Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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Volume 60, Issue 10
December
Displaying 1-8 of 8 articles from this issue
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Paper
Paper
  • Effect of Heat Treatment on Microstructure and Mechanical Properties of Harmonic-Structured Composite with Pure Titanium and Ti – 48 mol%Al Alloy
    Hiroshi FUJIWARA, Reo YOSHIDA, Hiroyuki MIYAMOTO, Kei AMEYAMA
    2013 Volume 60 Issue 10 Pages 413-419
    Published: October 15, 2013
    Released on J-STAGE: October 31, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.413
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    A harmonic-structured composite with pure titanium and Ti–48mol%Al alloy was produced by mechanical milling and spark plasma sintering process for an improvement of low ductility at room temperature. The harmonic–structured composite has the network area having fine-grained Ti–48mol%Al and the dispersed area having coarse–grained titanium. The effects of the heat treatment at 873 K, 973 K and 1073 K on the microstructure and mechanical properties of the harmonic-structured composite with pure titanium and Ti–48mol%Al alloy was investigated in detail. The microstructure of the harmonic-structured composite is hardly changed after the heat treatment at 873 K, 973 K and 1073 K, except the grain coarsening of titanium in the dispersed area. The Vickers hardness of the harmonic-structured composite remains high hardness after the heat treatment at 873 K, 973 K and 1073 K in spite of 16.5 vol% Ti – Al alloy. The tensile result reveals that the harmonic-structured composite after the heat treatment at 873 K exhibits high strength and especially high ductility.
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  • High-Energy Milling of Silicon Nitride Powder
    Toshiyuki NISHIMURA, Xin XU, Yoshinobu YAMAMOTO, Koji KIMOTO, Naoto HI ...
    2013 Volume 60 Issue 10 Pages 420-427
    Published: October 15, 2013
    Released on J-STAGE: October 31, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.420
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    Silicon nitride nanopowder was fabricated from a silicon nitride sub-micrometer powder by high energy milling. The sub-micrometer Si3N4 powder, 2 mol% of Al2O3 and 5 mol% of Y2O3 are mixed and then high-energy milled with Si3N4 balls as milling media in a Si3N4–lined pot filled with N2. Silicon nitride nanopowder with about 20 nm in diameter was obtained by high-energy milling at 475 rpm for 4 hs. Phase identification by XRD and TEM observation showed that the high-energy milled powder consisted of nanopowder with glassy phase. Effect of metallic aluminum was invesigated as a grinding additive. The addition of metallic aluminum enhanced the high-energy milling. These results suggest that nanopowder can be prepared by grinding method.
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  • Electric Current Assisted Sintering of Nitride Nanoceramics
    Toshiyuki NISHIMURA, Naoto HIROSAKI
    2013 Volume 60 Issue 10 Pages 424-427
    Published: October 15, 2013
    Released on J-STAGE: October 31, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.424
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    Silicon nitride nanoceramic was fabricated from silicon nitride nanopowder prepared by high energy milling. An electric current assisted sintering was used for densification. Aluminium nitride nanoceramic was fabricated from aluminium nitride nanopowder, using the electric current assisted sintering. A liquid phase sintering is effective for the fabrication of the nanoceramics. Densification was acceralated and sintering temperature could be lowered by a liquid phase formed by reaction of sintering additives and oxide on the surface of nitride ceramic particles.
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  • Fabrication of High Strength and Toughness Ceramics Using Pulsed Electric-Current Pressure Sintering of ZrO2(Y2O3)–Al2O3 Solid Solution Powders Prepared by the Neutralization Co-precipitation Method
    Kenta YAMAMOTO, Masaki KATO, Ken HIROTA, Hideki TAGUCHI, Hideo KIMURA, ...
    2013 Volume 60 Issue 10 Pages 428-435
    Published: October 15, 2013
    Released on J-STAGE: October 31, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.428
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    ZrO2 composite ceramics containing 25mol%Al2O3 and a small amount of Y2O3, i.e., 75mol%ZrO2 (0.5～2.0mol%Y2O3: 0.5～2.0Y)–25mol%Al2O3 ceramics, have been fabricated by sintering cubic ZrO2 solid solution (ss) nano-powder prepared via the neutralization coprecipitation method. Their sintering was performed using a pulsed electric-current pressure sintering (PECPS) at 1300～1350˚C for 10 min under 60 MPa in Ar. Dense tetragonal-ZrO2 (ss) ceramics containing α–Al2O3 were composed of 135 − 150 nm grains with a high relative density ≥99.9%. They showed extreme high bending strength (σb≥1 GPa) and high fracture toughness (KIC≥15 MPa • m1/2) simultaneously. FE-SEM observation revealed that these mechanical properties were originated from homogeneous distribution of α–Al2O3 particles around the t–ZrO2 matrix; the precipitation of α–Al2O3 could be achieved by adopting both the (ss) powders containing α–Al2O3 and PECPS.
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