Abstract
The Al-4wt%Cu-Sn alloys with up to 0.064wt% Sn were solution-treated at 520°C, quenched and sub-sequently aged at temperatures ranging from 0 to 200°C. Then, the aging curves of those specimens were studied in relation to aging temperatures (TA), aging times (tA) and Sn contents, by resistivity measurements and transmission electron microscopy.
The results obtained were as follows.
(1) The shape of aging curves showed a continuous change according to TA, tA and Sn content. For instance, the aging retardation in the initial stage of aging in ternary alloys was observed. However, the transition of this retardation to acceleration seemed to occur in the latter stage of aging, more clearly with increasing Sn contents and rising TA.
(2) Transmission electron micrographs of ternary alloys aged at 100°C showed co-existence of two sorts of G. P. zones different in dimension and distribution-density, suggesting that the aging behaviors of Al-Cu-Sn alloys was related to those zones: for instance, the aging retardation would be caused by one of two sorts of zones, that is, finely and densely distributed one at low TA. However, further experiments would be needed to make clear the aging behaviors of Al-Cu-Sn alloys.
