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Volume 55, Issue 8
August
Displaying 1-9 of 9 articles from this issue
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Paper
Paper
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Shigeru Kikuchi, Noboru Baba2008 Volume 55 Issue 8 Pages 555-560
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSCr-Cu-Te alloy prepared by PM method showed better performance than conventional Cr-Cu alloy for electric-contacts of vacuum insulated switches. In order to improve insulation performance by decreasing vaporization of Te, optimization of Te addition was conducted.
As the performance of Cr-Cu-Te is determined by the bonding strength between Cr particles and Cu matrix, the boundary layer between Cr and Cu was investigated by TEM, STEM and EDS. The boundary layer contained Cu, Cr and Te, and is considered to be multiple ternary intermetallic compounds.
Based upon an assumption that the bonding strength depends on area of the boundaries and natures of the boundary, those two factors were changed by using 3 different sizes of Cr particles and amount of Te addition. In case of coarse (>53 μm) Cr particles, even 0.05% addition of Te showed the effect as significant as that of 0.1 or 0.2% addition, while that of fine (22-45 μm) Cr particles requires more than 0.1%.
Possible mechanisms of the boundary layer and the gap were discussed.View full abstractDownload PDF (1261K) -
-Temperature Measurement of the Laser Irradiation Spot-Tatsuaki Furumoto, Takashi Ueda, Takashi Tsukamoto, Naoto Kobayashi, A ...2008 Volume 55 Issue 8 Pages 561-567
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSThe layered manufacturing technique is one of the most effective processes for the manufacture of prototypes, tools and functional end products. A variety of components, such as polymer, ceramic, paper and metal powder, has been applied to date for the achievement of manufacturing objectives. Selective Laser Sintering (SLS) and Melting (SLM), in particular, are two of the most versatile techniques, able to cover a wide range of materials. In this study, in-process monitoring of the processing temperature at laser irradiation spot is proposed by using two-color pyrometer, which has been developed by the authors. In order to investigate the consolidation characteristics of chromium molybdenum steel (SCM) based powders with a Yb fiber laser, the maximum temperature at the irradiation spot of a laser beam was measured under various experimental conditions. The influence of the laser power and diameter of laser beam on the temperature were evaluated. As a result, it was revealed that the maximum temperature during laser irradiation changed under the influence of laser power and particle size of powders. The temperature increased with the increase of laser power, and was greatly influenced by the particle size of the powders. The temperature after laser irradiation decreased rapidly to room temperature.View full abstractDownload PDF (1467K) -
Hiroshi Komatsu, Mitsutaka Haruta, Daisuke Kan, Hiroki Kurata, Seiji I ...2008 Volume 55 Issue 8 Pages 568-572
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSEpitaxial thin films of La2CuSnO6 have been grown on (001)-oriented SrTiO3 substrates by a pulsed laser deposition method. The obtained films had the layered arrangement of Cu2+ and Sn4+ ions and also the 2-fold superstructure within the ab plane making a 2a×2a×2c tetragonal double-perovskite unit cell. Analysis of the interface between the La2CuSnO6 film and the SrTiO3 substrate has revealed that the first B-site cation of the prepared La2CuSnO6 film is Cu. We have also succeeded in controlling the Cu/Sn ordering in the perovskite structure by changing the deposition temperature. The dielectric constant of the layered thin film is as twice as that of the random film suggesting the large anisotropic dielectric property of La2CuSnO6.View full abstractDownload PDF (1214K)
Special Issue: A New Development of Hard Material Technologies
Summarization
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Hideaki Matsubara2008 Volume 55 Issue 8 Pages 574
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSDownload PDF (107K)
Memorial Lecture of JSPM Award
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Hitoshi Sumiya, Tetsuo Irifune2008 Volume 55 Issue 8 Pages 575-581
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSSuper-hard nano-polycrystalline diamond up to 5 mm in diameter has been successfully synthesized by direct conversion from high-purity graphite under static pressures above 15 GPa and temperatures above 2573 K. The polycrystalline diamond has a very fine texture consisting of diamond grains of several tens of nanometer in size, and has an extremely high hardness, which is equivalent to or even higher than that of single crystal diamonds. It is presumed that the microstructural features (very fine mixed structure consisting of granular and lamellar grains, no secondary phases) lead to the extremely high hardness. The very fine microstructure and extremely high hardness of the polycrystalline diamond promise well its applications as high-precision and high-efficiency cutting tools of the next generation.View full abstractDownload PDF (1452K)
Paper
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Shingo Nakane, Yoshihiro Nakayama, Masaki Kato, Ken Hirota, Toshiyuki ...2008 Volume 55 Issue 8 Pages 582-587
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSCarbon nanofiber (CNF)-dispersed B4C nanocomposites containing 2.5 vol% Al2O3 as a sintering aid were fabricated directly from mixtures of amorphous B and C, CNF, and Al2O3 powders by pulsed electric-current pressure sintering (PECPS) at 1800°C for 10 min under 30 MPa in a vacuum. Dispersion of CNF into the B4C matrix up to ∼15 vol% introduced the enhancement of densification. A 15 vol% CNF/B4C nanocomposite revealed excellent mechanical properties: a bending strength (σb) of ∼710 MPa, a Vickers hardness (Hv) of ∼36 GPa, and a fracture toughness (KIC) of ∼7.6 MPa·m1/2, in comparison with those (σb∼530 MPa, Hv∼29 GPa, and KIC∼4.3 MPa·m1/2) of monolithic B4C.
