当前，稀土镁合金因成本昂贵限制了其广泛应用。低成本Mg-Zn系合金兼具固溶和沉淀强化作用，在高强耐热方面极具潜力；其含GP区的与基体共格、半共格或非共格的主要强化相的沉淀过程尚未明确，探明其沉淀机制具有重要意义。本项目采用基于相-组织尺度的面心立方微观离散格点相场法，从基于电子-原子尺度的第一性原理计算中获取参数，构建三维含GP区的密排六方晶格微观相场模型，计算Mg-Zn、Mg-Zn-Cu、Mg-Zn-Cu-Zr合金在不同工艺下非平衡态的GP区、沉淀相序列、析出机制、原子占位、有序-无序、簇聚、体积分数、标度律等，重点研究早期序列、非平衡相、后期粗化、全程形貌演化；同时与第一性原理热力学、力学性质计算相耦合，研究各非平衡相的热力学稳定性、强度、塑性等宏观性能，并进行实验验证。本项目可拓展相场、第一性原理方法的适用范围，并为低成本高性能镁合金设计提供一种多尺度研究思路。

Mg-RE alloys are costly and limited in wide application; Mg-Zn alloys are cheaper and have high strength due to the aging solution and some precipitates. The potential precipitates can be coherent, semi-coherent and non coherent to its matrix, and the precipitates can be GP zones and some non equilibrium meta-stable phases or structures. Yet the corresponding precipitation sequence and mechanism is not yet clear. So, it’s significant to study the precipitation mechanism of Mg-Zn, Mg-Zn-Cu and Mg-Zn-Cu-Zr alloys under elastic field. Here, the Micro Phase Field Method-MPFM for fcc alloys system based on atom-phase-microstructure scale will be mainly employed, and the 3-Dimensional (3D) MPFM for hcp Magnesium alloys will be developed, some required parameters will be acquired by First Principles Method-FPM based on electronic-atomic scale. The potential precipitates, occupied sites, order-disorder, clustering, volume fraction, scaling law etc. of meta-stable phases for different Mg-Zn, Mg-Zn-Cu and Mg-Zn-Cu-Zr alloys at different degree of elastic field will be calculated, and the project planned to focus on studying the early precipitation sequence, the middle meta-stable phenomenon, the later coarsening law and the whole course morphology evolution of precipitates. Then the results will be compared with thermodynamic and mechanical properties of first-principles calculation to study the macroscopic properties of each meta-stable phase, such as thermodynamic stabilities, strength and plasticities, and will be verified through experiments. The project can help to provide a method for component and strengthening design of Mg-Zn, Mg-Zn-Cu and Mg-Zn-Cu-Zr alloys and extend the application of phase field simulation, and we expect to match a kind of multi-scale dynamic process description approaching the fact well without given model and route for the first-principles calculation.