EVOLUTION OF {111} RECRYSTALLIZATION TEXTURE IN Al-Mg-Si ALLOY SHEETS PROCESSED BY SYMMETRIC AND ASYMMETRIC COMBINATION ROLLING

摘要

A new rolling process consisting of conventional symmetric rolling and subsequent asymmetric warm rolling at relatively low reduction was adopted to improve deep drawability of 6xxx series aluminum alloys for automotive body panels. The aim of this rolling process is to rotate the P-fiber texture developed during symmetric rolling around the transverse direction (TD) with shear strain by asymmetric warm rolling, i.e. to form the TD-rotated P-fiber texture including {111} components favorable for increasing r-value. Recrystallization textures after T4-treatment for the symmetrically cold rolled and asymmetrically warm rolled AA6022 sheets varied significantly depending on roll speed ratio and reduction in asymmetric warm rolling. On the appropriate rolling conditions, {111 }<110> orientation was developed as a main component of recrystallization texture from the TD-rotated P-fiber rolling texture. Although deformed microstructure showed orientation distribution ranging from shear texture components to P-fiber components, the proportion of {111} and {001 (-oriented subgrains and recrystallized grains increased with the progress of recovery and recrystallization. The comparison of recrystallization behavior among materials asymmetrically rolled under different conditions suggests that deformed microstructure with a smaller {001}-oriented region is more favorable for growth of {111} recrystallized grains.