Age-Hardening Behavior and Phase Transformation of Mg-9.2gd-1.9y-1.8zn-0.5zr Alloy

In this paper, the age-hardening behavior and phase transformation of Mg-9.2Gd-1.9Y-1.8Zn-0.5Zr alloy were systematically studied. The results showed that the aging strengthening effect of the alloy is significant at 225°C. In under-aging stage, the second phases are mainly nucleation, supplemented by growth. In peak-aging stage, the nucleation and growth of the second phases proceed simultaneously. A large number of main strengthening phases (β′ and β 1 phases) precipitated, and the hardness of the alloy increased by 21.7% to the peak. In over-aging stage, the second phases are dominated by growth, supplemented by nucleation. With the increase of aging time, the size of β 1 phases increased and changed to stable β phases, and the hardness of the alloy decreased. Subsequently, β and LPSO phases gathered in the alloy, and lamellar LPSO phases transformed into block LPSO phases