Pages 398-401
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    A novel method to prepare the nano-sized Pt metal catalysts is proposed. Mesoporous silicas containing highly dispersed titanium oxide species (Ti-HMS) can act as the platform to generate highly dispersed Pt metal particles. Characterization by Pt LIII-egde XAFS, CO adsorption, and TEM analyses revealed that the size of formed Pt metal particles depends on the presence of titanium oxide species and that the smaller sizes of Pt metal particles was obtained with increasing the Ti contents in the silica matrix. These nano-sized Pt metal catalysts are useful as efficient catalysts for NO reduction, and higher conversion could be attained with smaller size of Pt metal particles. The present technique using Ti-containing mesoporous silicas as catalyst supports make a great contribution to minimize the amount of precious metals in order to meet today’s industrial requirements.
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  • Kohmei Halada, Masanori Shimada, Kiyoshi Ijima
    2008 Volume 49 Issue 3 Pages 402-410
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    Forecasts up to 2050 are made of consumption of the following metals: Fe, Al, Cu, Mn, Zn, Cr, Pb, Ni, Si, Sn, rare earths, Mo, Li, Sb, W, Ag, Co, In, Au, Ga, Pt and Pd. The forecasts are based on the linear decoupling model of the relation between per capita metal consumption and per capita GDP. The models of each metal are applied to the economic development model of BRICs and G6 countries. According to these forecasts, the overall consumption of metals in 2050 will be five times greater than the current levels, and demand for metals, such as Au, Ag, Cu, Ni, Sn, Zn, Pb and Sb, is expected to be several times greater than the amount of their respective reserves. Demand for Fe and Pt, which is considered to be optimistic about the resource exhaustion, will also exceed the current reserves. Urgent measures are needed to find alternatives from common resources and to shift into sound materials circulation society.
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  • Kohmei Halada, Masanori Shimada, Kiyoshi Ijima
    2008 Volume 49 Issue 3 Pages 411-418
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    The decoupling statuses of the consumption of 22 kinds of metals from economic growth were analyzed. Metals were Fe, Al, Cu, Cr, Zn, Mn, Pb, Ni, Co, Sn, Sb, Si, Mo, W, Li, In, Ga, Ag, Au, Pt, Pd and rare earths. The relations between the per capita annual consumption of each metal and per capita GDP were approximated by a two-steps linear formula of yM=aM,1 X (X<cM) and yM=aM,2 X+bM,2 (X>cM), where yM is the annual consumption of a metal M, and X is GDP per capita. Metals which had only a single relation of yM=aM,1 X were judged to be in a state of coupling. When aM,1>aM,2, the state was judged to be decoupling. Furthermore, a metal was judged to be in a state of absolute decoupling when aM,2<0. The metals which tended to exhibit characteristics of absolute decoupling were Au, Sn, Zn and W, while Cu and Pb were borderline. While Fe, Al, Ni, Mo, Sb, Ag, Pd are decoupling from per capita GDP, Si and Pt are still coupled with economic growth. In the cases of Co, Li, In, Ga and rare earths, a new coupling relation with economic growth has developed over the past several years.
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  • Keizo Kashihara
    2008 Volume 49 Issue 3 Pages 419-423
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: December 05, 2007
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    The relationship between crystal rotation axis orientations and active slip systems was investigated in an aluminum tricrystal deformed under compression to a strain of 0.15. Schmid factors of slip systems were examined for three component crystals. After compression, slip bands near a triple junction were observed using a scanning electron microscope. Crystal rotation axis orientations were calculated by comparison of the crystal orientations before and after deformation. One of the three component crystals yielded various crystal rotation axis orientations. The active slip systems in the crystal, which generate crystal rotation relative to the initial orientation, were estimated from the slip bands, crystal rotation axis orientations, Schmid factors and ⟨112⟩ lattice rotation axis orientations. Here, the lattice rotation axis orientations are assigned to individual slip systems, since they operate toward ⟨110⟩ directions on {111} planes. Based on the estimation of active slip systems, in an area far from the triple junction of the crystal, the crystal rotation relative to the initial orientation was introduced by imbalance operation of the primary and additional slip systems. In the vicinity of the triple junction, the crystal rotation was generated by three slip systems with different amounts of slip operations. The two additional slip systems on the same slip plane were partially activated along a straight boundary.
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  • C. Y. Cui, Y. F. Gu, D. H. Ping, T. Fukuda, H. Harada
    2008 Volume 49 Issue 3 Pages 424-427
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: January 10, 2008
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    Phase constituents and compressive yield stress of Ni-Co base alloys have been investigated. The results showed that two-phases of γ and γ′ were the main constituents in all the alloys. Ni3Ti-type (η) phase was observed in the alloys with lower Co and Ti content (alloy20); while a new intermetallic (Ni,Co,Cr)3(Ti,Al) phase with a hexagonal structure was detected in the higher Co and Ti containing alloy(alloy50). At temperatures lower than 1023 K, the compressive yield stress increased with increasing Co content up to 28.6 mass% and Ti content up to 7.4 mass%, but decreased with more Co and Ti addition. At temperatures higher than 1273 K, all the alloys showed similar yield stress.
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  • Atsushi Sugino, Keita Uetsuki, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi ...
    2008 Volume 49 Issue 3 Pages 428-434
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: January 17, 2008
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    Hydroxyapatite formation on the surface of materials in the body is an essential condition for demonstrating osteoconduction after implantation in bony defects. This paper reports a technique for providing hydroxyapatite formation properties to titanium metals by using specially designed surface topography followed by thermal oxidation. Two pieces of titanium thermally oxidized at 400°C were set together in a V-shape with varied mouth opening. They showed the formation of hydroxyapatite on both facing surfaces after exposure to a simulated body fluid (SBF), when the gap height was approximately less than 600 μm. Moreover, pure titanium specimens with macro-grooves less than 1000 μm in depth and 800 μm in width were able to form hydroxyapatite deposits in SBF within 604.8 ks, after they were thermally oxidized at 400°C for 3.6 ks. Hydroxyapatite also formed on the internal surfaces of macro-grooves made in Ti-15-Zr-4Ta-4Nb within 604.8 ks of soaking in SBF, after the sample was thermally oxidized at 500°C for 3.6 ks, whereas it was not deposited on alloy made of Ti-6Al-4V extra low interstitial processed in the same way. These findings indicate that titanium and its alloys can be conferred with hydroxyapatite-forming ability, i.e. osteoconduction, within a controlled spatial gap and thermal oxidation. We conclude that bioactive titanium substrate showing osteoconduction can be produced by using a specially designed surface topography followed by thermal oxidation at an appropriate temperature.
