抄録
The hot-rolled 7075 alloy specimen was solution-treated at 470°C, quenched, overaged at temperatures ranging from 200 to 400°C, cold-rolled and finally solution-treated at 470°C for different times. Recrystallized grain structures were examined by using optical, scanning and transmission electron microscopes.
It was confirmed that overaging at 400°C was most effective for getting fine recrystallized grains. This is due to the fact that coarseη precipitates larger than about 1μm, formed during overaging, were apt to act as nucleation sites for new grains in the deformed matrix during final heat-treatment. The cold-workability was improved, when the overaged specimen was successively aged at a lower temperature. In the specimen subjected to high cold-reduction, finer recrystallized grain structure was brought about.
