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Volume 46, Issue 10
Displaying 1-17 of 17 articles from this issue
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Tomohiro Takida, Tadashi Igarashi, Tetsuji Hoshika, Yutaka Hiraoka1999 Volume 46 Issue 10 Pages 1025-1030
Published: October 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMolybdenum sheets with two types of elongated coarse-grain structures (trade name: TEM) were developed by heavy duty rolling and recrystallization treatment of sintered molybdenum bodies with lmass% La2O3. One type has spindle-like grains (S-TEM) and the other has stacked plate-like grains (P-TEM). Three-point bending tests were carried out on S-TEM and P-TEM at 77K to 300K, to investigate the effects of grain structure on their ductile-to-brittle transition characteristics such as maximum strength and ductile-to-brittle transition temperature (DBTT).
The aspect ratio (LRD/W) of grains on the perpendicular plane to the rolling direction and the number of grains (Ng)along the normal direction of sheets were estimated as parameters of the grain structure. The following results were obtained.
(1) Molybdenum sheets with elongated coarse-grain structures (S-TEM and P-TEM) had a higher fracture strength at low temperatures and a lower DBTT, than pure molybdenum and TZM with equiaxial-grain structures.
(2) Cracks are initiated at a fine equiaxial-grain near the surface of the specimen and propagated across elongated coarse-grains remaining on the cleavage-fractured surface.
(3) Fracture strength increased and DBTT decreased with Ng, of S-TEM.
(4) P-TEM with fewer residual fine equiaxial-grains had a lower DBTT and higher maximum strength.View full abstractDownload PDF (4537K) -
Tomohiro Takida, Tadashi Igarashi, Mamoru Mabuchi, Mamoru Nakamura, Yo ...1999 Volume 46 Issue 10 Pages 1031-1036
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFine-grained sintered molybdenum alloys dispersed with 0.8mol% ZrC or TaC particles were prepared by mechanical alloying and spark plasma sintering, and tensile properties of the molybdenum alloys were investigated at 300K and at 1170-1770K. The particle-dispersed alloys exhibited much higher strength than a pure molybdenum which was fully recrystallized. Furthermore, the ZrC particle-dispersed alloy showed a large elongation of 120% at 1770K.These excellent tensile properties of the particle-dispersed alloys are attributed to fine-grained microstructure and uniform dispersion of the fine particles.View full abstractDownload PDF (4054K) -
Shoji Umeda1999 Volume 46 Issue 10 Pages 1037-1043
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effects of chemisorbed H2, CO2 and CO on the saturation magnetization of nickel have been investigated on fine particles of nickel supported and not supported.
Apparatus provided with "Hall Effect Generator" circuit and the permanent magnet of the intensity of 0.5T, was designed for in situ measurements of magnetization after gas adsorption.
Change of magnetization with gas amount adsorbed at the room temperaure was measured. The reduction of magnetization by adsorbed gas causes solely from pairing of electron spins. The value of ε is numerically the number of spins cancelled per the hydrogen atom adsorbed on nickel by pairing in the d band. The values of ε for the various nickel particles have been determined. The obvious influence of particle size over the range 20 to 360Å in radius on ε for coprecipitates was not observed. But the magnetic data showed clear examples of support influence in changing the value of ε. The effect of chemisorbed hydrogen on ε appears to be almost independent of the surface coverage for supported nickel coprecipitate exhibiting the superparamagnetism. However, the values of ε decrease with the surface coverage of hydrogen for the samples contained larger metallic particles than the catalysts showing the superparamagnetic behavior. The ε value for nickel-zeolite impregnate is 0.85 and very close to that of massive nickel, Ni-Al2O3, or Ni-kaolin-supported samples in the range of low hydrogen coverage. A possible reason for the low value of ε in Ni-SiO2-Al2O3 is explained by chemical interaction in the interfaces between the support and nickel metal.View full abstractDownload PDF (444K) -