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  • Takamitsu Kino, Toshihiro Kuzuya, Keiichi Itoh, Kenji Sumiyama, Takahi ...
    2008 Volume 49 Issue 3 Pages 435-438
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: January 30, 2008
    JOURNALS FREE ACCESS
    CuInS2 nanoparticles (NPs) have been synthesized via thermal decomposition of metal-thiolate in high boiling temperature solvent. This method does not require toxic, unstable and expensive raw materials. Nearly monodispersed NPs with average diameter ranging from 1.8 to 2.8 nm are obtained. The NPs are found to be compositionally copper rich, Cu:In:S=1.6:1.0:1.3. They exhibit size-dependent optical properties such as photoluminescence (PL) and optical absorption, indicating quantum confinement effects. In PL spectra, the stokes-shifts (∼300 meV) from the absorption band edge and their broad PL spectra indicate that PL is ascribed to a donor-acceptor transition. These results demonstrate that chalcopyrite NPs are promising candidates for luminous and solar cell materials.
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  • Yoshihiro Terada, Tatsuo Sato
    2008 Volume 49 Issue 3 Pages 439-442
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: January 23, 2008
    JOURNALS FREE ACCESS
    Creep rupture tests were performed for a die-cast Mg-Al-Mn alloy, AM50, at 34 kinds of creep conditions in the temperature range between 423 and 498 K. The creep curve is characterized by a minimum in the creep rate followed by an extended accelerating stage. The minimum creep rate (\\dotεm) and the creep rupture life (trup) follow the phenomenological Monkman-Grant relationship; trup=C0⁄\\dotεmm. It is found for the die-cast AM50 alloy that the exponent m is unity and the constant C0 is 0.13, independent of creep testing temperature. The values of m and C0 are compared with those for other die-cast magnesium alloys.
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  • K. Nogita, C. M. Gourlay, J. Read, T. Nishimura, S. Suenaga, A. K. Dah ...
    2008 Volume 49 Issue 3 Pages 443-448
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    Phosphorus is often added to wave-solder baths as an anti-oxidation agent. Despite this practice, there is little information on how phosphorus influences the solidification and flow properties of new lead-free solders such as Sn-0.7Cu-0.05Ni. This paper investigates the effects of phosphorus content on microstructure and maximum fluidity length in Sn-0.7Cu-0.05Ni-xP alloys containing 0–0.08 mass% phosphorous. Ppm levels of phosphorous are found to cause Sn-xP, Ni-xP-(Sn) and Cu-xP-(Sn) intermetallic compounds to form in the liquid solder. The IMCs are less dense than liquid Sn and float towards the surface of the melt driven by buoyancy. It is shown that P-free Sn-0.7Cu-0.05Ni solidifies with a near-eutectic microstructure whereas, when P is added to this alloy, a significant volume fraction of primary Sn dendrites form once the P content exceeds ∼0.01 mass% P. It is further shown that P additions decrease the ability of Sn-0.7Cu-0.05Ni to flow as it solidifies.
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  • Junya Okazaki, David Alfredo Pacheco Tanaka, Margot Anabel Llosa Tanco ...
    2008 Volume 49 Issue 3 Pages 449-452
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    Defect free palladium (Pd) and gold (Au) alloy membranes (4–5 μm thickness) supported on the porous α-alumina tubes were fabricated by electroless plating technique followed by thermal annealing. Contents of Au were adjusted from 0 to 10 mass% by controlling the concentration of K[Au(CN)4] in the electroless plating solution. The alloy membranes were characterized by the X-ray diffraction analysis, SEM observation, and elemental analysis with EDX and ICP-atomic emission spectrophotometry (ICP-AES). The performances of the Pd-Au alloy membranes were evaluated with respect to the hydrogen flux, perm-selectivity and long term operation tested at 600°C.
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  • Hiroo Takahashi, Hitoshi Takamura, Masuo Okada
    2008 Volume 49 Issue 3 Pages 453-456
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
    JOURNALS FREE ACCESS
    Mixed oxide-ion and electronic conductive thin films with the composition of (Ce0.85Sm0.15)O2−δ-15 vol%MnFe2O4 (CSO-MFO) were prepared on porous yttria stabrized zirconia substrates by a spin coating process, and their oxygen permeation flux densities were measured. The porous substrates were prepared from ZrO2-3 mol%Y2O3 (3YSZ)-33 vol%carbon and NiFe2O4. 3YSZ porous substrates were obtained from 3YSZ-33 vol%carbon by sintering at 1350°C under Ar for 5 h and following oxidation at 800°C under air for 2 h. For 3YSZ-33 vol%NiFe2O4, the optimum condition was sintering at 1400°C under air for 5 h and following reduction at 800°C under H2 for 2 h. A CSO-MFO film was prepared by a spin coating process on the substrate. The thickness of the CSO-MFO was approximately 150 nm. Oxygen flux density of the CSO-MFO sample was found to be 8.9×10−8 mol·cm−2·s−1.
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  • Yasutaka Kamata, Riki Kataoka, Daisuke Kyoi, Atsunori Kamegawa, Masuo ...
    2008 Volume 49 Issue 3 Pages 457-460
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
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    A novel intermetallic compound of MgNi was synthesized from amorphous MgNi by high pressure technique. Crystal structure, thermal stability and hydrogenation property of the compound were studied. The crystallized MgNi was synthesized at 573 K for 2 h under the pressure of more than 5 GPa, and was found to exhibit a CuTi-type structure with lattice parameters of a=0.2997(1) nm, c=0.3166(2) nm. The MgNi was decomposed into Mg2Ni and amorphous phase at 575 K and decomposed into Mg2Ni and MgNi2 over 682 K. Moreover the MgNi was hydrogenated into novel hydride with a CsCl-type structure at 355 K under 2 MPa hydrogen. This novel hydride with a lattice parameter of a=0.3215(1) nm was decomposed into Mg2Ni and MgNi2 over 428 K under an Ar atmosphere.
