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Volume 19, Issue 1
Displaying 1-4 of 4 articles from this issue
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Yoshimichi Masuda, Noboru Sakai1972 Volume 19 Issue 1 Pages 1-6
Published: June 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTri-axial compression tests were made on copper, zinc and aluminium powders of specified in particle shapes and sizes under hydrostatic confining pressure up to 360 kg/cm2. By the examination of mechanical behaviours of each powder during compaction, the following results were obtained: The principal stress ratio, σ2/σ1, for each powder showed a nearly constant value during compacting up to the maximum pressure of this test. The ratio depended mainly on the powder material and it increased about 5 and 24% for copper and zinc powders respectively, when 1 wt% of zinc stearate was added as a lubricant. The friction angles calculated from these values were about 43°, 44° and 45°, for aluminium, copper and zinc powders in the unlubricated condition. The change in shearing strength of all powders during compaction could be expressed in the form of Mohr-Coulomb yield criterion.View full abstractDownload PDF (394K) -
Takashi Kimura, Yukio Inaguma1972 Volume 19 Issue 1 Pages 7-11
Published: June 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effects of both presintering and sintering times and temperatures on the volume change and tensile property were investigated with iron-l%carbon powder compacts. The presintering was carried out under the condition where carbon hardly diffused into iron, and the sintering was done under the easy-to-diffuse condition.
The two-stage sintering decreased the volume change (expansion) of the powder compacts during the sintering and improved both the tensile strength and the elongation compared with the conventional process. The improvement is considered to be caused not only by the bonding of iron particles, but the activation of the iron particle surface by hydrogen gas during the presintering.View full abstractDownload PDF (353K) -
Shu Yamazaki, Naoyuki Sori, Michiyasu Komatsu1972 Volume 19 Issue 1 Pages 12-17
Published: June 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of Co addition on some properties, particularly low-temperature ductility of doped tungsten wire have been studied.
In particular, wires produced by additions of 0.01-0.06 weight % of Co together with common doping agents, Al2O3, SiO2 and K20 have shown a remarkably improved ductility before recrystallization. Increasing amounts of Co were effective in significantly increasing the maximum elongation. These wires at 0.39 mm diameter have shown the maximum elongation of 12-26% at room temperature after annealing, and the content of gaseous impurities in these wires have been effectively lowered.
These wires containing 0.01-0.03% Co are not only remarkably ductile before recrystallization but have also superior in qualities to those of ordinary doped products after recrystallization, for example excellent in high temperature sag resistances essential to lamps and tubes as well as in ductility.View full abstractDownload PDF (3255K) -
Kiyoshi Mirumachi, Kenzo Hijikata1972 Volume 19 Issue 1 Pages 18-22
Published: June 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSCorrosion tests on cemented carbides in acids at room temperature and at 95°C were carried out by the authors and it was shown that cemented carbides were attacked predominantly due to the dissolution of Co as the binder metal.
In the present work, relation between corrosion rates of WC-Co alloy and potential differences of hot-pressed WC-electrode vs Co-electrode in NaCI aq. (0-25 wt%) were examined at 19°C. The corrosion rate of WC-Co alloy in NaCI aq. decreased with decreasing of the potential difference between WC- and Co-electrodes and the concentration (2 wt%) of NaCI aq. showing the maximum corrosion rate likely corresponded with that showing the maximum potential difference (410 mV). Therefore, it could be qualitatively noted that the corrosion of WC-Co alloy in NaC1 aq. was caused by local galvanic action between WC grains and Co matrix on the surface of the alloy. In this case, because soluble oxygen played as a depolarizer, increased content of soluble oxygen in NaC1 aq. increased the corrosion rate:
Co: Co→Co+++2e-
WC: 2Na++2e-→2Na(on WC), 2Na+2H2O→2Na++2OH-+2H(on WC)
Depolarization reaction:
2H(on WC)+1/2O2(in NaCl aq.)→H2OView full abstractDownload PDF (343K)
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