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Volume 18, Issue 2
Displaying 1-6 of 6 articles from this issue
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Jiro Shibata, Shigenori Tanabe, Minoru Hirano1971 Volume 18 Issue 2 Pages 43-49
Published: August 25, 1971
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn order to investigate the expansion of Fe-Cr3C2 compacts during sintering, the dilatometric analysis and microscopic examination were systematically carried out by using Fe-Cr3C2 mixed powder compacts which contain up to 30 wt % Cr3C2.
The results were summarized as follows:
(1) An abnormal expansion appeared in the temperature range between 1050° and 1250°C, and the expansion increased with the increase of Cr3C2 content in the compacts up to 10 wt % Cr3C2, but at higher contents decreased with the increase of Cr3C2 content.
(2) This expansion appeared not only in the compacts prepared with reduced iron powders, but also in those of electrolytic, pulverizied electrolytic and carbonyl iron powders, although some difference were observed between them.
(3) The expansion observed in the Fe-Cr3C2 compacts did not appear in Fe-Cr, Cr-C, Fe-C and Fe-Cr-C mixed powder compacts, but in the 8.7 Cr-1.3C-Fe mixed powder compacts which corresponding to 10 wt % Cr3C2-Fe there appeared at high temperature.
(4) Changes in dimensions of specimens under elevated temperature could be well accounted for from their change in the microstructures.View full abstractDownload PDF (6107K) -
Etsuo Otsuki, Yoshimichi Masuda1971 Volume 18 Issue 2 Pages 50-55
Published: August 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe influence of alpha-gamma transformation on the sintering behaviour of powder compacts and wire couples of pure iron, Fe-Ni alloys (1-21 wt% Ni) and Fe-Co alloy (5 wt% Co), which were sintered in cyclic fashion over the temperature range containing alpha-gamma transformation temperature or not, was studied. Results obtained are summarized as follows.
(1) In the cyclic sintering of pure iron, sintering rate of the powder compact was suppressed by alpha-gamma transformation, but sintering of wire couples was impossible due to the transformation strain.
(2) In the cyclic sintering of Fe-Ni and Fe-Co alloys, the sintering rate was markedly promoted by alpha-gamma transformation due to the superplasticity caused by phase transformation.
(3) The difference in the sintering behaviours between pure iron and other ferrous alloys originated from the difference of extent of transformation stress and creep resistance of the materials.View full abstractDownload PDF (4733K) -
Tetsuro Yamaguchi, Tsutomu Shinpo, Hajime Murayama, Masayuki Iijima1971 Volume 18 Issue 2 Pages 56-63
Published: August 25, 1971
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSProperties of high-speed tool steel produced by means of powder metallurgy technique are researched.
Compared with the ordinary melting process, the following advantages are gained:
(1) High-speed tool steels produced by powder metallurgy acquire higher and more uniform mechanical properties.
(2) A very fine-grained and uniformly distributed carbide structure is obtained.
(3) At all testing temperatures below 550°C, a comparatively higher hardness value is obtained.View full abstractDownload PDF (8711K) -
Hiroaki Yanagida1971 Volume 18 Issue 2 Pages 64-67
Published: August 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSProbable mechanisms for the non-linear voltage-current characteristic of ZnO-Bi2O3 composite ceramic are discussed. The non-linearity is explained with an equivalent circuit related to the texture of composite ceramic. The continuous thin layer of bismuth oxide is considered as resistances. The boundary, zinc oxide grain-bismuth oxide layer-zinc oxide grain, forming an n-p-n junction works as a transistor.View full abstractDownload PDF (195K) -
Sintering Process and Mechanism of Reaction between PbO and PZTOsamu Yamaguchi1971 Volume 18 Issue 2 Pages 68-72
Published: August 25, 1971
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe sintering process and the mechanism of reaction between PbO and PZT were investigated by using thermal dilatometer, chemical analysis, isothermal shrinkage and electron microscope.
Results obtained are summarized as follows.
(1) The sintering process was classified in the order of four stages; linear expansion (0-400°C), solid state reaction (400-750°C), shrinkage (750-850°C) and grain growth (800-900°C).
(2) The reaction rate was found to be expressed by the Dander's type and seemed to be controlled by diffusion.
(3) In the sintering of the specimen consisted of non-stoichiometric PZT associated with the liquid phase(PbO), the shrinkage was proportional to n power of the time, and the slope representing this relation was divided into three parts. These parts seemed to be due to rearrangement, solution-reprecipitation and grain growth of PZT. The slope of the solution-reprecipitation stage had the n value of about 1/3, which coincided with the case derived by Kingery, that is, the diffusion controlled mechanism of PZT in the presence of a liquid phase.
(4) This sintering specimen did not show an exaggerated grain growth within 180 minutes (firing time), at various temperatures.View full abstractDownload PDF (2774K) -
Effect of B2O3 Addition on Product of PZTOsamu Yamaguchi, Fujio Harumi1971 Volume 18 Issue 2 Pages 73-74
Published: August 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn this paper a small amout of B2O3 was added to PbO-PZT ceramics which were prepared in the molar ratio of PbO:TiO2:ZrO2=1.1:0.48:0.52.
By the addition of B2O3 the temperature for product of PZT was produced by firing at about 500°C and also the sintering was remarkably promoted under such conditions.View full abstractDownload PDF (1105K)
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