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Volume 55, Issue 10
October
Displaying 1-11 of 11 articles from this issue
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Paper
Paper
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Mechanical and Electrical Properties of Si3N4-SiC Composites with Network Structure of SiC ParticlesKatsunori Yamada, Nobuo Kamiya2008 Volume 55 Issue 10 Pages 685-691
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSMechanical and electrical properties of Si3N4/SiC composites, which dispersed SiC particles from micrometer size to nanometer size, were investigated. Furthermore, the analysis of the dispersion morphology of SiC particles was statistically carried out, and then the average gap width between SiC particles in networks Si3N4/SiC composites was calculated. Both bending strength and elastic modulus of the Si3N4/SiC composites could be improved by forming the network structure with the segregated SiC particles of nanometer size. The electric conductivity of Si3N4/SiC composites was improved by forming the network morphology with semiconductive SiC particles of 0.03 μm diameter, which set the gap width in the range of 20 to 90 nm interval.View full abstractDownload PDF (1293K)
Special Issue: Recent Advances of Sintering Technologies on Metals, Alloys and Related Powders
Summarization
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Akira Kawasaki2008 Volume 55 Issue 10 Pages 694
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSDownload PDF (138K)
Paper
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Hiroyuki Y. Suzuki, Kenji Shimizu, Shigeo Tanaka2008 Volume 55 Issue 10 Pages 695-702
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSIn High-Speed Centrifugal Compaction Process (HCP), powders are prepared as slips and deposited on bottom of molds under huge (10,000 g) centrifugal force to form green compacts. It looks severe process, but the force acting on the mold is less than several tens MPa. Therefore, the HCP is a mild compacting method from a view points of compacting mold. In the present study, we developed plastic compacting mold for the HCP. The hollow shape in the compacting mold is obtaind by selectively dissolving another plastic mold (master mold) buried in it. For releasing green compact from compacting mold, the whole mold is heated and the compacting mold is thermally decomposed. Proper selection of compacting mold resin, filler and binder resin in green compact makes releasing of the compact stress-free. Released compact can be sintered but minute cracks remains there.View full abstractDownload PDF (1469K) -
— Fabrication of Tiny and Multiple Holed Nozzle for Diesel Engine —Hiroyuki Y. Suzuki, Mamoru Nagai, Koji Matsuzaki, Masataka Arai, Yoshi ...2008 Volume 55 Issue 10 Pages 703-708
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSHigh-Speed Centrifugal Compaction Process (HCP) is a kind of wet compacting method for fine powders suitable for net shape fabrication of complex shape parts with hollow spaces. In the present study, we aim to develop diesel engine fuel injection nozzles using this technique. A plastic core with multiple thin bars (which become nozzle holes) are buried into fine metallic powder compact by the HCP. Then, the core and binder resin in the green compact are thermally decomposed in a vacuum furnace. We developed a proper procedure for de-binding. The de-binded compacts can be sintered uniformly to the relative density of 96 %, having sufficient strength for fuel injection.View full abstractDownload PDF (1522K) -
Ryuzo Watanabe, Noriharu Yodoshi, Hidemi Kato, Akira Kawasaki2008 Volume 55 Issue 10 Pages 709-714
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSThe equations for the densification control by viscous flow in the hot pressing of metallic glass powders are derived and a criterion for the full densification thereof and an approach for the porosity control are proposed. The kinetic equations are derived on the basis of Arzt's hot pressing theory; in which the densification is modeled by the contraction of the Bolonoi cell of the random dense packing of spherical particles. The constitutive equation for the viscous flow is obtained from the hitherto proposed creep rate equation setting the rate exponent to be unity. The hypothetical constraint for the deformation due to the three grain edges formed in the later stage of densification is taken into account as a modification of the pressure term in the kinetic equations. The relative density is expressed as functions of hot pressing time and the ratio of the viscosity and the pressure. It is shown that the time required for full densification of metallic glass powders depends only on the viscosity/pressure ratio. The criterion for the full densification is expressed as a straight line on the time-viscosity/pressure ratio plane, which divides the area into full-dense and porous areas. The porosity control of the metallic glass powder compacts is also demonstrated as another practical application of the present theory. The results are discussed on the basis of the reported data.View full abstractDownload PDF (809K) -
Noriaki Matsubara, Katsu Yanagimoto, Akira Kawasaki2008 Volume 55 Issue 10 Pages 715-719
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSThe compressive behavior and sintering condition of Ni-based metallic glass sintered body produced by precise hot pressing was investigated in this study. Ni-based metallic glass powder prepared by a gas atomizing process was sintered under the condition of processing temperature 863 K, processing pressure 200 MPa, which enabled to achieve sintered bodies of nearly full densification without crystallization. These processing condition were found in previous study using precise hot pressing.
The compression test was conducted using amorphous sintered body described above. The compressive strength, Young's modulus, and elastic elongation are 1929 MPa, 94.8 GPa, and 0.021, respectively. The amorphous sintered body has high strength and lower Young's modulus than crystalline metals. These compressive characteristics are the same as bulk metallic glass manufactured by casting. Sintering condition of Ni-based metallic glass sintered body was observed using transmission electron microscope. While the contrast was observed in metallic glass powder boundaries, oxides, micro pores, and crystals weren't found, which demonstrated excellent sintering properties obtained by the diffusion mechanism.
