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Volume 25, Issue 1
Displaying 1-6 of 6 articles from this issue
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Jiro Shibata, Shigenori Tanabe1978 Volume 25 Issue 1 Pages 1-6
Published: February 25, 1978
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSInfluence of Al powder addition on the sintering process of Fe powder compact was made by means of dilatometric and microscopic examinations, X-ray diffraction, E.P.M.A. and D.T.A. The results were summarized as follows.
(1) An intermediate phase (Fe2Al5) was produced by the interaction of molten Al and solid Fe at the melting point of Al at 660°C, where an expansion and an exothermic phenomenon were observed in the Fe-Al mixed powder compacts.
(2) This expansion was due to the penetration of molten Al into the interfaces between Fe particles, leaving pores at the place where the solid Al had been located.
In this stage, the cracks were generated at these interfaces in the case of ore reduced Fe-Al mixed powder compacts. It was very difficult to eliminate the large pores and the cracks in more advanced stages of the sintering process. The exothermic phenomenon was thought to be caused by the formation of Fe2Al5.
(3) It was proved that for the carbonyl Fe-Al mixed powder compacts of composition over y-loop, the sintering was remarkably accelerated by the process stabilizing the a-Fe phase with the diffusion of Al into the Fe matrix from Fe2Al5 at high temperature.
On the other hand, the sintering of ore reduced Fe-Al mixed powder compacts was disturbed by the difficulties to uniformly diffuse Al into larger Fe particles and to repair the cracks.View full abstractDownload PDF (4725K) -
1st Report, Comparison of Sintered Material and Bar MaterialMasanori Yoshikawa, Takeo Kushida1978 Volume 25 Issue 1 Pages 7-12
Published: February 25, 1978
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSThis investigation is carried out to develop the measuring apparatus which is suitable to measure internal friction in sintered material and find out the causes of internal friction in sintered iron material comparing with that in bar material.
Internal friction in sintered iron material increases greatly with the increase of stress amplitude and varies little with frequency. This is termed “hysteresis-type.” This internal friction is probably due to the large irreversible plastic deformation and small thermoelastic effect. Internal friction in Armco iron material increases greatly with the increase of frequency and increases a little with the increase of stress amplitude. This is termed “relaxation-type.”
Internal friction in Fe-C sintered materials decreases and shows the minimum value at 1%, and increases with the increase of carbon content. The decrease of internal friction with the increase of carbon content is due to the disappearance of ferromagnetism and the increase of the density. The increase of internal friction with the increase of carbon content is due to the increase of free carbon content and the decrease of the density.View full abstractDownload PDF (4097K) -
Tôru Kôno1978 Volume 25 Issue 1 Pages 13-15
Published: February 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSTensile strength and elongation of Fe-Sn system sintered compacts prepared by adding intermetallic compound Fe3Sn (2.7μ) into Fe powders were measured. The results obtained were as follows;
1) Diffusion of Sn into Fe powders was extremely rapid. For example, by sintering at 890°C for 30 minutes Fe-2%Sn compacts pressed at 5t/cm2, completely alloyed structures were obtained.
2) Mechanical properties of sintered compacts were distinctively affected by phase structure in the sintering and those which sintered in the field of γ-loop were excellent. Specimens sindered in the α-regions were extremely brittle.
3) Tensile strengthes of compacts sintered in the field of γ-loop exhibited a linear relationship versus Sn-content at every temperature.View full abstractDownload PDF (2332K) -
Hiroyasu Mitani, Kenji Suzuki1978 Volume 25 Issue 1 Pages 16-19
Published: February 25, 1978
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSRegardless of Ni contents in slack-quenching Cu-14 wt%Al-Ni sintered specimens, we obtained a maximum value of the internal friction at about 50°C in their heating curves, where Q30°C-1 obtained at 30°C always amounts to about 80% of Q50°C-1 and the concentration dependency of Q30°C-1 coincides with that of Q50°C-1.
The results obtained were as follows:
(1) The maximum value of Q30°C-1 of Cu-Al-4 wt%Ni and Cu-Al-8 wt%Ni sintered alloys with different Al contents were found around 14 wt%Al in both the cases.
(2) Q30°C-1 of Cu-14wt%Al-Ni sintered alloys increased up to 6 wt%Ni, kept the maximum value constantly between 6 and 9 wt%Ni, and decreased over than 9 wt%Ni.
(3) Judging from the X-ray diffraction patterns, we confirmed that the height of the above-mentioned convex curve corresponds to the quantity of γ' martensite, where the slack-quenching Cu-14 wt%Al-8 wt%Ni sintered alloy composed of only single phase of γ' martensite shows the maximum value of Q30°C-1.View full abstractDownload PDF (1577K) -
Osamu Yamaguchi, Tadashi Yasuhara, Kiyoshi Shimizu1978 Volume 25 Issue 1 Pages 20-25
Published: February 25, 1978
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe effects of particle size on the sintering of PbTiO3 containing a small amount of PbO-TiO2-Al2O3-SiO2 glass were investigated under various atmospheres.
The PbTiO3 powders with the average particle sizes of 0.27, 0.18 and 0.11 μm containing 0.01 wt% glass powder were pressed into pellets at 3 ton/cm2 and sintered at 1100-1200°C for 0.5-7 hrs in various atmospheres. All the sintered compacts had a grain size of 0.8-7.2 μm and a bulk density of 7.02-7.74 g/ cm3. The order of the sinterability in various atmospheres of PhTiOa was O2>PbO> air> N2. The green and sintered densities and the microstructures of compacts in the sintering process were affected by the particle size distribution of the PbTiO3 powder. The dielectric constant of the compacts depended on the sintered density, grain size and the variation of the composition with the evaporation of PbO in the sintering process. The best PbTiO3 compact having a density of 7.74 g/cm3 and a grain size of 1.8 μm was obtained from the 2.7 fsm powder by sintering at 1120°C for 1 hr in oxygen, and the dielectric constant at 1 MHz of this compact was 268 at room temperature.View full abstractDownload PDF (3986K) -
Toshikazu Tanaka1978 Volume 25 Issue 1 Pages 26-29
Published: February 25, 1978
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMn-Zn ferrites with predetermined oxygen contents and nearly theoretical density were prepared from mixture of MnO, ZnO and Fe2O3 by sintering in the atmosphere of appropriate partial pressures of oxygen. The sintering process were determined on the basis of mechanisms how the formation of Mn-Zn ferrite from mixture of the oxides and the densification of the preform occur with changing sintering temperature. The process for densification without grain growth was necessary to prepare ferrites without pores. The oxygen content in a Mn-Zn ferrite was controlled by making the oxygen partial pressure in the atmosphere equal to the equilibrium oxygen partial pressure of the Mn-Zn ferrite with a desired oxygen content, mainly, in the densification process.
The electrical resistivity of these ferrites was independent of applied frequencies below 20 MHz, and decreased with increasing Fe and/or decreasing oxygen content.View full abstractDownload PDF (1817K)
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