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  • Mitsuhiro Matsuda, Toru Hara, Minoru Nishida
    2008 Volume 49 Issue 3 Pages 461-465
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
    JOURNALS FREE ACCESS
    An antiphase boundary (APB)-like structure in the B19 martensite of Ti-Pd alloy has been investigated by transmission electron microscopy. High-resolution and high-angle annular dark-field scanning transmission electron microscopy images demonstrate the presence of an APB-like contrast along the (001) basal plane of the B19 martensite. The contrast is not inherited from the APB with a displacement vector of the type R=(1⁄2)⟨111⟩ in the B2 parent phase. These facts suggest that the boundary is induced by the local heterogeneity of atomic movements during the martensitic transformation. Therefore, we have newly proposed that the APB-like structure in the B19 martensite is defined as the displacive transformation-induced APB.
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  • Katsuya Inoue, Kozo Shinoda, Shigeru Suzuki, Yoshio Waseda
    2008 Volume 49 Issue 3 Pages 466-470
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    X-ray diffraction, transmission electron microscopy, and X-ray absorption spectroscopy were used for characterizing the role of nickel in the transformation of Green Rrust 2(SO42−) (GR2). GR2(SO42−) was synthesized from the solution of ferric and ferrous sulfate and that of sodium hydroxide. The suspension containing GR2(SO42−) with and without nickel was oxidized by passing oxygen gas into the aqueous solution, in which GR2(SO42−) was transformed into ferric oxyhydroxides. The pH and oxidation reduction potential (ORP) values of the aqueous solution were monitored during the transformation of GR2(SO42−). In addition, the concentrations of iron and nickel in the solution during the transformation of GR2(SO42−) were analyzed by using inductively coupled plasma atomic emission spectroscopy. The reaction conditions of the GR2(SO42−) suspension were found to be strongly influenced by the addition of nickel. The reaction product goethite, which was transformed from GR2(SO42−), also appeared to be stabilized by the addition of nickel. These results indicate that the species of the solid particles formed in the solution are controlled by the addition of foreign elements.
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  • Naoki Miyano, Akihiro Takahashi, Jun Miyazaki, Kei Ameyama
    2008 Volume 49 Issue 3 Pages 471-478
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
    JOURNALS FREE ACCESS
    This study focuses on the entire shape of the α precipitate in Ti-22V-4Al in terms of the interphase and elastic strain energies generated between the precipitate and matrix. In order to consider a transformation strain, the volumetric strain and strain relaxation by a misfit dislocation on the interphase boundary are calculated. Firstly, the atomic matching model is employed for determining the preferred habit planes by evaluating the results of geometrical atomic matching. Subsequently, the precipitate configuration that consists of the preferred habit plane is determined by the elastic strain with the minimum value. Then, the elastic strain surrounding and within the predicted precipitate is examined by an FEM analysis, which can be used to calculate the anisotropic elastic strain depending on the shape of the precipitate. A comparison of these results with regard to the precipitate observed by TEM elucidates the determination of the ideal shape of the precipitates in BCC/HCP systems; the optimum configuration of the precipitate that consists of the preferred habit plane is determined by the tradeoff relationship of two factors; one is the strain relaxation due to an increment in the broad face plane, and the other is the decrease in the total elastic strain as the surface ratio approaches a regular square.
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  • Koutarou Takeda, Kouji Yamashita, Yoshinori Murata, Toshiyuki Koyama, ...
    2008 Volume 49 Issue 3 Pages 479-483
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
    JOURNALS FREE ACCESS
    Interdiffusion coefficients of the refractory elements in Fe-Cr-X (X=Mo, W) and Fe-Mo-W ternary alloys were measured on the basis of the modified Boltzmann-Matano method for ternary systems. The cross interdiffusion coefficient, \\ ildeDCrWFe was positive in Fe-Cr-W ternary alloy, indicating that W accelerates interdiffusion between Fe and Cr atoms. On the other hand, the cross interdiffusion coefficient, \\ ildeDCrMoFe was negative in Fe-Cr-Mo ternary alloys, indicating that Mo suppresses interdiffusion between Fe and Cr atoms. In addition, the cross interdiffusion coefficient, \\ ildeDWMoFe was positive in Fe-Mo-W diffusion system. This result implies that Mo addition accelerates interdiffusion between Fe and W.
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  • Yuhki Tsukada, Yoshinori Murata, Toshiyuki Koyama, Masahiko Morinaga
    2008 Volume 49 Issue 3 Pages 484-488
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    In Ni-based superalloys, the rafted structure is known to form in the early stage of creep and to get into wavy morphology in the final stage of creep at elevated temperatures. This rafting phenomenon is essentially related to the anisotropic relaxation of the lattice misfit between the γ and γ′ phases due to the creep strain under the external stress. In this study, in order to simulate comprehensively from the formation to collapse processes of the rafted structure by the phase-field method, a new idea that the anisotropy increases with simulation time is employed in the calculation of the elastic strain energy in alloy. This idea corresponds to the phenomenon that creep strain increases with creep time. The results are in good agreement with the microstructural change observed in practical Ni-based alloys.
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  • Junji Imai, Tadashi Hamada, Tokuteru Uesugi, Yorinobu Takigawa, Kenji ...
    2008 Volume 49 Issue 3 Pages 489-493
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    In Fe-Cr-Ni-Al stainless steels, surface alumina layer with good adhesion is formed by heat treatment at a high temperature in oxidizing atmosphere and can prevent burrs from being formed in grinding of cutting edges. On the other hand, as the precipitation velocity of Ni-Al B2 phase particles dispersed in the matrix of these steels is remarkably high, it is hard to obtain a full solid-solution condition without any fine precipitates by conventional solution treatment. And, the dispersed particles increase the hardness of the material and it is impossible to decrease the hardness sufficiently to form the cutting blade only by the annealing after cold rolling. According to the process developed in this study, most of the B2 phase particles are dissolved once, cooled slowly and, thus, combined with remaining particles to form coarse particles. As a result, precipitation of fine particles is prevented and softening necessary to form into given shapes is achieved.
