Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
Volume 39, Issue 4
Displaying 1-17 of 17 articles from this issue
  • [in Japanese]
    1992 Volume 39 Issue 4 Pages 246
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
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  • Tsuneyuki Ide, Kazunori Nakano, Ken-ichi Takagi
    1992 Volume 39 Issue 4 Pages 247-253
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    The ternary Fe-6%B-x%Mo alloys have a composite microstructure consisting mainly of a complex boride Mo2FeB2 as a hard phase and a ferritic binder. The mechanism of liquid phase sintering of this alloy was investigated by means of dilatometry, differential thermal analysis, X-ray diffraction, and scanning electron microscopy. A fine composite microstructure of Mo2FeB2 and ferrite was produced from powders of Fe, Mo and FeB by a reaction sintering process involving two liquid phases. The hard phase Mo2FeB2 is produced in the compact prior to liquid formation. Above 1, 365K, considerable densification results from the initial stage rearrangement of the solid phases (austenite and Mo2FeB2) coexisting with the first formed liquid phase (L1). Another liquid (L2) which forms above 1, 415K, where Mo2FeB2 is the only coexisting solid phase, is required for complete densification. L2 having a high solubility for Mo2FeB2, provides for solution/reprecipitation process which characterize the intermediate stage of liquid phase sintering. The effective separation of the initial and intermediate stages by L1 and L2 is considered essential for the control of the sintered microstrucure of the ternary alloy.
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  • Hideshi Miura, Tadatoshi Honda, Randall M. German
    1992 Volume 39 Issue 4 Pages 254-259
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    The authors have reported previously the carbon control on 4600 steels formed by metal injection molding (MIM) techniques using elemental powders. In the present paper, mechanical properties of the 4600 steels are investigated as comparing with that of the full-densified materials by Ceracon Process and some factors affecting the properties are discussed taking the structure into account.
    Sintered 4600 steels with elemental powders showed the better ductility than that of commercial sintered alloy steels with the same strength level because of the high density and the uniform distribution of finer spherical pores. Heat treatment improved the strength of 4600 steels with elemental powders over 2000MPa without loss of ductility (the elongation was over 3%), which showed the more excellent properties than those of conventional powder forged steels. This result indicates that it is possible to attain high performance ferrous materials by MIM techniques.
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  • Toshikazu Sugimura, Maki Narita, Mikio Kitamura
    1992 Volume 39 Issue 4 Pages 260-265
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
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    An impregnated cathode was manufactured by Hot Isostatic Pressing (HIP) with the mixed powders of W and electron emissive material.
    The effect of the HIP parameters on the sintering condition was investigated using SEM, X-ray diffraction and density measurement, and the relation between sintering condition and emission properties was discussed. The results were as follows;
    The densification was accelerated with increasing of HIP temperature and HIP holding time. As densification advanced, reaction between W and electron emissive material was progressed, resulting in decreasing of effective components and increasing of ineffective components of the emission properties. On the other hand, as the densification advanced, the better emission properties were obtained. We consider the emission properties depends rather on the contact area of W and electron emissive material than the amount of effective components.
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  • Hideshi Miura, Shinji Yoshihara, Tadatoshi Honda
    1992 Volume 39 Issue 4 Pages 266-271
    Published: April 15, 1992
    Released on J-STAGE: December 04, 2009
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    Explosive compaction of ceramic powders (α-Si3N4, SiC) and whiskers (β-Si3N4, SiC) were performed by using cylindrically axi-symmetric direct method. The mandrel was inserted into the center of container to increase the compacting pressure, and the momentum trap was adopted for avoiding the development of cracks in a compact. Sintering was treated to the explosively compacted ceramics under the various temperature and appropriate atmosphere. The effects of mandrel, momentumtrap and sintering conditions on the compact characteristics has been investigated by means of microhardness test, optical and scanning electron microscopy and density measurement. The obtained reslts are as follows:
    It was found that the mandrel was very efficient in increasing the compacting pressure. In such a case, the mandrel made of Cu was more effective than that made of Al. In the explosively compacted Si3N4 whisker with Cu mandrel, maximum hardness reached 1400Hv. By adoption of the momentum trap, the cracks in a compact was gradually decreased as the weight of momentum trap increased. The density of the explosively compacted ceramics was incresed by even lower sintering temeparature as compared to conventional temparature. This seemed to be due to the activated condition of compacts by the through of shock waves which moved ceramic particles at high velocity and caused the particle refining and the cleaning of the particle surface.
