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Volume 33, Issue 7
Displaying 1-9 of 9 articles from this issue
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[in Japanese]1986 Volume 33 Issue 7 Pages 339-343
Published: September 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (333K) -
Makoto Kume, Mamoru Senna1986 Volume 33 Issue 7 Pages 344-347
Published: September 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA commercial fine-powdered alpha-alumina was ground and mechanically activated in air by a centrifugal ball-mill. The activated powders were compacted at 18-200 MPa and fired at 1150-1450°C in air. The fired density increased by ca. 15% due to grinding for 1 h although the linear shrinkage of the fired compact remained almost unchanged. The compressive crushing strength increased up to ca. 300% and decreased with prolonged grinding time. The densification of the fired compact was enhanced either by grinding the starting powder or by raising the firing temperature. The mean pore size Rso decreased by grinding, while it increased with increasing temperature. The results of scanning electron microscopy and porosimetry on the fired compacts suggested that the porosity and mean pore size of the fired materials can be controlled by preliminary grinding of the starting powders.View full abstractDownload PDF (2677K) -
Hyo-Duk Namu, Kunihiro Nagata, Hideji Igarashi, Kiyoshi Okazaki1986 Volume 33 Issue 7 Pages 348-352
Published: September 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSLead-lanthanum zirconate-titanate (PLZT) powders were prepared by molten salt synthesis and solid state reaction. PLZT powder formation in the presence of fused salt was completed at lower temperature than that in solid state reaction, and the particle size of the powder increased markedly with increasing heating temperature. The dielectric, piezoelectric and optical properties of both ordinary fired and hotpressed PLZT ceramics fabricated from these powders were investigated. The electromechanical coupling factor and optical transmittance of PLZT ceramics from molten-salt-synthesized powders were smaller than those from solid state reaction, probably due to the substitution of Na and K ions (in NaCl-KC1) for Pb ion in PLZT ceramics.View full abstractDownload PDF (2563K) -
Hajime Izawa, Shinichi Kikkawa, Mitsue Koizumi1986 Volume 33 Issue 7 Pages 353-355
Published: September 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSSingle phase of sodium trititanate could be obtained by a hydrothermal reaction of TiO2 With NaOH aqueous solution having concentration less than 3 N under the conditions of above 400°C and above 17 MPa. The product was fibrous Na2Ti3O7 of 20-100μm in length and less than 1μm in width. Fibrous H2Ti3O7 of 10-30μm long and less than 1μm wide could be obtained by ion exchange of the fibrous Na2Ti3O7 in HCI aqueous solution.View full abstractDownload PDF (2761K) -
N. Nakanishi, T. Shigematsu, T. Sugimura, H. Okinaka1986 Volume 33 Issue 7 Pages 356-360
Published: September 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe authors have experimentally found that the martensitic transformation propagates isothermally during aging the 2.2 and 5.0 mol%-PSZ ceramics in the temperature range about 423-628 K after being sintered at 1873 K in air. As a result of this experiment, it was suggested that the so-called degradation of Y2O3-PSZ ceramics occurring at temperature around 473 K is mainly due to the microcrack propagation induced by the expansion of isothermally produced martensite. To make clear the mechanism of the isothermal propagation of martensite, which is first formed at the specimen surface region and then propagates into the interior, the authors proposed a model which can explain the C-type behaviour of time-temperaturetransformation diagram obtained in this experiment. Since the following three factors, (i) sintering temperature, (ii) circumstance and (iii) the diffusibility of oxygen ions, are thought to have an important effect upon the C-curves, these problems must be experimentally studied hereafter.View full abstractDownload PDF (325K) -
Hidenori Kuroki1986 Volume 33 Issue 7 Pages 361-366
Published: September 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCylindrical compacts, φ10×h10 mm, for the size measurement and cubic compacts, 10 mm in size, for the dilatometry were formed of an electrolytic iron powder by die-wall lubricating alone, or by admixing 0.3-1.5 wt% of zinc-stearate.
During pressing at 200-800 MPa the diameters of the cylindrical compacts and the die-cavity were larger than the original diameter of die-cavity size by 0.01-0.07%. The ejection of compact from the die was accompanied by some radial spring-back in the compact; that is, some 0.04-0.17% of expansion in comparison with the original die size.
