The microstructural evolution of an Al–Zn–Mg–Cu alloy during homogenization

The evolution of microstructure in an Al–Zn–Mg–Cu alloy during homogenization has been studied. The evolution of primary eutectic structure consists of three processes as follows: dissolving of Mg(Zn,Cu,Al)2, nucleation and growth of Al2CuMg particles while its fraction increases, coarsening of Al2CuMg together with the decreasing of its fraction. A novel phase transformation of the primary eutectic structure from Mg(Zn,Cu,Al)2 to Al2CuMg is observed during homogenization. The Al2CuMg particles formed in the primary MgZn2 phase, and grew along the eutectic microstructure. The size and morphology of Al7Cu2Fe exhibited no change.