众所周知，结构相变本质上是从离散的微观结构发展到宏观性质变化的多尺度过程。传统实验和经典理论仅能获得相变行为与宏观条件之间的关系，无法给出相变发生的具体细节，对相变压力的分散性、相变过程的差异性等现象也难以给出物理解释。随着计算材料科学的兴起，基于晶格尺度的模拟方法为结构相变的机理研究提供了新的技术手段；与此同时，基于激光加载平台的原位X射线衍射技术迅速发展，使动载荷下结构相变的微观过程观察成为可能。由此，本项目综合运用不同物理尺度的模拟技术与宏微观实验诊断技术，以单晶铁BCC-HCP结构相变为例深入研究动载荷下结构相变的动力学性质。通过本项目研究，进一步揭示动载荷下结构相变的发生机理，阐明剪切变形和应变率两关键因素对相变阈值及形核模式的影响规律，建立结构相变形核与生长过程的多物理尺度描述方法，发展具有微观物理基础的结构相变动力学模型。

As we all know, structural transformation is essentially a multiscale process from discrete microstructure to macro property change. The traditional experiment and classical theory can only obtain the relationship between the transformation behavior and the macroscopic conditions, but can not give the specific details of the transformation. It is also difficult to give a physical explanation for the phenomena such as the dispersion of the transformation pressure and the difference of the transformation process. With the rise of Computational Materials Science, the simulation method based on lattice scale provides a new technical means for the study of the mechanism of structural transformation. At the same time, the in-situ X-ray diffraction technology based on laser loading platform develops rapidly, which makes it possible to observe the microscopic process of structural transformation under dynamic load. Therefore, the project plans to comprehensively use the simulation technology of different physical scales and the diagnosis technology of macroscopic and microscopic experiments, and take the BCC-HCP structural transformation in single crystal iron as an example to study the dynamic properties of structural transformation under dynamic load. Through the research of this project, the occurrence mechanism of structural transformation under dynamic load will be further revealed, the influence law of shear deformation and strain rate on transformation threshold and nucleation mode will be clarified, the multiscale description method of structural transformation nucleation and growth process will be established, and the dynamic model of structural transformation with microscopic physical basis will be developed.