Effect of strain rate on dynamic recrystallization mechanism of Mg-Gd-Y-Sm-Zr alloy during hot compression

Strain rate plays an important role in the hot deformation process of materials. In this work, hot compression experiments were conducted on Mg-Gd-Y-Sm-Zr alloy at the strain rates of 0.001-1 s-1 by Gleeble thermal simulation machine. The deformation behavior and microstructure evolution were studied in detail, and the dynamic recrystallization (DRX) mechanism was discussed. The results show that the flow stress of the alloy increases with the increasing strain rate. Deformation bands (DBs) are formed inside some grains at the strain rates of 0.1-1 s-1, which increase interfaces in the microstructure and hinder the dislocation movement. DRX grains are formed at the regions of DBs and original high angle grain boundaries (HAGBs). The DRX mechanism at high strain rates includes DBs induced DRX and discontinuous dynamic recrystallization (DDRX). At low strain rates and small strain, the dislocations first accumulate at the original HAGBs, and DDRX occurs in the alloy. The subgrains with low angle grain boundaries (LAGBs) are formed inside the initial grains through sufficient dynamic recovery (DRV) as strain increases, and LAGBs will gradually transform into HAGBs with the increasing misorientation angle. The DRX mechanism shows the synergistic effect of DDRX and continuous dynamic recrystallization (CDRX) at low strain rates.