Effect of a new upsetting process with large height-to-diameter ratio on the microstructure of Mg-Gd-Y-Zn-Zr alloy

In this study, a new upsetting process with large height-to-diameter ratio is proposed, which breaks the limitation of the traditional upsetting process on the height-to-diameter ratio of the billet. The Mg-9.5Gd-4Y-2.2Zn-0.5Zr (wt.%) alloy bar with a height-to-diameter ratio of 6.5 was successfully upset and its microstructure evolution was investigated. The alloy underwent dynamic recrystallization (DRX) during upsetting, and the microstructure refinement was obvious, with the highest recrystallization ratio of 46.3 % in the center of the billet and the average grain size of 20.2 mu m. The basal texture was roughly parallel to the metal flow lines in each region, and weakened as the recrystallization rate increases.