The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform

Hidehiro Yoshida - One of the best experts on this subject based on the ideXlab platform.

  • Superplastic deformation of transparent hydroxyapatite
    Scripta Materialia, 2013
    Co-Authors: Hidehiro Yoshida, Byung-nam Kim, Hyoung-won Son, Young-hwan Han, Sukyoung Kim
    Abstract:

    Abstract Transparent, nanocrystalline hydroxyapatite with an average Grain Size of 170 nm was fabricated by spark plasma sintering. The superplastic flow behavior of the hydroxyapatite specimen was examined at temperatures ranging from 950 to 1050 °C. The hydroxyapatite specimens exhibited superplasticity under the test conditions examined. A maximum elongation of 486% was achieved at 1000 °C and an initial strain rate of 1.0 × 10 –4  s −1 . The excellent tensile ductility in transparent, nanocrystalline hydroxyapatite was attributed to the very Fine Grain Size and pore-free microstructure.

  • spark plasma sintering of transparent alumina
    Scripta Materialia, 2007
    Co-Authors: Keijiro Hiraga, Koji Morita, Hidehiro Yoshida
    Abstract:

    Transparent alumina with a Fine Grain Size (0.27 μm) was obtained by controlling the heating rate during spark plasma sintering processing. The alumina sintered at 1150 °C with a heating rate of 8 °C/min has a residual porosity of 0.03% and an in-line transmission of 47% for a wavelength of 640 nm. We show that a low heating rate has an effect on the densification and transparency of alumina for sintering at 1150 °C.

Tetsuya Senda - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Recrystallization during the Sliding Wear of Alumina at Elevated Temperatures
    Journal of the American Ceramic Society, 1996
    Co-Authors: Hanning Xiao, Tetsuya Senda, Eiichi Yasuda
    Abstract:

    In previous studies, a very Fine Grain Size surface layer of several micrometer thickness has been consistently observed in the wear track of alumina couples after wear at elevated temperatures. Detailed microstructural observations have revealed that dynamic recrystallization is the most probable mechanism for the surface layer formation. In this study, Grain Size and thickness of the surface layer are reported for the samples tested under various wear conditions. Both the Grain Size and the thickness are dependent on the testing temperature, nominal contact pressure, and the sliding velocity. The strain rate and the local temperature of the wear surface are estimated taking frictional heat into account and the Zener-Hollomon parameter Z = e exp (Q/RT) is calculated. A logarithmic plot of the Grain Size and Z yields a good linear relationship. This linearity and the slope of -0.21, similar to that previously reported for metals, further substantiate that dynamic recrystallization occurring in the wear surface is responsible for the formation of the Fine Grain Size surface layer.

  • Sliding Wear of Oxide Ceramics at Elevated Temperatures
    Journal of the American Ceramic Society, 1995
    Co-Authors: Tetsuya Senda, John Drennan, Reg Mcpherson
    Abstract:

    Sliding wear tests of sintered alumina and mullite consistently showed that the wear loss significantly decreased at 800°C and above by an order of magnitude. Microscopy of the room-temperature wear surfaces revealed a feature suggesting material removal by brittle fracture. Microscopy of the wear surface at 1000°C revealed that the immediate vicinity of the wear surface consisted of a very Fine Grain Size polycrystalline structure. The zone below this consisted of heavily deformed Grains containing dense dislocation networks forming a cellular structure. The results suggest that, at high temperatures, dynamic recrystallization at the wear surface forms the Fine Grain Size structure which suppresses further material removal.

Kenji Higashi - One of the best experts on this subject based on the ideXlab platform.

  • High-strain-rate superplasticity in an AZ91 magnesium alloy processed by ingot metallurgy route
    MATERIALS TRANSACTIONS, 2002
    Co-Authors: Hiroyuki Watanabe, Toshiji Mukai, Koichi Ishikawa, Kenji Higashi
    Abstract:

    High-strain-rate superplastic magnesium alloy, AZ91, was processed through the ingot metallurgy route. The relationship between working temperature and resulting Grain Size indicated that the Grain Size tends to decrease with decreasing working temperature in AZ91. Based on this preliminary result, the ingot was hot extruded at a relatively low temperature of 523 K with a reduction ratio of 44. A very Fine Grain Size of 1.7 µm was attained only by hot extrusion. The Fine-Grained structure was stable blow 573 K. Owing to the Fine Grain Size, high-strain-rate superplasticity was observed at temperatures of ∼ 548 K.

