Abstract
The Al-4wt%Cu-Sn alloy specimens of 0.11.0mm thickness containing 00.066wt%Sn were solution-treated at 520°c, quenched and subsequently aged at temperatures ranged from 100 to 250°c. The secondary defects which would develop in those specimens were examined in relation to the specimen thickness, Sn contents and aging conditions by means of transmission electron microscopy. The results obtained were as follows.
(1) The defect structure was observed in each specimen only when the specimen was aged, and it changed with the specimen thickness; in other word, dislocation loops were only observed with the disappearence of helical dislocations when the specimen thickness exceeded about 0.3mm.
(2) Using the specimen of about 0.4mm thickness, it was confirmed that the loop size decreased and the loop density increased with increasing Sn contents under a given aging condition. In the specimens with higher Sn contents, they appeared to be almost stable during aging at low temperatures. The width of loop free zone formed near the grain boundary increased with increasing Sn contents and with lowering aging temperature.
(3) Some discussions were given as to the above phenomena, but the true influence of Sn atoms on the defect structure of the binary alloy could not be fully understood.