Interfaces between CNF and B4C matrix were investigated using high-resolution TEM and Eels. Thin Al-B-C-O layer with a several nm order thickness was observed along with CNF, and Eels showed that the densification and mechanical properties of CNF/B4C nanocomposites might be related to this thin binding layer.View full abstractDownload PDF (1206K) -
Shigeaki Sugiyama, Satoshi Sato, Hitoshi Taimatsu2008 Volume 55 Issue 8 Pages 588-592
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSWC-W2C-TiC ceramics were prepared by reactive hot-pressing of WC and Ti powder mixtures at 1800°C, and were examined for reaction products, microstructure and mechanical properties. As the mole fraction x of Ti in the powder mixtures (1-x)WC-xTi was increased, the reactant WC was decreased and the products W2C, TiC and (Ti, W)C was increased. Sintered bodies were dense up to x=0.1. Above this value, the porosity of sintered bodies was increased, and their mechanical properties were much degraded in comparison with WC. Sintered bodies for x=0.05 to 0.075 had relatively good mechanical properties: Young's modulus, Vickers hardness and fracture toughness values higher than 500 GPa, 24 GPa and 4.5 MPa m1/2, respectively.View full abstractDownload PDF (792K) -
Keizo Kobayashi, Kimihiro Ozaki, Shuji Tada, Toshiyuki Nishio, Sachie ...2008 Volume 55 Issue 8 Pages 593-598
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSThe new process that combined a pulsed current sintering and mechanical alloying for a short time was developed to sinter WC-FeAl hard metal homogeneously. WC-11.5mass%FeAl alloy was synthesized in this process, and the sintering mechanism was clarified. In this process, it developed that FeAl phase was synthesized after molten Al generated during a sintering. Furthermore, the effect of the WC particle size on the mechanical properties of WC-11.5mass%FeAl alloy was examined. As a result, the sintered body having transverse rupture strength of 1.7 GPa was provided in this process by using a WC powder of average particle diameter 2.0 μm. When amount of FeAl of the WC-FeAl alloy was increased, the FeAl phase of the sintered body became coarse. Therefore the transverse rupture strength and the hardness of the WC-30mass%FeAl alloy lowered than those of WC-11.5mass%FeAl alloy. When WC-11.5mass%FeAl alloy with a WC powder of average particle diameter 2.0 μm was synthesized in this process, the large size sintered body of the 100 mm diameter was able to be produced.View full abstractDownload PDF (1417K) -
Kenji Metoki, Hiroki Koike, Toshiyuki Takahashi, Koji Hayashi2008 Volume 55 Issue 8 Pages 599-606
Published: 2008
Released on J-STAGE: November 27, 2008
JOURNAL OPEN ACCESSThe steel-cutting type is changing from wet process type to semi-dry or dry process type, and the cutting speed is turning to higher range in recent years. The cemented carbides for such cutting tools needs high creep resistance as well as high wear resistance and high fracture toughness. In this study, the effect of WC grain size distribution on the steady state creep rate was investigated on WC-Cr3C2-Co cemented carbides for getting a guiding principle of the improvement of the creep resistance. It was found that the steady state creep rate at a fixed mean grain size became considerably smaller together with the increase of creep rupture time by widening the grain size distribution. The results were considered from the viewpoint of the climbing motion of dislocations pile-uped in front of WC grains by using three kinds of model alloys.View full abstractDownload PDF (1342K)
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