Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
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Volume 45, Issue 6
Displaying 1-20 of 20 articles from this issue
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  • Microstructure and Properties of Si-Ti-C-O Fiber-Bonded Ceramics
    Toshihiro ISHIKAWA, Shinji KAJII, Kenji MATSUNAGA, Toshihiko HOGAMI, Y ...
    1996 Volume 45 Issue 6 Pages 593-598
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.593
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    The microstructure and mechanical properties of Si-Ti-C-O fiber-bonded ceramics (Tyrannohex (R)) produced by hot-pressing pre-oxidized Si-Ti-C-O fibers with a surface oxide (SiO2 and TiO2) layer of 250, 430 and 580nm thickness were investigated. The hot-pressing temperature and pressure were 2023K and 50MPa, respectively. Tyrannohex, which was produced using the pre-oxidized fiber with a surface oxide layer of 250nm thickness, showed a close-packed structure with 90% of volume fraction (Vf) of the fiber. The interstices were packed by an oxide material, which existed on the surface of the raw fiber. It was observed that the oxide material changed to TiC-particle dispersed structure by a reaction between TiO2, which existed on the fiber's surface, and excess carbon in the fiber during hot-pressing. Moreover, an interfacial carbon layer (10-20nm) around the fiber was formed. Tyrannohex showed very high fracture energy (8900J/m2) by Chevron notched beam method. Tyrannohex (Vf=90%) showed elastic fracture behavior without any plasticity even at 1673K, because all the fibers were restricted by the close-packed structure. At all the contact points of the fibers, an interfacial carbon layer existed without oxide material. About 90% of the initial strength was maintained after heat-treatment in air for 1000 hours because of an effective formation of a protective oxide layer on the surface.
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  • Effect of SiC Addition to the Mechanical Properties of Al2O3/TiC/Ni Symmetric Functionally Graded Materials
    Kimiaki TANIHATA, Zhensi LI, Yoshinari MIYAMOTO
    1996 Volume 45 Issue 6 Pages 599-603
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.599
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    Symmetrically graded materials of the Al2O3-SiC/TiC/Ni/TiC/SiC-Al2O3 system were fabricated by SHS/HIP. Strong residual compressive stress can be induced in the outer layer due to the thermal expansion mismatch between the outer and inner layers, resulting in simultaneous enhancement of hardness, toughness and strength of the outer layer. The dispersion of SiC in the outer Al2O3 layer increased the residual stress comparing with the Al2O3/TiC/Ni/TiC/Al2O3 system because the thermal expansion coefficient of the outer layer was reduced with SiC having smaller thermal expansion coefficient than Al2O3. Stress analysis was carried out for both systems by means of finite element method, and the relations of the internal stress distribution and mechanical properties were discussed.
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  • Chemical Stability of Ca or Sr Doped Lanthanum Chromites under High Temperature Reduced Atmosphere
    Hua-Bing ZHOU, Hiroaki TAIRA, Hiroshi TAKAGI, Kunisaburo TOMONO
    1996 Volume 45 Issue 6 Pages 604-608
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.604
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    Lanthanum chromites ((La, A) (Cr, M) O3; A=Ca, Sr, M=Co, Ni, Cu, Zn) were synthesized and characterized from their density, thermal expansion coefficient and chemical stability. Cobalt doped lanthanum calcium chromites with La-site/Cr-site ratio>1 were densely sintered at 1400°C, and it is possible to adjust the thermal expansion coefficient to that of YSZ by controlling the amount of dopants. Lanthanum strontium chromites with La-site/Cr-site ratio=1 were not densely sintered at lower temperature than Ca-doped, but kept enough strength after reduction treatment. difference of strength change after the reduction treatment between Sr-doped and Ca-doped ones is related to the difference in lattice expansion after the treatment.
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  • Effect of Oxidation on Fracture Mechanical Properties of Isotropic Graphite
    Tadahiro NISHIKAWA, Sawao HONDA, Wataru NITTA, Manabu TAKATSU
    1996 Volume 45 Issue 6 Pages 609-613
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.609
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    The mechanical properties and fracture behavior of isotropic graphite were investigated after oxidation at 400 or 500°C in air. The bending strength after oxidation was affected significantly by the surface roughness, which was depended on open pores estimated by kerosine. The bending strength decreased with increasing porosity, given by σ=σ0exp(-bp), where σ0 and b were constants. The fracture energy of isotropic graphite was obtained from the load-displacement curve by using a CT specimen. The total fracture energy and elastic fracture energy decreased with the extended oxidation, accompanied with weight loss and increase of porosity. Pores were not localized at the fracture surface after oxidation, but the number of pores increased with oxidation time. The modified fracture energy could be determined by the calculated fracture area A', which was estimated from the area A for non-oxidized specimen and the porosity p for the oxidized specimen, as A'=A(1-p2/3). The modified fracture energy of isotropic graphite after oxidation was constant and independent of the degree of oxidation.
