Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Volume 37 , Issue 412
Showing 1-17 articles out of 17 articles from the selected issue
  • Kazuo FUZITA, Masayoshi MIKI, Masao OKUBO
    1988 Volume 37 Issue 412 Pages 1-4
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Stress corrosion cracking is the most numerous and the most serious problem in the corrosion problems in chemical plants. So the prevention of stress corrosion cracking is the most important theme. In this paper, the following examples and their preventive methods are given; SCC of austenitic stainless steel in chloride solution, caustic embrittlement of carbon steel in vertical boiler, SCC of Type 304 in electrolysis plant and SCC of Hastelloy alloy.
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  • Hitoshi UCHIDA, Keiji KOTERAZAWA
    1988 Volume 37 Issue 412 Pages 5-10
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The effect of tensile axis on stress corrosion cracking (SCC) of SUS 310S steel single crystals in a boiling MgCl2 solution (42%) at 416K was studied under the constant-loading conditions.
    The threshold stress for SCC decreased in order of tensile axes of [111], [101] and [001], and was independent of Schmid factors for the primary slip system. Cracks were preferentially nucleated from the micro-pits at slip steps by plastic deformation and grew along the ‹110› direction on the {100} plane in every type of specimens. The fracture surface of [001]-oriented specimen was observed to be flat, but those of the rest contained steps composed of other {100} planes, too. It was found that the normal stress to the {100} crack plane vs. fracture time curves in all types of specimens coincided well. This fact suggests that the crack growth is strongly controlled by the normal stress to the {100} plane which makes the smallest angle with respect to the tensile axis.
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  • Toshitsugu FUKAI, Yutaka KITA, Toshio ANZAI
    1988 Volume 37 Issue 412 Pages 11-16
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The susceptibility to polythionic acid stress corrosion cracking of stabilized austenitic stainless steel weldments was investigated as a function of their sensitization measured by EPR method. The results showed that type 321 and 347 stainless steels became susceptible to stress corrosion cracking when the sensitization index in EPR test exceeded the value of 10%.
    In order to prevent the stress corrosion cracking of the weldment throughout the long time service of 105 hours or more, some countermeasures such as a stabilizing heat treatment should be provided to the type 321 and 347 weldments when they are used over 480°C and 430°C, respectively.
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  • Kazuo YAMANAKA, Kazuhiro OGAWA, Takao MINAMI, Hiroo NAGANO
    1988 Volume 37 Issue 412 Pages 17-23
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The effect of niobium as a stabilizing element and the effect of thermal cycles on welding of the corrosion resistance of 75%Ni-15%Cr (Alloy 600) were investigated. The results are summarized as follows:
    (1) The effects of weld thermal cycle and sensitizing heat treatment on the intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) of Alloy 600 containing carbon more than 0.01 wt% can be explained by the behavior of chromium carbide precipitation at the grain boundaries.
    (2) In Alloy 600 containing carbon more than 0.01 wt%, a suitable addition of niobium (Nb/C_??_30) prevents degradation of corrosion resistance due to the sensitization caused by the chromium carbide precipitation.
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  • Teruo KANEKO, Akio IKEDA
    1988 Volume 37 Issue 412 Pages 24-29
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    An application of slow strain rate tensile (SSRT) test to evaluation of sulfide stress cracking (SSC) susceptibility of low alloyed steel was investigated. A ductility loss parameter of IL=(L0-L)/L0×100% was used, where L0 is the elongation to failure in air and L is that in H2S containing media.
    The dependece of IL on strain rate in the range of 10-4 to 10-7s-1 was influenced by test temperature. IL increased with decreasing strain rate below 50°C, while the maximum embrittlement was attained at 10-5s-1 when the test was performed at 80°C. This phenomenon might suggest the importance of an interaction between dislocation and hydrogen.
    The ductility loss IL showed a significant correlation with strength level and microstructure. IL increased with increasing strength level, and the limiting strength, above which extremely poor ductility was obtained, became higher as the homogeneity of microstructure was improved. These behaviors were in good agreement with the results of conventional uniaxial tensile type SSC tests.
