The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- ...The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- eld scanning transmission electron microscopy (HAADF-STEM). After under-ageing for 2 h, the precipitates in the alloy are ordered solute clusters with rare earth atomic columns exhibiting hexagonal ring structure, zigzag GP zones and β' in its early formation. After peak-ageing for 18 h, the precipitates are mainly β' and new rod-like β'p accompanied with β'. After over-ageing for 100 h, the precipitates are β',β1, long-period stacking ordered (LPSO) building block known as γ′ and 14H-LPSO.β' has the three-dimensional shape of convex lens with smaller length-to-width ratio viewed along <0001>α than that in the EW75 alloy. The excellent thermal stability of this alloy can be attributed to the γ' and 14H-LPSO retarding the growth of β' and β1, low diffusion rate of rare earth atoms and physical character of β' and β1.展开更多
基金Projects(51871195,51501015) supported by the National Natural Science Foundation of ChinaProject(TC170A5SU-1) supported by Ministry of Industry and Information Technology,China
文摘The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- eld scanning transmission electron microscopy (HAADF-STEM). After under-ageing for 2 h, the precipitates in the alloy are ordered solute clusters with rare earth atomic columns exhibiting hexagonal ring structure, zigzag GP zones and β' in its early formation. After peak-ageing for 18 h, the precipitates are mainly β' and new rod-like β'p accompanied with β'. After over-ageing for 100 h, the precipitates are β',β1, long-period stacking ordered (LPSO) building block known as γ′ and 14H-LPSO.β' has the three-dimensional shape of convex lens with smaller length-to-width ratio viewed along <0001>α than that in the EW75 alloy. The excellent thermal stability of this alloy can be attributed to the γ' and 14H-LPSO retarding the growth of β' and β1, low diffusion rate of rare earth atoms and physical character of β' and β1.