Katsuyoshi Kondoh, Atsushi Kimura, Yoshinobu Takeda, Ryuzo Watanabe1999 Volume 46 Issue 10 Pages 1044-1052
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn-Situ directly nitrided and sintered AI-AIN composite material has been developed by utilizing a chemical reaction between aluminum and nitrogen gas at temperatures below 823K. It shows superior mechanical properties to those of conventionally premixed and sintered AI-AIN composite. It is primarily due to good bonding of the in-situ formed AIN to the matrix. The advanced P/M aluminum alloy shows an extremely low friction coefficient, such as 0.004 to 0.008 under oil lubrication. It also has excellent wear resistance and anti-seizure property compared to I/M aluminum alloys with hard anodized plating. This is because micro oil grooves existing along in-situ formed AIN seems to work as oil pits and make it easy to keep hydraulic lubrication with thin oil films on the sliding surface.View full abstractDownload PDF (10156K) -
Keiichi Maekawa, Mituharu Takita, Hiroyuki Nomura1999 Volume 46 Issue 10 Pages 1053-1057
Published: October 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSMetal injection molding process has been applied for Ti-6Al-4V alloy and the effects of process conditions have been studied on microstructure formation and mechanical properties of the compacts. Sintering at 1223K results in relative density higher than 96%. Oxygen content increases with sintering time, which gives an undesirable effect on elongation of the sample. Tensile strength about 950 MPa has been obtained, which is at the same level with that of cast alloy. The equi-axis a structure increases with time of sintering. The coarse a structure has been shown to give local sites for crack initiation.View full abstractDownload PDF (5309K) -
Slip Casting and SinteringSaburo Sano, Kenichi Koizumi, Takumi Banno, Yasuo Shibasaki, Kiichi Od ...1999 Volume 46 Issue 10 Pages 1058-1061
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis study is concerned with the fabrication of engineering ceramics with complicated shapes by using the Slip Casting Process. In the previous report, we showed the conditions for preparing well-dispersed and high solid content Y-PSZ slurries. In this report, we will show the results of slip casting and sintering of Y-PSZ. High density green bodies, form 46 to 50% of the theoretical density, were obtained by the slip casting using well-dispersed and high solid content slurries of 3 kinds of starting powders. From high density green bodies, high density sintered bodies, above 99%, were obtained at the sintering conditions at 1500°C, 2h, in air for 3 kinds of starting powders. The bending strength for sintered bodies showed from 1 to 1.2GPa when the green bodies were sintered at from 1350 to 1500°C in air.View full abstractDownload PDF (281K) -
Shinichi Sakano, Koichi Haneda, Masaru Yokoyama, Toshihiko Sato1999 Volume 46 Issue 10 Pages 1062-1067
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe morphology and magnetic properties of ultrafine Me1-xZnxFe2O4 particles (Me=Mn2+, Co2+, Ni2+, Cu2+) prepared by a chemical coprecipitation with no subsequent heating method have been explored. The X-ray diffraction data and TEM observations indicate that cubic-structured spinel particles are formed in granular shape in the entire region of Zn2+ concentration for every case only except for a case at X=0 of Me=Ni2+. An incremental linear relation between the lattice parameter and Zn2+ concentration is also observed for Me=Co2+, Ni2+ and Cu2+, but not for Me=Mn2+ with no simple relations, while the crystallite size (D311) obtained from X-ray line broadening, which is consistent with TEM observations as well, decreases with the higher Zn2+ concentration for all cases, nevertheless the coercivity (1Hc) decreases, in other words the magnetic property is softened as is verified with mossbauer measurements.
