Static recrystallization and grain growth during annealing of an extruded Mg–Zn–Zr–Er magnesium alloy

Microstructure stability is essential to maintain a fine grain structure for an alloy throughout its processing. The effects of Er addition and its existing form on the static recrystallization and grain growth during annealing of an extruded Mg–1.5Zn–0.6Zr magnesium alloy were studied in this paper. The results showed that microstructure stability was much improved by Er addition and the best thermability was obtained in 2 wt.% Er-containing alloy. For the incomplete dynamic recrystallization (DRX) microstructures extruded at a lower temperature of 350 °C, Er addition increased the resistance of static recrystallization; and for the complete DRX microstructures extruded at a relatively high temperature of 420 °C, Er addition suppressed grain growth. The difference in microstructure stability was then correlated with the microstructure features. Both the intermetallic phase and the solute atoms of Er in α-Mg matrix contributed to the microstructure stability. Moreover, it is believed that the existing form of Er–Zn atom pairs in the α-Mg solid solution favored the most to improve the thermal stability of the alloy.