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Cho S.,Tohoku University | Kikuchi K.,Tohoku University | Miyazaki T.,Tohoku University | Kawasaki A.,Tohoku University | And 2 more authors.
Acta Materialia | Year: 2013

We have, for the first time, fabricated chromium (Cr) carbide nanostructures on multiwalled carbon nanotubes (MWCNTs) in a MWCNT-copper (Cu) composite by adding small amounts of Cr. A single nanocrystal of carbide was epitaxially grown on the sidewall of chemically treated MWCNTs through the diffusion of solute Cr atoms to defects in the MWCNTs. Carbide has an island-shaped morphology with a maximum size of several hundred nanometers. The phase of the generated Cr carbide nanostructures was mostly Cr7C 3, as determined by electron beam diffraction using the nanobeam diffraction mode of a transmission electron microscope. In particular, the Cr carbide nanostructures formed at radially unzipped sites were connected to the outermost wall and some inner walls of the MWCNTs. This is expected to increase the load-bearing capacity of the MWNCTs because the inner walls contribute to the load transfer, which is very effective for improving the mechanical and thermomechanical properties of the composites. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Okouchi H.,Fukuda Metal Foil and Powder Co. | Okouchi H.,Kumamoto University | Seki Y.,Kobelco Research Institute | Sekigawa T.,Mitsubishi Group | And 2 more authors.
Materials Science Forum | Year: 2010

Interests in magnesium alloys increase as eco-material for its lightweight, and many investigations have been carried out on the development of manufacturing processes and alloy development. In 2001, Mg97Zn 1Y2 (at%) alloy with a tensile yield strength of 610 MPa and an elongation of more than 5 % has been developed by rapidly solidified powder metallurgy (RS P/M) processing. The developed alloy was characterized by a novel phase with long period stacking ordered (LPSO) structure. Recently, we have investigated new compositions for LPSO RS P/M Mg-Zn-Y-X alloys in order to improve the corrosion resistance of the RS P/M Mg97Zn 1Y2 alloy with maintaining the superior mechanical properties. Consequently, we have developed a RS P/M Mg96.7Zn 0.85Y2Al0.45 alloy with high strength and high corrosion resistance. The RS P/M Mg96.7Zn0.85Y 2Al0.45 alloy contained the LPSO phase and exhibited a tensile strength of 525 MPa, an elongation of 9 % and a fatigue strength of 325 MPa, which were similar to those of the RS P/M Mg97Zn 1Y2 alloy. However, the corrosion resistance of the RS P/M Mg96.7Zn0.85Y2Al0.45 alloy was 1.5 times that of the RS P/M Mg97Zn1Y2 alloy. The specific tensile yield strength, the specific fatigue strength and the corrosion resistance of the RS P/M Mg96.7Zn0.85Y2Al 0.45 alloy were about 1.7 times, 1.8 times, and twice those of extra-super-duralumin (7075-T6 or 7075-T73), respectively. © (2010) Trans Tech Publications.

Miyakawa S.,Fukuda Metal Foil and Powder Co. | Nishida M.,Fukuda Metal Foil and Powder Co. | Nishiyama N.,Tohoku University | Miura H.,Tohoku University | Inoue A.,Tohoku University
Materials Research Society Symposium Proceedings | Year: 2011

A non-equilibrium Cu-Zr-Ag alloy was designed for the development of an alternative electric connector to Cu-Be alloys. This work aims at producing a Cu-Zr-Ag sheet using a hot-powder-rolling (HPR) process. The sheets were produced by a sequential process of HPR, preannealing, and cold rolling, using Cu 93.5Zr 5.5Ag 1 (at.%) alloy powder produced by an argon gas atomization method. The Cu 93.5Zr 5.5Ag 1 alloy sheet has a tensile strength of 1188 MPa and a conductivity of 33.2% IACS, which are similar values to those of Cu-Be alloys. In this paper, we optimize the conditions of the HPR process and reveal the correlation between the microstructure and properties of the Cu-Zr-Ag sheet produced by the HPR process. In addition, we discuss the alloy's applicability for use as a connecter material. © 2011 Materials Research Society.

Tanaka M.,Fukuda Metal Foil and Powder Co. | Terai S.,Fukuda Metal Foil and Powder Co. | Arami Y.,Fukuda Metal Foil and Powder Co.
Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy | Year: 2011

Cu-Ni-Sn system alloy had been found as high strength by causing the spinodal decomposition of the matrix. Properties of this alloy have been well investigated in the casting process, but not so well in the PM process. Therefore, the sintering and heat treating experiments using each of alloyed and mixed powders of Cu-9mass% Ni-8mass%Sn system carried out to reveal the better condition in the PM process. The results indicated that the sintered compacts using alloyed powder had all homogeneous structures, but those using mixed powder had heterogeneous structure. Furthermore, when sintered compacts using alloyed powder was aged at 623 K for 3.6 ks after sintering, it showed the highest strength with characteristic modulated structure caused by spinodal decomposition. In addition, it was necessary to cool the sintered compacts down to 573 K within 260 s after sintering to obtain supersaturated solid solution avoiding aging during the cooling process.

Kimura S.,Fukuda Metal Foil and Powder Co. | Kimura S.,University of Fukui | Nishimura F.,University of Fukui | Kim J.-H.,University of Fukui | And 2 more authors.
Journal of Fluorine Chemistry | Year: 2014

TiAl alloy particles (300 μm) prepared using plasma rotating electrode processing (PREP) were treated by surface fluorination using fluorine gas (F2) at 25-200 °C in pressure of 101 kPa for 3 h. Depending on the reaction temperature, the TiAl alloy surface components and structure differed markedly. Below 125°C, the oxides (TiO2 and Al 2O3) on TiAl particles were gradually changed into oxyfluorides (TiOF2, AlOF, etc.). At temperatures higher than 150 °C, the oxyfluorides were converted into fluorides (TiF4 and AlF3), which were hydrolyzed easily with moisture in air. Regarding the oxidation resistance, the oxyfluorides on the surface of TiAl were able to restrain less than 0.8% of the weight increase of TiAl particles, even at 1000 °C. However, the fluorides created at temperatures higher than 150 °C were affected negatively by the oxidation resistance. To optimize the beneficial effects of surface fluorination on the oxidation resistance of TiAl alloy, it is necessary to control the surface F/O contents. © 2014 Elsevier B.V. All rights reserved.

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