Quasi-in-situ observations of low-angle grain boundaries, twins and texture evolution during continuous annealing in a cold-rolled Mg Zn Gd alloy

Abstract The evolution of texture, low-angle grain boundaries and twins in a cold-rolled Mg-Zn-Gd alloy during continuous annealing at 250 °C were tracked by quasi-in-situ X-ray diffraction and quasi-in-situ electron backscatter diffraction method, and the influence of extension twins on texture was discussed. The results show that during the whole annealing process, the main texture component is always split toward transverse direction (TD) and the tilting angle hardly changes. However, the peak position changes between the two TD texture components. During continuous annealing, most pre-existing low-angle grain boundaries retain their original misorientation (including angles and axes) and hardly migrate. In addition, a new low-angle grain boundary occurs when two grains with similar orientation grow to connect with each other. Boundaries of pre-existing extension twins tend to migrate with different velocity. Moreover, with the migration, extension twins grow and gradually swallow their matrix grains completely, and thus re-orientate the TD orientations of twinned-grains from one side to another. Considering that nuclei display no preferred orientation between +TD and –TD, the changing peak position is considered to be caused by the migration of ETBs.