Although the trend in enhanced variation of the saturation magnetization with Zn2+ contents is similar to one for bulk materials for X=0-0.6 regions, the values are always small compared to bulk values, for more than X=0.6 the effect of high magnetic moment of ultrafine ZnFe2O4 plays a role. To interpret the low magnetization, by assuming a core model and a presence of magnetically inactive surface layer in a particle, the thickness of the layer is obtained for each sample. A correlation of the larger thickness with the larger magnetical softness of the relevant materials has been suggested.View full abstractDownload PDF (3471K) -
Keizo Kobayashi, Kimihiro Ozaki, Akira Sugiyama, Toshiyuki Nishio1999 Volume 46 Issue 10 Pages 1068-1072
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMg-x mass%Fe (x=0, 5, 10, 20) alloys were synthesized by mechanically alloying of elementary Mg and Fe powder for 180ks milling under 66kPa argon gas atmosphere using by a planetary ball milling. The obtained MA powders were composite materials of Mg and Fe, the reaction between Mg and Fe did not occurred during the MA process. After the MA process, Mg-Fe powders not containing more than 10mass%Fe became disc shape and Mg-20mass%Fe powder became grain of 2mm. In the case of Mg-15mass%Fe, the obtained MA powder became big blocks by the joining of the MA powders during the MA process. The Mg-15mass%Fe MA powder was able to consolidate by pulsed current sintering at 773K under a pressure of 19MPa. It was observed that the fine and homogenius Fe particles dispersed in the sintered body. In the MA process of Mg-15mass%Fe, the bulky compact was obtained by the controlling of a milling condition.View full abstractDownload PDF (6012K) -
Nobuyuki Tamari, Isao Kondoh, Takahiro Tanaka, Masakazu Kawahara, Masa ...1999 Volume 46 Issue 10 Pages 1073-1076
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAn effect of sintering pressure and rising speed of temperature on the densification, bending strengths and microstructure of alumina ceramics prepared by spark-plasma-sintering was investigated at 1350°C or 1400°C for 0.3ks. No effect of spark-plasma-sintering was observed at a sintering pressure of 10MPa. Above 10MPa, the spark-plasma-sintering brought higher densities in comparison with the hot-press. But the sintering pressure was too high to accelerate the grain growth and the strengths deteriorated. Slower the rising speed, higher the densities. However the rising speed was too slow to promote the grain growth and the strengths dropped. It is necessary to select the proper sintering pressure and rising speed in the case of firing the materials by the spark-plasma-sintering.View full abstractDownload PDF (4317K) -
[in Japanese]1999 Volume 46 Issue 10 Pages 1078
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (86K) -
Mitsuya Hashii1999 Volume 46 Issue 10 Pages 1079-1084
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMechanical alloying process was studied in the Fe75Al25 system from elemental powders using a dry tumbler ball mill. In the X-ray diffractions, the peaks of the Fe and the Al phases became weak with milling time. The powder milled for 1800ks showed the same patterns as a case of supersaturated solid solution, α-Fe(Al), or very fine Fe3Al. The particles became large in size and lamellar structure formed in the initial milling stage. Scanning electron microscope observations showed that the difference in the contrast of the back scattered electron micrograph of each layer in the lamellar structure was diminished as milling time. The powder became fine (particle size: from 5 to 20μm) after 1800ks. An (Fe3A1+α-Fe) phase formed after milling for 1800ks and annealing at 1500K.View full abstractDownload PDF (6952K) -
Akito Takasaki1999 Volume 46 Issue 10 Pages 1085-1089
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThree kinds of Ti-Al powders, Ti72Al28, Ti57Al43 and Ti48Al52, mechanically alloyed by a planetary ball mill in a hydrogen gas atmosphere (0.1 MPa) for alloying time of 30 h were consolidated by cold isostatic pressing and sintering in a vacuum. The densities and Vickers hardness of the consolidated samples were measured and then were compared with those obtained from powders mechanically alloyed in an argon gas atmosphere as well as those without mechanical alloying (MA). The hydrogen atmosphere enhanced the solid-solid reaction accompaning with the assistance of dynamical process of MA and accelerated the formation of amorphous phase or the refinement of the powders without forming a hydride phase after a longer MA process. The microstructures of the consolidated samples after MA were not dependent on gas atmosphere and could be estimated from the Ti-Al binary phase diagram. Higher density as well as higher Vickers hardness could be expected in the consolidated samples obtained after MA in hydrogen gas atmosphere.View full abstractDownload PDF (4013K) -
Masafumi Suzuki, Tatsuhiko Aizawa1999 Volume 46 Issue 10 Pages 1090-1096
