The role of co-clusters in the artificial aging of AA6061 and AA6060

Abstract

In this study the role of Mg, Si-co-clusters formed during long-term natural aging on the artificial aging behavior was investigated by hardness measurements for the alloys AA6061 and AA6060. It was found that kinetics and age hardening response of artificial aging at common temperatures (e.g. 170 °C) are lowered by a strong presence of co-clusters, but enhanced at high temperatures (e.g. 250 °C) for AA6061. Co-cluster formation in the alloy AA6060 increases the age hardening response at 170 °C, but barely influences kinetics in both temperature regions. The co-cluster dissolution was analyzed by a model based on temperature dependent reversion of the hardness, which showed similar activation energies for both alloys. It is supposed that the different behavior of the alloys AA6061 and AA6060 can be explained by solute-vacancy interactions.