Deformation behavior, microstructure evolution and hot workability of Mg-3.7Gd-2.9Y-0.7Zn-0.7Zr alloy

The deformation behavior of Mg-3.7Gd-2.9Y-0.7Zn-0.7Zr magnesium alloy has been investigated by thermal compression test conducted on a Gleeble-1500D thermal simulator in the temperature range of 375-475 °C and strain rate range of 0.001-1 s-1. It indicates that the addition of RE, the introduction of LPSO phases and the segregation of Zr element near the grain boundaries contributed to the high activate energy (Q = 354.08 kJ/mol) of the present Mg alloy. The long period stacking ordered (LPSO) phase could not only strengthen the alloy and contribute to the nucleation of dynamic recrystallization, but also re-precipitate in the recrystallization grains. The processing map based on MDMM and Murty’s instability criterion was more precise than the one based on DMM and Prasad’s instability criterion. The processing map exhibited two workable regions with sufficient dynamic recrystallization: 415-435 °C, 0.001-0.006 s-1 and 435-475 °C, 0.01-1 s-1. The flow instability was prone to occur at low temperature and high strain rate associated with the appearance of bands of flow localization and cracking.