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  • Thermal Shock Resistance of β'-Sialon-BN Composites Prepared by Pressureless Sintering and Reaction Bonding
    Seiji HAYAMA, Masakuni OZAWA, Suguru SUZUKI, George Sy CHUA, Kunji YAM ...
    1996 Volume 45 Issue 6 Pages 614-619
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.614
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    The thermal shock resistance of β'-Sialon-BN composites prepared by two different sintering processes, pressureless sintering (PLS) and reaction bonding (RB), were investigated with respect to the effect of hexagonal-BN content. The addition of BN showed increasing porosity for PLS body and crack extension for RB body. The water quenching thermal shock test showed that PLS body had better thermal shock resistance, especially for BN 20 mass%, than RB body. The results could be explained using Hasselman's theory, indicating that PLS bodies have shorter crack length with higher crack density.
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  • Preparation and Dielectric Properties of Anisotropic BaTiO3 Ceramics Using Doctor Blade Method
    Takashi HAYASHI, Norihiko SHIMURA, Isamu HIRONAGA
    1996 Volume 45 Issue 6 Pages 620-623
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.620
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    Grain orientated BaTiO3 ceramics were fabricated using a doctor blade technique with BaTiO3 fibers. A small amount of niobium oxide was added in order to depress the influence of potassium ion contained in BaTiO3 fibers which deteriorates dielectric properties. The following results were obtained;
    (1) BaTiO3 ceramics exhibited anisotropic dielectric properties. The dielectric constants of BaTiO3 ceramics in the plane perpendicular to the tape casting direction were higher than those in the parallel direction.
    (2) The addition of a small amount of niobium oxide to BaTiO3 improved the dielectric properties.
    (3) Nb2O5-added anisotropic BaTiO3 ceramics exhibited grain orientated microstructure.
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  • Thermally Stimulated Luminescence in X-Ray Irradiated Oxide Glasses Doped with Ce (III)
    Katsuhisa TANAKA, Kazuyuki HIRAO, Hideki TANAKA, Naohiro SOGA
    1996 Volume 45 Issue 6 Pages 624-629
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.624
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    Thermally stimulated luminescence has been observed in X-ray irradiated alkali borate and sodium silicate glasses doped with Ce3+. The emission wavelength is about 360nm which corresponds to the 5d-4f transition of Ce3+. For the alkali borate glasses doped with Ce3+, oxygen hole center and electron trapped nearby alkali ion induced by X-ray irradiation contribute to the thermally stimulated luminescence, while Sm3+ acts as an electron acceptor in the thermally stimulated luminescence of alkali borate glasses codoped with Ce3+ and Sm3+. In both cases, Ce3+ is ionized by X-ray to form Ce4+ and an electron which is trapped by an impurity level (oxygen hole center or Sm3+ in glasses with or without Sm3+, respectively). The thermal stimulation excites the electron (electron trapped nearby alkali ion or Sm3+), which transfers to the 5d level of Ce3+. The electronic transition from the 5d to the 4f levels gives rise to the emission observed. The temperature which gives the maximum emission intensity in the glow curve tends to decrease as the concentration of Na2O increases in the sodium borate glasses doped with Ce3+ and Sm3+. In contrast, the temperature corresponding to the maximum emission intensity is independent of the glass composition for the sodium silicate glasses doped with Ce3+ and Sm3+. These facts suggest that the compositional dependence of local basicity for Sm3+ ion site in sodium borate glasses is different than that in sodium silicate glasses.
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  • Color Change of Glass and Glass-Ceramics in Bi2O3-CdO-Al2O3 System
    Danping CHEN, Yoshinari MIURA, Tokuro NANBA, Yasuaki MURATA, Akiyoshi ...
    1996 Volume 45 Issue 6 Pages 630-636
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.630
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    Color change and its mechanisms for glasses and glass-ceramics in the Bi2O3-CdO-Al2O3 system prepared under various melting and annealing conditions were investigated. It was suggested that brown color of the glasses with comparatively low Bi content which were obtained by melting at high temperatures was caused by metallic Bi while deep green color of the glasses with comparatively high Bi content resulted from Bi2+ and defects. The deep color of the glasses markedly faded after annealing treatments for long time. Formation of the transparent glass-ceramics was assumed to be related to the oxygen defects. Color of the glass-ceramics was explained in term of oxygen defects and crystalline phases formed by annealing treatments.