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  • Song Li, Guoqiang Xie, Dmitri V. Louzguine-Luzgin, Akihisa Inoue
    2008 Volume 49 Issue 3 Pages 494-497
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    New Ni-Zr-Cu-Ti-Al bulk metallic glasses (BMGs) were fabricated on the basis of ternary Ni-Zr-Al alloys. The addition of Cu and Ti increased the glass-forming ability (GFA) of Ni-Zr-Al alloys. These BMGs exhibited high thermal stability and relatively large supercooled-liquid region. With the substitution of Ni by Cu from 0 to 19.2 at%, the GFA of Ni-Zr-Ti-Al alloys was enhanced and its glass transition temperature Tg, onset crystallization temperature Tx, and onset melting temperature Tm all decreased. When Cu content was 24 at%, the GFA decreased again. The BMG rod with a maximum diameter of 2 mm was fabricated in the Ni43.7Zr19.2Cu19.2Ti13.9Al4 alloy and the compression tests indicated that it had high fracture strength of about 2400 MPa, Young’s modulus of 121 GPa, elastic strain of 0.02 and plastic strain of 0.009 at ambient temperature.
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  • Ichiro Seki, Hisamichi Kimura, Akihisa Inoue
    2008 Volume 49 Issue 3 Pages 498-501
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    Since Ti-based glassy alloys have high strength and high corrosion resistance, it is useful for an application field of substitution material for biomaterials such as living body bone. For the biomaterial use, the glassy alloys are required to substitute the harmful elements for the human body such as Ni. In the present study, we prepared the Ti47.4Cu42Zr5.3TM5.3(TM = Co, Fe) glassy alloy sheets by a twin-roller casting method, and investigated their thermal stability and mechanical properties. The prepared alloy sheets had flat surfaces with highly white luster, and exhibited a distinct glass transition typical to a glassy phase. The super-cooled liquid region ΔTx defined by the difference between the glass transition temperature (Tg) and the onset temperature for crystallization (Tx) is 50 K for the Ni-containing alloy, 36 K for the Co-containing alloy and 32 K for the Fe-containing alloy. All the alloy sheets exhibit good bending ductility and their Vickers hardness is in the range of 590 to 600.
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  • Shengli Zhu, Xinmin Wang, Masahiro Yoshimura, Akihisa Inoue
    2008 Volume 49 Issue 3 Pages 502-505
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    The spark plasma sintering process has been used to fabricate Ti40Zr10Cu36Pd14 glassy alloy/hydroxyapatite composites. XRD, DSC, SEM and compression testes were used to examine the microstructure and properties of the composites. No crystallization was observed in the glassy alloy matrix. The glass transition temperature (Tg) is independent of the HA addition and the onset temperature of crystallization (Tx) slightly decreases with increasing HA content. The sintered composite exhibited reduced value of Young’s moduli as compared with the as-cast Ti40Zr10Cu36Pd14 bulk glassy alloy.
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  • Sangmin Lee, Hidemi Kato, Takeshi Kubota, Kunio Yubuta, Akihiro Makino ...
    2008 Volume 49 Issue 3 Pages 506-512
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    Effects of Y addition on the glass forming ability (GFA) of a Fe-B-Nb marginal glass former, and annealing effects on glassy/supercooled liquid phases as well as soft magnetic properties in the multicomponent Fe-B-Nb-Y alloy system were investigated. The origin of highly improved GFA in the multicomponent system is discussed with related to a characteristic exothermic phase transformation, chemical short range ordering, in the supercooled liquid region due to the positive heat of mixing between Nb-Y elements. The separating tendency between Nb and Y elements is considered to suppress precipitation of metastable Fe23B6 and α-Fe crystalline phases, thus to result in highly improving GFA and distinct high thermal stability against heat treatment of the alloy system. In addition, a glassy ring was fabricated by copper mold casting and magnetic properties were investigated before/after heat treatment.
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  • Takahiro Okuno, Asahi Kawashima, Hiroaki Kurishita, Wei Zhang, Hisamic ...
    2008 Volume 49 Issue 3 Pages 513-517
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    Since the invention of bulk glassy alloys, a number of studies have been performed at ambient temperatures or above. However, little is known about mechanical properties of bulk glassy alloys at cryogenic temperatures. In this study, we investigated the effects of temperature and strain rate on the mechanical properties of a Cu45Zr45Al5Ag5 bulk glassy alloy fabricated by high pressure die casting methods. Compression tests were performed for the Cu45Zr45Al5Ag5 bulk glassy alloy rods with a diameter of 3 mm at temperatures of 298, 223, 173 and 77 K and at strain rates from 5×10−5 to 5×10−3 s−1. It is found that the maximum compressive stress and plastic strain to failure increase monotonically with decreasing testing temperature. Multiple shear bands are observed on the side surface of the specimen deformed plastically at cryogenic temperatures. The maximum compressive stress and plastic strain are almost independent of strain rate. The reason for the changes in the maximum compressive stress and plastic strain with temperature and strain rate is discussed.
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  • Masahiko Hatakeyama, Takeshi Toyama, Yasuyoshi Nagai, Masayuki Hasegaw ...
    2008 Volume 49 Issue 3 Pages 518-521
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    Nanostructural evolution of Cr (Cr-rich) precipitates in a Cu-0.78%Cr-0.13%Zr alloy has been studied after aging and overaging (reaging) by laser assisted local electrode 3 dimensional atom probe (Laser-LEAP). This material is a candidate for the first wall and divertor components of future fusion reactors. After prime aging at 460°C, Cr precipitates enriched with Zr were observed. Further reaging at 600°C caused the precipitates to grow to almost spherical Cr precipitates with 5 nm (1 h) in diameter and plate-like ones with 20 nm (4 h), respectively. Zr and impurities of Si and Fe were concentrated around the Cr precipitates, resulting in an almost pure Cr cores with interface regions enriched with Zr and the impurities. Probably, the strain induced by the incoherency of BCC Cr with matrix FCC Cu is relaxed by the formation of the enriched regions.
