Enhanced formability of Al-Mg-Si-Zn alloy sheet via dislocation structure and texture during cold rolling

The effects of cold rolling deformation on microstructure, texture, and formability of Al-Mg-Si-Zn alloy were systematically investigated using OM, SEM, TEM, XRD, and tensile tests. The results indicated that the effect of cold rolling deformation on the recrystallized microstructure and texture of the sheets mainly depended on the differences in dislocation structure and texture distribution. With the increase of cold rolling deformation, the dislocation structure gradually changed from a mixture of density dislocation walls and microbands to a lamellar bands structure, the large-angle boundary gradually increased, and the size of dislocation cells gradually decreased, which indicated a gradual increase of the stored deformation energy. In addition, the deformation texture increased gradually with the raise of cold rolling deformation. After T4P treatment, the recrystallized grain size gradually reduced with the increase of cold rolling deformation. The main recrystallization textures in the sheets with 41 % and 55 % deformation were Cube {001}<100> and CubeRD {310}<001> textures, respectively. The CubeND {001}<310> texture was predominantly present in the sheets with 69 % and 82 % deformation, meanwhile some P {011}<233> texture was also observed in the sheets with 82 % deformation. It was found that the dislocation structure and deformation texture distribution formed in the sheet with 82 % cold rolling deformation contributed to smaller recrystallized grains and weaker P texture after solution heat treatment, which enhanced the average plastic strain ratio r value and improved the formability.