Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 55 , Issue 11
Showing 1-18 articles out of 18 articles from the selected issue
  • Setsuo Takaki, Shunji Iizuka, Kouki Tomimura, Youichi Tokunaga
    1991 Volume 55 Issue 11 Pages 1151-1158
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effect of cold working on the recovery and recrystallization behavior of lath martensitic structure has been investigated in a 0.2%C low alloy steel by means of optical and transmission electron microscopy. Cold working in the lath martensitic steel causes an intrusion of slip bands into the matrix, and resulting in the destruction of the lath martensitic structure and the formation of a dislocation cell structure around slip bands. The volume fraction of such a damaged martensite increases with increasing deformation rate. In the specimens subjected to heavy cold rolling above 80% reduction, the undamaged lath martensitic structure could rarely be observed and the dislocation density becomes one order of magnitude higher.
    On annealing at 973 K (below AC1 temperature), there is a large difference in the recovery and recrystallization behavior between the damaged and undamaged areas. Recrystallized ferrite grains preferentially nucleate within the damaged area and encroach on the undamaged area where the speed of recovery is slower than that in the damaged area. With increasing prior deformation rate, the recovery and recrystallization of the matrix are markedly promoted, corresponding to an increase in volume fraction of the damaged martensite and in dislocation density.
    Thus, it is concluded that cold working before annealing plays a role in destroying the lath martensitic structure and increasing the dislocation density, leading to increases in both of nucleation and growth rate of recrystallized ferrite grains.
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  • Hee Teak Shin, Junichi Kaneko, Makoto Sugamata
    1991 Volume 55 Issue 11 Pages 1159-1166
    Published: 1991
    Released: April 04, 2008
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    Precipitation hardening of a supersaturated solid solution of extended solubility obtained by rapid solidification of an Al-8%Mn-2%Cr alloy has been studied for the materials with or without plastic working prior to aging treatment. Mechanical alloying (MA) treatment was applied as cold working, and hot extrusion at 673 K was carried out as hot working. Specimens of four different thermal and mechanical histories; rapidly solidified flakes, extruded P/M material from the flakes, MA powder and extruded P/M material from MA powder were precipitation treated. The peak hardness in age hardening was increased by applying plastic working prior to aging treatment. The results indicate that cold-worked MA powders showed the highest peak hardness, followed by hot extruded P/M material from cold-worked MA powder and hot extruded P/M material from rapidly solidified flakes. The peak hardness of rapidly solidified flakes was the lowest. Precipitation hardening is caused by precipitation of the G phase, (Mn, Cr) Al12, and an increased peak hardness was obtained by introduction of heterogeneous sites by plastic working. The major constituent phases of this alloy were CrAl7 in as-rapidly solidified flakes, CrAl7 and the G phase in as-extruded flake-P/M materials, MnAl6 and the G phase in as-extruded MA-P/M materials, and the G phase in age hardened P/M materials.
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  • Yukio Inokuti, Fumio Saito
    1991 Volume 55 Issue 11 Pages 1167-1173
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Computer color mapping for the primary grains near the growing front of secondary Goss-oriented grain in 3%Si steel was performed with an image analyzer using crystallographic orientation data measured by a Kossel examination.
    The results are summarized as follows:
    (1) Primary grains of {100}⟨001⟩∼⟨0 kl⟩ are virtually unconsumed by the secondary Goss grain. Its result is consistent with the results of the previous experiments.
    (2) The alternate configuration of primary grains having two equivalent orientations of near (342) [\bar430] and (342) [4\bar30] grains is also virtually unconsumed by the secondary Goss grain.
    (3) The primary grains mentioned in (1) and (2) are formed during the decarburization and primary recrystallization treatment from the same deformed grains after cold rolling.
    (4) The above-mentioned primary grains, which are unconsumed by the secondary Goss grain, have highly oriented crystallographic planes, but their axes deviate from each other.
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  • Jirou Harase, Shozaburo Nakashima, Yakichirou Kawamo, Satoshi Arai
    1991 Volume 55 Issue 11 Pages 1174-1181
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The Fe-3%Si steel containing inhibitors of AlN and MnS which was cross-rolled to 80% reduction evolved small numbers of (100) [011] secondarily recrystallized grains when annealed in 85%H2-N2 atmosphere and a secondary recrystallization texture having near (110) [001] when annealed in 100%N2 atmosphere.
    The difference of the secondary recrystallization behavior due to the annealing atmosphere was discussed as follows.
    (1) The evolution of (100) [011] secondary recrystallized grains is considered to be due to the relatively higher intensities of (100) [011] and the matrix orientations having the Σ7 orientation relationship with the (100) [011] in the midplane of the thickness of the specimen before grain growth.
