Hot Deformation and Dynamic Recrystallization of 7075 Al Alloy in the Extruded State

The thermal deformation behavior of extruded 7075 Al alloy under the conditions of strain rate of 0.001 ~ 1 s⁻¹, temperature of 350-500 °C and deformation of 30-70% was investigated by isothermal compression test. A strain-compensated Arrhenius constitutive equation was established. Based on the established dynamic recrystallization kinetic model, the influence of thermal deformation parameters on the dynamic recrystallization behavior of the specimens was investigated. In conjunction with the microstructure of the process specimens, the effects of strain rate, temperature and strain on the nucleation mechanism of dynamic recrystallization (DRX) were investigated. The results show that the DRX volume fraction increases with decreasing strain rate, increasing temperature and increasing degree of strain during thermal deformation. Continuous dynamic recrystallization (CDRX) prevails at high temperatures and low strain rates; while, geometrical dynamic recrystallization (GDRX) occurs at high strain. As the strain rate rises, discontinuous dynamic recrystallization (DDRX) becomes the primary DRX mode. The texture strength decreases as the degree of recrystallization increases, leading to a more homogeneous grain orientation distribution.