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Volume 39, Issue 7
Displaying 1-12 of 12 articles from this issue
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Teruo Takahashi1992 Volume 39 Issue 7 Pages 529-538
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA new process is proposed and tested in order to prepare oxide- and carbide-dispersion-strengthened coppers, combining the mechanical alloying using elemental powders as starting materials and following heat-treatment. The oxide-dispersion-strengthened coppers prepared in the present study did not show good mechanical properties because of the remarkable growth of oxide particles and the separation of pure copper from alloyed powder by heating.
In copper-transition metal-carbon systems, although the mean particle sizes of carbides precipitating in mechanically alloyed podwers increased slightly as the heating temperature increased, they were smaller than those of oxides. The. thermal stability of carbide-dispersion-strengthened copper was better than that of oxide-dispersion-strengthened copper. Mechanical properties of the carbide-dispersion-strengthened copper was excellent. For example, the ultimate tensile strength of 2.5 vol%carbide alloy was 650-725 MPa, and the elongation was 11-12%. The electric conductivity was improved up to 80 %IACS in 2.5vol%TiC-dispersion-strengthened copper by heating at 1273 K for 18.0 ks or at 1323 K for 7.2 ks. It was concluded that the carbide-dispersion-strengthened copper was superior than the others.View full abstractDownload PDF (11289K) -
Keizo Kobayashi, Takeshi Takayanagi, Kenji Miwa1992 Volume 39 Issue 7 Pages 539-541
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical alloying of Ti-base intermetallic compound (Ti -C- 20mass%Ni, Ti -30mass%Al, Ti -26mass%Si) was performed using a vibrational ball mill in Ar or N2 under diminished pressure. The effect of nitrogen on the mechanical alloyed Ti-base intermetallic compound was studied by X-ray diffraction, EPMA and DSC.
Results from X-ray diffraction, EPMA and DSC suggested that the synthesis of TiN was carried out in N2 atomosphere under diminished pressure and tended to retard the MA reaction. And the heat treatment of powder, which was mechanical alloyed in Ar under diminished pressure, at 1173K for 1.8ksec in N2 flow made the needle-like shape of the crystals.View full abstractDownload PDF (3119K) -
Application to Mo and WAkinori Saito, Toshio Sano, Yasunari Kaneko1992 Volume 39 Issue 7 Pages 542-545
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPowders were synthesized by using spark discharge between molybdenum or tungsten rotating disk electrode and wire electrode.
In the case of molybdenum electrodes in deionized water, molybdenum and molybdenum oxide (MoO3) were formed in spherical and irregular shape particles. By applying tungsten electrodes, spherical particles of tungsten and tungsten oxide (W3O) were formed. In the case of both the molybdenum and tungsten electrodes in silicone oil, spherical particles formed consist of metal (Mo, W), metal carbide (Mo2C, W2C) and silicon carbide.View full abstractDownload PDF (3387K) -
Hisashi Kaga, Yoshihiro Taya, Isao Shimono, Hiroshi Katayama1992 Volume 39 Issue 7 Pages 546-552
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSUsing vacuum mechanofusion system developed previously, we coated spherical Al2O3 powders of 45 micron diameter with Cu powders of 0.2 micron diameter. The effects of the atmospheric pressure on the mechanofusion behavior of Al2O3/Cu particles were disscussed on the base of the particle size distribution data and the SEM observation results on the appearance of the mechanofusion particles.
