Understanding effects of deformation parameters on dynamic recrystallization-dependent superplasticity in an Al-Cu-Li alloy

Abstract

Aluminum alloys with initial unrecrystallized structures generally exhibit better superplasticity and are produced more efficiently and cost-effectively than fully recrystallized ones. However, the underlying recrystallization and deformation mechanisms of dynamic recrystallization (DRX)-dependent superplastic aluminium alloys under varying deformation parameters are not yet fully understood. This study investigates the effects of deformation parameters, Al₃Zr dispersoids, and coarse secondary particles on DRX and superplasticity in an Al-Cu-Li alloy. The alloy achieves a maximum elongation of 780 % at 430 °C and 0.002 s⁻¹, primarily due to continuous dynamic recrystallization (CDRX) and grain boundary sliding (GBS). Under optimal conditions, deformed grains transform into equiaxed recrystallized grains through sub-grain rotation and coalescence, with GBS dominating subsequent deformation. Lower Zener-Hollomon parameter (lnZ) conditions promote dynamic recovery (DRV) and sub-grain growth, hindering grain refinement and superplastic deformation. Conversely, higher lnZ values inhibit recrystallization due to insufficient thermal driving force and lower DRV, resulting in retained banded grains and reduced elongation. Cu-rich secondary phases enhance CDRX but lose efficacy with their dissolution and coarsening at low lnZ conditions. This work provides insights into DRX-dependent superplastic mechanisms and offers guidance for optimizing deformation parameters to enhance the performance of aluminum alloys.