Study on inhomogeneous characteristics and optimize homogenization treatment parameter for large size DC ingots of Al-Zn-Mg-Cu alloys

The microstructures and mechanical properties evolution from the surface to the center of Al-Zn-Mg-Cu alloy ingots obtained by direct casting were revealed. Homogenization treatment research status for Al-Zn-Mg-Cu alloy has been reported in the paper which indicated that it was very necessary to optimize the homogenization parameter further. Based on the consideration of low energy consumption, easy operation, and good effect, a new homogenization parameter applying to large size DC ingots of Al-Zn-Mg-Cu alloy was determined. A new homogenization kinetic equation deriving from Gauss diffusion mathematical model was established and applied to verify the optimum homogenization parameter. In addition, the microstructure evolution, Brinell hardness, thermal analysis of the ingots treated at different parameters was studied. The final result shows that the microstructures and mechanical properties from the surface to the center of the ingots are not uniform and the optimum homogenization parameter is 470 °C × 12 h + 480 °C × 8 h which is also appropriate according to the new homogenization kinetic model.