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Volume 47, Issue 4
Displaying 1-17 of 17 articles from this issue
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Naoya Sukegawa, Toshio Sano, Satoko Horikoshi, Hiroyuku Takeishi2000 Volume 47 Issue 4 Pages 341-346
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn powder Metallurgy process, some dynamic powder compaction methods have been proposed because they have advantages of giving uniform density distribution even for high-aspect-ratio parts and breaking surface oxides of powders, comparing with static powder compaction methods.
Constitutive equations considering strain-rate effect are usually used to analyze the dynamic deformation of solid materials. One-dimensional dynamic analyses using static stress-strain relations were carried out so far. However, in case of powder materials, constitutive equation considering the strain-rate effect has not been applied.
In this paper a Malvern-Type constitutive equation, Eε=σ+K(σ-f(ε)) for powder materials is employed to analyze dynamic behavior of powder materials. A constant, K, in the equation is obtained by comparing the experimental and analytical results in terms of plastic strain distribution at longitudinal in a container. In the case of rapidly solidified Al-Li powder, K=2×105 is obtained.
This method can widely be applicable to get dynamic constitutive equations for powders.View full abstractDownload PDF (481K) -
Keiko Kikuchi, Yan-Sheng Kang, Akira Kawasaki2000 Volume 47 Issue 4 Pages 347-352
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn order to meet various power requirements in the next century, thermoelectric (TE) power generation system has been focussed on a candidate of direct energy conversion systems with a nuclear heat source. An important thing in the TE power generation system is to use efficiently the heat source by means of high density induction of thermal energy for the TE module. The present work investigated a compliant pad which can served as both electrode and conductible coupling between TE module and heating or cooling duct. This pad demands (1) a high flux, direct conduction path to heat source and heat sink, (2) the structural flexibility to protect the TE module from high stress due to thermal expansion, (3) electrical insulation of the electrode from heating or cooling duct, (4) an extended durability by a simple FGM structure. In this paper, optimization for FGM was performed by using thermal stress analysis and thermal conduction analysis, densification of nickel and alumina powder, and process of manufacturing nickel/alumina/nickel symmetric FGM were investigated.View full abstractDownload PDF (4792K) -
Koichi Yanai, Mutsumi Hirai2000 Volume 47 Issue 4 Pages 353-363
Published: April 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe radial die wall pressure during uniaxial powder compression and unloading processes was measured using various kinds of Al2O3 powders. The radial pressure during compression increased with increasing compaction pressure linearly and decreasing BET specific surface area of the powder. The radial pressure during unloading decreased due to plastic deformation of the green pellet. The residual pressure after unloading increased with increasing compaction pressure. The residual pressure normalized by the radial pressure during compression increased with increasing BET specific surface area of the powder.View full abstractDownload PDF (718K) -
Suguru ItouÅ, Takeshi Yamamoto, Akira Otsuki, Keiichi N. Ishihar ...2000 Volume 47 Issue 4 Pages 364-368
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe purpose of this reseach is to propose a new recycle system of an iron, which is simpler, lower cost and lower energy consumption than the current recycle system. The concept of this system is called "active disassembly" a material includes an actuator which operates under special surroundings. Since large equipment and re-smelting will not be needed, it will be easy to recycle an iron and steel. In this research, Terbium was used as an actuator because rare earth metals have a nature of absorbing hydrogen gas and the volume change during absorbing hydrogen gas. The iron base new material was formed, which includes Th actuator network spread into Fe particle boundary during the sintering process. The Th acutuator was triggered under hydrogen atomosphere and pulverized itself. The material showing the most suitable Tb network was Fe-2at%Tb sintered at 1673K for 600s and became embrittle after heat treatment under hydrogen atomosphere. The recycled materials can be obtain by sintering the pulverized material again at 1673K for 600s. KEY WORDS active disassembly, hydrogen, embrittlementView full abstractDownload PDF (3384K) -
Jun-ichi Yamamoto, Masa-aki Naka, Toshiya Shibayanagi, Masakatsu Maeda2000 Volume 47 Issue 4 Pages 369-374
Published: April 15, 2000
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSβ-FeSi2 was successfully produced by making use of the combined process of mechanical alloying (MA) and spark plasma sintering (SPS). The MA was perforomed under the Ar gas atomsphere using mixed powders of pure iron and silicon having the mole fraction of 1: 2. The SPS process was performed at 1073 K with the heating rate of 1.33 K/s and the holding time was ranging from 0 to 15 ks. The combined process was quite effective for the production of β-FeSi2, where the minimum SPS time required was found to depend on the MA time. The shortest SPS holding time of Os was achieved for the powders mechanically alloyed for 72ks.