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  • Change in Preferential Orientation of α Phase Transforming from β' Cu-Zn Alloys with Zinc Concentration
    Susumu IKENO, Osamu KUME, Hitoshi YOSHIMOTO, Hiroshi ANADA, Kenji MATS ...
    1996 Volume 45 Issue 6 Pages 637-642
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.637
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    In order to clarify the effect of Zn concentration on the habit planes of α phase in the β' matrix, an embossing method and SEM-ECP observation were applied to Cu-39.6 mass%Zn alloy and Cu-43.2 mass%Zn alloy. In the both alloys, α phase, which always exists as a pair of plates, had a straight line at the center of the triangular α phase as one of the feature. For the relatively lower Zn content alloy (Cu-39.6 mass%Zn alloy), the habit plane of α phase in β' matrix was found near {3 17 18}m plane of the matrix. In this case, four kinds of crystallographically equivalent habit planes, (3 17 18), (3 18 17), (3 17 18) and (3 18 17) existed, and the values of these habit planes were almost equal to those of {5 27 29}m obtained for Cu-41.7 mass%Zn alloy. For the relatively higher Zn content alloy (Cu-43.2 mass%Zn alloy), the habit plane of α phase in β' matrix existed near {3 14 14}m plane of the matrix. Merely two kinds of crystallografically equivalent habit planes, (3 14 14) and (3 14 14) were found in this alloy.
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  • Simulation of Quenching-Tempering Process Based on Metallo-Thermo-Mechanics
    Dong-Ying JU, Masato SAHASHI, Takahiro OMORI, Tatsuo INOUE
    1996 Volume 45 Issue 6 Pages 643-649
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.643
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    This paper is concerned with the metallo-thermo-mechanical simulation considering the interaction among phase transformation, temperature and stress/strain by the finite element technique for a quenching-tempering process. Here, a method for evaluating the change of volume fraction due to phase transformation, controlled by a diffusion mechanism in the heating process before quenching and tempering process, is presented. Some results of simulation for the ring shaped model of a carbon steel are compared with the experimental data to verify the analytical results, and discussions are also given on the operating conditions in the quenching-tempering process.
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  • Tensile Deformation Behaviour of Rubber Composite Plate
    Takeji ABE, Masahiko HASHIZUME, Kunihiko TAKESUE, Mamoru OCHI, Ichiro ...
    1996 Volume 45 Issue 6 Pages 650-655
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.650
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    Deformation behaviour of inhomogeneous composite rubber plate under tensile deformation was studied experimentally and numerically. Two kinds of natural rubber plates were bonded together to make the composite specimen. Strain distribution in the plate was measured from the displacement of the dot marks pasted on the specimen surface. The finite element method for incompressible elastic body was used for the numerical simulation of tensile deformation both under the plane strain and the plane stress conditions. A parameter called constraint ratio was introduced to describe the deformation behaviour of inhomogeneous material, and comparison was made between the experimental and the numerical results.
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  • Improvement of Fracture Toughness of Aluminum-Lithium Alloy 8090 Plate by Double Aging
    Shuhei OHSAKI, Kazunori KOBAYASHI, Kazuhiko YOSHINO, Makio IINO, Toshi ...
    1996 Volume 45 Issue 6 Pages 656-660
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.656
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    The short-transverse fracture toughness behavior of aluminum-lithium alloy 8090 plate was investigated by using a CNSB (chevron notched short bar) specimen. The fracture toughness KQVM was reduced with a progress of the first-step aging. The double-aged (DA) alloy, which was subjected to the initial underaging (UA2) at 433K followed by the second-step aging at a higher temperature for a short time, exhibited a fairly improved KQVM and a superior strength-toughness balance in comparison with the single-aged alloy, good enough to satisfy the toughness requirement in aircraft design, KQVM/σys≥2.5√mm, where σys is yield strength. The increase in toughness by DA treatment is attributed to the relaxation of intense slips due to dissolution of shearable δ' phase and growth of δ'-PFZ width, leading to the inhibition of intergranular fracture.
