Effects of Cu content on the precipitation process of Al-Zn-Mg alloys

摘要

Heat treatable Al-Zn-Mg alloys can be strengthened by the precipitation of second phase particles. In this article, four Al-Zn-Mg-based alloys with different Cu contents have been prepared. The effects of Cu content on the aging behaviors of the whole precipitation process of the prepared Al-Zn-Mg alloys have been investigated using hardness tests, transmission electron microscope, selected election diffraction patterns, and their simulations. It has been shown that a certain amount of Cu promotes a rapid hardening response at the early stage of aging and the nucleation of both GP-II zones and the η' precipitates. However, the addition of Cu above 3 wt% in alloys would decrease the accelerating effect of the transition from the GP-II zone to the η' precipitates. The η precursor has been observed in Cu-containing alloys and it can retard the transition to the stable phase.