  • high strain rate superplasticity at low temperature in a zk61 magnesium alloy produced by powder metallurgy
    Scripta Materialia, 1999
    Co-Authors: Hiroyuki Watanabe, Toshiji Mukai, Mamoru Mabuchi, Kenji Higashi
    Abstract:

    In the present study, superplastic behavior of a pseudo single phase magnesium alloy, ZK61, was investigated at about half the absolute melting point. The material was produced by the P/M route, and had a Fine Grain Size of [approximately]500 nm. It is demonstrated that the P/M ZK61 alloy can behave in a superplastic manner at a high strain rate of 1 [times] 10[sup [minus]2] s[sup [minus]1] albeit at the low temperature.

  • High-strain-rate superplasticity in ultrahigh-carbon steel containing 10 wt.% Al (UHCS-10Al)
    Scripta Materialia, 1996
    Co-Authors: Eric M. Taleff, Kenji Higashi, Mamoru Nagao, Oleg D. Sherby
    Abstract:

    The present study represents a new processing route by which high-strain-rate superplasticity can be obtained in a two-phase, Fe-base alloy. For this study, an ultrahigh-carbon steel containing 10 wt.% Al (UHCS-10Al) was processed by a powder-metallurgy technique. Mechanical attrition was used to introduce a large degree of cold work into pre-alloyed powders, creating the very Fine microstructural features necessary for high-strain-rate superplasticity. Because this material contains two phases, {alpha}-Fe and {kappa}-carbide (Fe{sub 3}AlC{sub x} where x = 0.5 to 1), in the range of processing temperatures, a Fine Grain Size was produced upon consolidation and retained during deformation. It is this Fine Grain Size which is responsible for the high-strain-rate superplastic behavior observed.

Reg Mcpherson - One of the best experts on this subject based on the ideXlab platform.

  • Sliding Wear of Oxide Ceramics at Elevated Temperatures
    Journal of the American Ceramic Society, 1995
    Co-Authors: Tetsuya Senda, John Drennan, Reg Mcpherson
    Abstract:

    Sliding wear tests of sintered alumina and mullite consistently showed that the wear loss significantly decreased at 800°C and above by an order of magnitude. Microscopy of the room-temperature wear surfaces revealed a feature suggesting material removal by brittle fracture. Microscopy of the wear surface at 1000°C revealed that the immediate vicinity of the wear surface consisted of a very Fine Grain Size polycrystalline structure. The zone below this consisted of heavily deformed Grains containing dense dislocation networks forming a cellular structure. The results suggest that, at high temperatures, dynamic recrystallization at the wear surface forms the Fine Grain Size structure which suppresses further material removal.

Eiichi Yasuda - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Recrystallization during the Sliding Wear of Alumina at Elevated Temperatures
    Journal of the American Ceramic Society, 1996
    Co-Authors: Hanning Xiao, Tetsuya Senda, Eiichi Yasuda
    Abstract:

    In previous studies, a very Fine Grain Size surface layer of several micrometer thickness has been consistently observed in the wear track of alumina couples after wear at elevated temperatures. Detailed microstructural observations have revealed that dynamic recrystallization is the most probable mechanism for the surface layer formation. In this study, Grain Size and thickness of the surface layer are reported for the samples tested under various wear conditions. Both the Grain Size and the thickness are dependent on the testing temperature, nominal contact pressure, and the sliding velocity. The strain rate and the local temperature of the wear surface are estimated taking frictional heat into account and the Zener-Hollomon parameter Z = e exp (Q/RT) is calculated. A logarithmic plot of the Grain Size and Z yields a good linear relationship. This linearity and the slope of -0.21, similar to that previously reported for metals, further substantiate that dynamic recrystallization occurring in the wear surface is responsible for the formation of the Fine Grain Size surface layer.