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  • Takenori NAKAYAMA, Kazuo FUJIWARA, Kazutoshi SHIMOGORI, Mutsuhiro MIYA ...
    1988 Volume 37 Issue 412 Pages 30-35
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The stress corrosion cracking (SCC) life time of turbine rotors in actual nuclear and fossil power plants was analyzed by a statistical method and was estimated to obey an exponential probability distribution. Then, the laboratory accelerated test condition to exhibit such an exponential probability distribution was investigated using 3.5NiCrMoV steel forgings which are being used most widely as a material for low pressure turbine rotors. The exposure of double U-bend specimens in liquid/gas interface of undeaerated 30% NaOH aqueous solution was found to be most fitted for the purpose. Under this condition, the effects of alloying elements and mechanical strength/microstructure on SCC life were studied. The reduction of P content and/or the addition of a small amount of Nb in steel and the reduction of mechanical strength were effective to prolong the SCC life of turbine rotors.
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  • Masaki UEKADO, Shozo OKAZAKI, Masanori KIYOSHIGE, Kazushi TSUJIMOTO
    1988 Volume 37 Issue 412 Pages 36-42
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    An investigation was made on the effect of small amount of Cu on the stress corrosion cracking in welds of Al-Zn-Mg series A7N01 alloys. The environments used were 3.5% NaCl solution, 36g/l CrO3+30g/l K2Cr2O7+3g/l NaCl solution and atomospheric exposure.
    The results obtained are as follows:
    The weld heat affected zone has higher susceptibility to stress corrosion cracking than the other position. Stress corrosion cracking fracture principally occurs in the weld heat affected zone about 0.5-2mm far from the weld bond.
    The addition of Cu increases strongly the resistance to stress corrosion cracking in aged alloys. Especially the addition of Cu increases the initiation time of stress corrosion cracking, but does not improve so effectively the resistance to crack growth rate da/dt corresponding to region II. From the practical point of view, it is necessary to add a small amount of Cu (less than 0.2%) to avoid stress corrosion cracking in aged welds of A7N01 alloy.
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  • Koji YAMAKAWA, Naoyuki KAJITA, Megumi MURAKAMI, Takakazu HIRAYAMA
    1988 Volume 37 Issue 412 Pages 43-49
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Stress corrosion cracking (SCC) was investigated by spectral analysis of corrosion potential signals. Caustic cracking of carbon steel (S10C) and SCC of stainless steel (SUS304) in various chloride solutions were studied. The marked change of the power spectral density (PSD) in the frequency domain was observed in the vicinity of 5mHz for caustic cracking of carbon steel and in the frequency range from 10 to 100mHz for SCC of stainless steel. It was also observed that the corrosion potential signal in 20%NaCl+1%Na2Cr2O7 solution was bigger than in 42%MgCl2 solution or 60%CaCl2 solution for SCC of Stainless steel. By comparing PSD with the changes of elongation and corrosion potential, the following conclusion was obtained: the increase of PSD might be related to the breakdown of passive film and the generation of cracks for caustic cracking of cabon steel, while its increase might be attributed to the localized change in the passive film for SCC of stainless steel.
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  • Michio INAGAKI, Hideki MINE, Mototsugu SAKAI
    1988 Volume 37 Issue 412 Pages 51-54
    Published: January 15, 1988
    Released: June 03, 2009
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    Ternary graphite intercalation compounds of cobalt metal and tetrahydrofuran (THF) were synthesized by the reaction between binary compound KC8 and cobalt chloride in THF solution at room temperature. By the so-called quenching process, residue compounds containing cobalt metal and THF were obtained. From these residue compounds, exfoliated graphite was obtained by rapid heating to high temperatures, in which minute cobalt particles were dispersed homogeneously and which could be formed to magnetic graphite sheets by compression.
