Microstructure and Texture Evolution of Mg-14Gd-0.5Zr Alloy during Rolling and Annealing under Different Temperatures

Mg alloys containing high rare earth (RE) elements are hard to be rolled due to their low ductility and high strength at low temperatures. Therefore, rolling at high temperatures is necessary for these alloys. In this work, a Mg-14Gd-0.5Zr (wt%) alloy was rolled one pass with 40% reduction at high temperatures over 450 degrees C. The effects of rolling temperature on the microstructure and dynamic recrystallization behavior were analyzed in detail by the electron backscattered diffraction (EBSD) method. The results revealed that the alloy shows good rollability at high temperature due to the activity of non-basal dislocations and twins. However, dynamic recrystallization is difficult to take place because of the easy activation of multi-slip system and thus more accumulated strain energy. However, Gd segregation was observed at the grain boundary and it is inferred that the segregation can partially enhance the dynamic recrystallization ratio. Statically recrystallized grains with large size took place after short-term inter-pass annealing treatment ranging from 450 degrees C to 500 degrees C, and formed basal texture. The result suggests that the formation of basal texture during short-term annealing treatment was attributed to the growth of dynamic recrystallized grains caused by weakened Gd segregation.