During de-waxing at 600°C (873K) for 30 min and sintering at 1100°C (1373K) for 60 min in dissociated ammonia, the compacts expanded in the radial direction only when they contained zinc-stearate and were heated rapidly at the rate of several hundred degrees per minute. While those compacted by die-wall lubricating alone, and/or heated slowly at l0°C/min exhibited some shrinkage almost of the same order as the expansion by the spring-back. No correlation, however, was found between the expansion and the shrinkage.
On the dilatometer, the compacts were heated slowly at 10°C/min in hydrogen. Some of the compacts containing zinc-stearate, expanded in the lateral direction and shrank in the pressing direction simultaneously during the early stage of de-waxing.View full abstractDownload PDF (455K) -
Hidenori Kuroki1986 Volume 33 Issue 7 Pages 367-372
Published: September 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCylindrical compacts, 40 mm in diameter by 40 mm high, were made from three different iron powders by die-wall lubricating alone or admixing 0. 1-1.5 wt% of zinc-stearate at 196588 MPa, de-waxed at 600-Cfor 30 min, and sintered at 8001200-C for 5-600 min in dissociated ammonia. Small-sized Charpy specimens were cut out from the compacts in the pressing (or axial) direction and in the radial direction.
The anisotropy of the impact value-the ratio of the axial value VA to the radial one VR-was most remarkable in the sintered compacts of the electrolytic powder, which showed the largest weight loss of green compacts in the rattler-test among the three-atomized, electrolytic and reduced-powders used.
The specimens with their length in the pressing direction showed very low impact values over a wide temperature range; the impact value vs. the temperature curve was rather flat. On the fractographs, flat pores perpendicular to the pressing direction, consequently parallel to the fracture surface, were observed.
The anisotropy as well as the dimensional change by axial spring-back during the unloading and ejection after the compaction increased with the amount of zinc-stearate admixed.
In the axial direction, the increases of the impact value and of shrinkage concurred during sintering.View full abstractDownload PDF (2532K) -
Effect of Microstructures on the Creep PropertyMasao Morishita, Hiroshi Nagai, Keiichirou Shoji1986 Volume 33 Issue 7 Pages 373-378
Published: September 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSEffect of microstructure on the creep properties of nickel base superalloys, IN-100 and Merl-76, prepared by following three methods was investigated at 1005K.
1) Swaging after liquid phase sintering due to incipient melting of alloy powder.
2) HIP'ing of alloy powder.
3) Casting.
The results obtained were as follows:
(1) Fine y-grain IN-100 was obtained by swaging after liquid phase sintering. The creep rupture lives of fine v-grain IN-100 (32 and 62 um) by swaging were longer than that of cast IN-100 (700 um).
(2) When y-grain size of swaged IN-100 after liquid phase sintering was equivalent to that of HIP'ed IN-100, steady state creep rate of those alloys was equal. However, creep rupture ductility of HIP'ed IN-100 was smaller than that of swaged IN-100.
(3) Steady state creep rates (e) of IN-100 and Merl-76 were dependent on their y-grain sizes. s of Merl-76 was smaller than that of IN-100 when y-grain sizes of both alloys were equivalent.View full abstractDownload PDF (2549K) -
Nobuyasu Kawai, Minoru Hirano, Katsuhiko Honma, Tsuneo Tatsuno1986 Volume 33 Issue 7 Pages 379-385
Published: September 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe aim of this study was to determine the optimum nitrogen and carbon content in P/M high-speed steels by evaluating cutting performance.
P/M high-speed steels SKH 51 (AISI M2) and SKH 10 (AISI T15) with various content of nitrogen and carbon were prepared by Hip'ing gas atomized powders. Nitrogen was added to steels by heat treating the powders in nitrogen gas before Hip'ing.
The results of cutting tests indicated that in cutting SNCM439, tools containing higher nitrogen have significantly good cutting performance, and
1) 0.5% nitrogen and 0.81.0% nitrogen were the optimum content in SKH 51 and SKH 10, respectively.
2) The optimum carbon equivalent of SKH 51 and SKH 10 was 0.9% and 1.5%, respectively.
But in case of work materials which includes abrasive carbides, the steels containing nitrogen were found to have the inferior cutting performance to the nitrogen-free steels.View full abstractDownload PDF (2454K)
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