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  • Naokage Tanaka, Dong-Liang Peng, Kenji Sumiyama, Takehiko Hihara
    2008 Volume 49 Issue 3 Pages 522-526
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
    JOURNALS FREE ACCESS
    Ti cluster assemblies have been prepared by a plasma-gas-condensation cluster deposition system, where the Ar gas flow rate (RAr) was fixed and the He gas flow rate (RHe) was varied. The microstructure of Ti clusters has been observed by a transmission electron microscope (TEM). The mean Ti cluster size, dm, decreases with increasing RHe. Ti clusters are hexagonal close-packed (hcp) for dm>15 nm, while they are face-centered cubic (fcc) for dm<15 nm. The critical cluster size between the fcc and hcp phases is much larger than the theoretically predicted value and that (5–7 nm) for mechanically milled Ti powders. The fcc phase formation is attributed to the negative internal pressure in small Ti clusters. Moreover, Ti cluster assemblies have been prepared via the above-mentioned procedures with slight introduction of oxygen gas in the deposition chamber, and investigated by high resolution TEM, electron diffraction, and optical transmittance measurements. No clear core-shell morphology is observed in the partially oxidized Ti cluster assemblies.
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  • Jean-Claude Crivello, Tohru Nobuki, Toshiro Kuji
    2008 Volume 49 Issue 3 Pages 527-531
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    Copper and iron are immiscible elements according to the equilibrium phase diagram, but they can form metastable phases by mechanical alloying process.
    In this present work, mixtures of Cu-Fe powders in the range 0, 12, 25 and 40 atomic% of Fe have been prepared by ball milling. The analysis of alloyed samples shows a single phase described in the fcc-Cu structure, except for the 40%-Fe compound, which presents the additional bcc-Fe phase. The study of microstructure and magnetic properties under thermal treatments suggests a decomposition of the metastable phase with increasing temperature.
    In the Cu-richer domain, the fcc cell parameter increases with increasing Fe content. This effect is explained from the fact that the ferromagnetic Fe phase is dispersed in the form of nanosized particles in the paramagnetic Cu matrix, in agreement with previous reports.
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  • Hiroshi Hamasaki, Kazuhiro Shinbata, Fusahito Yoshida
    2008 Volume 49 Issue 3 Pages 532-537
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
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    A system for material parameter identification by depth-sensing micro-indentation, Finite Element (FE) simulation and optimization has been developed. In this system, the material parameter identification is treated as an optimization problem by minimizing the difference between experimentally obtained indentation load vs. penetration (P-h) curves and the corresponding FE simulation results. To reduce the computation time, a multipoint approximation response surface methodology (MARS) is used in combination with the interaction of high- and low-fidelity analysis algorithms. Using this system, the viscoplastic properties of a lead-free solder (Sn-3.5Ag-0.75Cu) were identified. This identification method has been confirmed by comparing the obtained material parameters with those determined from uniaxial compression tests.
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  • Taichi Murakami, Ryoji Sahara, Daisuke Harako, Masahiro Akiba, Takayuk ...
    2008 Volume 49 Issue 3 Pages 538-547
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: January 23, 2008
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    The effects of 25 kinds of solute elements on hardness and grain size in annealed Pt-based binary alloys were investigated together with cold workability and a hardness variation with a cold rolling reduction. Gain size largely varied depending on solute elements and their concentrations, and so the decrement in grain size per 1 at% solute addition was evaluated based on grain size difference between pure platinum and a respective alloy. This value markedly reduced in the low solute concentration range below 5 at%, followed by a sluggish reduction in the higher solute concentration range. Hardness values obtained in all alloys were corrected considering contribution of hardening due to grain refinement, and solid solution hardening was evaluated by the increment in hardness per 1 at% solute addition. The lattice constants of pure platinum and alloys were measured to calculate the size misfits. The increment in hardness increased with the increase in the size misfit in all alloys, and this relationship was clearly divided into two groups depending on whether the binary alloy system is a completely miscible type or a type with the solubility limit. The increment in hardness in the latter type of alloys was much higher than that of the former, and this value became larger with the increase in the inverse value of the solubility limit in Pt-based binary alloy. The superior cold workability and very similar work hardening behavior were observed in all Pt-based binary alloys.
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  • Akira Shimamoto, Hiroshi Ohkawara, Sung-mo Yang, Dae-kue Choi, Satoshi ...
    2008 Volume 49 Issue 3 Pages 548-553
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
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    Various stainless steels were investigated to examine the new NDE technique. The new NDE technique did not depend on either magnetization or demagnetization of materials. The magnetic flux caused by stress concentration in stainless steels was examined with the ultra sensitive magnetic flux density meter. Tensile and biaxial fatigue tests were conducted to observe the magnetic flux leakage. Results from biaxial fatigue tests indicated that the measured magnetic flux curves had local periodical cycles with global increasing tendencies. The defect evaluation would be possible by comparing the flux density value at the stress concentration regions with that of other areas.
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  • Masataka Hakamada, Akira Watazu, Naobumi Saito, Hajime Iwasaki
    2008 Volume 49 Issue 3 Pages 554-558
    Published: March 01, 2008
    Released: February 25, 2008
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    Continuously-casted Mg-9Al-1Zn-1Ca (in mass%) alloy (Mg-Ca alloy) and Mg-9Al-1Zn alloys (Ca-free Mg alloy) were forged at 573 K and their mechanical properties were investigated by tension tests at ambient temperature and 573 K. The forged Mg-Ca alloy showed higher 0.2% proof stress than the forged Ca-free Mg alloy. The high strength for the Mg-Ca alloy was attributed not only to grain refinement by hot forging, but also to the strengthening mechanisms arising from the difference in thermal expansion and geometrical incompatibility between Mg matrix and second phase. The Ca addition decreased the elongation to failure; however, the decrease was reduced for the forged specimens, compared to the unforged specimen. This results from segmentation of the second phases by the hot forging. Also, the forged Mg-Ca alloy showed a large elongation of 284% at 573 K.
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  • Meng-Yin Tu, Wen-Hsiung Wang, Yung-Fu Hsu
    2008 Volume 49 Issue 3 Pages 559-564
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
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    This study investigates the relationship between the morphology and the fracture behavior of upper bainite in JIS SK5 steel. The cleavage crack path was found to lie on {001}α, {112}α or {123}α using electron backscatter diffraction (EBSD) from the fracture surface. Additionally, most of the bainite sheaf boundaries were found to be high-angle boundaries. If the cleavage planes are presumed to lie uniquely on {001}α, then most of the deviations of the angles between two K-S variants in a given austenite grain are high-angle deviations. According to TEM diffraction analysis, the orientation relationship of cementite/bainitic ferrite satisfies the Bagaryatskii relation, and the habit plane of cementite precipitated in the bainite sheaf locates on (0\\bar11)α||(100)θ. Cementite does not significantly affect the propagation of a cleavage crack. Hence, cleavage cracking deflects at grain boundaries or bainite sheaf boundaries, but only reinitiates at the cementite/bainitic ferrite interface.
