Nanocrystalline Materials: Mechanical Properties

Abstract

Nanocrystalline (nc) materials are defined as the ones with the average grain size less than 100nm. As the grain size is considered as the characteristic length scale in defining these materials, they fall under the class of 3-dimensional nanomaterials (Gleiter, 2000). These novel class of materials have exhibited exciting and often superior properties in comparison to their conventional counterparts (Kumar et al., 2003, Meyers et al., 2006). As the grain size is reduced to such a finer scale, the volume fraction of grain boundaries and other interfacial regions increases and these interfacial regions play a very significant role in governing the final inherent behavior of a given material. While adapting these materials for various engineering applications either at bulk scale or small scale, the mechanical properties, that they display both in as-fabricated condition as well as during service, are very important. This article will review the present state of the art understanding of the major mechanical properties of nc materials. This will include discussions of the elastic properties, hardness and strength, ductility, deformation and fracture behavior, superplasticity, strain rate sensitivity and the possible deformation mechanisms. The deformation characteristics are discussed based both on direct experimental results and computer simulation studies.