Recrystallization behavior and kinetic analysis of an Al-Cu-Li alloy during hot deformation and subsequent heat treatment

Abstract

Al-Cu-Li alloys exhibit enhanced performance when possessing a high substructure proportion and a low recrystallization proportion. To achieve this, it necessitates a thorough understanding of recrystallization behavior during its hot working and heat treatment. To this end, isothermal compression tests were conducted on an Al-Cu-Li alloy in the temperature range of 350–500 °C and strain rate range of 0.01–10 s−1. The deformed specimens underwent solution treatment at 530 °C/2 h followed by water quenching, and aging treatment at 155 °C/27 h. The microstructures of the deformed and heat-treated specimens were characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). During hot deformation, continuous dynamic recrystallization (CDRX) dominates when the natural logarithm of the Zener-Hollomon parameter (lnZ) >26 and discontinuous dynamic recrystallization (DDRX) predominates when lnZ ≤ 26. A low proportion kinetic model associated with lnZ was constructed to describe the DRX behavior, and the model parameters were optimized using genetic algorithm (GA) to improve accuracy. During heat treatment, substantial static recrystallization (SRX) occurs following deformation at lnZ > 30, while it is limited when lnZ < 27. The comparison of average geometrically necessary dislocations (GNDs) before and after heat treatment reveals that the consumption of dislocations increases with increasing lnZ. Statistical analysis indicates that the density of low/medium angle grain boundaries (L/MAGBs) can be increased and the recrystallization fraction can be decreased within the lnZ range of 24 to 27. Therefore, these specific hot deformation conditions are recommended as the optimal hot working window for the Al-Cu-Li alloy.