Effects of initial microstructure on hot deformation behavior of Al-7.9Zn-2.7Mg-2.0Cu (wt%) alloy

The homogenization (470 degrees C/24 h) and annealing treatment (400 degrees C/1 h) before hot deformation were applied in the Al-7.9Zn-2.7Mg-2.0Cu alloy to control the initial microstructure. The secondary phase were remained after annealing treatment and most of secondary phases dissolved into the matrix after the homogenization. The hot deformation behaviors of homogenized and annealed Al-7.9Zn-2.7Mg-2.0Cu alloys were investigated, and effects of initial microstructure were discussed. The solute atoms dissolved into the matrix, and dynamic re crystallization was difficult at low deformation temperature in the homogenized alloy. In the case of the annealed alloy, the particles were remained to serve as nucleation sites, which can promote recrystallization by particle stimulated nucleation (PSN) at low deformation temperature. With increasing the deformation temperature, PSN effect was weak, and continuous dynamic recrystallization (CDRX) was the dominant deformation mechanism in the homogenized and annealed alloys. CDRX was easier and high-efficiency at high deformation temperature and high strain rate in the homogenized alloy.