    (2) The evolution of the secondary recrystallized grains near (110) [001] is considered to be due to the relatively higher intensities of (110) [001] and the intensity of the matrix orientations having the Σ9 orientation relationship with the (110) [001] near the surface of the specimen before grain growth.
    (3) The occurrence of the (100) [011] secondary recrystallization when annealed in 85%H2-N2 is considered to be due to the shift of the nucleation site for the secondary recrystallization into the midplane where the inhibitor intensity is relatively higher, while the relative decrease in the inhibitor intensity near the surface layer results in the normal grain growth in the surface layer.
    It is considered to be the reason for the occurrence of the (110) [001] secondary recrystallization in the surface layer when annealed in 100%N2 atmosphere that the secondary recrystallization takes place at the temperatures lower than 1273 K in the very thin surface layer of the specimen where the intensity of the inhibitor, due to the lower amounts of MnS and AlN, is relatively lower, while the higher inhibitor intensity results in the prevention of the grain growth in the inner layer of the sheet.
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  • Zhou Xu, Taku Sakai
    1991 Volume 55 Issue 11 Pages 1182-1188
    Published: 1991
    Released: April 04, 2008
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    The effect of single and multiple peak dynamic recrystallization (DRX) on the static softening taking place in hot deformed copper was studied by means of the interrupted compression test at a temperature of 723 K and a true strain rate of 2×10−3 s−1. The softening curve after dynamic recovery consists of two stages followed by complete softening. In contrast, the softening curve after DRX consists of three distinct stages with the respective inflection plateaus, followed by incomplete softening. Under a single peak DRX, the softening curve changes monotonically with straining from a sigmoidal to three distinct stages. Under a multiple peak DRX, the softening behavior changes periodically with straining, which can roughly correspond to the appearance of multiple peak flow. It is concluded that the static softening after DRX is sensitively affected by not only the volume fraction of DRX structure in the deformed matrix, but also the distribution of three kinds of DRX grains, i. e. DRX nuclei, growing DRX grains and strain hardened DRX grains.
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  • Kouichi Maruyama, Hiroshi Oikawa
    1991 Volume 55 Issue 11 Pages 1189-1193
    Published: 1991
    Released: April 04, 2008
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    The theta concept has been proposed to predict long-term creep properties. Several constitutive creep equations have been used in the concept to describe creep curve up to tertiary creep stage, for example
    (This article is not displayable. Please see full text pdf.)
    \ oindentwhere Ai, Bi, a, b and α are material constants determined by the curve fitting to a measured creep curve. Physical significance of the equations, however, is not well elucidated.
    Physical backgrounds of the two equations have been discussed on the hypothesis that creep equation must be derivable from the Orowan equation. Equation (\ efeq1) seems to be hardly derived from Orowan equation, whereas Eq. (\ efeq2) is the simplest form of creep equations derivable from the Orowan equation. For dislocation creep, the rate constant α of Eq. (\ efeq2) takes the following form:
    (This article is not displayable. Please see full text pdf.)
    \ oindentwhere C is a constant, D the diffusion coefficient and n the stress exponent. It is expected from this equation that the temperature depedence of α accords with that of diffusion. This expectation has been experimentally confirmed, suggesting that the assumptions made to derive Eq. (\ efeq2) are physically reasonable.
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  • Norihito Ikemiya, Sigeta Hara, Hirohumi Maki, Kazumi Ogino
    1991 Volume 55 Issue 11 Pages 1194-1198
    Published: 1991
    Released: April 04, 2008
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    Densities and surface tensions of LiF-MF3 (M: Nd, Gd, La) binary systems were measured under Ar gas by the maximum bubble pressure method. The results obtained were as follows:
    (1) Molar volume of the melt in the LiF-LaF3 system satisfied the additive rule on volume, while those for two other binary systems deviated positively from the additive rule near the eutectic composition.
    (2) Surface tensions of melts in these binary systems are deviated negatively from Guggenheim’s equation for ideal solution.
    (3) Assuming that the binary melts behave as the regular solution, for the LiF-LaF3 system the interaction energy ω calculated from the thermochemical data is in good agreement with that computed from the surface tension by Guggenheim’s equation. For the LiF-NdF3 system, the computed value of ω from the surface tension is three times larger than that from the thermochemical data and it is similar to that for the LiF-GdF3 system. We concluded that behavior of LaF3 is different from that of NdF3, GdF3 in LiF-MF3 (M: Nd, Gd, La) systems.