The mechanofusion behavior of Al2O3/Cu particles depends on the atmospheric pressure, i.e., the volume percent of Cu composite particles decreases as the pressure become lower. The composite particles mechanofused under the pressure of 1.0×105SPa became dark due to oxydation. At the pressure of 5.3×10-2Pa, the composite particles indicated intrinsic Cu metallic color.View full abstractDownload PDF (4577K) -
Hisashi Kaga, Yoshihiro Taya, Hiroshi Katayama, Yoshikazu Hamaguchi1992 Volume 39 Issue 7 Pages 553-558
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSUsing the vacuum mechanofusion apparatus which has been reported. we tried to coat Cu core particles with Al2O3 covering particles. Mechanofusion in air gave a lower yield of composite particles, while mechanofusion in vacuum or Ar-replaced atmosphere gave a higher yield. That is to say, the yield of the composite particles was enhanced by decreasing the partial pressure of O2 in the residual pressure. The MS analysis revealed that gases such as CO. CO2, CH4. etc generated during the mechanofusion at low residual pressures. Under SEM. many micro dents were observed on the naked surface of the composite particles after detaching Al2O3 particles by irradiation of supersonic wave. The AES detected Cu on the full surface of the uncomposite Al2O3 particles. When the mechanofusion processing time is short, the reacted Al2O3 particles on a Cu core particle can be distinguished separately. The longer the mechanofusion processing time, the smoother the surface of the composite particles. When the mechanofusion processing time is long enough, no boundaries between the reacted Al2O3 particles on a Cu core particle can be distinguished. A physical scheme of the formation of composite particle is proposed.View full abstractDownload PDF (2748K) -
Toshimasa Morooka, Eiji Yuasa, Matsuru Kushida1992 Volume 39 Issue 7 Pages 559-563
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAmorphous alloy powder of 57at%Ti-Cu is prepared by the mechanical alloying of the elemental Ti and Cu powders by using a Spex Mixer/Mill Model 8000. The amorphization reaction is monitored by X-ray diffraction, scanning electron microscopy and differential thermo analysis. During the milling a layered structure of the crystalline elements is developed. These layers become thinner and the amorphous parts grow, when the alloying period is increasing. The X-ray diffraction patterns begin to show broad peaks from the MA period of 36ks. The crystallization temperature of CuTi is presumed around 650K from the results of DTA and X-ray diffraction.View full abstractDownload PDF (1797K) -
Nobuo Asahi1992 Volume 39 Issue 7 Pages 564-568
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSEffect of milling mode (the ratio of milling period to pause one) on amorphization of mixed Ni33Zr67 powders by mechanical alloying(MA) was examined using high-speed vibratory ball mill. Three modes were determined by measuring temperatures on inner wall of vessel during MA with Chromel-Constantan(CRC) thermocouple, that is, mode A(the maximum temperature reached at 370 K), mode B(the maximum one 423 K) and continuity(continuous milling. 480 K after 150 ks of milling). The amorphization rate of the specimen by the mode A milling was slower than that by the continuous one, judging from the results of X-ray diffractometry and differential scanning calorimetry. Also, the thermal stability of the amorphous phase obtained was higher in this order: continuity, mode B and mode A.View full abstractDownload PDF (216K) -
Tsuyoshi Itsukaichi, Munetaka Hosokawa, Kiten Iga, Minoru Umemoto, Isa ...1992 Volume 39 Issue 7 Pages 569-574
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical alloying (MA) of elemental Sm and Fe powders in a laboratory ball mill was conducted to prepare Sm2Fe17Nxpermanent magnet. MA resulted in the formation of an amorphous phase with α-Fe in a wide composition range of Sm-Fe binary system. A single Sm2Fe17 phase was obtained after the subsequent heating of MA powder of the nominal composition of Sm15Fe85. The MA powder of Sm15Fe85 milled for 360ks was heated at various temperatures in the range 973-1073K and nitrided in an atmosphere of purified N2 gas flow for various times in the range of 0.3-21.6ks at 703K. It was observed that coercivity depends on both the heating temperature and nitriding time. When the MA powder was nitrided at 703K for 3.6ks, coercivity was observed to be higher as the heating temperature is lower. The coercivity showed a peak with nitriding time and the peak coercivity was obtained with shorter nitriding time as the heating temperature is lower. The effect of MA time on coercivity was studied under the condition of heating temperature 973K and nitriding at 703K for 3.6ks. The coercivity showed a peak with MA time and the largest coercivity was obtained at around 1080ks of MA. The dependence of coercivity on the heating temperature, nitriding condition and MA time was discussed in relation with the powder particle size and the crystal grain size of MA powder.View full abstractDownload PDF (1395K) -