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  • Shunzo Tashima, Masayuki Sumita, Hidenori Kuroki
    1992 Volume 39 Issue 4 Pages 272-276
    Published: April 15, 1992
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    An investigation was made of the characteristics of the green compacts, the compacts semisintered at 800°C and those sintered at 1250°C, in order to check the segregation of particle size in the centrifugal compaction process of ceramics.
    Two alumina powders were used. One was a 0.22 μm powder (size range: 0.1-0.3μm) and the other was a 0.77 μm powder (size range: 0.2-1.0μm). These were dispersed with a ball mill. The coefficients of the viscosity of the slips were in the range of 40-2000mPa⋅s.
    The fracture surfaces of the 0.22 μm powder compacts semi-sintered at 800°C were observed by S EM, and showed the particles 0.1-0.3 μm in size distributing uniformly from the bottom to the top in the compacts. On the other hand, the bigger particles of about 1.0μm in size were shown concentrating at the bottom in the 0.77 μm powder compacts.
    When the compacts were made from the 0.22 μm powder which had a narrow particle size range, the moisture of the green compacts, relative green density, sintered density and dimensional change of the compacts, were uniform in the vertical direction. The compacts made from the 0.77 μm powder having a wide particle size range, however, showed no uniformity in those characteristics, and a particle size segregation was observed in them.
    As a conclusion, a powder with a narrow particle size range must be used in order to obtain a uniform compact in the centrifugal compaction process.
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  • [in Japanese]
    1992 Volume 39 Issue 4 Pages 278
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
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  • Ryuzo Watanabe, Akira Kawasaki
    1992 Volume 39 Issue 4 Pages 279-286
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
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    Powder Metallurgical (P/M) processing of thermal-stress relief type of functionally gradient materials (FGM) was reviewed on the basis of the work achieved by the authors' laboratory of Tohoku University. The role of thermal stress relaxation function in thermal barrier performance was emphasized. The processing routes of FGM were briefly summarized, in which the sintering balance for different mixing conditions of metals and ceramics and the fineness of compositional profile were mentioned. Spray deposition technique and differential temperature sintering have been developed of material species. The characteristic microstructural transition in a graded materials and the accompanying property transion were demonstrated. Two aspects in designing an optimum compositional profiles were described for the reduction of the thermal stress generated during processing ( during cooling from sintering temperature) and in a temperature gradient of thermal barrier situation. Two kinds of thermal loading tests were applied for the evaluation of thermal barrier performance of P/M FGM; a thermal shock test and a differential thermal loading test. The thermal stress conditions during the testing were discussed.
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  • Hiroshi Kimura, Shinichi Kobayashi
    1992 Volume 39 Issue 4 Pages 287-290
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
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    A novel P/M processing is developed, which consists of plasma sintering with the aid of an applied stress and a temperature gradient and a high quality powder production of amorphous TiAI by mechanical alloying, for the fabrication of a functionally gradient materials(FGM) of zirconia-titanium aluminide system. Our processing makes it possible to obtain a FGM of FSZ/TiAl without a visible crack-like discontinuity throughout an overall cross section with a short-time sintering of 300 s and a relatively low applied stress ranging from 29 to 59 MPa. Plasma sintering leads to a full dense compaction, mainly via viscous flow in amorphous TiAl matrix, in layers between TiAI and 50%-TiAl/FSZ, and a relatively high hardness of 807 Hv for 7-phase TiAl including a small amount. of α2(Ti3Al) and at the maximum, 1016 Hv at 25 %FSZ/TiAl. These higher levels are explained by strengthening mechanisms of nano-meter scaled grain and FSZ particle dispersion respectively. Two-step plasma sintering with a greater temperature gradient realizes the enhanced hardness and relative density of FSZ-rich layers.
