中文摘要：

本文利用高分辨透射电子显微（HRTEM）技术并结合增强漫散射信息的HRTEM像处理分析方法研究了Mg-15.4Gd-1.6Nd（wt.%）合金200℃时效0.5 h后的结构特征。结果表明,合金时效初期的结构表现为稀土（RE）原子再分布形成的各种局域有序结构,其尺寸很小,一般只有几个nm,处于析出相形成的胚芽阶段。这些结构与传统意义上的β″相（DO19结构）有区别,本文称为β″关联相。在原子层次研究了β″关联相的结构,认为其由单层DO19结构、DO19结构和RE原子聚集三种基本的团簇单元组成。并利用高分辨像模拟法和动力学衍射模拟法进行了计算,结果表明本文建立的结构模型是合理的。

英文摘要：

By means of high-resolution electron transmission microscopy（HRTEM） and an image processing method with diffused reflections being relatively enhanced,structural characteristics in early aging stage at 200 ℃ has been studied for the Mg-15.4Gd-1.6Nd（wt.%） alloy.The results show that its early-aging-stage structure is characterized by formation of various local ordering of RE solute atoms due to their rearrangements in the Mg matrix.These local ordered structures which can act as embryos of precipitates are quite small with a size of only a few nanometers.The mixture consisted of various locally ordered structures is named a β″-related structure,which is structurally different from an ideal β″-phase with the D019 structure.Three types of ordered configurations of RE atoms,which are DO19-segment,mono-layered DO19 and RE-concentrated layers,have been identified in the β″-related structure.Both HRTEM imaging and dynamical electron diffraction simulations based on these ordered configurations and their mixture can reproduce the observed characteristics quite well,indicating that the model we proposed for the β″-related structure is reasonable.