Origin of extension twinning-mediated static recrystallization and unique parallel alignment of (0001) poles to transverse direction in Mg-3Al-0.4Mn (mass%) alloy sheet

The origin of unique parallel alignment of (0001) poles to transverse direction (TD) was investigated using Mg-3Al-0.4Mn (mass%) alloy sheets rolled with different process conditions. When rolling was performed with intermediate reheating, the alloy showed a sluggish static recrystallization (SRX) behavior during post-annealing, facilitating the nucleation and growth of statically recrystallized grains from extension twins. This resulted in the apparent texture component with the parallel alignment of the (0001) poles to the TD, and the sheet exhibited good ductility for both the rolling direction (RD) and TD. In contrast, continuous rolling without intermediate reheating led to the formation of severely deformed regions near double twins. SRX was promoted at such regions, forming a typical basal textural feature with weak RD-split of the (0001) poles. Although extension twins were formed after the continuous rolling, SRX was facilitated at the severely deformed regions with double twins, and the formation of the unique alignment of the (0001) poles to the TD was suppressed. The RD-split texture led to the large elongation to failure along the RD, while it along the TD decreased owing to the narrow distribution of the (0001) poles toward the TD, resulting in the in-plane anisotropy in ductility.