| In order to examine the effects of fast neutron irradiation on the precipitation process in Al-4%Cu alloy, hardness measurement and transmission electron microscope were employed. Specimens were irradiated to 2.8×10^(19), 3.4×10^(20) and 1.2×10^(21) nvt neutron doses in the Japan Materials Testing Reactor. Their electron micrographs prior to annealing or at the early stage of annealing at 200℃ showed G. P. 2 and even θ` plates, which it can not normally expect to form. The kinetics of growing of θ`plates in Al-4%Cu alloy were measured by means of hot stage transmission electron microscopy, and the lengthening data of θ`plate measured at each temperature and at each neutron dose have been interpreted in terms of the various equations for recent ledge theories of growth. The calculated diffusivity and frequency factor of Arrhenius` equation of specimen irradiated to 2.3×10^(19) nvt neutron are much larger than the un-irradiated one. This may be attributed to excess vacancies or interstitials produced by irradiation. It is concluded that neutron irradiation does not only bring the enhancement of heterogeneous nucleation, but also give rise to enhanced diffusion of solute atom, and the more the neutron dose increases, the greater the growth rate becomes. |
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