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  • Fracture Toughness and SCC Behavior of 7075 Aluminum Alloy under Mixed-Mode I-II Loading
    Shuhei OHSAKI, Masaki UTSUE, Hisashi YOKOFUJITA, Makio IINO
    1996 Volume 45 Issue 6 Pages 661-666
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.661
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    Under mode I, II and mixed-mode I-II loading, the fracture toughness and SCC response of aluminum alloy 7075-T6 plate have been studied in the S-L and L-S orientations. The fracture toughness in S-L under mixed-mode loading coincides with K1c for K2/K1<1 and K2c for K2/K1>1, where K1c and K2c are the fracture toughness under mode I and mode II respectively, and K2/K1 is the stress intensity ratio. The former fracture occurs due to a preferential intergranular delamination controlled by a normal stress component on grain boundaries, while the latter fracture proceeds in a trangranular shear mode. The SCC growth rate under the mixed-mode loading decreases with an increase of K2 component, and under the pure mode II loading SCC growth becomes more difficult. Based on the experimental results and discussions of stress-induced hydrogen accumulation at crack tip the intergranular SCC of 7075-T6 can assumed principally controlled by hydrogen embrittlement, and an anodic dissolution reaction involved in the mode II SCC process plays an assisting role in lamellar crack joining in transgranular fracture.
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  • Experimental Investigation for Modeling of Elastic-Plastic-Damage Materials
    Investigation of Damage Surface under Multiaxial Loading
    Kunio KAMIYA, Sumio MURAKAMI
    1996 Volume 45 Issue 6 Pages 667-674
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.667
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    Applicability and fundamental aspects of the irreversible thermodynamics theory of elastic-plastic-damaging materials are discussed by performing a series of multiaxial damage tests. The changes of Young's modulus, Poisson's ratio and shear modulus under tension and torsion are first observed for thin tubular specimens of spheroidized graphite cast iron. The Acoustic Emission (AE) count rate is also measured in order to detect the onset and the development of material damage. The changes in the elastic properties are related to the AE count rate. Then, by performing damage tests under proportional and nonproportional loading, the initial and subsequent damage surfaces are identified by use of AE count rate. The conditions of loading, unloading and neutral loading for the damage surface are established by the experiments. The influence of the hydrostatic stress on the initial damage surface is found larger than that of subsequent surfaces.
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  • Growth Behavior and Crack Distribution Characteristics of Small Surface Cracks of Age-Hardened Al-Alloy 2017-T4
    Masahiro GOTO, Norio KAWAGOISHI
    1996 Volume 45 Issue 6 Pages 675-679
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.675
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    In order to study the fatigue behavior of an age-hardened Al-alloy 2017-T4, rotating bending fatigue tests were carried out on the plain specimens. The initiation and propagation behaviors of cracks were investigated by the successive observation of surface. The crack growth pass was analyzed and then the growth law of small surface cracks was studied. Moreover, the length distribution of all the cracks, which were larger than 0.01mm and were initiated within the specific region (area: 10-20mm2), was examined. The region was set on the replicas gathered from the midsurface of specimen.
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  • Cracking Process and Delamination Strength of WC Film Coated by High-Speed Flame Spraying
    Keijiro NAKASA, Masahiko KATO, Fumiaki EGAWA, Masanobu KAMATA, Nobuhik ...
    1996 Volume 45 Issue 6 Pages 680-686
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.680
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    WC ceramic was coated on the smooth specimen of annealed tool steel (JIS: SKD6) by high-speed flame spraying, and the tensile test of the specimen was carried out to obtain interfacial energy, where the load was applied parallel to the film. With increasing load the film is divided repeatedly by occurence of cracks, and the film delamination begins after the crack interval reaches a certain value. The crack interval of film at the delamination increases and the interfacial energy slightly decreases with an increase in film thickness. The finite element analysis shows that the tensile stress at the center of film and the shear stress at the edge of film decrease with a decrease in film length, and the difference between both stresses increases with a decrease in film thickness. The analysis not only shows that the repeating film division continues as long as the tensile stress in the film reaches a critical tensile strength σc before the shear stress at the interface reaches a critical shear strength τc, but also explains the film thickness dependency of crack interval. By considering the analysis and the result of experiment, the crack interval, Lc, at the delamination of film can be expressed by the following equation,
    Lc/B2=α(σc/τc)(B1/B2)κ
    where, B1 and B2 are the thickness of film and substrate, respectively, and α and κ are the constants.
