【摘要】 镁合金长周期堆垛有序相(Long Period Stacking Ordered,LPSO)微观结构的清晰描述对镁合金LPSO相形成及强化机制的研究具有十分重要的意义。借助第一原理计算及高分辨成像模拟研究,我们得到了难以通过实验方法获得的关于镁合金LPSO相原子尺度微观结构的清晰描述。研究发现,Zn、Y合金元素在LPSO相中易于形成多种ZnmYn(Mg)团簇。基于Zn6Y8(Mg)团簇,我们构建了14H相晶体学模型Mg142Zn12Y16,其高分辨模拟像几乎再现了高分辨实验像。基于该模型,我们计算确定了14H相的热力学稳定性、弹性常数及弹性模量。此外,基于Mg-Zn-Y合金LPSO相的计算研究,我们推断X6Z8(Mg)团簇可看作镁合金Mg-X-Z中LPSO相形成的"特征结构单元",理论上可基于该"结构单元"构建相应镁合金LPSO相模型并通过计算方法判别该合金中LPSO相形成的可能性(X、Z为任一合金化元素)。更多还原

【Abstract】 The detailed characterization of the long-period stacking-ordered(LPSO) microstructures is absolutely essential for clarifying its formation and strengthen mechanism. We uncovered the microstructure of LPSO phase at atomic scale in detail via first-principles calculations and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM) simulations, which are difficult to be achieved solely using experimental methods. The study demonstrated that the additive elements of Zn and Y are easy to cluster into the forms of ZnmYn(Mg). The characteristics of 14 H LPSO phase observed with HAADF-STEM were successfully reproduced with the present 14 H LPSO structural model Mg142Zn12Y16, which was constructed based on the cluster of Zn6Y8(Mg). Furthermore, we calculated and evaluated the thermodynamic stability, the elastic constants and elastic moduli of 14 H LPSO phase based on the proposed model. Based on the present study, we inferred that the cluster of X6Z8(Mg) can be considered as the ‘characteristic structural units’ of LPSO phases, and thus then the structure and the formation probability of LPSO phase in Mg-X-Z alloy may be evaluated in theory based on these ‘characteristic structural units’(X and Z are any alloying elements).更多还原