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  • Hyoung-Ho Lee, Junji Shibata, Ji-Whan Ahn, Hwan Kim
    2008 Volume 49 Issue 3 Pages 565-571
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
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    In our previous report, ethylamine was confirmed to have an affirmative effect on the improvement of structural stability of MCM-41 mesostructure. It was also found that the addition of ethylamine causes structural changes. This report presents an in-depth study on the effect of alkylamine with a short alkyl chain by analyzing produced mesoporous structures. It is found that ethylamine dissolves into cetyltrimethylammoniumbromide (CTAB) micelles when it is added together with ethanol. Several different short chain alkylamines were also examined without adding ethanol. With an increase in the hydrophobic chain length, indications of amine participation as a cosurfactant are intensified. The amine species participating in the templating process is identified to be neutral. The amines conditioned in a pH range above pKa are found to strongly affect pore-to-pore distance and textural mesoporosity by dissolving themselves in micelles. Effect of short chain alkylamine is discussed with considerations of energy changes associated with micelle formation.
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  • Shigeru Ueda, Katsunori Yamaguchi, Yoichi Takeda
    2008 Volume 49 Issue 3 Pages 572-578
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
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    Phase equilibrium and oxygen partial pressure for the Fe-S-O system from eutectic temperature to 1673 K were investigated by chemical equilibrium techniques and the EMF method. The liquid phase is saturated with Fe, FeO, Fe3O4 and FeS. The partial pressure of oxygen increases remarkably with departing from the liquidus saturated with Fe. According to the Gibbs-Duhem equation and Schumann’s method, the activities of Fe and the partial pressure of S2 for the liquid phase are derived.
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  • Haruo Baba, Yasuyuki Katada
    2008 Volume 49 Issue 3 Pages 579-586
    Published: March 01, 2008
    Released: February 25, 2008
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    Austenitic stainless steels were produced based on a Fe-23 mass%Cr-4 mass%Ni alloy with varying nitrogen (0.7–1 mass%) and molybdenum contents (0–1 mass%), through electro-slag remelting (ESR) under high nitrogen gas pressure. The effects of nitrogen on crevice corrosion behavior in an acidic chloride solution were investigated, and the passive film of the crevice corrosion area after corrosion tests was analyzed using X-ray photoelectron spectroscopy (XPS). At the same time, the effects of nitrogen on the passivation behaviors after scratching were also investigated. During crevice corrosion at a noble potential of 0.7 V (SCE), the nitrogen in solid solution in the steel dissolves into the solution as NO3, and its concentration increases with the nitrogen content in the steel. It was also established that the number of corrosion spots, the corrosion loss, and the maximum depth of corrosion all decrease with the increase in the nitrogen content present in the steel and the applied potential. Such results can be attributed to the presence of NO3 dissolved into the aqueous solution. On the other hand, results from scratch tests show that the increase in the amount of added nitrogen decreases the peak value of passivation current as well as the amount of electricity during repassivation, suggesting that nitrogen stimulates the passivation process and suppresses the occurrence of crevice corrosion. XPS analysis shows the presence of nitrogen as nitrides and NH3 in the surface layer of crevice corrosion and the internal layer of passivation films.
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  • Masatsugu Kamiya, Takao Yakou, Tomohiro Sasaki, Yoshiki Nagatsuma
    2008 Volume 49 Issue 3 Pages 587-592
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: January 30, 2008
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    The effect of eutectic Si or primary Si on the machinability of Al-Si alloy castings, where eutectic Si or primary Si was served to improve the chip breakability were investigated. To enhance chip breakability, eutectic Si made the chips thin, and cracks that formed in primary Si during machining acted as nuclei for chip breaking. Eutectic Si had a stronger effect on surface roughness than primary Si, and eutectic Si reduced the adhesion on the cutting edge. The decrease in adhesion on the cutting edge led to a corresponding decrease in surface roughness. The cracking of primary Si was responsible for the increase in surface roughness in hypereutectic alloys. Tool wear increased with increasing amount of eutectic Si. In hypereutectic alloys, tool wear was accelerated by the contact between the tool and cracked primary Si.
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  • H. K. Kim, T. Nakayama, J. Shimizu, K. Kimura
    2008 Volume 49 Issue 3 Pages 593-599
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
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    Thermoelectric properties of metal (V, Co, Zr, Sr, W)-doped β-rhombohedral boron (β-Boron) were examined in the temperature range from 353 K to 1073 K. Doping with V (V1.5B105), which preferentially occupy the A1 sites, results in a great increase of electrical conductivity σ and a negative Seebeck coefficient S, while doping Co, Zr, Sr or W (M1.0B105, M=Co, Zr, Sr or W) also increases the σ though S remains positive. By crushing and hot pressing as-melted samples, the thermal conductivity κ was decreased to almost half of that of arc-melted samples. As a result, V-doped and hot-pressed n-type β-Boron had a ZT value of about 0.01 at 885 K, which approaches that of boron carbide, which exhibits the maximum ZT value among the boron-rich icosahedral cluster solids.
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  • Nittaya Keawprak, Rong Tu, Takashi Goto
    2008 Volume 49 Issue 3 Pages 600-604
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: January 23, 2008
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    Sr-Ru-O in the ratio of Ru to Sr (RRu/Sr) from 0.5 to 1.2 were prepared by spark plasma sintering (SPS) and the effect of composition on the electrical conductivity (σ), thermal conductivity (κ) and Seebeck coefficient (S) was investigated. All compositions yielded dense sintered mass with around 90–100% of a theoretical density. SrRuO3 and Sr2RuO4 in a single phase were obtained at RRu/Sr=1.0 and 0.5, respectively. The second phases were identified, i.e., RuO2 and Ru at RRu/Sr>1.0 and Sr3Ru2O7 and Sr2RuO4 at RRu/Sr<1.0. The σ increased with increasing RRu/Sr in the RRu/Sr range from 0.8 to 1.2 at room temperature exhibiting a metallic behavior, whereas the σ showed a semiconducting behavior at RRu/Sr=0.5. The κ was around 2 to 7 Wm−1 K−1 at RRu/Sr=0.8 to 1.2 at room temperature and slightly increased with increasing temperature and RRu/Sr. The κ decreased with increasing temperature at RRu/Sr=0.5. The S was around 25–40 μV K−1 at room temperature, almost independent of compositions. The S slightly decreased with temperature at RRu/Sr=0.8 to 1.0, whereas the S increased with temperature and showed a maximum around 500 to 600 K at RRu/Sr=1.2. The S significantly decreased with increasing temperature at RRu/Sr=0.5. The highest dimensionless figure of merit (ZT) was 0.06 at RRu/Sr=1.2 at 600 K.
