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Volume 46, Issue 11
Displaying 1-17 of 17 articles from this issue
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Yoshikazu Suzuki, Katsuyoshi Shimokawa, Hideki Minagawa, Yoshinobu Ued ...1999 Volume 46 Issue 11 Pages 1123-1128
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRecently published thermophysical data on molten materials from many researchers greatly differ. Accurate data are needed for predicting material production processes by computer simulation.
The thermophysical properties of molten semiconductors were investigated under microgravity conditions. The wettability and electrical resistivity between the solid-liquid surface of silicon or germanium and ceramic plates were examined under normal gravity.
Comparing published data with the experimental results, some discrepancies and validity along with visible results were discovered, and the points of problems are discussed. We report guidlines that can be used to obtain the thermophysical properties of pure materials with a high degree of accuracy.View full abstractDownload PDF (5777K) -
Wen-bo Du, Kiyohiko Tatsuzawa, Tatsuhiko Aizawa, Junji Kihara1999 Volume 46 Issue 11 Pages 1129-1135
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of the green microstructure in the swaged Al2O3 with 98% reduction in area by the controlled fracture forming (CFF) on its grain growth behavior was investigated. The kinetics of grain growth in the Al2O3 compacts fabricated by the CFF process and by conventional process was estimated. The results indicate that both Al2O3 compacts obey a cubic law, but the grain growth rate constant K of the conventionally processed Al2O3 is 6 times as large as that of the swaged Al2O3 with 98% reduction in area. The retardation of grain growth in the swaged Al2O3 is attributed to the pores which are homogeneously distributed in the microstructure due to the flow and rearrangement of particles during the CFF process. The increase in number of pores per grain is responsible for the decrease in velocity of grain boundary migration. The mechanism for retardation of grain growth in the swaged Al2O3 is considered to be the pore-controlled mechanism.View full abstractDownload PDF (2072K) -
Kota Kataoka, Nobuyuki Nakamura, Toshihiro Tsuchiyama, Hideto Goto, Se ...1999 Volume 46 Issue 11 Pages 1136-1140
Published: November 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSMixtures of ferritic stainless steel powders with 12mass%Cr and 23mass%Cr were compacted and subjected to Nitrogen Gas Atmosphere Sintering (NGAS) treatment at 1473K in N2 gas atmosphere of 0.1MPa in order to produce high nitrogen stainless steels with a (martensite (α') + austenite (γ)) composite structure. Microstructure of the NGAS-treated materials was investigated by means of optical microscopy and X-ray diffractometry in relation to the mixture ratio of both powders. The mechanical property of the materials was evaluated by three-points bending test and tensile test.
During the NGAS treatment, the 12mass%Cr and 23mass%Cr powders absorb 0.3mass%N and 1.0mass%N respectively, and this leads to the transformation from ferrite (α) to γ. On the following air-cooling from 1473K, the γ phase transforms to α' in the 12mass%Cr material, while it retains stably at room temperature in the 23mass%Cr material. The structure ratio (α'/γ) of the NGAS-treated materials can be controlled by changing the mixture ratio of both powders.
