Fatigue of Micro/Nano Metals

As materials with nanoscale dimensions are used in various industrial applications such as semiconductors, sensors, and micro- or nano-electromechanical-systems, the investigations on their mechanical behavior have been attracting many engineers/researchers. Especially, the knowledge on fracture mechanics/mechanism in the nanometer scale becomes important in terms of the reliability of small devices. Of course, this contributes an essential understanding of the strength of macro-components as well. The fatigue behavior is one of the key issues in terms of reliability. Extensive experimental works have been conducted on the crack initiation mechanism in the fatigue of bulk metals. These have reported that the dislocation structures induce specific slips on the surface known as persistent slip bands (PSBs), which brings about a crack on the surface. However, the size of under-structure is in micron-scale independent of specimen size. As small metals in the micron- or nanometer-scale cannot have enough space to form the understructure, the cracking mechanism must be different from the one of bulk counterparts. My team has investigated the fatigue behavior of micro- and nano-metals in this decade [1–11]. In this talk, we present the characteristic fatigue damage/failure process and mechanics of small metals. Especially, we introduce our novel experimental methodology of TEM/SEM in situ observations for the investigation.