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSInstead of the conventional melting and solidification method, which requires high temperature processes, new P/M approaches on the route of mechanical alloying are highlighted to make near-net shaping of the refractory metal aluminides and silicides. In particular, P/M approach starting from mechanically alloyed precursor is proposed and developed in the present study for preparing refractory metal silicides. Since reaction temperature required to form silicides can be lowered by using mechanically alloyed precursor, the final intermetallic compound is expected to have fine-grained microstructure. SiC whisker reinforced MoSi2 is fabricated to improve the toughness at room temperature. The proposed two-step reactive forging processing is effective to improve the relative density of final products for near-net shaping.View full abstractDownload PDF (3408K) -
Tatsuhiko Aizawa, Toshiro Kuji, Hiroaki Nakano, Ken-Ichi Ichige1999 Volume 46 Issue 10 Pages 1097-1102
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMg2Ni alloy has been and is still highlighted as a candidate hydrogen storage material to be working instead of LaNi5, which is a typical commercial material at present. This alloy is superior to other hydrogen storage alloys with respect to hydrogen absorbing capacity, light weight, long-life usage as a battery and adaptivity to Ni-Cd type batteries. New processing is required to make precise control of chemical composition in alloying, to reduce absorbing temperature of hydrogen and to avoid from various contaminations. In the present study, the bulk mechanical alloying is applied to solid-state synthesis of Mg2Ni alloys instead of the milling-type mechanical alloying or the conventional P/M approaches. The present method is favored for the precise control of chemical composition within the tolerance of 1% or less, the fabrication of dense green compact of Mg2Ni, which prevents itself from burning or oxidation and, the microstructure control to yield nano-grained powder compact. Furthermore, low temperature phase can be available to lower hydrogen absorbing temperature. XRD, TEM and Sievert method are utilized to make characterization of the synthesized Mg2Ni and to evaluate its thermo-dynamic properties, respectively.View full abstractDownload PDF (2263K) -
Hideki Kyogoku, Shinichiro Komatsu1999 Volume 46 Issue 10 Pages 1103-1107
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTiNi shape memory alloy was fabricated by powder injection molding, and tensile and recovery stress tests were carried out on the alloy. The effects of sintering conditions on the microstructures and mechanical properties of the sintered alloy were investigated. Ti gas-atomized powder and carbonyl Ni powder mixed well with polyamide binder and injection-molded into a mold for tensile test specimens. The injection-molded compacts were debound at 593 K and then sintered at 1173 K, 1223 K and 1423 K for various sintering times. The density and microstructure of the sintered compacts were influenced greatly by the sintering temperature. The tensile strength and elongation of the sintered compacts were much less than those of the same alloy made by spark-plasma sintering, because the density of the former were much lower than that of the latter. The obtained alloy, however, showed apparent shape memory effect.View full abstractDownload PDF (5928K) -
Akira Sugiyama, Keizo Kobayashi, Kimihiro Ozaki, Akihiro Matsumoto, To ...1999 Volume 46 Issue 10 Pages 1108-1112
Published: October 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMagnetic properties of Tb-Dy-Fe alloy made by the mechanical alloying (MA) and the pulsed current sintering method was investigated. The MA was performed in a planetary ball mill. The powders were prepared by the MA of the mixture of the elemental Th, Dy and Fe powders for (TbxDy1-x)Fe1.8 (x=0-1.0). The MA powders were heat treated at several temperature and consolidated at 1073K. From the result of VSM analysis, it was found the coercivity of the MA powder milled after 360ks was large and the magnetization was small. After heat treated at 673K, coercivity of the powder became smaller and magnetization of the powder became larger. It is conjectured that materials with small coercivity shows good magnetostrictive properties. The magnetic hysteresis loop was not depend on the composition of (TbxDy1-x)Fe1.8 (x=0-1.0). It is considered that the large current passed the sample would create the magnetic field around the sample during SPS. But magnetic anisotropy of the sintered sample was not observed by the VSM. Magnetostriction of sintered (Tb0.5Dy0.5)Fe1.8 alloy was as large as TbFe2 which was made by A.E. Clark and H.S. Belson.View full abstractDownload PDF (2119K) -
Hirotsugu Takizawa, Masayuki Ito, Kyota Uheda, Tadashi Endo1999 Volume 46 Issue 10 Pages 1113-1117
Published: October 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSVarious 14-group elements were inserted in the skutterudite-type CoSb3 host lattice under high-pressure and temperature conditions of 8 GPa and 550°C using the Belt-type high-pressure equipment. It was found that various elements could be inserted in the body-centered vacant site, resulting in the formation of new filled-skutterudites MxCo4Sb12 (M: Ge, Sn, Pb). The composition and the degree of space-filling were determined by the Rietveld analysis and the density measurements. Maximum space-filling was determined to be 50% for M=Ge, 100% for M=Sn, and 70% for M=Pb. The inserted Sn atom shows anomalous large thermal vibration amplitude, while Pb atom does not. The Ge atom locates the position slightly deviated from the ideal body-centered position.View full abstractDownload PDF (365K)
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