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Volume 51, Issue 7
Displaying 1-12 of 12 articles from this issue
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Hiroki Moriwake, Isao Tanaka, Hirohiko Adachi2004 Volume 51 Issue 7 Pages 487-491
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSStability against chemical reduction is one of most important material property for high temperature thermistor materials. In this paper, material design of spinel type MgCr2O4 by first principles calculation in collaboration with experiments was discussed. MgCr2O4 is known to show Cr-deficit p-type semi-conduction in the elevated temperature region. The theoretical calculations of Cr-vacancy formation energy showed preferred formation of Cr-vacancies and their stability in oxidizing atmosphere, while their instability in reduction atmosphere. The stable semi-conducting Po2 region (i.e. 1 to 10-10 atm at 1000°C) of MgCr2O4 was determined by precise experiments. First principles calculation can be a powerful tool for the ceramic material design, when they are used in collaboration with precise experiments.View full abstractDownload PDF (428K) -
Kiyotaka Katou, Tsutomu Sonoda, Akira Watazu, Yasuo Yamada, Tadashi As ...2004 Volume 51 Issue 7 Pages 492-498
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTo make sure of applicability of metal injection molding (MIM) to aluminium based materials, the sintering pure Al specimens of thin sheet were prepared fromthe compound consisted of Al powder and organic binder of metal injection molding: The effects of process conditions on the properties of sintered specimens were investigated.
First of all, the effcts of debinding and sintering atomosphere on the densities of sintered specimens were investigated. The density of the specimen debound in Ar gas was higher than that debound in air after sintering.
Therefore, the density depends on the sintering atomsphere. It also increases with increasing the degree of vacuum at sintering. The relative densities of the specimens debound in Ar gas and sintered at 650°C for 7.2ksec in vacumm of 10-2Pa order were 86%, 90% and 96% when the average particle size were 20μm, 10μm and 3μm, respectively. The sintered pure aluminium compact, using 3μm powder, had the excellent tensile strength of 120MPa and elongation to fracture of 19% at room temperature.View full abstractDownload PDF (5889K) -
Yutaka Yanaba, Koji Hayashi2004 Volume 51 Issue 7 Pages 499-503
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn the previous studies on the fracture of hard or brittle materials such as hardmetals, cermets, ceramics and glass whose un-notched test piece fractures to several fragments, we have semi-theoretically derived and experimentally verified a new equation which correlates the total macroscopic fracture surface area (Smf) of all fragments of each un-notched test piece and its transverse-rupture strength (σm) with the fracture toughness (KIC) of the material: σm=ΨKICSmf1/2. Here, Ψ is a factor including test piece size and test method, etc., and the value of Ψ was clarified to hardly depend on the kind of materials.
In this study, we investigated whether this equation can be applied to ductile hot tool alloy steels which have extremely higher KIC and fracture not to several fragments, but to only two fragments even in the case of un-notched test piece, differing from the above hard or brittle materials. As the result, it was concluded that the equation substantially can be applied also to such ductile steels if a sharply notched test piece showing a brittle fracture mode is used.View full abstractDownload PDF (1882K) -
[in Japanese]2004 Volume 51 Issue 7 Pages 506
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (79K) -
Akira Fujiki, Yukihiro Maekawa, Yoshimi Sugaya, Takashi Shibano2004 Volume 51 Issue 7 Pages 507-514
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe authors have reported several papers on the warm compacted automotive P/M sprockets with normal sintering and high temperature sintering. Warm compacted and normal temperature sintered sprockets are applied to roller chain system in non-DIG (Direct Injection Gasoline) engines. Warm compacted and high temperature sintered sprockets are applied to silent chain system in DIG engines. This time we won the JSPM technology development award on these new sprockets, so we summarize the background and the history of this development.View full abstractDownload PDF (2291K) -
Norimitsu Hirose, Junichi Asami, Akira Fujiki, Kazuya Oouchi2004 Volume 51 Issue 7 Pages 515-521
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe relationships between Young's modulus, shear modulus and Poisson's ratio of sintered materials and porosity were investigated for use as practical P/M machine parts. Three types of steel powders were prepared and then compacted, sintered, and heat-treated under various conditions. Porosity had the greatest influence on Young's modulus, shear modulus, and Poisson's ratio. Especially, Poisson's ratio was affected by the pore shape, which depended on the type of powder, sintering temperature and atmosphere, and heat treatment.
For the more practical use of powder compositions, there was little influence by the sintering atmosphere on the Poisson's ratio of the sintered and heat-treated materials. For a partially alloyed powder (Fe-4mass%Ni-1.5 mass% Cu-0.5 mass%Mo)+0.8mass%C powder, Poisson's ratio versus porosity depended only on the sintering temperature at a porosity below 20%. In this case, a simpler approximate equation of Poisson's ratio of the sintered and heat-treated specimen versus porosity was proposed as follows: ν=0.300-0.266P+0.579P2 at 1423 K (sintering temperature) or ν=0.304-0.264P+0.548P2 at 1523KView full abstractDownload PDF (3803K) -
Tomohisa Futagawa, Nobuyasu Kawai2004 Volume 51 Issue 7 Pages 522-526
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis research has investigated the influence of the chemistry of the materials, heat treatment and the methods and conditions of fracture on fractal dimendions of fractuered surfaces in order to express quantitatively the roughness of fractured surfaces with fractal dimensions. The results obtained are described in the following.
1. The roughness of fractured surface can be expressed quantitatively with fractal dimensions.
2. Fractal dimensions were influenced by the changes in grain sizes.
3. The fractal dimension of fracture split connecting rod for a passenger car made in USA is relatively low and the surfaces of sample V with low dimension matched well.
