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Ishibashi, Toshihiro*; Tomota, Yo*; Sugaya, Satoshi*; Toyokawa, Hiroyuki*; Hirade, Tetsuya; Horita, Zenji*; Suzuki, Hiroshi
Materials Transactions, 54(9), p.1562 - 1569, 2013/09
Bulky averaged microstructural parameters like vacancy density, texture, intergranular stress, etc. for 99.99% Cu subjected to Equal-Channel Angular Pressing (ECAP) were investigated using Accelerator-based gamma-ray-Induced Positron Annihilation Spectroscopy (AIPAS) and neutron diffraction. The Doppler-broadening parameter (S) for positron annihilation peaks of AIPAS increased by the first ECAP cycle and then decreased slightly with further ECAP cycles. Upon annealing, the S recovered at a lower temperature for the eight-cycle ECAP processed sample than for the one-cycle processed sample. The texture and intergranular stresses generated by ECAP are determined by neutron diffraction analyses. Changes in FWHM and intensity of neutron diffractions monitored in situ during annealing indicate the early onset of recrystallization in the eight-cycle ECAP sample. These bulky averaged data show good agreements qualitatively with local SEM/EBSD observations and the results of mechanical tests.
Saito, Toru*; Suzuki, Hiroshi; Ishibashi, Toshihiro*; Tomota, Yo*
Nihon Kikai Gakkai Rombunshu, A, 74(744), p.1118 - 1125, 2008/08
The residual stresses in a forged part made of an aluminum alloy with grain size of approximately 1.0 mm were determined by neutron diffraction where the oscillation method was employed. An optimal range of the oscillation is discussed from the relations between the gauge volume and the number of crystal grain. It is found that the stress measurement could be performed with the oscillation range of 
3 degrees if 1000 grains exist in a gauge volume. The influence of diffraction plane reveals that adoption of (311) requires smaller oscillation angle than (111), (220) or (200). The hydrostatic tensile stress of about 100 MPa was observed inside the part, which was caused by thermal misfit strains caused during cooling after the heat treatment.
Saito, Toru; Terakado, Katsuyoshi*; Ishibashi, Toshihiro*; Katayanagi, Kazue*; Machiya, Shutaro; Tomota, Yo*
no journal, ,
no abstracts in English
-rays and application to material studyToyokawa, Hiroyuki*; Hirade, Tetsuya; Tomota, Yo*; Ishibashi, Toshihiro*; Sugaya, Satoshi*; Suzuki, Ryoichi*
no journal, ,
The brittleness of materials might be affected by defects, dislocations and impurities. However it is not well understood. Clarifying these problems is very important to make reliable models for estimating the degradation of materials for atomic energy. Injecting high energy photons with more than 1.02 MeV to materials can produce electron/positron pairs. Collimated MeV-energy--rays with several mm diameters can produce needle shaped positron distribution. By use of the produced positrons, it is possible to make 3D views of defect distribution or cross section of electro/positron pair production at deeper region of materials. This method is expected to be applied for measurements in atmosphere or high-temperature/high-pressure environments. We succeeded to obtain CT images of the transmission view and electron/positron pair production cross section of reinforcing bars in concrete by use of 5 mm diameter 9.1 MeV -rays. We also measured S-parameters for defects in metal samples.
