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Volume 27, Issue 2
Displaying 1-6 of 6 articles from this issue
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[in Japanese]1980 Volume 27 Issue 2 Pages 39-44
Published: March 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (4316K) -
Junichi Hojo, Akio Kato1980 Volume 27 Issue 2 Pages 45-49
Published: March 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSSintering behavior of ultrafine powders of WC and Mo2C (particle size<1μ) obtained by CVD method was investigated under the atmospheres of hydrogen and vacuum with emphasis on the effects of particle size and atmosphere on their sinterabilities.
The sinterabilities of the WC and Mo2C powders were higher in vacuum than in hydrogen. The fine WC powders gave the sintered bodies with the relative density of 100% by the sintering at -1700°C in vacuum. The relative densities of sintered bodies of the fine Mo2C powders reached 94-99% at 1500°C in vacuum. The sintered bodies of the fine carbide powders had fine-grain structures with the grain size of 0.5-2μ. The effect of atmosphere on the sintering of the carbide powders was interpreted on the basis of the different chemical behaviors of free carbon and surface oxide layer in hydrogen and in vacuum.View full abstractDownload PDF (1580K) -
Kenichi Nishigaki, Hironori Yoshimura, Hidekazu Doi1980 Volume 27 Issue 2 Pages 50-55
Published: March 25, 1980
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe results obtained are as follows;
(1) A1N decomposed in sintering process and the resulting free Al diffused into the binder phase to form γ' phase {Ni3Al(Ti)}.
(2) The grain size of the Ti carbonitride particles after sintering did not change by the addition of A1N. The formation of undesirable aluminum oxide particles, which was recognized in the case of the addition of NiAl, was not found in this case. However, large pores were observed in the alloy with 2% A1N.
(3) Addition of 1% A1N was found effective for improving both R.T. hardness and R.T. as well as T.R.S. at elevated temperatures.
(4) Continuous as well as intermittent cutting tests in turning steel with the 1% A1N added alloy exhibited the most excellent wear and shock resistance.View full abstractDownload PDF (2797K) -
Deformation of Grain and Grain Boundary of Polycrystalline Ni-Zn Ferrite During Hot-Pressing ProcessTomozo Nishikawa, Yasunori Okamoto, Shigeki Enomoto1980 Volume 27 Issue 2 Pages 56-59
Published: March 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDeformations of grain and grain boundary of polycrystalline Ni-Zn ferrite were studied by microscopic method, which seem to play some important roles on the densification during hot-pressing process as well as diffusion mechanism. Polycrystalline specimen of Ni-Zn ferrite with the size of 10×10×10 mm was compressively deformed at a temperature range from 1250 to 1360°C. Even at a fairly low temperature (1250°C), grain boundary sliding (the quantity was very small though), plastic deformation of grain itself by dislocation movement, developement of cross and wavy slips in a grain, and rotation of a grain in the polycrystal were observed without failure of the polycrystal. And also, with these deformations of grain, grain boundary was slightly corrugated. At higher temperatures, remarkable changes different from those lower temperature deformation modes were characterized by grain boundary migration and corrugation. Especially, grain boundary migrated in the same manner as thermally activated grain growth and the ghost lines distinctly remained in the original place of grain boundary after the boundary migration. These ghost of grain boundary may have important effects on the segregation of chemical constituents of the ferrite in grain boundary region.View full abstractDownload PDF (4584K) -
Kazuhiko Majima, Naoyuki Ishigaki, Kazuo Terada, Hiroyasu Mitani1980 Volume 27 Issue 2 Pages 60-65
Published: March 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSUsing mixed powder compacts of Sm-(60.5-65.5)wto%Co composed of SmCo5 and 60wto%Sm-40wt %Co powders, the sintering characteristics for Sm-Co system were studied mainly by means of the dilatometric method, and also the maximum energy product (BH)max was investigated in relation to the added amount of 60wto%Sm-40wt%Co powder and the sintering temperature.
The results obtained were summarized as follows: The contracting phenomena due to the liquid phase sintering by the addition of 60wt%Sm-40wt%Co powder, appeared remarkably in the temperature range higher than 1100°C during heating process, and it was confirmed that both the shrinkage ratio and the sintered density ratio became maximum at about Sm-61.5wtooCo as the composition ratio and 1180°C as the sintering temperature. On the other hand, the composition ratio and the sintering temperature showing the maximum value of (BH), ax were found at about 62.5wt%Co and 1130°C, respectively, where the former shifted to higher Co content and the latter to lower temperature than the cases of sintered density-ratio, respectively.View full abstractDownload PDF (3222K) -
Yasuo Shibasaki, Shigeto Kanaoka, Hideyo Tabata1980 Volume 27 Issue 2 Pages 66-68
Published: March 25, 1980
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSLarge dendritic oxide (hematite) was prepared by firing the mixture of a-Fe2O3 and Sb2O3 in the reducing atmosphere with the use of rice-chaff. The mechanism of the dendrite formation was interpreted as follows:
The early stage dissolution of a-Fe2O3 into Sb2O3 melt is followed by the evaporation of Sb2O3 with the increase of temperature, which consequently leads to the precipitation of dendritic nuclei of magnetite (Fe2O4) on the melt surface, because of strongly reducing atmosphere. The mixed melt climbs through the dendrite nuclei by the capillary action, and the successive evaporation of the solvent (Sb2O3) results in the rapid growth of Fe2O4 dendrite. Since the dendrites have large surface area, they are readily reoxidized to ferric oxide (a-Fe2O3) during cooling stage, retaining the skelton structure of the magnetite dendrite.View full abstractDownload PDF (1321K)
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