The relative density of each sinter is around 90% (4.44g/cm3) to its ideal density, and especially the density of 97.4% was obtained for the sinter which was mechanically alloyed for 72ks, followed by the SPS treatment for 600s.View full abstractDownload PDF (2110K) -
Shigetoshi Muranaka, Toshiniko Shigematu2000 Volume 47 Issue 4 Pages 375-378
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMgIn2O4 films were reactively deposited with assistance of rf discharge at an oxygen pressure of 4 × 10-2 Pa and at a substrate temperature between room temperature and 550°C. The dependence of the structure of the films and their physical properties on the substrate temperature was studied. It was found that crystallized films were deposited at 250 and 350°C, while films were almost amorphous at room temperature. The crystallinity of the films was also reduced at and above 450°C because of deviation of the film composition from stoichiometry. The crystallized films were highly transparent with an average transmission of about 80 %, and by heat treatment in H2 gas, became very conductive having a resistivity of about 8 × 10-2Ωcm.View full abstractDownload PDF (239K) -
[in Japanese]2000 Volume 47 Issue 4 Pages 380
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (106K) -
Satoru Ishihara, Fumihiro Wakai2000 Volume 47 Issue 4 Pages 381-385
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDensification behavior by hot isostatic pressing in precursor-derived Si-C-N system ceramics has been investigated in order to obtain dense ceramic bulk derived from polymer precursor. In advance of the experiments of densification, the deformation behavior of as-pyrolyzed monolith at high temperatures has been investigated. The as-pyrolyzed ceramic monolith which had many pores showed deformation of several % strain in uniaxial compression tests at the temperatures higher than 1400°C. Then, hot isostatic pressing of both as-pyrolyzed monolith and pyrolyzed powder compacts has been performed for the densification. The density of the monolith increased more than 20%, and many pores disappeared during the hot isostatic pressing at 1600°C and 980 MPa. However, the size of residual pores became larger than the initial pore size before the treatment. On the other hand, dense ceramics were obtained by hot isostatically pressing the pyrolyzed powder compaction. In the case of the treatment at 1400°C, the microstructure maintained the amorphous matrix. These dense materials were able to be more deformed at 1600°C than the as-pyrolyzed monolith. Also, in case of the Si-C-N-B ceramics, similar dense materials were obtained by the techniques of hot isostatic pressing of powder compaction.View full abstractDownload PDF (5448K) -
Takashi Goto, Takashi Ono, Toshio Hirai2000 Volume 47 Issue 4 Pages 386-390
Published: April 15, 2000
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSIr films were prepared by metal organic chemical vapor deposition (MOCVD), and their electrochemical properties as the electrode for oxygen gas sensors were investigated. The Ir films consisted of It granules (1 to 3nm in diameter) and amorphous carbon surrounding each Ir granules. The charge transfer at the nano-graular Ir film electrode/ zirconia solid electrolyte/gas interface was about 100 times greater than that for other platinum electrodes below 500°C. The emf values of the oxygen cell constructed from the nano-granular Ir film electrode and zirconia solid electrolyte showed the Nernstian theoretical values even at 300°C.View full abstractDownload PDF (1604K) -
Ken-ichi Tajima, Hae Jin Hwang, Mutsuo Sando, Koichi Niihara2000 Volume 47 Issue 4 Pages 391-395
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSLead zirconate titanate (PZT) based composites were prepared from commercially available PZT powder and a small amount (0.1 - 1.0vol%) of nano-sized alumina or magnesia, and their mechanical and piezoelectric properties were evaluated. The fracture strength of the composites increased with increasing second phase content due to grain size reduction, particularly in the case of PZT/MgO composites, which showed a significant improvement in strength. The planar electromechanical coupling factor, Kp, of the composites remained unchanged. As a consequence, highly reliable PZT composites with high strength (140 MPa) and Kp (60%) have been fabricated.View full abstractDownload PDF (3584K) -
