| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2005: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2004: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
Aluminum transition-metal alloy systems have many quasicrystal - phases. A reversible quasicrystal-crystal transformation was studied for the Al-Ni-Fe decagonal quasicrystal by high resolution X-ray diffraction method. To make a comparison, a successive transformation of the Al-Ni-Co decagonal quasicrystal was studied.
(1) Ideal single crystals of the Al-Ni-Fe decagonal phase, which has no phason strains, were obtained by being annealed at 850℃. After being annealed at 600℃, these decagonal single crystals were transformed completely into Al_<13>Fe_4 approximant single crystals without twin structures. Next, after being re-annealed at 850℃, the ideal decagonal phase was recovered from the approximant phase. Moreover after being annealed at 700℃, the decagonal phase were transformed again into the approximant phase without twin structures. Therefore, the reversible transformation between the decagonal quasicrystal and the approximant crystal was observed in single crystals of the Al-Ni-Fe decagonal phase.
(2) In the Co-rich Al-Ni-Co decagonal phase classified by 5f and 5f_<HT>, single crystals of several groups with different phason strains were obtained. In extremely Co-rich region at the high temperature 1000℃, ideal decagonal quasicrystals were appeared. In comparatively Co-poor region above 900℃, one-dimensional quasicrystals, which has one-dimensional linear phason strain along one two-fold axis, were formed. Moreover, semi-one-dimensional quasicrystal, which has small linear phason strain along another two-fold axis in addition to above-mentioned strains, was discovered by synchrotron x-ray measurements. At 800℃, decagonal phases with random phason strains were observed. Therefore, these results suggest that the Co-rich Al-Ni-Co decagonal phase shows the successive transformation from a decagonal quasicrystal through a one-dimensional quasicrystal to an approximant crystal. And the dependence of phason strains on the composition and the temperature was decided.
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