Differences in Recrystallization Behavior between the Surface and Center Layers of Hot-Rolled Thick Plate of 5xxx Aluminum Alloy

Abstract:

A 5xxx series aluminum alloy hot-rolled thick plate with a final rolling temperature of 300?°C was used to systematically investigate the effects of different annealing processes (300–500?°C, 0.5–8?h) on its microstructure, mechanical properties, and electrical conductivity. The results show that increasing the annealing temperature significantly promotes recrystallization in the surface layer, while recrystallization in the center proceeds more slowly. Due to the high dislocation density and sufficient dynamic recovery introduced during hot rolling, continuous recrystallization via subgrain coalescence and growth dominates in the surface layer during annealing. In contrast, discontinuous recrystallization prevails in the center owing to its lower stored energy and fewer nucleation sites. After annealing at 450?°C for 2?h, the recrystallization fraction reaches 66.6?% at the surface but only 18.9?% in the center. With increasing annealing temperature, hardness and strength decrease, while elongation and electrical conductivity increase. Holding time has a relatively minor influence on mechanical properties, and 2?h is identified as the optimal duration. This study clarifies the mechanism underlying the difference in recrystallization behavior between the surface and center of hot-rolled thick plates during annealing, providing a theoretical basis for optimizing annealing processes.