Microstructural evolution and constitutive analysis combined with weight optimization method of Al-7.82Zn-1.96Mg-2.35Cu-0.11Zr alloy during hot deformation

Abstract

Isothermal hot compression tests of Al-7.82Zn-1.96Mg-2.35Cu-0.11Zr alloy were carried out on a Gleeble-3500 thermo-simulator in the temperature range of 573–733 K and strain rate range of 0.001–1 s−1. Stress-strain curves show that work hardening effect progressively exceeds softening effect with increasing strain rate. Microstructural evolution shows that two kinds of dynamic recrystallization exist in the hot compression process, which includes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) and the dominant mechanism is continuous dynamic recrystallization, which occurs under the combined action of progressive subgrain rotation and misorientation increase. Five constitutive models were constructed to describe the hot deformation behavior. Weight optimization model has lower average absolute relative errors (AARE) value of 2.78%, root mean square error (RMSE) value of 2.73 and higher correlation coefficient (R) value of 0.997, and gives weight factors at different temperatures. The revised constitutive model with considering the comprehensive effects of lattice diffusion, grain boundary diffusion and the results of weight optimization gives relatively high prediction precision with AARE value of 4.64%, RMSE value of 4.92 and R value of 0.995, which is second to that of weight optimization model. The main diffusion mechanism is dominated by grain boundary diffusion at 573–693 K and lattice diffusion at 733 K.