Dynamic recrystallization behavior and microstructure evolution of a new Mg-6Zn-1Gd-1Er alloy with and without pre-aging treatment

To compare the dynamic recrystallization (DRX) behavior, microstructure evolution, and texture change of a new Mg-6Zn-1Gd-1Er alloy with and without pre-aging treatment, the uniaxial hot compression tests were carried out in the range of 10−3 s−1-1 s−1 and 280 °C–380 °C. The results show that both the fraction and size of DRX grain increase with the increase of temperature, while the increase of strain rate shows the opposite trend. The microstructure mostly exists as a necklace structure, while there are a lot of twins in the microstructure at the condition of 280 °C/1 s−1. DRX grains mainly nucleate and grow through the mechanisms of continuous dynamic recrystallization (CDRX), particle stimulated nucleation (PSN), and twin-induced dynamic recrystallization (TDRX). The pre-aging treatment sample is more conducive to DRX than the solution heat-treated sample at the same deformation conditions. This is mainly because the deformation activation energy of the alloy with pre-aging treatment is lower, and the interaction of the pre-existed precipitates with dislocations promotes the DRX behavior. At the condition of 380 °C/10−3 s−1, compared with the solution heat-treated sample, the pyramidal slip was active in the deformed grains of PT of pre-aging treatment alloy, which corresponded to the PT split from CD to TD and tilt about 15°. Similarly, at the condition of 380 °C/1 s−1, the main deformed grains of PT1 and PT2 in the pre-aging treatment sample tilted the basal texture from CD to TD under the action of pyramidal slip to form a bimodal texture.