Investigation of precipitation behavior and related hardening in AA 7055 aluminum alloy

The precipitation behavior and related hardening in AA 7055 aluminum alloy aged at 120 and 160 degrees C was investigated in detail. GPI zones were the dominant phase in the alloy upon ageing at 120 degrees C for 60 min. The metastable eta' phase begins to precipitate in the alloy after being aged at 120 degrees C for 60 min, and turns to be the main phase after ageing for 300 min. When the alloy was aged at 160 degrees C, the precipitation was significantly promoted. The results also revealed that the transformation of small GPI zone to eta' phase is the dominant mechanism for eta' formation. Formation and growth of GPI zones and eta' phases led to the increase of the yield strength, while formation and coarsening of eta resulted in the decrease of the strength. eta' is responsible for the peak hardening of this alloy. (C) 2008 Elsevier B.V. All rights reserved.