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Volume 26, Issue 6
Displaying 1-7 of 7 articles from this issue
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Ichiya Endo, Hiroshi Kubo, Yasuaki Morioka, Shunji Itoh1979 Volume 26 Issue 6 Pages 195-200
Published: August 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe electrical resistivity of compacts of commercial iron powders during sintering process was measured, and the influences of green density, sintered density and sintering atmosphere, as well as those of reduction and oxidation treatments of powders, were investigated and discussed.
The main results are as follows;
(1) The resistivity of compacts decreases remarkably during heating from room temperature to 350°C, and increases gradually between 350 and 800°C, and then decreases slightly or is kept constant between 800 and 1000°C.
(2) The change in resistivity during sintering above about 350°C can be qualitatively explained in considering on the effect of neck growth between particles.
(3) The temperature at which the resistivity becomes minimum rises as the thickness of oxide films on the particles increases.View full abstractDownload PDF (439K) -
Ichiya Endo, Hiroshi Kubo, Shunji Itoh1979 Volume 26 Issue 6 Pages 201-206
Published: August 25, 1979
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSElectrical resistivity changes of water-atomized unreduced steel powder compacts during sintering process were measured and compared with the dilatometric changes. Release of gases from powders during heating in vacuum was also studied in connection with reduction of oxide films on the particle surfaces.
The results obtained are as follows:
(1) The electrical resistivity of unreduced powder compacts changes drastically during heating from room temperature to about 600°C. Especially an anomalous change in resistivity is observed between 300 and 400°C in coincidence with active release of gases due to the decomposition of goethite on the particle surfaces.
(2) The reduction of oxide films on the particle surfaces occures mainly in the temperature range 800-900°C showing the maxium of resistivity.
(3) The α↔γ transformation is not observed in the resistivity measurements, while it is observed clearly in the dilatometric measurements.View full abstractDownload PDF (2176K) -
Hisashi Suzuki, Koji Hayashi, Wan Jae Lee1979 Volume 26 Issue 6 Pages 207-212
Published: August 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSBending creep-rupture strength of WC-(6-20)%Co high carbon alloys was investigated at 700-900°C for the rupture time up to 2 hr in relation to the carbide grain size (1.3-3.8 μm) and domain size of binder phase (60-500 gm).
The results obtained were as follows; (1) As the test temperature increased, the creep-rupture strength of each alloy having a given domain size tended to show a maximum with increasing carbide grain size. On the other hand, the strength of the alloys having a given carbide grain size increased with increasing domain size. (2) In each alloy, it was generally observed that microcracks were first formed at WC/WC interfaces and then connected each other to yield a main stable crack. The growth rate of main stable crack, therefore, appeared to correlate with the formation rate of microcracks. (3) The high temperature creeprupture strength of WC-Co cemented carbides would be controlled by the WC/WC interfaces.View full abstractDownload PDF (2080K) -
Hisashi Suzuki, Koji Hayashi, Yosuro Taniguchi, Fumio Nakayama1979 Volume 26 Issue 6 Pages 213-217
Published: August 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSHigh temperature transverse-rupture strength (T.R.S.) of WC-10%Co medium carbon alloys affected by the addition of several carbides such as TiC, V4C3, Cr3C2, ZrC, NbC, Mo2C, HfC was studied mainly at 1000°C. The amount of each addition-carbide was controlled to be generally 5 mol% in the binder phase.
It was found that T.R.S. of WC-Co alloy at 1000°C increased by the addition of these carbides, especially by ZrC. The adequate amount of ZrC was found about 3 mol% in the binder phase, considering the room temperature T.R.S. The increase in strength by ZrC addition was thought to be due to the improvement in the strength of domain (or grain) boundary of the binder phase.View full abstractDownload PDF (7409K) -
Hideo Kayano, Ryoko Takagi, Yoshio Hasegawa, Katsuaki Suganuma1979 Volume 26 Issue 6 Pages 218-222
Published: August 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAlloy powder particles of Fe-13Cr ferritic steel (sus 410) were coated with organometallic complex and with titanium alkoxide each in 3%. Fine particle carbide or oxide, as a thermal decomposition product, was thus dispersed uniformly, to give a dispersion-strengthened ferritic steel. These materials developed were compared with a sintered Fe-13Cr alloy and a Fe-13Cr alloy added 3% comercial TiO2 powder. The materials coated with organometallic complex and with alkoxide at room temperature and 600°C are higher in strength than the Fe-13Cr. While in the material added 3% titanium acetylacetynate as an organometallic complex in particular, not only the strength but also the elongation is increased. They were electron irradiated to 13 dpa at 400-450°C using an ultra-high voltage electron microscope. No void was observed.View full abstractDownload PDF (5240K) -
Hideo Kayano, Ohno Hironori, Ryoko Takagi, Hiroshi Takaku, Yoshio Hase ...1979 Volume 26 Issue 6 Pages 223-227
Published: August 25, 1979
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA new dispersion-type sintered neutron absorbing alloy has been developed. An organometallic complex of highly neutron absorbing Gd, Sm and In is melted by heating to 200°C. Powder particles of Fe-13Cr are then coated with the molten complex, followed by powder rolling and sintering. Because of this pro-cedure of heating and decomposing the thin film of an organometallic complex, the fine carbide particles of uniform size are distributed uniformly in the alloy and the grain growth is suppressed. The resulting neutron absorbing material has thus high values of both hardness and mechanical strength at room temperature and also in ductility.View full abstractDownload PDF (2121K) -
Kenji Suzuki, Hiroyasu Mitani1979 Volume 26 Issue 6 Pages 228-231
Published: August 25, 1979
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSBy using an acoustic method, the duration of reverberation of γ′-Ni·Al bronze sintered alloy was compared with those of Cu-10wt%Sn, Fe-10wt%Cu and α-Ni·Al bronze sintered alloys. The relationship between the duration of reverberation and internal friction was discussed. It was found that the duration of reverberation in this γ′-Ni·Al bronze sintered alloy is extremely shorter than those in other alloys, and decreases linearly with increasing internal friction.View full abstractDownload PDF (2845K)
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