4. It is necessary to adopt much smaller span than 10μm of measurement to evaluate small rough surface like dimples on ductile fractured surface.View full abstractDownload PDF (2912K) -
Koki Kanno, Yoshinobu Takeda, Anders Bergmark, Lindqvist Björn, Y ...2004 Volume 51 Issue 7 Pages 527-535
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPartially diffusion bonded alloy has been used for components which require high mechanical properties. Secondary operations as a carburizing are used for these materials to achieve higher strength. Pre-alloyed 3Cr-0.5Mo steel powder can have excellent mechanical properties when it is sintered at 1250°C, followed by secondary operations: carburising or shot peening. This time the fatigue strength of 520MPa has been achieved after the same shot peening process by adjusting cooling rate of Carbon/Carbon Composite Mesh Belt Furnace for 3Cr-0.5Mo steel powder. The influence of sintering conditions on chemical analysis and the effect of controlling cooling rate on fatigue strength are discussed. Pre-alloyed 1.5Cr-0.5Mo steel powder are also discussed. Finally the paper describes the simulation methods of residual stress after shot peening.View full abstractDownload PDF (652K) -
Takahiro Nozu, Youichi Murakami, Naruhiko Inayoshi, Hiroaki Takei, Ter ...2004 Volume 51 Issue 7 Pages 536-541
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRecently automotive fuel pumps installed in the fuel tank are still striving to increase the demands for high efficiency and high quality assurance. And as automotive supply continues to become increasingly global, the pumps have been used under various inferior gasoline containing higher sulfur concentrations in developing markets as compared with in general industrialized markets. Traditionally bronze alloy of Cu-Sn-C system is mainly used for the typical bearing of fuel pump applications. However it is very difficult to improve remarkably on the tribological performances of the demands for higher efficiency and so on. And what is more, the relatively high sulfur and sulfide contents gasoline is easy to cause sulfuration corrosion.
In order to obtain excellent tribological performances and superior resistive to sulfuration, various copper based alloy of sintered bearings are investigated by powder metallurgy method. As a result, nickel silver alloy of Cu-Ni-Zn-C system shows both superior resistive to sulfuration and excellent tribological performance under the relatively high sulfur contents gasoline lubrication.View full abstractDownload PDF (4383K) -
Shin Tajima, Takeshi Hattori, Mikio Kondoh, Hiroshi Okajima, Masaki Su ...2004 Volume 51 Issue 7 Pages 542-547
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSintered Iron was one of good soft magnetic materials. However, its magnetic flux density was smaller than those of wrought magnetic iron. The small magnetic flux density was caused by low sintered density. In order to increase the sintered density, we developed a new warm compaction technique using die wall lubrication (WC-DWL) with lithium stearate. According to the method, very high-density of sintered body could be fabricated. Pure iron powder compacted at 1176 MPa and sintered at 1523 K had properties as follows; sintered density=7.76 Mg/m3, μm=5300, B160=1.16 T, B240=1.28 T, B400=1.40 T, B2k=1.60T, and bHc=110A/m. Some of the sintered iron showed anisotropic dimensional change and anisometric microstructure, which were linked to abnormal grain growth up to several mm in length. This anomaly was the more pronounced the higher the green density of the specimens was.View full abstractDownload PDF (3551K) -
Tetsuji Saito2004 Volume 51 Issue 7 Pages 548-553
Published: July 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMn, Al, and C powder mixtures were mechanically alloyed using a conventional ball mill and a high-energy ball mill in an argon atmosphere. Although the mechanically alloyed powders prepared by the conventional ball mill retained the original powders, the powders prepared by the high-energy ball mill did not retain the original powders and consisted of α-Mn solid solution. However, no intermetallic compounds such as the magnetic τ phase and high temperatures ε phase were formed during the mechanical alloying. The magnetic τ phase was obtained by subsequent annealing of the mechanical alloyed powders as was the case for the gas atomized powders. It was found that annealing of the powder mixture, without mechanical alloying, resulted in the formation of the small amount of the magnetic τ phase. However, the mechanical alloying significantly increased the amount of the magnetic τ phase in the annealed powders. This was due to the thorough mixing of Mn, Al, and C powders by the mechanical alloying. The magnetic properties of the annealed powders were deeply dependant on the annealing temperature. The optimally annealed mechanical alloyed powders showed a large saturation magnetization with a high coercivity comparable to those gas atomized counterparts.View full abstractDownload PDF (2386K) -
Hiroyuki Matsumoto, Teruhiko Fujiwara, Nobuyuki Ikuta, Kazuya Konno, T ...2004 Volume 51 Issue 7 Pages 554-558
Published: July 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe objective of this study was to investigate differences in microstructures and magnetic properties on the Fe-Cr-Co type magnets due to the processing variables, such as initial powders and sintering temperatures of spark plasma sintering (SPS). The Fe-Cr-Co powders with a grain under 80μm were prepared by spray conversion process. The sintered Fe-Cr-Co compacts achieve high relative densities (about 98%) by process conditions with 39 MPa at 1223 K for 7 minutes using spark plasma sintering. The stable high magnetic hardening of the compacts was performed after heat treating with the miscibility gap, producing modulated structures consisting of two phases an iron-rich phase (a1) and chromium-rich phase (a2). According to above results, The SPS is recognized to be superior on sintering conditions (in shorter time and at lower temperature) to the conventional furnaces. So that Spark plasma sintering has a high possibility of being applied as a method of sintering Fe-Cr-Co magnet in the near future.View full abstractDownload PDF (4001K)
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