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  • Keiko Sasaki, Minoru Matsuda, Tomohiro Urata, Tsuyoshi Hirajima, Hidet ...
    2008 Volume 49 Issue 3 Pages 605-611
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
    JOURNALS FREE ACCESS
    A Paraconiothyrium sp. WL-2 of Mn-oxidizing fungus is highly tolerant to Mn2+ ions, and capable of oxidizing more than 380 mg dm−3 of Mn2+ ions, leading to the formation of a large amount of insoluble Mn(III, IV) oxides. The biogenic Mn oxides were characterized by X-ray diffraction, FT-Infrared spectroscopy, elemental analysis, measurement of specific surface area, scanning electron microscopy, and measurement of zeta potential, in comparison with the synthetic Mn oxides. It was found that the biogenic Mn oxide is poorly crystalized birnessite, with higher porosity and much more weakly bounded Mn(II) on the surface than the synthetic Mn oxide. Cobalt(II) ions were sorbed and incorporated as Co(III) into the structure of the biogenic Mn oxide. Sorption efficiency in the biogenic Mn oxide was 5.6 times as high as that in the synthetic ones. Relation of the relased Mn2+ ions to the immobilized Co suggested that Mn(IV) is preferentially used as oxidants over Mn(III) in the biogenic Mn oxide, and emphasized that the existence of Mn(III) in the biogenic Mn oxide activates the geochemical cycles of Mn and the other involved elements in environments.
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  • Takaaki Wajima, Kazuharu Yoshizuka, Takashi Hirai, Yasuyuki Ikegami
    2008 Volume 49 Issue 3 Pages 612-618
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
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    During quarrying, waste stone cake is discharged as industrial waste. In this study, we attempted to convert waste sandstone cake to zeolitic materials using alkali fusion method. By varying the experimental conditions different types of the product were obtained, e.g. zeolite-X, zeolite-P, hydroxysodalite, tobermorite, and nepheline. The siliceous minerals in the cake were transformed into soluble phases, while calcite remains in the solid after 24-agitation following alkali fusion. The optimum condition of zeolite-X synthesis in the product is that the mixed ratio of NaOH to the cake is 1.6, fusion temperature is 600°C, and heating time at 80°C is less than 12 h. The results of the sorption experiments suggest that the product can be applied in environmental field such as the removal of pollutant.
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  • Shih-Hsien Chang, Shih-Chin Lee, Tzu-Piao Tang
    2008 Volume 49 Issue 3 Pages 619-623
    Published: March 01, 2008
    Released: February 25, 2008
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    The aim of this paper was to study the effects of die life through shot peening treatments on AISI H13 steel, and tests were performed to study the influential parameters of the shot peening process. To evaluate the effects of microstructure and the die life of AISI H13 steel after steel shot peening processes, we conducted and evaluated roughness tests, micro hardness and wear tests, and SEM microstructure inspections. The shot peening process was conducted under a pneumatic peening machine. Experimental results showed that 0.3 mm steel shots and 30 minutes at 451 kPa of shot peening treatment was optimum for AISI H13 steel for improving wear resistance and the die life of steel. It enhanced the surface hardness to HV 561 and extended ability of the limit wear resistance for AISI H13 steel. Dislocation microstructure emerged on the steel surface by shot peening. In particular, this technology has been successfully applied to forging die, and is able to improve and extend the die life of steel 2 to 3 times.
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  • Jhewn-Kuang Chen, Tzu-Piao Tang, Sen-Fu Chan, Shih-Hsien Chang
    2008 Volume 49 Issue 3 Pages 624-628
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 06, 2008
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    0–25 mass% of ∼2 um and ∼20 um TiC powders are added to vanadium and chromium containing steel powders to form metal matrix composite tool steels. The metal and ceramic powders are encapsulated and hot isostatically pressed for densification. Their density and mechanical properties are characterized. Product densification of over 99.9% theoretical density is achieved. Its hardness is found to increase with the amount of TiC addition. Product with over HRc65 hardness is obtained with addition of 25 mass% coarse TiC particles in which the matrix and strengthening particles intermix uniformly. The fine TiC particles distributed as packs at the intergranular regions of the matrix phase and give less hardening effects. The flexural strength is reduced by TiC addition regardless of TiC particle size, because the flexural strength is controlled mainly by crack initiation and less by crack propagation. For impact test, brittle fracture is induced by high strain rate which initiates the cracks with ease in both matrix and hard phases. The impact toughness is thus increased slightly with TiC showing fine particles are more effective in blocking crack tip propagation in high strain rate testing condition.
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  • Kojiro Akiba, Mitsutoshi Ueda, Kenichi Kawamura, Toshio Maruyama
    2008 Volume 49 Issue 3 Pages 629-636
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    The continuous monitoring of the oxygen chemical potential at a surface of a growing oxide surface formed in high temperature oxidation of a metal was developed. During the oxidation of nickel and cobalt at 1373 K in Ar-21%O2 gas, the oxygen chemical potentials at the surface of formed NiO scale and CoO scale were slightly smaller than that in the atmosphere, because the growths of these oxide scales were mainly rate-limited by the diffusion of the constituent ions in the scales. The difference of the oxygen chemical potential between at the surface of CoO scale and in the atmosphere was larger than that between at the surface of NiO scale and in the atmosphere under the same oxidation condition, since the oxygen consumption rate for the oxidation of cobalt was larger than that of nickel. In the case of the oxidation of iron at 1373 K in Ar-CO-CO2 gas mixture, the oxygen chemical potential at the surface of formed FeO scale decreased largely from that in the atmosphere, since the growth of FeO scale was very fast and mainly rate-limited by the mass transport from gas phase to the scale surface. The oxygen chemical potential at the surface of FeO scale increased with increment of CO2 concentration in the atmosphere.