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  • Kunihiko Nakashima, Kenji Takihira, Katsumi Mori, Nobuya Shinozaki
    1991 Volume 55 Issue 11 Pages 1199-1206
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The interfacial properties between liquid Fe-O alloy and alumina substrates with different purities, 99.9% and 96%Al2O3, were measured by the sessile drop method. The interfaces of samples after the experiment were examined by SEM and EPMA.
    It was found that the contact angle increased and the work of adhesion decreased with increasing oxygen concentration in the iron in the range of less than 0.010%. These phenomena were attributed to the dessociation of Al2O3. For 96%Al2O3, the Ca and Mg rich layer was observed at the Fe-Al2O3 interface. Whereas, at higher oxygen concentrations, the contact angle decreased with increasing oxygen concentration. Under these conditions, the formation of the hercynite or the penetration of iron into the grain boundaries of Al2O3 substrates were observed.
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  • Motoi Hara, Toshio Hisaichi, Koichi Itoh, Yutaka Shinata
    1991 Volume 55 Issue 11 Pages 1207-1215
    Published: 1991
    Released: April 04, 2008
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    In order to investigate the effect of gas atmosphere on the hot corrosion of nickel and Ni-Cr alloys in molten Na2SO4, the corrosion behavior of nickel and Ni-Cr alloys in molten Na2SO4 at 1173 K under (SO3 + SO2 + O2) mixture and pure SO2 and O2 atmospheres were evaluated by the measurement of corrosion loss, the observation of corrosion morphology and the electrochemical measurement. The corrosion loss of nickel and Ni-Cr alloys measured under the mixed atmosphere containing SO3 was larger than those measured under the pure SO2 and O2 atmospheres. Under the mixed atmosphere containing SO3, the corrosion loss of Ni-Cr alloys was smaller that that of nickel. It was found from the observation of corrosion morphology that the corrosion loss corresponded to the thickness of the oxide layers formed on the specimens. The cathodic polarization curves of Ni-Cr alloys measured in molten Na2SO4 indicated that the limiting current density from the corrosion potential observed under the mixed atmosphere containing SO3 was higher than those observed under the pure SO2 and O2 atmospheres. This suggests that SO3 can be readily reduced in molten Na2SO4 in comparison with SO2 and O2. The dependence of the corrosion behavior in molten Na2SO4 upon the gas atmosphere for nickel and Ni-Cr alloys could be explained by the partial polarization curves presumed from the electrochemical results. Consequently, it was thought that the large corrosion losses observed for nickel and Ni-Cr alloys under the atmosphere containing SO3 were attributed to the fact that SO3 strongly acted as an oxidizing agent for the corrosion process in molten Na2SO4.
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  • Shinya Yao, Hirokazu Tanaka, Zensaku Kozuka
    1991 Volume 55 Issue 11 Pages 1216-1221
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    When commercial Pr6O11 powders were repeatedly deoxidized and oxidized by heating up and cooling down under a constant oxygen partial pressure, the starting temperature Tde of the phase transition PrOx(σ)→Pr2O3(A) was dependent on the number of heating runs. There are at least two factors affecting the Tde value. The temperature Tde was obviously highest on the first heating run. In order to clarify the factor increasing Tde, PrnO2n−2 phases quenched into ice-water on various heating runs were subjected to powder X-ray diffraction (XRD) analysis. For all the CaF2-related structures on the first heating run, additional peaks were observed; the main two peaks appeared around 2θ=29°. These peaks were not observed for the hexagonal Pr2O3(A) and all the phases re-oxidized from the Pr2O3(A). The following properties of the microstructure exhibiting the additional peaks in XRD analysis were clarified: (i) it does not disappear through phase transitions among the CaF2-related structures, (ii) it disappears once the phases change to hexagonal Pr2O3(A), (iii) after that, it never appears again even for the CaF2-related structure; and (iv) its existence does not have any effect on the phase transitions among CaF2-related phases, but prevents the phase transition PrOx(σ)→Pr2O3(A). For the cubic Pr2O3(C) produced from commercial Pr6O11 powders at 873 K uncler a very low oxygen partial pressure, the corresponding additional peaks around 2θ=29° reduced to one. The additional peaks are possibly interpreted as the diffractions due to a superlattice structure involved in the bulk. PrO2 involved in commercial Pr6O11 powders makes it difficult to detect the additional peaks. The formation of the phases exhibiting the additional peaks in XRD analysis may be deeply related to the production processes of the commercial Pr6O11 powders.