Masato Uehara, Koji Eto, Hideaki Maeda, Junichi Hojo2000 Volume 47 Issue 4 Pages 396-399
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAmorphous composite powders are useful to fabricate ceramic nanocomposite. The nanostructure is formed by phase separation and crystallization during sintering. Si3N4-BN composite powder was prepared by a vapor phase reaction method and heated in N2 with and without Y2O3-Al2O3 sintering aid. Particle coarsening was observed above 1400°C in monolithic Si3N4, whereas the particle growth was retarded in Si3N4-BN composite. α-Si3N4 was detected above 1400°C in monolithic Si3N4, but Si3N4-BN composite was still amorphous even at 1600°C. When the sintering aid was used, β-Si3N4 was formed at 1600°C in monolithic Si3N4 and Si3N4-BN composite. The phase separation of BN was investigated by IR spectroscopy. The phase separation of Si3N4-BN composite powder became significant at 1600°C and the crystallization was stimulated by the sintering aid. It was confirmed from TEM observation that BN was segregated on the surface of Si3N4 particle.View full abstractDownload PDF (3116K) -
Ritsuko Tsuzuki, Eiji Yuasa2000 Volume 47 Issue 4 Pages 400-405
Published: April 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe formation of amorphous phase, which are invented by Al, Ni and Zr powder, were investigated. Oscillatory ball mill was used to carry out MA (mechanical alloying) in this investigation. DMA (Double Mechanical Alloying) method was also taken, where binary amorphous phases were firstly formed by MA, and the third element powder was added to those amorphous phases, and milled by MA again. The results of DMA were compared with the results of normal MA. For MA of Al-Zr mixed powder, amorphous phases were formed for 72ks in the case of Al-40-50 mol%Zr, while Ni-Zr amorphous phases were obtained at the same milling time for Ni-35-60 mol%Zr. Ternary Al-Ni-Zr amorphous phases were successively obtained by 72 ks of DMA for 30-40 mol%Al and MAed amorphous Ni-35-60 mol%Zr mixed powders. From these results, it was shown that the DMA method was more effective and prepare a wide range ternary amorphous phase than conventional MA method. Furthermore it was confirmed that the hardness of Al-Ni-Zr amorphous alloys decreased with increasing Ni/Zr and Al/(Ni-Zr) ratios, resulted in stable amorphous phases up to higher temperature.View full abstractDownload PDF (398K) -
Kazuhiko Kita, Hiroyuki Sasaki, Junichi Nagahora, Akihisa Inoue2000 Volume 47 Issue 4 Pages 406-411
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNano-structured Al-based alloys with additions of Ni have been prepared by electron beam evaporation. The composition dependence of the resulting microstructures and mechanical properties has been studied. The Al-Ni deposits consist of Al and A13Ni with a grain size below 100nm. Vickers hardness increases with the Ni-content and reaches values as high as 320Hv at a Ni content of around 20at.%. At higher Ni contents Vickers hardness remains almost constant at this high level. Upon annealing the Al and Al3Ni grain grow and Vickers hardness decreases. The change of Vickers hardness follows the Hall-Petch relationship. The dispersion strengthening by the intermetallic phase of AI-Ni deposits would be estimated from the Orowan-mechanism. It is therefore concluded that the effects of both grain size refinement and dispersion strengthening contribute to the achievement of high Vickers hardness. The continuous electron beam evaporation technique is an effective method to produce nano crystalline high strength bulk material.View full abstractDownload PDF (3221K) -
Satoshi Ichikawa, Hideki Ichinose, Kunio Ito2000 Volume 47 Issue 4 Pages 412-416
