Investigation on Fracture Mechanisms and Size Effects of Nano-Films Using Nano-Mechanical Testing System based upon in-situ Observations and Analyses

我们建立了一个实验装置来阐明亚微米厚金属薄膜的断裂力学和机制。该系统可在受控力学条件下对裂纹尖端等应力集中部位局部区域进行变形/断裂的原位FESEM观察和EBSD晶体学分析。系统实验阐明了厚度对铜纳米膜断裂韧性的影响（断裂韧性随厚度减小而减小）、铜纳米膜疲劳裂纹扩展的特征机制（裂纹尖端前形成的侵入/挤压扩展）、疲劳裂纹闭合的存在及其对疲劳裂纹扩展性能的影响，以及厚度对铝纳米膜蠕变性能的影响。

We developed an experimental setup for clarifying the mechanics and mechanisms of fracture in freestanding submicron-thick metallic films. This system can conduct in situ FESEM observation of deformation/fracture and EBSD crystallographic analysis on the local region at stress concentration sites such as crack tips under controlled mechanical conditions. Systematic experiments clarified the thickness effect on fracture toughness in copper nano-films where the fracture toughness decreases with a decrease in thickness, the characteristic fatigue crack growth mechanism of copper films where a fatigue crack propagates through intrusions/extrusions formed ahead of the crack tip, the presence of fatigue crack closure and the impact on the fatigue crack propagation property, and the effect of thickness on creep properties of aluminum nano-films.