Results of mechanical testings for the NGAS-treated materials indicated that both of strength and ductility were reduced with increasing the volume fraction of the 12mass%Cr powder, because the powder produces α' with brittle nature and the α' give a route of crack propagation.View full abstractDownload PDF (4865K) -
Katsuyoshi Kondoh, Atsushi Kimura, Ryuzo Watanabe1999 Volume 46 Issue 11 Pages 1141-1147
Published: November 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSBehavior of Tin and Magnesium on the surface of aluminum alloy powder during heating has been examined by in-situ analysis using XPS. Tin distributed in the aluminum alloy powder acts as a liquid state over 505K and is concentrated below the surface Al2O2 film which covers the powder. This phenomenon has no relation with Magnesium content in the powder. However, it is necessary to include Magnesium into the powder when Tin in the liquid state appears on the powder surface during heating. This is because Magnesium acts to deoxidize and destroy Al2O3 films. Therefore, the temperature of the appearance of Tin coincides with that of the appearance of the metallic aluminum after deoxidization of surface Al2O3 films, and it corresponds to the temperature range from 670K to 700K. The area of the exposed metallic aluminum at the particle surface decreases with increase in Tin content. This is because the liquid Tin is squeezed out from the reduced and cracked Al2O3 film and covers the particle surface.View full abstractDownload PDF (451K) -
Kazuo Isonishi, Hideaki Mizoe1999 Volume 46 Issue 11 Pages 1148-1153
Published: November 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSBulk material of Ti5Si3 intermetallic compound had been produced successfully by powder metallurgical technique. However, it was still very brittle. In the case of brittle intermetallic compound like Ti5Si3, it has been believed that it is really effective to form ductile phase to improve the toughness and ductility. We chose b-Ti as the second phase, for it was able to realize at the room temperature with the activity of b stabilizer. Therefore, we add V as a ternary element of Ti-Si system. In this paper, effect of V addition on powder fabrication by mechanical alloying, and phase formation during heating were investigated. The composition of MA powder, we studied here, were Ti-32mol%Si (Ti5Si3+α-Ti composition) and Ti-32mol%Si-10mol%V (Ti5Si3+β-Ti composition). By reducing Si content, mechanical alloying process was enhanced with comparison to Ti5Si3 stoichiometric composition. Diffusion of Si into Ti during heating or V into Ti during MA process played an important role in silicide formation and b-Ti stabilization.View full abstractDownload PDF (2231K) -
Kazuhiko Tanaka, Koji Hayashi1999 Volume 46 Issue 11 Pages 1154-1161
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNew tungsten carbonitride W(C, N)powder with 11-20 at% nitrogen had already been found by us to be synthesized by heating W+C mixed powder in N2 gas of high pressure(10-160 MPa)at 1523-1773 K. In this work, the synthesis of W(C, N)powder was tried by heating W+C and WO3+C mixed powders in NH3+H2 mixed gas of normal pressure(method I)and by heating W powder in CH4+NH3 mixed gas of normal pressure(method II), mainly at 1573 K for 3.6 ks. This try was based on the general concepts that the reactivities or activities of nitrogen and carbon atoms formed by the dissociation of NH3 and CH4 respectively are enormously high, compared with those of N2 and solid carbon, respectively. It was found that the products obtained by methods I and II were W(C, N) with nitrogen contents of 3 and 5 at%, respectively. The functions of NH3 and CH4 in the carbonitridation of W powder were also experimentally investigated in comparison with those of N2 and solid carbon, respectively.View full abstractDownload PDF (4164K) -
Wan Jiang, Tetsuo Uchiyama1999 Volume 46 Issue 11 Pages 1162-1166
Published: November 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMoSi2-oxides composites using fine aluminosilicate powder (<0.2, μm) have demonstrated excellent low temperature oxidation resistance and thermal shock resistance. These properties strongly depend on microstructural morphology and are obtained in composites that network-structures of both phases of MoSi2 and oxides are developed, i.e., in composites with oxides of 20-40 vol.%. When one phase is independently dispersed in the other phase, on the other hand, problems of low temperature oxidation and thermal shock occur. The low temperature oxidation problem occurs in the composites with oxides less than 15 vol.% and the thermal shock problem occurs in the composites with oxides more than 50 vol.%. These results will contribute to material design approaches for high temperature structural applications of MoSi2.View full abstractDownload PDF (4592K) -
[in Japanese]1999 Volume 46 Issue 11 Pages 1168
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (84K) -
Takeo Nakagawa1999 Volume 46 Issue 11 Pages 1169-1173
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPowder forming is one of the key technologies for making high valued sintered products with low cost. And powder sintering process gives us various applications not only in the mechanical parts but also in forming mold, grinding stone etc.... This paper reviews the researches and developments which were conducted in the past 30 years by the author at Institute of Industrial Science, University of Tokyo. Author's achievements includes normal powder forming (powder forging, slip casting, CNC press), sintered mold with fine pattern surface(porous mold, powder spray mold, rapid tooling), sintering of cast iron powder (powder forging of decarbonized cast iron, cast iron bond diamond grinding wheel), fiber metallurgy, high conductive metal/polymer composite and magnetic powder polishing. Many of these new processes are now used in the actual production.View full abstractDownload PDF (5626K) -
Keizo Kobayashi, Toshiyuki Nishio, Akihiro Matsumoto, Kimihiro Ozaki, ...1999 Volume 46 Issue 11 Pages 1174-1178
Published: November 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTi-5at%Cr, Ti-10at%Cr, Ti-20at%Cr and Ti-40at%Cr powders were synthesized by a mechanical alloying (MA) of elemental Ti and Cr powders using a planetary ball mill in argon gas atmosphere for 360ks. The obtained Ti-10at%Cr powder consisted of β-Ti phase and the MA powders containing more than 20at%Cr were composite materials of β-Ti and Cr, while the obtained Ti-5at%Cr powder consisted of α-Ti phase.