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  • W. G. Wang, K. C. Chang, K. Matsugi, G. Sasaki
    2008 Volume 49 Issue 3 Pages 637-642
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
    JOURNALS FREE ACCESS
    Aluminum borate whisker (Al18B4O33w, denoted by ABOw) reinforced AZ91D (Mg-9.1 mass%Al-0.7 mass%Zn) magnesium alloy composite was fabricated by squeeze casting. AZ91D/ABOw composite and AZ91D alloy were aged at 443 K in oil-bath. The composite exhibited an accelerated age-hardening response comparing with AZ91D alloy. Age-hardening efficiency of composite was better than that of AZ91D alloy. It was attributed to the interfacial reaction between AZ91D alloy matrix and ABOw. The interfacial reaction increased aluminum elements in the matrix and MgO interfacial reaction layer restrained the formation of interfacial precipitate, resulting in more amounts of continuous precipitates and smaller inter-precipitates spacing within the composite matrix.
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  • K. Kitamura
    2008 Volume 49 Issue 3 Pages 643-649
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
    JOURNALS FREE ACCESS
    Fracture surface energy is calculated for a one-dimensional exactly solvable model for tensile cracks. Temperature- and force-dependendent crack surface tension is obtained on the basis of the self-consistent Einstein approach. Equilibrium lattice vibrations result in strong reduction of crack surface tension. In stark contrast to the Griffth concept, surface tension is a crack-size-dependent quantity in the nanoscale range.
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  • Tadashi Inoue, Katsuhisa Yamauchi, Fumio Fujita
    2008 Volume 49 Issue 3 Pages 650-654
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
    JOURNALS FREE ACCESS
    The present study focused on improving the hot ductility and magnetic properties of PC Permalloy. An alloy with a chemical composition of 78.5 mass%Ni-4.3 mass%Mo-2.2 mass%Cu-0.47 mass%Mn-Fe exhibits the optimum permeability, with μ0.005 of 411,200 and μm of 437,400. The P-value of the alloy was 3.43. Addition of Boron caused undesirable deterioration of magnetic properties, while the effects of Magnesium and Calcium on magnetic properties were small. Mill trials using a 50-ton electric furnace revealed that PC Permalloy with a composition of 78.6 mass%Ni-4.2 mass%Mo-2.1 mass%Cu-0.57 mass%Mn-14 ppmCa-4 ppmS-Fe exhibits extremely high permeability (i.e., μ0.005, 233,000 to 499,000; μm, 368,000 to 568,000). High-permeability alloy sheets were obtained by controlling the P-value in the range of 3.45 to 3.49. The hot ductility of the alloy was markedly improved, and ingots and slabs were hot rolled without any corner cracks.
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  • Fei-Shuo Hung, Fei-Yi Hung, Che-Ming Chiang, Truan-Sheng Lui
    2008 Volume 49 Issue 3 Pages 655-660
    Published: March 01, 2008
    Released: February 25, 2008
    JOURNALS FREE ACCESS
    Sn-xAl powder complex materials are used as coating in building materials. This study coats complex colloid mixed with Sn-xAl powders and polyethylene on glass to examine the shield effect on electromagnetic interference (EMI). The results show that adding Al to the Sn-xAl powders can increase the electromagnetic interference (EMI) shield at lower frequencies. Notably, the number of cavities in the coating layer increased with the coating thickness, with the result that the EMI shield could not improve with an increase in the coating thickness at higher frequencies.
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  • Di Zhang, Kenjiro Sugio, Kazuyuki Sakai, Hiroshi Fukushima, Osamu Yana ...
    2008 Volume 49 Issue 3 Pages 661-670
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
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    The effect of the volume fraction of second-phase particles on the distribution of damaged particles and its relation to the tensile deformation behavior were investigated in the particle reinforced metal-matrix composites, Al-SiC. The spatial distributions of all SiC particles and the delaminated SiC particles were evaluated from their two-dimensional local number (LN2D). During tensile deformation, larger SiC particles in more highly clustered regions were more easily delaminated at the particle/matrix interface. The amount of particle delamination in the more highly clustered region increased with increasing volume fraction and strain during tensile deformation. A model was developed to explain the flow behavior of the composites; this showed a good fit to the experimental results in the presence of particle damage, especially when the spatial distribution of damaged particles was taken into consideration.
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  • Di Zhang, Kenjiro Sugio, Kazuyuki Sakai, Hiroshi Fukushima, Osamu Yana ...
    2008 Volume 49 Issue 3 Pages 671-680
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 14, 2008
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    A newly developed model was proposed to predict the flow and strain-hardening behavior of the heterogeneously dispersed Al-10 vol%SiC composites with particle damage in tensile deformation. The frequency of local number of particles was decomposed into several Poisson distributions and the frequency of local number of damaged particles was approximated by one Poisson distribution. Then, the flow stress was obtained by summation of strain-hardening rate for each decomposed distribution and/or relieved stress for the distribution of damaged particles. This model gave a good agreement with the experimental results.
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  • Hidetoshi Somekawa, Norio Maruyama, Sachiko Hiromoto, Akiko Yamamoto, ...
    2008 Volume 49 Issue 3 Pages 681-684
    Published: March 01, 2008
    Released: February 25, 2008
    [Advance publication] Released: February 20, 2008
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    Tensile, compression and fatigue tests were carried out on a commercially extruded Mg-Al-Zn alloy having an average grain size of about 15 μm. The tensile and compression tests at room temperature showed that the yield strength in tension was much higher than that in compression. The lower yield strength in compression resulted from its texture. The effects of the mechanical anisotropy on the fatigue behavior and its deformed microstructure were also investigated under a stress ratio of R=0.1 and −1. The fatigue strength, stress amplitude, at N=107 cycles under R=−1 and 0.1 was about 120 and 90 MPa, respectively. The mechanical properties and the deformed microstructure observations indicated that the formation of deformation twins was related to the between maximum stress and the yield strength in tension and compression: the deformation twins were formed in the sample (maximum stress is higher than the yield strength) and showed no deformation twins in the sample (maximum stress is lower than the yield strength).
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