长周期堆垛有序结构Mg-Zn-Y合金冲击加载下微观结构演变的原子模拟

The long-period-stacking ordered (LPSO) phase plays a critical role in producing excellent mechanical properties of magnesium alloys，and the formation of LPSO phase depends on stacking fault. At present, the mechanism of the microstructure evolution including stacking fault of LPSO magnesium alloys under shock-wave loading is not clear. Affect by the ultra-high temperature and pressure and ultra-fast reaction in shock-wave loading process, it is difficult to understand the microstructure evolution mechanism completely from experimental studies. In the present proposal, the modified analytic embedded atom method (MAEAM) potential functions are constructed, which is suitable to describe interatomic interaction between Mg-Zn, Mg-Y, Zn-Y and Mg-Zn-Y under the condition of high pressure. The non-equilibrium molecular dynamics associated with large scale parallel computing technique is used to simulate the microstructure evolution under shock-wave loading, and the main emphasis of our research is the influence of stacking fault on the formation and stability of LPSO phase. The effect of shock intensity and the LPSO phase volume fraction on the microstructure evolution is analyzed and the physical mechanism of the microstructure evolution under shock-wave loading is discussed. The accomplishment of the project will provide theoretical guidance for the high pressure synthesis of LPSO magnesium alloys.

长周期堆垛有序结构（LPSO）镁合金优异的力学性能依赖于LPSO相，而LPSO相的形成又取决于层错。目前，在冲击波作用下LPSO镁合金中层错等微观结构的演变机制尚不清楚。由于冲击波与材料的相互作用时间极短，且体系处于高压、高温极端状态，仅采用实验方法难以揭示冲击载荷下合金微观结构演变的物理机制。本课题拟构建适用于高压环境的分析型嵌入原子势函数，利用非平衡分子动力学方法结合大规模并行计算技术模拟研究长周期堆垛有序结构Mg-Zn-Y合金在冲击波作用下微观结构演变，重点研究堆垛层错对LPSO结构形成和稳定性的影响。分析冲击强度和LPSO相的体积分数对合金微观结构演变的影响规律，揭示冲击波作用下合金结构演变的物理机制，为LPSO镁合金的高压制备提供理论依据。

长周期堆垛有序结构（LPSO）镁合金优异的力学性能依赖于LPSO相，而LPSO相的形成又取决于层错。目前，在冲击波作用下LPSO镁合金中层错等微观结构的演变机制尚不清楚。由于冲击波与材料的相互作用时间极短，且体系处于高压、高温极端状态，仅采用实验方法难以揭示冲击载荷下合金微观结构演变的物理机制。本项目以半经验多体FS势函数模型构建了适用于高压冲击环境下的Mg、Zn、Y、MgZn、MgY、ZnY和MgZnY原子间相互作用势函数。利用所构建的势函数，采用非平衡分子动力学方法模拟研究了单晶镁、含棱柱形纳米孔的单晶镁、六方柱晶粒纳米多晶镁、含空位缺陷的单晶镁、单晶钇、镁锌合金、镁钇合金、具有长周期堆垛有序结构的镁锌钇合金的冲击响应和微观结构演变，从原子尺度揭示了冲击加载下镁及镁合金的塑性与相变机理，为高压冲击条件下镁合金的制备提供了理论依据。圆满完成了研究目标。