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  • Mechanical Properties of Wood-Mineral Composites Using the Water Glass-Boron Compound System
    Takeshi FURUNO, Shigeo AONO, Tohru UEHARA
    1996 Volume 45 Issue 6 Pages 687-693
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.687
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    The mechanical properties such as bending strength, hardness, and abrasion resistance of wood-mineral composites were investigated, which were made by introducing inorganic substances into wood using the water glass (sodium silicate)-boron compound system. The heartwood of Sugi (Cryptomeria japonica D. Don) and five kinds of boron compounds were used for the production of the composites. The impregnated specimens were treated with a 5% acetic acid solution to minimize the influence of alkali in the water glass solution.
    The weight percent gains (WPGs) in the composites varied from 20% to 65%, and the WPG values of 10-26% after the leaching procedure were obtained, demonstrating the formation of inorganic substances. The bending strength of the composites showed an increase of 6-25% in comparison with the untreated wood. The increase in the modulus of elasticity was also 16-41%, and it increased lineally with an increase in WPG. On the other hand, the strain at failure became lower than that of the untreated wood, and it had a tendency to reduce as the WPG increased.
    The Brinell hardness in the cross section showed a marked increase of 50-150% compared with the untreated wood. Because of increasing lineally with an increase in WPG, the enhancement of hardness in the cross section seemed to be due to the filling effect of inorganic substances. On the contrary, the hardness in the radial and tangential sections showed a reduction, and it tended to reduce with an increase in WPG. The reduction of hardness was considered to be closely related to the bulking and the wood deterioration resulting from soaking in an alkaline solution in the wood surface layer.
    The Taber type abrasion index in the radial and tangential sections tended to increase with an increase in WPG, showing the reduction of abrasion resistance. This reduction could be also explained by the influence of the bulking and the deterioration owing to alkali.
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  • Oxidation Behavior of Si3N4 at Low Oxygen Partial Pressures
    Hayato NANRI, Shingo ISHIDA, Nobuyuki TAKEUCHI, Koji WATANABE, Mitsuru ...
    1996 Volume 45 Issue 6 Pages 694-698
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.694
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    The oxidation behavior of Si3N4 containing small amounts of impurities in addition to 5 mass% Y2O3 and 5 mass% Al2O3 used as the sintering aids were examined at 1400°C for 15h at low oxygen partial pressures (PO2=0.2-1kPa). The oxidation reaction was followed by measuring the O2 consumption caused by oxidation every minute using a quadrupole mass spectrometer. The weight change of the bodies before and after the oxidation was measured and their oxidized surfaces were analyzed by SEM and EDX.
    α-cristobalite and Y2O3·2SiO2 were formed as the crystalline oxidation products and an apparently homogeneous protective layer was also formed on the oxidized surface after the oxidation at 1400°C for 15h at low oxygen partial pressures (PO2=0.2-1kPa).
    In the case of the oxygen partial pressure of 1kPa, the passive oxidation accompanied by weight gain and the active oxidation accompanied by weight loss were considered to be concurrent. In the cases of 0.5 and 0.2kPa, the passive oxidation was observed and any sign of the active oxidation could not be detected.
    These facts, contradictory to the generally accepted concept that lowering of oxygen pressure favors the active oxidation mechanism, indicate the marked depression of oxygen partial pressure in the flowing gas contacting with the sample surface at the downstream side in the case of 1kPa.
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  • Service Temperature Estimation for Gas Turbine Buckets Based on Microstructure Change
    Yomei YOSHIOKA, Nagatoshi OKABE, Daizo SAITO, Kazunari FUJIYAMA, Takan ...
    1996 Volume 45 Issue 6 Pages 699-704
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.699
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    This paper studies the microstructure chage of Ni-base superalloy IN738LC in the temperature range of 750-900°C, and develops a new method of predicting the service temperature of gas turbine buckets operated for 20000hr. The specimens of IN738LC were aged in the temperature range up to 24000hr to achieve the microstructure change. The growth rate of γ' diameter in IN738LC was proportional to 1/3 order of aging time, and γ' density was inversely proportional to aging time Accuracy of the predicted temperature based on the γ' diameter and density increased with increasing aging time and temperature. The metal temperature of actual 20000hr serviced buckets estimated by the microstructure change agreed with the thermal analysis at the leading edge portion which is a most reliable point for the analysis. This shows the availability of the proposed method.
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  • Developments of New Technology in Rock Mechanics -from Micro to Macro-
    V: From Rock Fracture Mechanics to Fractal Fracture Mechanics
    Hideaki TAKAHASHI, Kimio WATANABE
    1996 Volume 45 Issue 6 Pages 705-710
    Published: June 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.705
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