亚微米结构纯铝在变形初期的加工硬化率比粗晶纯铝高很多，但位错密度却反常下降，还会表现出退火强化的现象。目前的认识仅局限于位错源强化起重要作用，但对于出现这些现象的具体机制还不清楚。本项目拟通过实验和模拟相结合的方法，比较亚微米晶与粗晶纯铝中位错源的开动、位错与晶界的相互作用及位错之间的相互作用等方面的差异，进一步分析这些因素与位错密度演化及加工硬化之间的联系。实验上，通过原位XRD拉伸实验测量位错密度随应变的演化，通过TEM原位拉伸，观察分析位错行为，分析亚微米结构材料高硬化率的关键因素。模拟上，综合考虑微观结构和这些关键因素的相互作用，建立联系微观位错行为与宏观力学性能的离散位错动力学模型，结合相场位错动力学和分子动力学模拟，进一步地分析和补充实验所揭示的规律。以期深入理解亚微米结构材料变形和退火强化的微观机理，为亚微米结构材料延伸率的改善提供新思路。

Submicron structured pure aluminum has much higher strain hardening rate than that of coarse grained aluminum at the early stage of tensile test, however, it exhibits dislocation density reduction upon straining and hardening upon heat treatment. So far, understanding of these phenomena is limited to the recognition that dislocation source hardening plays an important role therein. In this project, we will utilize both experimental and simulation tools and techniques to investigate the characteristics on of dislocation behaviors in three aspects: dislocation source activation, the interaction between dislocations and grain boundaries, and the inter-dislocation interactions. Experimentally, the dislocation density evolution will be measured and the dislocation behavior will be analyzed respectively by in-situ XRD and in-situ TEM tensile test, to identify the key factors determining the high hardening rate of submicron materials. In simulation, a discrete dislocation dynamics model will be developed to relate local dislocation bahaviors to macroscopic properties, by considering the specific microstructures and the above identified key factors. The model is complemented by phase field dislocation dynamics and molecular dynamics simulations. The experiments and simulations are expected to work complemently to reveal the details. This project will help to deepen our understanding of the micro mechanisms of deformation and annealing hardening in submicron structured materials, and help to explore new methods for improvement on uniform tensile elongation.