稀土合金化高Si镁合金中的初生Mg2Si与Al-RE相在常规铸造条件下容易粗化，对其形态、尺寸与分布的有效控制是综合利用两种耐热相的强化作用和进一步提高镁合金耐热性的关键。本项目针对前期实验观察到Al-RE/Mg2Si相的弥散化、共析出现象展开深入研究，利用EBSD、HRTEM手段和三维重构技术对共析出相的结构、界面取向关系和形貌特征进行显微分析和定量表征，同时采用第一性原理计算，从原子尺度研究共析出相界面、稀土原子吸附Mg2Si表面的结构与特性，结合差热分析和热力学分析，阐明特定成分与温度条件下两种耐热相对各自析出行为的影响规律，以及稀土溶质原子对Mg2Si长大的影响规律，从而建立共析出相的晶体生长模型，揭示镁合金凝固过程中耐热相形核与长大的能量机制和结晶动力学机制。通过本研究，将有望提出基于成分与温度控制的多相合金组织调控方法，为开发高性能低成本耐热镁合金及其凝固控制技术提供科学依据。

It is very important to effectively control the morphology, size and distribution of the primary Mg2Si and Al-RE phases in the magnesium alloy with high content Si and RE (Rare Earth) elements in order to strengthen and improve the heat-resistant ability, because they are very easy to be coarsing under the conventional casting condition. .In this project, profound and systematic study on the dispersing and co-growth phenomenon of Al-RE and Mg2Si phases which was observed in our earlier research will be performed. The interfacial microstructure, orientation relationship and three-dimensional morphology of the co-growth phases will be quantitatively analyzed by using EBSD (Electron Back Scattering Diffraction), HRTEM (High-Resolution Transmission Electron Microscopy) and reconstruction technique based on the serial-sections method. Meanwhile, the first-principles calculation on atomic-scale will be employed to explore the structure and properties of Al-RE/Mg2Si interface and Mg2Si surface absorbed with RE atoms. The effect of two phases on the growth behavior of each other under special elemental content and in-situ reaction temperature, as well as the effect of RE atoms on the growth of Mg2Si phase will be analyzed by DSC (Differential Scanning Calorimetry) and thermodynamic methods. .The aim of this project is to build the growth model of co-growth phases, and to discover the energic mechanism of heterogeneous nucleation and the dynamic mechanism of primary Mg2Si phases’s growth. This study would be expected to propose a novel modifying method based on adjusting the content of RE elements and the reaction temperature, thus to provide scientific basis for developing high performance, low-cost heat-resistant magnesium alloy and the solidification controlling technique.