Static recrystallization mechanism in cold-rolled magnesium alloy with off-basal texture based on quasi in situ EBSD observations

Abstract

In this study, the deformation behavior of a Mg alloy with an off-basal texture during cold rolling and the static recrystallization in the cold-rolled sheet during subsequent annealing were investigated. To this end, an AZ31 sample having a texture with basal poles oriented along the transverse direction (TD) was rolled to a 20% reduction at room temperature, and the developed microstructure and its variation during annealing were analyzed by quasi in situ electron backscatter diffraction measurements. In the cold-rolled sample, numerous shear bands were formed throughout the material. In addition, several types of twins and intersections, such as {10–12} tension twins, {10–12}-{10–12} double twins, twin–twin intersections, and twin–grain boundary (GB) intersections, appeared in the non-shear-band region. After annealing for different durations, recrystallization occurred in both the shear-band and non-shear-band regions of the cold-rolled sample, but the recrystallization rates and grain growth behaviors remarkably differed between the two regions. At the early stages of annealing, recrystallization rapidly occurs in the shear bands with a large amount of internal strain energy. However, the formed grains are constrained within the shear bands during annealing. In the non-shear-band region, the recrystallization rate was slower than that in the shear-band region, but the recrystallized grains continued to form and grow during annealing, which strongly affected the final recrystallized microstructure. We conclude that the static recrystallization in grains with off-basal orientations and the resulting textural changes can provide new insight into developing Mg alloy sheets with high formability.