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  • Seo-Weon Kim, Makoto Sasaki, Hiroyuki Suzuki, Toshio Hirai
    1992 Volume 39 Issue 4 Pages 291-294
    Published: April 15, 1992
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    For the fundamental study on the fabrication processes of CVD⋅TiC/C functionally gradient materials, TiC-C composites in the C/(TiC+C) from 0 to 95 mol% were prepared by chemical vapor deposition (CVD) of a TiCl4-CH4-H2 system. The TiC-C composites from TiC to TiC-95.2mol%C were prepared by controlling C/Ti ratio in input gas. Thermal properties of the composites were affected by the composition and morphology of C phase and micro-voids. The thermal conductivity of the composites depended on the composition and densities. The thermal expansion coefficients of CVD⋅TiC-C composites up to about 50 mol% TiC nearly equal to that of CVD⋅TiC.
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  • Makoto Sasaki, Seo-Weon Kim, Toshio Hirai, Noriaki Sekiguchi
    1992 Volume 39 Issue 4 Pages 295-298
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    Plate-like deposits having a compositional gradient from TiC-91. 5mol%C to TiC were obtained on a graphite substrate by chemical vapor deposition (CVD). The CVC conditions used were as follows; a TiCl4-CH4-H2 system, a deposition temperature of 1673K, a total gas pressure of 1.3kPa, and a gas concentration ratio (mC/Ti) of 30.4 to 3.7. Cracks were observed in TiC-coated graphite (TiC NFGM), however, no crack in TiC/C FGMs. The cracking in TiC NFGM was thought to be due to the hoop and radial tensile stresses generated after CVD coating. Introduction of the C/TiC graded layer between the TiC layer and the substrate is effective to reduce the residual thermal stress.
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  • Hideki Hamatani, Nobuyuki Shimada, Yasutomo Ichiyama, Saburo Kitaguchi ...
    1992 Volume 39 Issue 4 Pages 299-302
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
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    This study was aimed at developing fabrication process of a larage-sized Functionally Gradient Mateials (FGM) by using Low Pressure Plasma Spraying (LPPS). The problem for the enlargment is the thermal distortion of substrates which occur during pre-heating and spraying. In order to solve this problem, it is neccesary to make clear the effect of substrate temperature on the distortion. This study showed that under the optimum condition, such as maximum temperature less than 600°C and temperature distribution less than 80°C of substrate during pre-heating, its distortion was successivily minimized.
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  • Yoshiyasu Itoh, Masashi Takahashi, Matsuo Miyazaki, Hideo Kashiwaya
    1992 Volume 39 Issue 4 Pages 303-308
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
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    The residual stresses of functionally gradient materials induced by a bonding process were analyzed by comparison with the direct bonding joints between different materials. In this paper, firstly, the gradation joints of stabilized zirconia/nickel based alloy composites were chosen for a finite element method analysis of residual stress distributions.
    It was verified that the residual stresses produced by uniform heating process decreased by use of the gradation techniques. Especially, the stress singularities at the edge of the interface of the direct bonding ioints could be disanneared in case of the gradation joints.
    Secondly, the effects of the gradation geometry and material constants, such as Young's modulus and thermal expansion coefficients on the residual stresses were investigated. As a result, it was found that the residual stresses could be effectively analyzed by application of a dimensionless parameter, which is σ(1-μ1)/(E112)ΔT) (σ; residual stress, μ1, μ2; Poisson's ratio, E1; Young's modulus of material 1, (α12); difference of thermal expansion coefficients between material 1 and material 2, ΔT ; temperature difference) in case of the gradation joints, and there was a tendency of decreasing the dimensionless residual stress with increasing the gradation thickness.