In addition, the gear-shaped sintered amorphous body was successfully manufactured, showing great potential for various applications in manufacturing.View full abstractDownload PDF (1189K) -
Yoshinori Itoh, Toshiaki Uematsu, Kenji Sato, Hideshi Miura, Mitsuo Ni ...2008 Volume 55 Issue 10 Pages 720-725
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSIn the previous papers, the sintered Ti-6Al-2Sn-4Zr-2Mo alloy compacts showed higher tensile strength than the Ti-6Al-4V alloy compacts, and the strengthening of Ti-6Al-4V alloy compacts were available by addition of fine Mo powder because of fine microstructural modification. In this study, the metal injection molding process was applied to produce the high strength α+β type titanium alloy compacts by addition of 4mass% Mo on the Ti-6Al-2Sn-4Zr-2Mo alloy compacts using Ti, Al-based pre-alloy and Mo powders. The effect of sintering conditions on the relative density, mechanical properties and oxygen content of the compacts were mainly investigated.
The relative density and tensile strength of sintered compacts were increased with increasing the sintering temperature and time, and reached up to 98% relative density and 1000MPa tensile strength by sintering at 1473K for 28.8ks. But the elongation of sintered compacts was below 10% at lower sintering temperature for short time or higher sintering temperature for long time. The microstructures of sintered compacts were consisted of acicular α and intergranular β phases, and the acicular α phase was finer than that of Ti-6Al-2Sn-4Zr-2Mo alloy compacts. Eventually, the tensile strength of Ti-6Al-2Sn-4Zr-6Mo alloy compact was reached up to 1010MPa with 14.7% of elongation by lower sintering temperature with prolonged sintering time.View full abstractDownload PDF (1167K) -
Toshiko Osada, Hideshi Miura, Yoshinori Itoh, Makoto Fujita, Nobuhiro ...2008 Volume 55 Issue 10 Pages 726-731
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSTi-6Al-7Nb alloy has been developed for more suitable biomaterial in place of Ti-6Al-4V alloy because of vanadium toxicity to human body. In this study, the metal injection molding process was applied to produce the Ti-6Al-7Nb alloy compacts using alloy powder. For comparison, the mixed elemental powders of Ti, Al and Nb, and pre-alloyed powders of Ti-Al and Al-Nb were also used. The effects of sintering conditions on the microstructures, relative density and mechanical properties of injection molded compacts were investigated. Sintered compacts using alloy powder showed relatively higher mechanical properties than the compacts using mixed powder. Eventually, the compacts using alloy powder were improved to be 900 MPa of tensile strength with 15% of elongation, which are comparable to the properties of wrought materials.View full abstractDownload PDF (1251K) -
Masaaki Hanao, Hidetaka Hayashi, Akira Kishimoto2008 Volume 55 Issue 10 Pages 732-737
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSWe have already fabricated ceramic mono-foams by expanding once-sintered dense shells utilizing the superplastic deformation of 3YSZ, 8YSZ, alumina and titania based ceramics. In the present study, granular coating method was applied to make a porous ceramics through the superplastically foaming method based on 3YSZ. Both mechanical strength and thermal conductivity were measured and compared with those of fully densified as well as conventional porous 3YSZ ceramics. Porous ceramics with porosity over 35 % can be fabricated with less than 15 vol% of foam agent. The mechanical strength and thermal conductivity were superior or comparable to those for conventionally fabricated porous ceramics with the same porosity level.View full abstractDownload PDF (1549K) -
Hideshi Miura, Toshiko Osada, Hideki Ishibashi, Kenta Okawachi, Makoto ...2008 Volume 55 Issue 10 Pages 738-742
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSSelective laser sintering (SLS) is one of the promising processes for rapid production of complex shaped parts. This paper investigates the characteristics of multi-layered compacts made by selective laser sintering using Ti-6Al-4V, Ti-6Al-7Nb powders toward fabrication of porous bone substitutes. The relative density and tensile strength were improved by optimizing the laser forming parameters. As a result, the maximum tensile strength was 550 MPa, 580 MPa for Ti-6Al-4V and Ti-6Al-7Nb compacts, respectively. In addition, although the linear laser irradiated section was not continuous due to the surface tension, it was possible to form the linear section by first low laser power irradiation (presintering) followed by second high laser power irradiation. Finally, density and compressive strength of the honey comb structure via this process were approximately similar to those of human bones.View full abstractDownload PDF (1176K) -
Hisashi Imai, Katsuyoshi Kondoh, Yoshiharu Kosaka, Akimichi Kojima, Ge ...2008 Volume 55 Issue 10 Pages 743-749
Published: 2008
Released on J-STAGE: December 05, 2008
JOURNAL OPEN ACCESSCharacteristics of 60Cu-40Zn brass powder compacts and their extruded materials were investigated. In 60Cu-40Zn brass powder billets consolidated by spark sintering, no vaporization of zinc occurred, and sintered billets with a high density over 99.9 % were obtained. These billets also had high tensile strength and elongation as well as cast brass ingots with the same composition. By the conditions of spark sintering; pressure of 40 MPa, temperature of 1053 K, sintering time of 1.8 ks, the extruded material of 60Cu-40Zn brass powder had an elongation over 50 %. Deformability for collapse test of the pipe extruded specimens also was high by spark sintering because of increasing α phase in extruded materials.View full abstractDownload PDF (1392K)
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