Effects of initial texture on deformation behavior during cold rolling and static recrystallization during subsequent annealing of AZ31 alloy

This study demonstrates that the initial texture of Mg alloy significantly affects the microstructure developed during cold rolling and the recrystallization behavior during subsequent annealing. In a sample with a texture oriented toward the normal direction (ND sample), thick and large-sized shear bands are intensively formed during cold rolling and the deformation is strongly localized along these bands. In contrast, in a sample with a texture oriented toward the transverse direction (TD sample), many {10-12} twins are formed at the early stage of cold rolling, and then, numerous small-sized shear bands are formed in these twins. Results of nanoindentation tests reveal that the cold-rolled ND sample has internal strain energy that is substantially concentrated along the shear bands, whereas the cold-rolled TD sample has a large amount of internal strain energy that is homogeneously distributed throughout the material; this latter behavior is strongly related to the extensive {10-12} twinning and the resultant microstructural variations in the TD sample. During subsequent annealing, recrystallization occurs locally along the shear bands in the ND sample, which leads to the formation of a bimodal grain structure comprising fine recrystallized grains and coarse unrecrystallized grains. In contrast, during subsequent annealing of the TD sample, static recrystallization occurs homogeneously throughout the material, which results in the formation of a uniform grain structure that mostly comprises equiaxed recrystallized grains.