The scale effect on the yield strength of nanocrystalline materials

The microstructure of the nanocrystalline can be divided generally into two parts: grain and interface. When the grain size is about or less than 10 nm, the interface can be divided into grain boundary and triple junctions. The mechanical performance of nanocrystalline materials with complicated microstructures is greatly different from that of the coarse grain materials. In this paper, the nanocrystalline material is considered as a composite with three phases: the grain core, the grain boundaries, and the triple junction. The model analysis for nanocrystalline material deformation is established and the relationship between yield strength and grain size is obtained. The obtained result explains the inverse Hall–Petch relation.