1Research Reactor Institute, Kyoto University, Osaka
By means of electron microscope observations based on the weak-beam method as well as the conventional technique, the size distributions of G.P.zones in Al-3.97%Cu alloy were measured for various stages of low temperature aging. The results obtained are summarized as follows:
(1) Weak-beam electron microscopy shows clearer images of G.P.zones and the size much closer to real size for small zones than the conventional technique. Individual G.P.zones could be identified and the diameters of G.P.(I)zones, 2-layer G.P.(II)zones and multi-layer G.P.(II)zones were measured by defining their structures.
(2) All of the size distributions measured represent the normal distribution function, except for very small G.P.(I)zones close to the minimum size of the zone structure. In case the G.P.(I)zone, 2-layer G.P.(II)zones and multilayer G.P.(II)zones coexist, each of these zone structures represents the normal distribution. The results suggest that the nucleation and growth of G.P.(I)zones as well as G.P.(II)zones occur by a random process.
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