Duplex Aging Treatment Research Articles

Structure and strength of an Al-Zn-Mg alloy after duplex aging treatment

Multiple aging has been applied to an Al-7.5 wt.% Zn-2.5 wt.% Mg alloy with a view to producing a duplex distribution of precipitate particles. A combination of a coarse distribution of η phase, together with finer η′ and GP zones, has been obtained. Transmission electron microscopy shows that coarse, well-defined slip bands occur on deformation of the alloy after a single aging treatment to peak hardness. A more homogeneous dislocation distribution is observed in the material after double aging treatment because of the presence of the incoherent phase in the alloy. Tensile tests indicate that no improvement in ductility occurs with duplex aging, but this may be owing to the larger grain boundary PFZ present.