Dissolution behavior of second phases in 7050 aluminum alloy

The dissolution behavior of equilibrium η(MgZn2), T(Al2Mg3Zn3), S(Al2CuMg) and Fe-containing Al7Cu2Fe insoluble phases of hot rolled 7050 aluminum alloy during solid solution treatment was studied. The dissolution kinetics data of the equilibrium phases were obtained by means of in-situ scanning electron microscope tissue detection method. On the basis of bulk diffusion controlled dissolution kinetics models, the effects of curvature and interfacial reaction on atomic migration rate were introduced, and the dissolution kinetics models of η, T and S phases were established. The results show that η and T phases of 7050 aluminum alloy can be completely dissolved within 2 min at the usual solution temperature (470℃); it takes a long time for S phase to completely dissolve, while the Fe-containing phase hardly dissolves; the curvature has little effect on the phase dissolution, but the dissolution rate can be greatly reduced by the interfacial reaction. The predicted results of the second-phase dissolution kinetics models are in good agreement with the measured results, such as η, T and S phase, which can provide guidance for optimizing the solid solution process of Al-Zn-Mg-Cu alloy