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Volume 29, Issue 8
Displaying 1-7 of 7 articles from this issue
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Shû Yamazaki1982 Volume 29 Issue 8 Pages 263-269
Published: November 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe effect of dopants during the stage of reduction, sintering, swaging and drawing has been investigated. Another investigation has been carried out to examine the effect of dope pore (bubble) dispersion on the formation of non-sag structure and on the high temperature tensile strength in tungsten wires. Additional Al to K and Si as dopant effectively increases K included in tungsten metal particles and therefore, results in increasing the contents of K in wires. Consequently, this factor contributes to the formation of numerous bubble rows and of large elongated recrystallized grains, and induces the high temperature tensile strength in wires. Improvement of bubble row dispersion is very important to get good quality of tungsten wires.View full abstractDownload PDF (8580K) -
Takayasu Goto, Naohiro Soga1982 Volume 29 Issue 8 Pages 270-274
Published: November 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSSiO2 glass was densified by a high pressure MA-8 apparatus composed of eight cubic WC anviles at pressure up to 80kb and temperature up to 920°C, The density of densified SiO2 glass was measured by means of sink-float method, and the stability of densified SiO2 glass accompanied with heat treatment was examined from the density change. It was found that MA-8 apparatus was very appropriate for obtaining the densified glass having no crack and large volume, because the pressure was very closed to the hydrostatic condition. The maximum densification of 2.673 g/cm3 was obtained at 71 kb and 920°C. This was much greater than the density of a-quartz. Reheating the densified SiO2 glass showed that the specimen densified at higher temperature was more stable, and that the density recovered to the original value by heating at 1000°C for a few hours. Activation energy calculated from the decrease of density at the relaxation process of densified SiO2 glass was about 6 kcal/mol. This value is very much smaller than the bonding energy and the activation energy for diffusion. This suggests that the densified state takes place through the displacement of atoms or atom groups in the network structure.View full abstractDownload PDF (396K) -
Mikio Kishimoto, Haruo Ando, Susumu Kitaoka1982 Volume 29 Issue 8 Pages 275-279
Published: November 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAcicular γ-Fe2O3 particles were coated with an oxide layer composed of almost all the Fe3O4 by the treatment in alkali solution containing Fe2+ at 45°C. The coercivity of the obtained particles decreased linealy with increasing Fe2+ content in the coated oxide layer. When the coated oxide layer was removed by soaking the particles in hydrochloric acid, the coercivity of γ-Fe2O3 particles was recovered to their normal value. Furthermore the coercivity of the coated particles was greatly enhanced by the heat-treatment in evacuated glass capsule at 50 to 300°C, and higher values were obtained by the heating at higher temperatures. The increase of coercivity was considered to be due to the formation of γ-Fe2O3-Fe3O4 solid solution by the heat-treatment. The variation of coercivity with the lapse of time observed in the particles annealed at 60°C was small compared with that of γ-Fe2O3-Fe3O4 solid solution. When the particles were heated at 300°C, however, a remarkable variation of coercivity as shown in γ-Fe2O3-Fe3O4 solid solution was observed.View full abstractDownload PDF (1536K) -
Kazuhiko Majima, Tatsuro Isomoto1982 Volume 29 Issue 8 Pages 280-285
Published: November 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAs a result of the diffusion experiment in the temperature range from 1200°C to 1400°C, it was recognized that the interdiffusion coefficients, D determined by Boltzman-Matano method, decreased monotonously with increasing Mo content, while the activation energies for interdiffusion increased monotonously with Mo content. On the other hand, from the intrinsic diffusion coefficients, DTi and DMo determined at 12.8±0.3at%Mo concentration by Darken's relation, it was shown that the diffusion velocity of Ti atoms was about four times as fast as that of Mo atoms, and this difference was confirmed to be one of the most important factors for the expanding phenomenon whose maximum was observed at 50 wt%Mo in the β region during sintering process for the Ti-Mo binary mixed powder compacts. (Received October 22, 1981)View full abstractDownload PDF (415K) -
Comparison of the Deformation Behaviour of Compacts of Zn-22Al Prealloy Powder and Mixed PowderKunio Okimoto, Tomio Sato1982 Volume 29 Issue 8 Pages 286-289
Published: November 25, 1982
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSDeformation behaviour of compacts of 78 zinc-22 aluminium powder is studied by the uniaxial tensile test. The compacts are made from both the prealloy powder, and the mixture of 78% zinc and 22% alumi-nium powder; the behavior of the compacts are thus compared. The results obtained are as follows:
1) Total elongation of the compact of prealloy powder reaches 440%; in the case of mixed-powder compact, however, it is less than 80%.
2) To obtain large elongation, the compact should be of granular structure and of no porosity.View full abstractDownload PDF (3541K) -
Hisashi Suzuki, Hideaki Matsubara, Koji Hayashi1982 Volume 29 Issue 8 Pages 290-293
Published: November 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe oxygen contents in TiC-Mo2C-Ni and Ti (C, N)-Mo2C-Ni alloy specimens (called TiC and Ti(C, N) alloys, respectively) were measured in relation to the carbon content of alloys and sintering conditions. Specimens were mainly in vacuum sintered.
It was found that the oxygen contents of both alloys were markedly decreased to the value as small as about 0.1 %, with increasing carbon content. The oxygen content of Ti(C, N) alloy was much lower, especially, in low carbon alloy, than that of TiC alloy. This result was considered to be due to the fact that the amount of oxygen absorbed during the process before sintering was smaller in Ti(C, N) powder because of its high resistance to oxidation.View full abstractDownload PDF (287K) -
Property of Graphite and Principle of Graphite NodularizationKiyoaki Akechi, Kenzo Hanawa, Takeo Nakagawa1982 Volume 29 Issue 8 Pages 294-297
Published: November 25, 1982
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSEach nodular graphite consists of a large number of crystallites, and each crystallite is so oriented that its basal planes are at right angles to the radii of a nodule. The graphite crystal, however, originally has a strong tendency to a preferential growth along the (0001) basal plane. Therefore, it must be concluded that nodular graphite in a sintered product can be formed during cooling as a result of the precipitating of super-saturated carbon atoms at pore-surface and subsequently piling-up of flake graphite in a pore as a spherical framework.View full abstractDownload PDF (286K)
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