The role of Al content on deformation behavior and related texture evolution during hot rolling of Mg-Al-Zn alloys

Effect of Al addition on microstructure and texture evolution during hot rolling of Mg alloys was investigated using Mg-(3, 6 and 9 wt%)Al-Zn series alloys. The results showed deformation behaviors, including twinning, dynamic recrystallization and activation of slip system, were affected by the increase of Al content. Compared with AZ31 Mg alloys, the rolled AZ91 sample exhibited strong basal texture and intensity of basal texture decreased by increasing rolling strain. Unlike double twins and contraction twins which were commonly observed in the hot rolling of AZ31 Mg alloys, twinning behavior was strongly suppressed by the addition of Al content. It was observed some grain-like extension twins nucleated inside unrecrystallized grains with ultrafine size in AZ91. The size of dynamic recrystallized grains in AZ91 was ultrafine compared to that of AZ31 due to pinning effect produced by small Mg17Al12 particles. These recrystallized grains were distributed along grain boundaries and would continuously coordinate further deformation strain after their nucleation. The increase of the area fraction of recrystallized grains resulted in a texture weakness during large strain rolling in AZ91. Geometrically necessary dislocation information was analyzed for the rolled samples. It showed prismatic slip took an advantage in AZ31 rather than AZ91 during hot rolling, which may be a reason for the weaker basal texture of unrecrystallized grains in AZ31.