Mechanical Property and Microstructure of Rolled 7075 Alloy under Hot Compression with Different Original Grains

Abstract

The hot compression of rolled 7075 alloys with different heat treatments was performed. The temperature ranged from 200 to 400 °C, and the strain rate was 0.01 s−1. The stress level decreases with the increasing temperature during compression, and the strength of the alloy in the original condition is higher than that of solution-treated (ST) alloy at the same deformation condition. The alloys with different heat treatments exhibit different anisotropic behaviors at 200 °C; the anisotropy for the alloys in both conditions becomes weaker with increasing temperature. Then, the corresponding microstructure was studied. The alloy’s microstructure in its original condition consists of fiber grains; however, many equiaxed grains are found after solution treatment due to the recrystallization. The grains with different shapes lead to different anisotropic mechanical properties. For the alloys in both conditions, the density of the dislocation decreases with increasing temperature during compression, and a certain number of subgrains were found when deformed at 400 °C due to the higher driving force and a higher rate of atomic migration. Meanwhile, it is observed that the precipitates of the alloy become coarser during higher-temperature deformation. Dynamic softening is dominant in high-temperature deformation, decreasing stress during hot deformation.