超级三晶交对纳晶材料力学行为的影响研究

This project will be performed by adopting the experimental, theoretical and numerical methods in three different scales. The physical and mechanical behaviors of the finest grains and their nucleation and stability at triple junctions of nanocrystalline materials will be studied in nanoscale. In microscale, damage evolution and the final fracture morphology of nanocrystalline materials with super triple junctions will be experimentally studied under different plastic strains. The effects of damage modes and the amount of the super triple junctions will also be investigated. Then, the influence of super triple junctions on sliding of grain boundary as well as the nucleation and evolution of voids and cracks at the triple junctions will be studied. Finally, these results will be verified by comparing to the experimental studies. In macroscale, three batches of specimens with nanocrystalline Cu, nanocrystalline Ag and Cu-Ag alloy of different amount of super triple junctions will be prepared. We will also study the macro stress-strain, elongation, strain hardening and strain rate sensitivity of these nanocrystalline materials through experimental measurements. A new constitutive model and finite element method of bulk nanocrystalline materials with super triple junctions will be developed based on the nanoscale and microscale research results and be verified by the macromechanic data. Quantitative design and preparation of nanocrystalline materials containing super triple junctions will be strongly supported by the established micro mechanics theory in this project.

本项目拟采用实验、理论和计算机模拟研究结合为一体的方式开展研究工作，具体按三个不同尺度展开。纳观尺度下，研究最细小晶粒的物理、力学性质及其在纳晶材料三晶交部位的形成与稳定性。微观尺度下，实验分析含超级三晶交的纳晶材料在不同塑性应变下的损伤演化及最终的断口形貌与损伤，考察损伤方式及不同超级三晶交含量对材料损伤演化的影响，研究超级三晶交对普通纳米晶晶界滑移、三晶交处孔洞和裂纹的萌生与演化的影响，并与实验研究进行分析验证。宏观尺度下，实验制备具有不同超级三晶交含量的纳晶铜、纳晶银和纳晶银铜混合块体材料各一批，实测所制备纳晶材料的宏观应力应变、延伸率、应变硬化及应变率敏感性等。基于纳观和微观的研究成果，发展含超级三晶交纳晶材料的本构模型和有限元模拟方法，并在得到宏观力学数据验证的基础上进行完善和优化。通过上述工作，为寻求定量设计和试制含超级三晶交的纳晶材料奠定一系列新的微观力学理论基础。

本项目采用实验、理论和计算机模拟研究结合为一体的方式开展研究工作，具体按三个不同尺度展开。纳观尺度下，研究了最细小晶粒的物理、力学性质及其在纳晶材料三晶交部位的形成与稳定性。微观尺度下，实验分析了含超级三晶交的纳晶材料在不同塑性应变下的损伤演化及最终的断口形貌与损伤，获得了不同超级三晶交含量对材料损伤演化的影响，得到了超级三晶交对普通纳米晶晶界滑移、三晶交处孔洞和裂纹的萌生与演化的影响，并与实验研究进行分析验证。宏观尺度下，实验制备了具有不同超级三晶交含量的纳晶铜、纳晶银和纳晶银铜混合块体材料各一批，实测了所制备纳晶材料的宏观应力应变、延伸率、应变硬化及应变率敏感性等。基于纳观和微观的研究成果，提出了含超级三晶交纳晶材料的本构模型，并在得到宏观力学数据验证的基础上进行了完善和优化。上述工作为寻求定量设计和试制含超级三晶交的纳晶材料奠定一系列新的微观力学理论基础。