冲击相变成核与生长过程对波剖面演化影响的研究

Wave profile is an important window to understand the phenomena of shock induced phase transitions, but the approach to interpretating the experimental wave profile are usually based on the assumption that the macroscopic properties of the mixed phase are homogeneous,therefore those models can only interpret the experiment results at the macro level, and can not understand the experimental wave profile from a more fundermental phase transitions mechanism.In this project, we propose a new approach to studying the wave profile evolution based on nucleation and growth. The main content will include following.Establish a multiphase phase-field model which can be applied to study the problems of shock indueced phase transitions; study the correspondence relation between the wave profile features and the informations of nucleation and growth; explore the influence of the macro loading conditions to the process of nucleation and growth in the mesoscale; carry out a series of wave profile measurement experiments of pre-heated bismuth, study the multiphase phase transition dynamics based on the numerical simulation of the wave profile.By the study of this project, it is expected to construct a new approach to studying the wave profile evolution of shock induced phase transitions,which can be used to interpret experimental results more precision and guide the exact experiment,and hence help us to better understand the phenomena of shock induced phase transitions.

波剖面是认识冲击相变现象的重要窗口，但目前解读实验波剖面的模型一般以混合相宏观性质均匀作为基本假定，因此只能在宏观层面解读实验结果，不能基于更基本的相变机制来认识实验波剖面。本项目拟采用相场模型，建立一种基于新相成核与生长的研究冲击相变波剖面演化的新方法。具体研究内容包括：建立适用于研究冲击相变波剖面演化的多相相场模型；研究实验波剖面的典型特征与样品内部成核状态和相边界传播规律的对应关系；研究宏观加载条件对细观尺度上的成核与生长过程的影响；开展预加热金属铋的波剖面测量实验，基于波剖面的拟合研究铋的多相相变动力学过程。通过本项目的研究，有望建立一种研究冲击相变波剖面演化的新方法，可用于准确解读实验结果及指导精密物理实验，有助于深入对冲击相变现象的认识。

波剖面的测量及解读是冲击相变研究的重要方法，经典的基于宏观混合相模型的解读方法不考虑相变的实际物理机制（尤其是成核与生长过程），波剖面作为认识冲击相变现象的重要窗口，其所包含的相变动力学信息并未被充分发掘。本项目建立了描述冲击相变动力学的相场模型，可基于新相成核与生长的思想研究波剖面的演化；通过理论和数值模拟研究了微观相边界传播及相互作用的基本规律，阐明了相边界传播的动力学关系在应力波与相边界的相互作用中具有的关键影响，其决定着反射波的性质及强度；基于成核与生长的思想解读实验波剖面所隐含的成核密度及分布、相边界传播的动力学特性。本项目所建立的模型及方法，对于深入认识和揭示冲击相变的微介观物理机制、准确解读实验数据、设计精密物理实验具有重要意义。