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  • Toshio Maruyama, Bi Xiao Fang, Kazuhiro Nagata
    1991 Volume 55 Issue 11 Pages 1222-1231
    Published: 1991
    Released: April 04, 2008
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    High-temperature oxidation of various intermetallic powders in the molybdenum-aluminum system was examined at a constant rate of heating in air. Powders of Mo3Al8 and MoAl4 exhibited good oxidation resistance. Molybdenum aluminide was coated on Mo by pack cementation at 1323 K using the pack of Al, NH4Cl and Al2O3. The aluminide coating consisted mainly of Mo3Al8. A thin layer of Mo3Al was also formed between Mo3Al8 and Mo. The coating layer grew by inward diffusion of Al. Several cracks were observed in the coating layer. The formation of cracks resulted probably from stress during cooling, which arose from the difference not only in molar volumes but also in thermal expansion coefficients. Oxidation behavior of the coated molybdenum indicated that the coated Mo3Al8 itself possessed the oxidation resistance with the formation of a thin film of alumina. However, the cracks degraded the resistance. The elimination of cracks in the layer is indispensable for the improvement of oxidation resistance.
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  • Hitoshi Tashiro, Hiroshi Sato
    1991 Volume 55 Issue 11 Pages 1232-1239
    Published: 1991
    Released: April 04, 2008
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    We have reported the systematic research about the effects of alloy elements on the pearlite lemellar spacing (LPS) and the degree of regularity of pearlite (LPA) in the preceding paper. In this paper, the effects of alloy elements on the drawability and the strength and ductility of the wire with a pearlite lamellar structure are discussed.
    It is well-known that the strength and ductility of the wire as drawn depend strongly on the wire diameter, but there are few researches on it. Therefore, we have studied the effect of alloy elements on the strength and ductility of fine wire under 0.5 mm as drawn chiefly. The main results are as follows.
    (1) The maximum drawing strain (MDS) and the attained maximum strength (AMS) change linearly with the logarithm of diameter of wire as patented.
    (2) MDS shows the maximum value in the condition of about 0.10 μm LPS. On the other hand, AMS increases as LPS decreases. In oredr to get higher MDS, it is important to control LPS in about 0.10 μm in patenting. Then, in order to get higher AMS, it is useful to make LPS as narrow as possible.
    (3) As the carbon content increases, MDS decreases. On the other hand, AMS of the fine wire as drawn is not affected by the carbon contents of 0.71-0.94%C.
    (4) The silicon makes the strength of the fine wire higher, but the effect depends on the drawing strain. So, we have to select the optimum addition according to the drawing strain.
    (5) The manganese lowers the ductility of the fine wire as drawn.
    (6) The alloy elements like chromium which makes LPS narrower are effective in increasing the strength of the fine wire.
    (7) The alloy elements like cobalt which makes LPA larger are effective in improving the ductility of the fine wire as drawn.
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  • Hideki Hamatani, Hisashi Kumaoka, Toshifumi Yahata, Toyonobu Yoshida
    1991 Volume 55 Issue 11 Pages 1240-1248
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    This study was aimed at developing integrated fabrication process for solid oxide cells (SOFC) with radio-frequency plasma spraying (RFPS) and/or hybrid plasma spraying (HYPS). Fundamental studies concerning particle velocity and deformation of ZrO2-12 wt%Y2O3 (YSZ) showed that even the lower particle velocities in RFPS (20 m/s) and HYPS (40-70 m/s) compared with the case in direct current plasma spraying (∼200 m/s), were found to be sufficient for the deformation of impinging molten YSZ particles on the substrate. RFPS, however, imposed a severe limitation on the substrate position because it led to short flying distance of molten particles. In this respect, HYPS was considered to be superior than RFPS. Actually, using 75 μm YSZ powder, HYPS made it possible to get not only dense YSZ coating with the relative density higher than 98% but also good gas permeability lower than 5.7×10−7 cm4/g·s (2500 mmH2O). Moreover, porous NiO and chemical stable LaCoO3 as electrodes could be prepared by Ar-O2 HYPS. Though the cell performance had not been investigated yet, these experimental results have proved that HYPS must be a strong candidate to open new aspects of the production process for SOFC, especially, from economical and engineering points of view.
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  • Masahiko Sakakihara, Yukio Ichinose
    1991 Volume 55 Issue 11 Pages 1249-1255
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Characteristics of films used for X-ray mask membrane demand the tensile stress against Si substrate and the high optical transmittance over 70 or 80% at the 630 nm wave length of He-Ne laser using for the alignment between mask and wafer. It was difficult to obtain an amorphous BN (a-BN) film satisfied those requirements. We investigated the effect of addition of carbon to a-BN films and, as the result, obtained the conditions to produce a-BNC films suitable for mask membrane.
