| Budget Amount *help |
¥7,200,000 (Direct Cost: ¥7,200,000)
Fiscal Year 1986: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1985: ¥6,400,000 (Direct Cost: ¥6,400,000)
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| Research Abstract |
In order to study the dynamical structure change during reversion in aluminium alloys, the synchrotron radiation-small-angle scattering measurements have been preformed. The major results obtained in the present study are summarized as follows.
(1) Depending on reversion temperatures, the structure changes have been classified into two categories as the complete reversion and the partial one. In the case of the complete reversion, the time-dependence of volume fraction of G.P. zones could be described in terms of Johnson-Mehl equation. Here the time exponent changed from 0.5 to 2.5 with increasing temperature.
(2) When the pre-aged specimen was annealed at temperatures above the zone solvus, the reversion process followed by two satges. At the first stage, the zone size did not decrease, but the solute concentration inside zones decreased. In the next stage, the zone size decreased to vanish.
(3) When the specimen was annealed at temperatures below the zone solvus, a part of zones survive
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d, of which the volume fraction could be calculated from the coexistence curve.
(4) When the pre-aged specimen was heated-up from room temperature with a constant heating rate, the solute concentration decreased firstly at relatively lower temperatures, but the zone size did not change. Temperature became enoughly so high that the zones resolved into the matrix according to the equilibrium relationship.
(5) In order to explain the above-mentioned experimental data, the theoretical model calculation using the diffusion equation with moving boundary has been performed.
(6) By using the fcc Ising lattice, the reversion process has been investigated.
(7) In conclusion, we made clear the mechanism of reversion process, by which the zones resolve into the matrix keeping the local equilibrium at the zone boundary.
(8) The structural change during the precipitation process in A1-Zn and A1-Ag alloys has been also investigated by means of the small angle scattering technique as well as the atom-probe field ion microscopy. Less
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