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Volume 16, Issue 4
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[in Japanese]1969 Volume 16 Issue 4 Pages 169-182
Published: August 25, 1969
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (941K) -
Seiya Ogawa, Tomoen Nakajima, Yasuo Uehara, Osamu Kobayashi, Takayasu ...1969 Volume 16 Issue 4 Pages 183-189
Published: August 25, 1969
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSOxidation of fine powders of Mn-Zn Ferrites prepared by the ‘co-precipitation’ method has been presented.
Differential thermal analysis showed a sharp exothermic peak corresponding to ‘hematite’ precipitation. A temperature of the peak, Tp, depends upon a heating rate φ and a crystallite size, ε, expressed by a simple relation:φ⋅ε∝exp(-Q/kTp), where Q=2.1±0.2eV. The relation indicates that the specific reaction rate is inversely proportional to crystallite size and that its temperature dependence is expressed by an activation process of 2.1eV. The size dependence could be explained by the oxidation of the total surface area and the temperature dependence by cation diffusion in Fe-poor Mn-Zn ferrite. Isothermal oxidation processes were studied by X-ray diffraction analysis and explained qualitatively by the same mechanism as the above relation.View full abstractDownload PDF (459K) -
Susumu Yamaya, Takeshi Sadahiro1969 Volume 16 Issue 4 Pages 190-195
Published: August 25, 1969
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSChanges in various properties of TiC-Ni-Mo alloys during sintering process were observed to study the effect of carbon content on the structure of intermediate phase formed around the TiC grain. The results are as follows.
(1) The wetting of TiC by Ni-Mo alloy were improved by increasing carbon content.
(2) With an increase in the carbon content, the carbide grains changed from angular to spherical forms. The grain size and the thickness of the intermediate phase of carbide were reduced.
(3) The structure of the intermediate phase were examined by X-ray microanalyser as follows. These results were demonstrated clearly by the presence of a molybdenum-rich zone at the edge of carbide coupled with a molybdenum-free region in the core of grains.
As the carbon content in TiC-Ni-Mo alloys increases, this molybdenum-rich zone was found to approach the core boundary, and the diffusion of nickel from the liquid nickel into the intermediate phase and the solution of carbide into the nickel binder were reduced.View full abstractDownload PDF (1893K) -
Fe-Cr-C SystemIkuo Yajima, Hajime Murayama1969 Volume 16 Issue 4 Pages 196-202
Published: August 25, 1969
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPhysical and mechanical properties of sintered Fe-Cr-C alloys have been studied. The results obtained were as follows:
(1) A maximum tensile strength of about 52 kg/mm2 were obtained for some sintered Fe-Cr-C alloys.
(2) Hardness increases with an increase of Cr content, their maximum value being at 2.0wt% of Cr.
(3) Wear resistivity of Fe-2 Cr-1C sintered alloys was about 1/2-1/3 times to that of the conventional pistonring cast iron.
(4) Heat resistivity of Fe-2 Cr-1C sintered alloy indicates micro vickers hardness number of 150-250 at 60°C and tensile strength of about 30 kg/mm2 at 600°C.View full abstractDownload PDF (5223K)
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