电脉冲对纯金属晶界和位错的作用机理及微观结构定向调控

As a promising method in materials processing, electric-pulsing can significantly alter the microstructures and improve the mechanical properties of materials due to its unique thermal, electrical, magnetic and mechanical effects. However, the underlying mechanisms for the microstructures and properties modification by electric pulsing have not yet been fully understood, and thus limits the industrialization of this technology. In this project, the microstructure evolution in pure metals without solid-state phase transformation under the action of electric pulses will be directly investigated by in-situ or ex-situ TEM and EBSD techniques to reveal the dominating factor. In the view of thermodynamics, the analysis focuses on whether the electric pulses can provide enough extra driving force for the movement of grain boundaries and dislocations. In view of kinetics, the analysis will focus on the characteristics and dynamics of grain boundary and dislocation evolution under electric-pulsing. A series of experiments is designed to systematically separate the factors on the acceleration of microstructure evolution by the physical effects along with electric-pulsing, such as selective heating, electron wind force and magnetic force. Suggested by our preliminary work, special attention will be paid to check whether selective heating effect is the dominant factor or not. This project aims to reveal the effects on the grain boundary mobility and dislocation evolution by electric pulsing and uncover the dominating factor. The results can extend the understanding of the electric pulsing technique and bring its application into a designable stage.

电脉冲因其独特的热、电、磁、力等物理效应，可用于材料的微观结构调控，在材料加工及处理方面有广泛的应用前景；然而其作用机理尚不明确，大大限制了电脉冲技术的进一步开发和推广。本项目拟以常压下无固态相变的纯金属材料为对象，采用原位或外原位的TEM和EBSD方法直接观察微观结构的演化，分别从热力学和动力学的角度，系统研究电脉冲对材料微观结构的影响，揭示起主导作用的物理效应。热力学方面，重点关注电脉冲能否为晶界或位错的运动提供额外的足够的驱动力；动力学方面，主要关注电脉冲作用下的晶界和位错的行为特征及迁移速率。通过设计多重对比实验，对电脉冲的各种物理效应进行分离观察研究，比较选择性加热效应、电子风力和磁效应对加速微观结构演化的贡献，在申请者前期研究的基础上，进一步明确选择性加热效应是否为主控因素。本项研究旨在揭示电脉冲对位错和晶界运动演化的作用机制及主控因素，有助于推进电脉冲技术的定向设计与调控。