Hot deformation characterization of a novel Al-Zn-Mg-Cu aluminum alloy through processing map and microstructure evolution

Abstract

The isothermal compression experiments of a novel 7A36 aluminum alloy were performed on Gleeble3500 thermal simulation equipment at temperature range of 350 °C ∼ 450 °C with an interval of 25 °C and strain rates of 0.01 s−1 ∼ 10 s−1. The influence of deformation conditions on flow stress, microstructure and thermal process performance were investigated. The constitutive equation and processing map were established. The optical microscopy (OM), field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the microstructure evolution. The results indicate that 7A36 aluminum alloy has steady rheological characteristics and a trend to dynamic softening. The alloy has positive strain sensitivity, the flow stress decreases with increasing of deformation temperature and decreasing of strain rate. The estimated activation energy in constitutive model is 153.703 kJ mol−1 which is close to that self diffusion in pure aluminum. The constitutive equation and microstructure evolution during isothermal compression process confirmed that dynamic recrystallization (DRX) should be the soften mechanism. The processing map exists two safe regions of domain 1 (380 ∼ 450 °C, 1 ∼ 10 s−1) and domain 2 (350 ∼ 450 °C, 0.01 ∼ 1 s−1). The specimens deformed at 450 °C/0.01 s−1 in domain 2 is proposed to be the optimum hot-working condition.