Koji Hoshino, Tohru Kohno1992 Volume 39 Issue 7 Pages 575-578
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA shrinkage mechamism of anode materials for molten carbonate fuel cells was discussed. Theoretical calculations were made by dividing the shrinkage process into the initial stage of plastic flow and the steady stage of steady-state creep of metals. The results showed that -ln(P0/P) ?? L and ε ?? L in the initial stage and ε ?? logt in the steady stage; where P0: initial porosity, P:porosity, L:surface pressure load, ε:nominal strain and t:time. A model was examined in a H2-CO2-H2O (79-19-2 vol%) mixture gas stream under 2.5-8.9kgf/cm2 at 650°C for 50-1, 000 hours. The anode was porous sintered pure copper (porosity;43±1%) made of spherical gas-atomized powder which was sieved to 74-105μm. The experimental results indicated the proportionality relations mentioned above.View full abstractDownload PDF (228K) -
Tetsuo Fujimori, Yasuhisa Yamamoto, Atsumasa Okada1992 Volume 39 Issue 7 Pages 579-583
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe synthetic diamond which has been applied to some sintering tools is known to reduce the strength at an elevated temperature. We clarified in the former report that the Cu precoating of the diamond is effective to prevent the deterioration during the sintering process.
In this study, the effect of the Cu precoating is examined by measuring the fracturing rate of the diamond and the formation-rate of holes of sintering tools after an actual cutting test under several cutting rates.
As the result, it was clarified that the fracturing rate of the Cu precoated diamond is lower than that of the noncoated one, there was no difference in the formation-rate of holes between the Cu coated and the noncoated diamond tips sintered at a short time as 0.3ks or a long time as 3.6ks, and the fracturing rate under an actual cutting can be estimated from the fracture strength obtained by the single-particle test of the strength.View full abstractDownload PDF (2875K) -
Osamu Terada, Akira Sasaki, Hisashi Suzuki1992 Volume 39 Issue 7 Pages 584-589
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe titanium carbide (TiC) based cermet has often been known as a material showing a higher resistance to wear than that of WC-Co cemented carbide in the use of tools for working steels. However, the brazing characteristic of cermet to tool steels is inferior to cemented carbide. Then, the studies on adhesion between the cermet and WC-Co alloy were made to get fundamental knowledges in making combination tools. The cermet and WC-Co alloy were pre-adhered at 1300°C, and finally adhered at 1360-1400°C . It was found that liquid binder of nickel appearing in cermet generally flowed out into WC-Co alloy during the course of adhesion, resulting in the hardness increase and the volume (dimension) decrease in cermet, and in the reverse phenomena in WC-Co alloy side. The flow out of liquid nickel of cermet occurred during rising temperature to adhesion temperature and lowering temperature from the above temperature. The amount of flow out of liquid nickel depended on the adhesion temperature, grain size, carbon content of specimens and cooling rate from adhesion temperature. The mechanism of flow out of liquid nickel was in detail discussed.View full abstractDownload PDF (8386K) -
Takeshi Nomura, Akira Satoh, Atsushi Hitomi, Yukie Nakano1992 Volume 39 Issue 7 Pages 590-594
Published: July 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDegradation of insulation resistance (IR) of Ni-electrode multilayer ceramic capacitors has been studied with special reference to the microstructure. Oxidation of dielectrics during annealing, after firing at low oxygen partial pressures, is effective to elongate the accelerated life of IR. Segregation layers along the surfaces of Ni electrode, rich in Fe and Mn oxides, are formed during the annealing process. It is supposed that deterioration of grain boundaries is responsible for the degradation of IR.View full abstractDownload PDF (2812K)
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