Microstructure evolution and recrystallization kinetics of Al-Cu-Li alloy during thermo-mechanical treatment with overaging and electrically-assisted annealing

An improved thermomechanical treatment (N-ITMT) containing electrically-assisted recrystallization annealing (EARA) was proposed for manufacturing fine-grained Al-Cu-Li alloys, based on overaging, cold asymmetric rolling and EARA. The corresponding microstructure evolution and mechanical properties were investigated. The coarse precipitates introduced by overaging changed the deformed microstructure, produced particle affected zones and weakened the shear band (SB) compared with that with no precipitates. The combined action of electric current and coarse precipitates completed the recrystallization within 5 s and the solution process within 180 s, refined the grain size, and improved the strength and ductility. Discontinuous static recrystallization (dSRX) and continuous static recrystallization (cSRX) were both considered recrystallization mechanisms for specimens with or without coarse precipitates. The dSRX for specimens with coarse precipitates mainly featured particle-stimulated nucleation (PSN), while it featured shear band nucleation for specimens with no precipitates. The athermal effect of electric current not only decreased the activation energy, increasing the nucleation rate during dSRX, but also accelerated the diffusion of atoms and vacancies, promoting recrystallization and solution treatment. The proposed N-ITMT containing EARA possesses the synergetic capacity of optimizing the microstructure and improving the strength and ductility of Al-Cu-Li alloys.