Effects of pre-rolling temperature treatment on recrystallization, serrated flow and fracture behavior of twin-roll-cast Al–Mg alloy sheets

In this study, Al–Mg alloy twin-roll-cast sheets produced using a newly developed process were subjected to room-temperature rolling after liquid-nitrogen cooling, room-temperature treatment, and holding at 200 °C, respectively. The effects of different pre-rolling temperature treatments on damage behavior, recrystallization behavior, and tensile deformation stability were investigated. The results show that the pre-rolling temperature treatment significantly affected the number and distribution of void defects. A large number of debonding voids formed uniformly along the thickness direction in the T2 sample, whereas voids in T1 and T3 were mainly concentrated near the lower surface of the sheet. Among the three samples, T3 exhibited the fewest void defects. The EBSD results indicate that T3 required a higher annealing temperature to achieve sufficient recrystallization because of its lower deformation stored energy. Although T1 and T2 had similar stored energies, T2 exhibited a larger local stress gradient near grain boundaries and defects, which facilitated the initiation of recrystallization. The tensile results show that deformation introduced by rolling increased the critical strain for the Portevin–Le Chatelier (PLC) effect. As the annealing temperature increased, the PLC behavior shifted toward a lower critical strain, a higher serration frequency, and a lower stress-fluctuation amplitude. Compared with T2, T1 and T3 exhibited modified stress-distribution states, which delayed the decrease in the PLC critical strain during annealing. These results demonstrate that pre-rolling temperature treatment can affect the tensile properties and deformation stability of Al–Mg alloy sheets by regulating cold-rolling damage, dislocation distribution, and recrystallization behavior.