Mg-7Gd-3Y-1Nd-1Zn-0.5Zr合金在240℃等温时效过程中析出相的演化（英文）

Precipitate evolution in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃

采用TEM和HAADF-STEM技术,研究Mg-7Gd-3Y-1Nd-1Zn-0.5Zr合金在240℃等温时效过程中析出相的形态与晶体学特征。经2h欠时效,析出相为稀土原子柱呈六角环状结构的有序溶质团簇、之字形GP区和早期形成的β'相。经18h峰时效,析出相主要为β'相和与其伴生的一种新型棒状相β'p。经100h过时效,析出相为β'相、β1相、长程堆垛有序(LPSO)构建块γ′相和14H-LPSO。β'相三维形貌呈凸透镜状,沿<0001>α方向观察,其长宽比小于EW75合金中β'相的长宽比。该合金优异的热稳定性归功于γ′和14H-LPSO阻碍β'和β1的生长、稀土原子低的扩散速率以及β'和β1相的物理特性。

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.