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  • Tetsuya SAHARA, Kiyoshi HIRAO, Yoshinari MIYAMOTO, Mitsue KOIZUMI
    1988 Volume 37 Issue 412 Pages 55-59
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    An investigation has been made on the synthesis of superconducting NbN and (Nb, Mo)N powders by a combustion reaction of nitriding their metal elements under high nitrogen pressures up to 10MPa. Nearly stoichiometric B1-NbN powders were prepared by the combustion reaction of Nb powders with a proper amount of NbN addition under 1-10MPa nitrogen pressures. The characteristics of this combustion reaction were investigated by measuring the propagating velocity of combustion for the packed reactants with various amounts of diluent. The superconducting transition temperature of NbN powders obtained was 16.9K, which is very close to the highest value of 17.3K reported for NbN up to now. On the other hand, Nb powders with 5, 10, and 20wt% Mo were burned under 10MPa nitrogen pressure in order to synthesize (Nb, Mo)N solid solutions. The combustion product of Nb with 5wt% Mo consisted of B1 phase only, while those with 10 and 20wt% Mo contained a small amount of residual Mo. The transition temperatures in the Nb-Mo-N system were 12.7-15.9K, which were lower than that of pure NbN obtained in this study.
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  • Hiromichi IWASAKI, Yasunari KANEKO
    1988 Volume 37 Issue 412 Pages 60-64
    Published: January 15, 1988
    Released: June 03, 2009
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    In this paper, fibrous hydroxyapatite (HAp), which is expected to be used as an implant material to periodontal bone defects, was prepared by using sodium alginate (Na-Alg.).
    The starting materials were prepared by dissolving Na4P2O7 into 5% Na-Alg. solution; Na-Alg./Na4P2O7 (weight ratio)=2.4, 2.6, 2.8, 3.0, 3.2, while the mixed solution of 0.15mol Ca(CH3COO)2 and 0.1mol CaCl2 was used as the spinning solution; pH=6.0, 6.5, 7.0, 7.5.
    The starting materials were spun through a nozzel of 0.1φmm into the spinning solution in a vessel of 16ml capacity. Gelatinous fibers obtained were aged, dried and calcined at 900°C for 1 hour. The thermal transformation of the calcined fibers and their compositions were examined by using X-ray diffraction, DTA, and chemical analysis. From these results, the optimum condition for preparing fibrous HAp was found to be as follows; Na-Alg./Na4P2O7=3.0, pH=6.5.
    In order to remove pores appearing during the heating process, the dried fibers formed under the optimum condition were heat-treated under reduced pressure (at 133Pa and 900°C for 3 hours). The resulting HAp fibers were about 30-40μm in diameter. It was also confirmed that the HAp phase in the fibers was maintained even after heat-treated at 1300°C for 1 hour in air.
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  • Yasunari KANEKO, Kei AMEYAMA, Hiromichi IWASAKI
    1988 Volume 37 Issue 412 Pages 65-69
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The formation of Si3N4 whiskers from rice hulls was studied. Si3N4 whiskers were synthesized by nitridation of SiO2-C system in N2-gas flows at 1400°C and 1450°C. The shape and microstructure of the whiskers were inspected by means of SEM and TEM. The whiskers of a cylindrical shape grew along the <1011> direction whithout any deffects. The phase of the whiskers was α-type and their diameter and length were 0.1 to 0.5μm and 300 to 1800μm, respectively. The droplet of Fe-Si system was found at the tip of the whiskers. It is suggested that the VLS mechanism controls the growth of whisker.
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  • Susumu SHIMA, Toshisuke NAKANISHI
    1988 Volume 37 Issue 412 Pages 70-76
    Published: January 15, 1988
    Released: June 03, 2009
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    Si3N4 power with sintering additives was compacted on a three-dimensional compaction device and the characteristics of this powder during compaction were investigated. It appeared that, to obtain a compact having the same density ratio, much lower pressure was required compared with the same powder without sintering additives. Material constants in the constitutive equations for the powders were determined from the experiments. These equations were then applied to the analysis of isostatic compaction by using the rigid-plastic finite element method. The shape of compacts and the distributions of density ratio and stress were calculated. They show that the difference in material constants used in constitutive equations affects the calculated results considerably.
