Research on the effect of aging time on the microstructure of 7055 aluminum alloy

7055 aluminum alloy is a typical age-hardening alloy whose properties change with microstructural evolution as a result of heat treatment. In this paper, the microstructural evolution of the alloy after solid solution treatment and manual aging is examined using SEM and TEM. Results show that, as aging proceeds, the precipitation phase gradually enlarges and thickens following the precipitation sequence of supersaturated solid solution (SSSS) → GPI zone → GPⅡ zone → η" phase → η' phase; some η phases formed during aging, which have two different nucleation mechanisms: homogeneous nucleation and heterogeneous nucleation, the S phases of the latter being marginally larger in size than those of the former. There is a transition in the transformation of (Al3Cu) in GPII zone into η' -phase.