Ti-10at%Cr powders synthesized by MA were consolidated to compacts by the pulsed current sintering at 1073K. The sintered compacts consisted of β-Ti and had 326Hv of vickers hardness.
When Ti-10at%Cr powder was prepared by MA process, the recovery of MA powder was not more than 40% of the starting materials in weight. The addition of lmass%Mg to the starting powders of the MA, improved the powder recovery of MA up to about 80%.View full abstractDownload PDF (411K) -
Norio Matsui, Katsuhiko Matsui, Keizo Kobayashi, Akira Sugiyama, Kimih ...1999 Volume 46 Issue 11 Pages 1179-1184
Published: November 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSFe-xat%Cr (x=28, 38, 48, 58, 68) alloy powders were synthesized by a mechanical alloying (MA) of elementary Fe powder and Cr powder using a planetary ball mill for 360ks under 1.33kPa argon gas atomosphere. The obtained MA powders were consolidated at 1173K for 0.3ks with a spark plasma sintering (SPS) apparatus, and the rectangular sintered bodies having a size of 30 mm in length, 5 mm in width and 2 mm in thickness were prepared. The sintered bodies were cut into the tensile specimen by grinding. The tensile strength increased and the elongation decreased with increasing the Cr content. This is due to increase in a ratio of the hard Cr powders. Fe-68at%Cr alloy produced by a cast could not be grind because of the creation of chromium oxide, but that produced by a MA-SPS process could be grind and the tensile strength of this alloy was about 1500MPa. As this alloy was inferior to other alloys in a milling condition of Fe and Cr, the numerical value in tensile strength of this alloy was scattered. Considering balance of tensile strength and elongation, Fe-48at%Cr was the best composition in the Fe-Cr alloys, because the tensile strength was about 1125MPa and the elongation was more than 5%.View full abstractDownload PDF (5933K) -
Tomita Masakazu, Ohhara Masaki, Sugiyama Daigo1999 Volume 46 Issue 11 Pages 1185-1189
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAtmosphere heat treatments with CH4/H2 mixture were applied to a batch sinter furnace. After debinding the injection molded SKH51 powder compacts, the 5 pieces of those were deoxdized in an alumina box with H2 under 840°C. Those were carburized in CH4/H2 mixture at 900°C for 1 h and sintered in decompressed Ar at 1230-1260°C for 1 h. The homogeneous sintered bodies without distortion could be obtained. All the relative densities were over 99% of theoretical density. The carbon contents were uniform among all the specimens and proportional to the ratios of CH4/H2.View full abstractDownload PDF (2512K) -
Hideshi Miura, Terumasa Hirano, Fumiaki Satou1999 Volume 46 Issue 11 Pages 1190-1195
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSVitreous enamels are one of ceramic coatings and have beautiful surface and excellent corrosion resistance. However, practical uses have been limited for the present, because they have a defect of low impact resistance. In this study, the influence of adding metal powders to enamel upon the adhesion was investigated, because the adhesion between enamel and substrate is the most important factor influencing the impact resistance.
