Improvement of superplasticity in AA5083 by equal channel angular extrusion and rolling

Al-Mg-Mn alloy AA5083 has been processed by equal channel angular extrusion (ECAE) followed by hot and cold rolling. The grain structure, crystallographic texture, intermetallic phases and superplasticity were investigated and compared with a conventionally hot and cold rolled AA5083 sheet. The intensive shear strain in ECAE has a very strong breakdown effect on the dendritic cast structure, which effectively changes the volume fraction and size of the intermetallic particles that provide particle stimulated nucleation upon recrystallisation. Consequently, the combination of ECAE and rolling leads to a finer and more thermally stable grain structure, with fewer very coarse constituent particles, resulting in a significant improvement in superplasticity through enhanced grain boundary sliding, with retarded formation and linkage of cavities.