This study aims to develop an in situ observation technique of micro-sizedmicron-scale metal specimens under fully-reversed tension-compression cyclic loading and to investigate the unique cracking process in low-cycle fatigue. The fatigue experiment was conducted on a microscale single crystal copper micron-scale specimen under a constant displacement amplitude. While crystallographic slip spread over the entire test section during the tensile first half-cycle, a locally concentrated slip band appeared during reverse loading (compression). In situ observations using scanning electron microscopy revealed that crystallographic slip occurred only near the localized band in consecutive cycles, and strain localization due to slip bands led to nanoscale extrusion/intrusion at the surface. This indicates that, unlike during the fatigue of a typical bulk pure metal, no characteristic dislocation substructure was formed during the extrusion/intrusion process. The extrusion/intrusion was the cause of failure of the micro-sizedmicron-scale metal specimen in fatigue. Moreover, the process required a much higher stress amplitude than in the case of bulk copper specimen. Thus, the fatigue cracking process for micro-coppercopper micro-scale specimen differs significantly from that for bulk copper specimen.

本研究的目的是开发一种在原位的观察技术微尺寸微米级金属试样下完全反转拉伸-压缩循环加载，并调查在低循环疲劳的独特裂解过程。疲劳试验在一个进行微尺度单晶铜微米级试样恒定位移幅度下。虽然在拉伸的前半个周期中晶体学滑移遍及整个测试段，但在反向加载（压缩）过程中出现了局部集中的滑移带。原位使用扫描电子显微镜的观察表明，结晶滑移仅在连续循环中仅在局部带附近发生，并且由于滑带引起的应变局部化导致表面处的纳米级挤出/侵入。这表明，与典型的块状纯金属的疲劳过程不同，在挤压/挤压过程中没有形成特征性的位错亚结构。挤压/挤压是微米尺寸的微米级金属样品疲劳失效的原因。此外，与散装铜试样相比，该过程需要更高的应力幅度。因此，微铜铜微尺度试样的疲劳开裂过程与散装铜试样的差别很大。