The adhesion was improved by adding any metal powders to enamel, and excellent adhesion enough for practical uses could be obtained by large amount of additives and high fusing temperature even without expensive pretreatment of substrate. Especially, this improvement of adhesion tended to depend on the volume content of additives, which seemed to be due to the mechanical binding between the roughened surface of substrate and the coating, and the chemical binding of intermediate transition layer formed by dissolving the oxide of substrate in a coating.View full abstractDownload PDF (4792K) -
Particle Dynamics Simulation and ExperimentHarunori Kitahara, Hidetoshi Kotera, Masakazu Higashimoto, Susumu Shim ...1999 Volume 46 Issue 11 Pages 1196-1200
Published: November 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe alignment of anisotropic magnetic particles, each of which has its own easy axis for magnetization, gives a great influence on the magnetic performance of permanent magnet. To investigate the movement and rotation of the particles during compaction in an applied magnetic field, we simulate the microscopic behaviour by particle dynamics calculation with a non-spherical axi-symmetric particle model. We also carry out experiments on compaction of Nd-Fe-B magnetic powders in an applied magnetic field. Lateral pressures appear to change by the application of magnetic field, while there is very little change in compacting pressure. The changes in the pressures are due to the Maxwell stress and also to the anisotropics structure induced by the magnetic field; the latter appears to be larger than the former. The results of compacting pressures are in a qualitative agreement with experimental ones, and the alignment of the easy axes is significantly influenced by the application of magnetic field.View full abstractDownload PDF (2169K) -
Junjiro Takekawa1999 Volume 46 Issue 11 Pages 1201-1206
Published: November 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSBoron (B) is known as the most useful sintering enhancer for ferrous powder.
In this study, the effect of B addition on the sintering of metal injection molded SUS316L steel powder compacts was investigated. 0.4 mass% B powder was mixed with the SUS316L steel powder using a centrifugal ball mill to obtain a uniform and fine dispersion.
It was shown that the binder removal (%) of the MIMed compacts remarkably droped when 0.4 mass % B was added. The sinterablity of the compacts with the B addition was much affected by the debinding temperature: The compacts debound below 300°C were readly sintered to near the theoretical density at relatively low temperature as 1190°C, whereas the compacts debound above 330°C had to be heated above 1240°C to obtain near the theoretical density. The mechanical properties of the compacts with the B addition were extremely sensitive to the sintering temperature. It was also shown that the carbon (C) contents of the sintered compacts with the B addition decreased with increasing both debinding and sintering temperatures.View full abstractDownload PDF (4873K) -
Hideshi Miura, Naohiko Era, Yoshiyuki Kato, Hideo Abo1999 Volume 46 Issue 11 Pages 1207-1211
Published: November 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSMetal Injection Molding (MIM) process is a manufacturing route for mass-production of high density, highperformance, and near net-shaped metal components. However, MIM processes have been still limited in the size of the components. A Quickset process (QSP) has been invented as one of solutions for the issue. A feature of QSP is the manufacturing of large size parts that can not be made by the usual MIM processes based on a thermoplastic binder system. Although assessment of the properties such as strength are important to design the reliable machine structural parts, there are few reports about the properties of the materials produced by QSP at the present time.
In this study, the behavior of properties (relative density, hardness, tensile and fatigue strength) for machine structural low alloy steels produced by QSP have been investigated. The tensile strength of QSP alloy steels were equivalent to those of MIM alloy steels. However the fatigue strength of QSP alloy steel was relatively low, because of the coarse pores due to the segregation of binder occurred at water freeze injection molding step.View full abstractDownload PDF (4405K) -
Mistuharu Takita, Yasuhiro Mizuno, Hiroyuki Nomura1999 Volume 46 Issue 11 Pages 1212-1216
Published: November 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe metal injection molding process (MIM) is a key technology which makes it possible to form complicated 3-dimensional parts in near net shape. Cast iron which contains graphite in the microstructure has unique properties such as solid lubricity and damping capacity in addition to castability. In this study, it is intended to synthesize high functional MIM products from cast iron powder. Water-atomized cast iron powder and binder are mixed and injected to the mold. The injected body is sintered after solvent debinding. By using cast iron powder with low oxygen content and the solvent debinding method, the oxidation is minimized, the debinding time is reduced and the process can be simplified. The maximum tensile strength is comparable to that of ductile cast iron. The estimated damping capacity is as high compared with that of gray iron. The high damping capacity with high tensile strength and reasonable wear resistance are considered to be obtained by the structure mixed with fine graphite particles and pores in pearlitic matrix.View full abstractDownload PDF (3907K)
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