    It was found that there were some optimum combinations of the deposition temperature and the gas flow ratio (CH3NH2/B2H6) . For example, with the gas flow ratios of 10 at 973 K, 0.53-1.6 at 1023 K and 0.53 at 1073 K, the films having the tensile stress of about 2×108 Pa and the optical transmittance of 70 or 80% were obtained.
    Moreovere, the thermal stress and the thermal expansion coefficient αf of the films were calculated from the stress vs temperature curves of the substrates with films. The αf is proportional to the Boron (B) contents as follows: αf=1.38×10−7×B−5.6×10−6 (B: mol%).
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  • Atsushi Hibino, Ryuzo Watanabe
    1991 Volume 55 Issue 11 Pages 1256-1262
    Published: 1991
    Released: April 04, 2008
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    The reaction mechanism of combustion synthesis of a TiAl intermetallic compound was analyzed by the observation of the reaction process in Ti and Al mixed powder compacts and by a model calculation of the reaction kinetics. A premix of Ti and Al powders was vacuum-heated in an electric furnace to cause self-sustaining reaction. The measurement of the rise in the temperature, the observation of microstructural evolution involved in the reaction process and X-ray phase analysis of the product were performed. It was observed that at the melting point of Al, Al melt surrounded Ti particles and the reaction started and proceeded towards the center of the Ti particle. The synthesis reaction has been analyzed using a spherical shell model which takes into account the microstructural change. The analysis has shown that the reaction is accelerated with reaction time, which is in accordance with the observed self-sustaining reaction. The relative contribution of the diffusion of Al in TiAl and the interface reaction between TiAl and Ti has also been quantified in dependence on the Ti particle size.
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  • Hiroki Esaki, Masaharu Tokizane
    1991 Volume 55 Issue 11 Pages 1263-1268
    Published: 1991
    Released: April 04, 2008
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    A mixture of elemental powders of Ti(50 at%) and Ni(50 at%) was subjected to a mechanical alloying (MA) by a ball milling process. The processed powder was offered to the vacuum hot pressing at 1223 K for 3.6 ks under 150 MPa. The compact (relative density of approximately 99.8%) consisted of ultra-fine TiNi grains. The average grain size was 0.6 μm in diameter. The results of the examination of the temperature dependence of 0.2% proof stress showed that the flow stress of the compact rapidly deceased with increasing deformation temperature. During the compressive deformation at 1223 K and the initial strain rate of 6.7×10−4 s−1, the compact showed a steady state flow at relatively lower stress level such as about 16 MPa. The grain structure remained approximately equiaxed during the deformation. The value of strain rate sensitivity exponent of flow stress, m, was to be 0.32 at 1223 K. From these results, the deformation behavior of the compact at this temperature was presumed to be of superplasticity. The superplastic TiNi compact showed a large recovery stress of 300 MPa when the compressively 5% deformed (at room temperature, 294 K) specimen was heated at 373 K. Moveover, the strain by the deformation was fully recovered by shape memory effect at this temperature.
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  • Kiyoshi Nogi, Hiroyuki Takeda, Masao Komatsu, Nobuya Iwamoto, Kazumi O ...
    1991 Volume 55 Issue 11 Pages 1269-1273
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Effect of applying a DC voltage on the interfacial reaction at the aluminum-zirconia interface was studied utilizing an oxygen ionic conductivity of zirconia. In this system, a reaction occurs at the interface even if a DC voltage is not applied. This study was carried out using a conventional transmission electron microscopy and/or a ultra-high voltage electron microscopy.
    Interfacial reactions were strongly affected by applying a DC voltage. Zr2Al3 and (Al2O3)δ were formed at the interface when a DC voltage was not applied. On the other hand, two phases were formed at the interface when a DC voltage was applied. One was the reaction layer which consisted of small grains. The other was α-Al2O3 or (Al2O3)δ.
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  • Shozaburo Nakashima, Kunihide Takashima, Jirou Harase, Katsuro Kuroki
    1991 Volume 55 Issue 11 Pages 1274-1281
    Published: 1991
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    A study was made on the effect of Sn addition on the secondary recrystallization of 3.8 mass%Si grain-oriented electrical steel.
    (1) With increasing Si content (3.0→3.7 mass%), secondary recrystallization is suppressed. This is attributed to the large size of primary-recrystallized grains, the small amount of Goss nuclei in the primary-recrystallized matrix and the less effective inhibitors for secondary recrystallization in the steel with a high content of Si.
    (2) Upon Sn addition to the steel with a high content of Si (3.8 mass%), secondary recrystallization occurs with a highly oriented Goss texture, which results in excellent magnetic properties. Sn addition is considered to eliminate urfavorable factors for secondary recrystallization caused by the increased Si content mentioned above.
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