The aging behaviour of a Mg-10Gd-3Y-1.0Zn-0.5Zr (wt.%) alloy with long-period stacking ordered phase at 275°C

Abstract

ABSTRACT We investigated the aging behaviour of a Mg-10Gd-3Y-1.0Zn-0.5Zr (wt.%) alloy with long-period stacking ordered (LPSO) phase at 275°C. Its peak hardness is about 116.4 HV after aging for 25 h. We unravelled the evolution of prismatic precipitates through transmission electron microscopy (TEM). The formation process is β′ (10h)→ β′ + β1 (15 h)→ β′ + β1 + β (≥20 h), where nano-scale phase benefits the transformation from β′ phase to β1 phase. In addition to the stable basal LPSO structures, the coexistence and competition balance between the prismatic β′, β1 and β phases synergistically contribute to the high hardness of the aged alloy. The number density of the prismatic precipitates is at the magnitude of 1020/m3. These prismatic precipitates during aging largely determine the hardness of the Mg alloys. The interaction between precipitates and stacking faults brings good compression property.