Effect of heat treatment on hot deformation behavior and microstructure evolution of 7085 aluminum alloy

The hot deformation behaviors of 7085 aluminum alloy treated by (a) homogenization and (b) solution treatment were studied by a series of compression testing over a temperature range from 300 degrees C to 450 degrees C with strain rate from 0.0001 s(-1) to 1 s(-1). The results show the flow stresses are sensitive to the deformation parameters and heat treatment conditions. The peak flow stress decreases with increasing deformation temperature and decreasing strain rate. The peak flow stress of the alloy after solution treatment is significantly higher than that of the alloy after homogenization treatment under the similar compression condition, especially at low deformation temperature. The peak flow stresses for the alloys after homogenization and solution treatment can be represented by the Zener-Hollomon parameter (Z) in the hyperbolic-sine equation with the hot deformation activation energy of 187.4 kJ/mol and 318.9 kJ/mol, respectively. The differences of both treated alloys on hot deformation behaviors were mainly attributed to precipitation characteristic. The flow stresses softening for the alloy after homogenization treatment is accounted for dynamic recovery and dynamic recrystallization. However, dynamic precipitation and coarsening as well as dynamic recovery are responsible for the flow stress softening at low deformation temperature while dynamic recovery and dynamic recrystallization are the main reasons for the flow stress softening at high deformation temperature for the alloy after solution treatment. (C) 2012 Elsevier B.V. All rights reserved.