Recrystallization behavior and its relationship with deformation mechanisms of a hot rolled Mg-Zn-Ca-Zr alloy

The microstructure-texture evolution of twin-roll-cast strips of an Mg-Zn-Ca-Zr alloy subjected to hot rolling and recrystallization annealing was investigated. Upon annealing, a distinctive change in the main texture components is observed from basal poles tilted towards the rolling direction (RD) to basal poles tilted towards the transverse direction (TD). X-ray diffraction analysis and EBSD measurements indicated that the distinct change of the texture components during recrystallization annealing is related to the weakening of the global texture intensity. It is demonstrated that the controlling mechanism of the microstructure development during the annealing is the growth of recovered volumes within deformed grains in a regime of a continuous type of recrystallization. Recrystallized grains developed from the {1 0-1 1}-{1 0-1 2} secondary twinned areas were observed, which show a restricted contribution to the recrystallized microstructure formed in a discontinuous type of recrystallization. In-grain misorientation axis analysis from the as-rolled microstructure indicates that prismatic < a > together with basal < a > slip become the dominant dislocation modes for the grains with their c-axis inclined relative to the normal direction. Several grains with the orientations of the basal pole split to the transverse direction are the {1 0-1 2} extension twins. This leads to a mirror symmetry of the basal poles along the transverse direction. It is observed that during recrystallization annealing, deformed volumes of grains containing {1 0-1 2} extension twins can recover effectively. This leads to the development of grains having the TD-split orientation in the regime of continuous static recrystallization also known as extended recovery.