Published: April 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNanocrystalline alloys were prepared by the inert-gas condensation and compaction method and were rolled. The deformed nanocrystalline alloys were examined by TEM and XRD in order to deduce the deformation mechanism. Tangled dislocations were not found in the grain of the deformed nanocrystalline Ag and Ag/Fe alloy by TEM. XRD measurements indicated that a normal preferred orientation of rolling was slightly developed in the Ag/Fe alloy but not in the Ag at all, even though the initial grain size was found to be smaller in the alloy than in the single component material. The grain growth occurred more or less by deformation. Hardness was not increased by deformation in the both materials. It is shown that the dominant deformation, especially in the single component material, is attributed to grain boundary sliding caused by grain boundary diffusion.View full abstractDownload PDF (5168K) -
Kenichiro Sasamori, Hisamichi Kimura, Akihisa Inoue, Yoshihiro Murakam ...2000 Volume 47 Issue 4 Pages 417-422
Published: April 15, 2000
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSRibbons of Al-Fe-Ti-M(M=V, Cr, Mn)alloys were prepared by melt-quenching(MQ)and their bulk alloys by the powder metallurgy(P/M)method using atomized powders. The ribbon Al-Fe-Ti-M(M=V, Cr, Mn)alloys produced at the circumferential velocity (Vc) of 40 m/s consisted of fcc-Al and amorphous phases. Maximum tensile fracture strength (σf) of the Al-Fe-Ti-M ribbons was 1170 MPa for Al93Fe3Ti2V2 alloy. The constituent structure was nearly the same as those for the powder and bulk Al-Fe-Ti-M(M=V, Cr, Mn)alloys. The bulk Al93Fe3Ti2Cr2 alloy consisted of quasicrystalline particles dispersed into fcc-Al. Decomposition temperature of these particles was 740 K. The ultimate tensile strength, 0.2% proof sterngth, plastic elongation, Young's modulus and Vicker's hardness were 650 MPa, 530 MPa, 4.4 %, 86 GPa and 190, respectively.View full abstractDownload PDF (1574K) -
Kimihiro Ozaki, Keizo Kobayashi, Akira Sugiyama, Toshiyuki Nishio, Aki ...2000 Volume 47 Issue 4 Pages 423-426
Published: April 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSAmorphous powder of Mg-Ni-Y system was prepared by mechanical alloying, and the amorphous bulk was produced by pulsed current sintering. The corrosion resistance was measured by polarization curve of the sintered amorphous specimen. After mechanically alloying of elementary powders for 400 h, Mg80Ni15Y5 and Mg80Ni10Y5B5 were obtained as powder but Mg80Ni5Y5B10 are obtained like a fish scale. Mg80Ni15Y5 powder consisted of amorphous phase and Mg2Ni compound as the result by XRD and DSC measurements. However, Mg80Ni10Y5B5 powder was almost amorphous phase. The bulk amorphous alloys were produced by pulsed current sintering of these amorphous powders at 423 K and 500 MPa. The pore ratio was about 0.6 %. The Mg amorphous alloys had higher corrosion potentials and lower corrosion current density than AZ91D alloy and pure Mg, and their corrosion resistances of Mg alloy were improved.View full abstractDownload PDF (1998K) -
Hisamichi Kimura, Akihisa Inoue, Kenichiro Sasamori, Hideki Ohtsubo, Y ...2000 Volume 47 Issue 4 Pages 427-432
Published: April 15, 2000
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSZr65Al7.5Cu27.5(Z-3), Zr65Al10Cu15Ni10(Z-4)and Zr55Al15Cu15Ni10Ti5(Z-5)glassy wires with a large supercooled liquid region were produced by a newly designed method, i. e., melt extraction using an arc furnace. The wire has a circular cross section and a smooth peripheral surface, but small flaws are observed on the surface. The Tg and Tx of the Z-4 and Z-5 glassy wires are nearly the same as those of the melt-spun glassy ribbons. The Z-4 glassy wire has a large super coold liquid region of 95 K. The coefficient of thermal expansion of the Z-4 glassy wire is 9.2 × 10-6K-1 and the temperature of electrical resistance of the Z-5 glassy wire is-9.0×10-5 K-1, respectively. Tensile fracture strength and elongation are 1170 MPa and 1.9 %, respectively, for the Z-3 glassy wire and 1590 MPa and 2.2 %, respectively, for the Z-4 glassy wire. The fracture surface consists mainly of a vein pattern which is the same as that for amorphous alloys.View full abstractDownload PDF (5270K)
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