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Volume 56, Issue 1
January
Displaying 1-6 of 6 articles from this issue
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Special Issue: Evaluations of Technologies and Products in Powder Metallurgy Processing
Summarization
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Takashi Itoh2009 Volume 56 Issue 1 Pages 2
Published: 2009
Released on J-STAGE: February 03, 2009
JOURNAL OPEN ACCESSDownload PDF (137K)
Paper
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Nobuhiko Matsumoto, Toshitake Miyake, Mikio Kondoh, Kimihiko Ando2009 Volume 56 Issue 1 Pages 3-8
Published: 2009
Released on J-STAGE: February 03, 2009
JOURNAL OPEN ACCESSWe have already reported that lithium stearate as the die wall lubricant enabled warm compaction at the pressure range up to 2000 MPa without the internal lubricant and that the high green density of almost pore free density was obtained. Since this high green density results in the high sintered density and the low dimensional change, the cost reduction of finish machining besides the improvement of mechanical properties are expected. However in some low alloy sintered steels, the high pressure warm compaction above 1200 MPa followed by high temperature sintering causes the blister which results in the decrease in the density during the sintering. In this study, inhibition of the blister is investigated and the beneficial effects of the small amount additives of the easily oxidizable metal elements are revealed. As a result of controlling the blister, the low alloy sintered steels highly densified more than 7.7 g/cm3 are realized and extremely good mechanical properties are obtained.View full abstractDownload PDF (1437K) -
Ayako Miura, Wei Dong, Noriharu Yodoshi, Akira Kawasaki, Katsu Yanagim ...2009 Volume 56 Issue 1 Pages 9-17
Published: 2009
Released on J-STAGE: February 03, 2009
JOURNAL OPEN ACCESSThe mono-sized [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 metallic glass micro spherical particles with narrow size distribution and high sphericity have been successfully prepared by Pulsated Orifice Ejection Method (POEM). The desired size of particles can be formed by adjusting process parameters, such as the rod displacement, the time for reaching the pulse voltage from zero voltage, the applied pressure and so on. The glassy fraction determined by enthalpy released for the particles during continuous heating in DSC, based on 70.23 J·g−1 as the enthalpy released of a fully amorphous particle (as proved by X-ray diffraction), shows that the changes of phase in one particle from single amorphous phase to amorphous crystalline mixed phase and then overall crystalline occur within the range of 350 mm and 400 mm in diameters. The critical cooling rate for the occurrence of crystalline in single amorphous phase is estimated to be within the range of 700 and 800 K·sec−1, which is slightly lower than that measured by time-temperature transformation diagram of the bulk metallic alloy, and supposed to be affected by the initial temperature of the melt.View full abstractDownload PDF (1524K) -
Atsushi Hibino, Shingo Yabe2009 Volume 56 Issue 1 Pages 18-25
Published: 2009
Released on J-STAGE: February 03, 2009
JOURNAL OPEN ACCESSIn the rapid sintering processes e.g. laser sintering, SPS, and combustion synthesis, the gases released from the powder strikingly affect the quality of the produced material. Therefore, in this paper, the gas release behavior of Fe powder was analyzed by gas chromatograph method. The gases such as CO2, CO, CH4, C2H6, and C3H8 were detected from Fe powder during the sintering process. Especially, a great volume of CO2 gas was released from the Fe powder. The carbon atom constituting these gas species might originate from the carbon contained in the Fe powder. Furthermore, the gas release behavior of the Fe powder dipped into liquid N2 and the Fe powder annealed in N2 gas atmosphere were investigated. In the treated Fe powder, the oxygen gas and nitrogen gas combined with the Fe powder as adsorption gas, solute gas and metal-gas compound. The oxygen release and the nitrogen gas release increased in the high temperature range of over 600°C. From the reaction analysis, it was guessed that these gases were caused by the dissociation reactions of the Fe3O4 and Fe4N phases with phase transformation.View full abstractDownload PDF (1278K) -
Mitsuharu Matsuno, Takashi Itoh2009 Volume 56 Issue 1 Pages 26-29
Published: 2009
Released on J-STAGE: February 03, 2009
JOURNAL OPEN ACCESSDimagnesium silicide (Mg2Si) is a promising thermoelectric material for energy conversion over intermediate temperature range (300 to 600°C). This material has advantages of the constituent elements in abundance in the earth's crust and of the nontoxicity of its processing by-products as an environmental symbiosis thermoelectric semiconductor. However, there are few research reports about this material for improving thermoelectric performance because of difficulty of its synthesis. In this study, Mg2Si was synthesized from Mg and Si powders by a liquid-solid phase reaction (LSPR) method, which is effective in synthesizing a compound from the two elements having sufficiently different melting points. The powder synthesized by LSPR method was compacted and then sintered by a pulse discharge sintering (PDS) process. Influence of sintering conditions on thermoelectric properties of Mg2Si was investigated. The thermoelectric properties of each sintered sample were measured at temperature of RT to 600°C. The thermoelectric properties of the sintered sample were, however, strongly affected by the sintering temperature and/or the sample density. The sample sintered at 730°C for 30 min under 60 MPa had the maximum dimensionless figure of merit of 0.27 at 516°C. This value is higher than the previous report.View full abstractDownload PDF (1513K) -
Yuji Ikuta, Takashi Itoh2009 Volume 56 Issue 1 Pages 30-34
Published: 2009
Released on J-STAGE: February 03, 2009
JOURNAL OPEN ACCESSA new process for manufacturing thermoelectric modules was proposed, and thermoelectric performance of the modules were evaluated. Both powders of p-type FeCo3Sb12 and n-type Co0.92Ni0.08Sb2.96Te0.04 compounds were alternately filled into 4×4 square holes of an insulating mold. The powders in the holes were compacted and sintered simultaneously at 903 K in vacuum for 20 min under the pressure of 60 MPa by a pseudo hot isostatic pressing (pseudo HIP) method, in which one-directional load is transmitted isostatically to the sample through the alumina powder filled around the sample. The sixteen sintered elements (1.9 mm×1.9 mm×9.0 mm) in the mold were electrically connected in series using silver paste. Then, a thermoelectric module was constructed by parallel sandwiching the mold with glass plates of 0.5 mm in thickness. The thermoelectromotive force was 591 mV at the temperature gradient of 356 K, and the internal resistance in the module was 2.77 Ω. In this case, the output power of 31.5 mW was obtained and the power density of 576 W/m2 was estimated. The value of output power was less than that of the theoretical calculation.View full abstractDownload PDF (1163K)
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