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  • Masahiro Tanaka, Akira Kawasaki, Ryuzo Watanabe
    1992 Volume 39 Issue 4 Pages 309-313
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    The powder metallurgical fabrication of a functionally gradient material for thermal barrier use of a specific material combination of SiC-AIN/Mo is described. The results of thermomechanical tests for non-FGM have shown that the samples HIP'ed at 2123K at the pressure of 200MPa for 2h from mixture of SiC and AIN powders have a sufficient thermal barrier property with high fracture strength even at elevated temperature than monolithic SiC and AIN. The designing of the compositional distribution was made on the basis of the calculation of the overall heat transfer in a temperature difference of 1000K. According to the optimum compositional distribution, the sinterd compact of the functionally gradient material of SiC-AIN/Mo was successfully fabricated.
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  • Jun Takada, Hiroyuki Matsumoto, Hideyuki Kuwahara
    1992 Volume 39 Issue 4 Pages 314-317
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    Plasma nitriding behavior has been studied for Fe-Cr alloys nitrided by plasma in a mixted gas of N2 and Hz at temperatures from 450 to 550°C in order to discuss an application of plasma nitriding process for providing a functional gradient material. Two nitrided layers are formed:an external layer of γ '-Fe4N and an internal layer where small CrN particles disperse in α-Fe matrix. The growth of the internal nitrided layer is controlled by diffusion of nitrogen in the matrix metal. The internal nitrided layer exhibits higher hardness due to dispersion of small CrN particles. Hardness in nitrided Fe-3%Cr alloy gradually decreases as the distance from the specimen surface increases. The change in hardness is ascribed to that in volume fraction of CrN particles.
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  • Hideyuki Kuwahara, Jun Takada
    1992 Volume 39 Issue 4 Pages 318-321
    Published: April 15, 1992
    Released on J-STAGE: May 22, 2009
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    To discuss plasma nitriding process as a kind of preparing process of functional gradient material, various characteristics of the layers nitrided by plasma of a mixed gas of nitrogen and hydrogen were studied. Fe-18Cr-9Ni alloy was nitrided at the range of temperature from 723 to 823 K for various periods (3.6 ks to 108 ks), and then each specimen was immediately quenched into iced water. Microstructural observa-tion, x-ray diffraction examination, measurement of hardness, EPMA analysis of nitro-gen, chromium, nickel, and iron, and chemical analysis of the surface layer of sepci-men were conducted. TEN observation of extracted CrN particles was also carried out to determine their mean diameter. The main results are as the follows: (1) The plasma nitriding is available for preparing FGM. (2) The profile of dissolved nitrogen in the nitriding layer, in which CrN was precipitated, decreased continueously from the specimen surface to the nitriding front. (3) The nitrogen is dissolved to 1.73wt% at 823 K. This nitrogen content is equal to about 10 times of the reported values. (4) The mean size of the CrN particle is 7nm in diameter.
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  • Hideyuki Kuwahara, Yohichi Tomii, Jun Takada
    1992 Volume 39 Issue 4 Pages 322-325
    Published: April 15, 1992
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    To make clear the feasibility of the plasma carburizing for preparing a functional gradient material, the characteristics of the plasma-carburized layer of Fe-0.15C alloy have been studied. Samples were carburized at the range of temperature from 1173 K to 1273 K for various periods (0.6 ks to 4.8 ks) using plasma of a mixed gas of methane and hydrogen. Microstructural observation, x-ray diffraction examination, and measurement of hardness were conducted. Both analyses of carbon using EPNA and hydrogen using IMA were also carried out on the cross section of some specimens. The main results are as the follows: (1) The plasma carburizing is available for preparing FGM. (2) The profile of hardness is analogous to that of hydrogen concentration rather than that of carbon. (3) The superhardness which shows higher than hardness of the usual quenched sample is attained at inner region where carbon content is lower than that at the specimen surface. Thus, the superhardness results from the effect of hydrogen and carbon.
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