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  • Tsugio SATO, Kiyotaka HARYU, Tadashi ENDO, Masahiko SHIMADA
    1988 Volume 37 Issue 412 Pages 77-82
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Nonoxide ceramics of hot-pressed AlN, hot-pressed Si3N4, sintered Si3N4, hot-pressed sialon and hot-pressed B4C were oxidized in wet nitrogen and/or wet air atmosphere at 1.5 to 20kPa of water vapor pressure and in dry air at 900-1400°C. All specimens were oxidized by both dry air and water vapor at high temperatures. AlN formed α-Al2O3 film on the surface above 1150°C. The oxidation rate of AlN increased with increasing water vapor pressure. The oxidation rate of AlN in wet nitrogen was much greater than that in wet air. Si3N4 and sialon formed oxide films consisting of SiO2, Y2Si2O7 and YAlO3. The oxidation kinetics obeyed the usual parabolic law. The oxidation rate in wet nitrogen, however, was unaffected by water vapor pressure and increased with increasing Y2O3 content. The apparent activation energy for the oxidation of Si3N4 based ceramics was about 800kJ/mol. On the other hand, since the oxidation of B4C by water vapor and dry air above 900°C resulted in weight loss, the formation of BO or HBO2 seemed to be the main reaction. The oxidation rate of B4C by water vapor above 900°C could be expressed by the surface chemical reaction controlled kinetics with the apparent activation energy of 200kJ/mol.
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  • Suguru INAMURA, Masao TAKAHASHI, Kohji NOBUGAI, Fumikazu KANAMARU, Hir ...
    1988 Volume 37 Issue 412 Pages 83-86
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The effect of Al on the resistance against oxidation of Ti1-xAlxN films prepared by the rf-sputtering method was investigated.
    ESCA spectra of the samples exposed in air for one day at room temperature showed that Ti2p3/2 peak shifted to the higher binding energy side by adding AlN and oxidation of the surface of the Al-bearning films was reduced in comparison with TiN.
    The Oxidation of Ti1-xAlxN at high temperatures in O2 gas flow was examined by thermo-gravimetry. TiN was converted to TiO2 above 600°C in O2 gas flow, while the NaCl-type Ti0.65Al0.35N, Ti0.3Al0.7N (a new crystal phase) and the Wurtzite-type Ti0.15Al0.85N were stable below 800°C but oxidized at 900°C in O2 gas flow. Each oxidized sample was a mixture of TiO2, Al2TiO5, Al2O3 and AlN.
    In N2 atmosphere, the NaCl-type Ti0.65Al0.35N was stable below 800°C, but decomposed to two nitrides, TiN and AlN, at 1000°C. This phase separation is surely related to the oxidation of Ti0.65Al0.35N described above.
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  • Jiro FUKUNAGA, Xiu-Jian ZHAO, Masayoshi IHARA, Rikuo OTA, Yoshito ONOD ...
    1988 Volume 37 Issue 412 Pages 87-93
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    11B NMR spectra, density and refractive index were measured for the CaO-Ga2O3-B2O3 glasses and interpreted in term of the structure. Distribution of the fraction, NBO4, of boron atoms that are four-coordinated for the CaO-Ga2O3-B2O3 glasses showed roughly pattern as that for the CaO-Al2O3-B2O3 glasses. It was found that the CaO-Ga2O3-B2O3 glasses contain a considerable fraction of four-coordinated B3+ ions at the composition in which Ga2O3/CaO ratio is equal to unity, while the CaO-Al2O3-B2O3 glasses contain almost no four-coordinated B3+ ions at the same composition ratio, Al2O3/CaO=1.
    Ca3+ ions in this glass have a coordination number of four has been shown by NBO4 values and Raman study. Ga3+ ions takes the form of GaO4- groups with Ca2+ ion as a charge compensator and the form of GaO4 groups involving one tripod oxygen.
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  • K. Kikuchi, H. Tsuji, I. Nishiguchi
    1988 Volume 37 Issue 412 Pages 94-100
    Published: January 15, 1988
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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