Author : Liang Tian and Lin Li

Nanostructured materials, whose characteristic microstructure size is under 100 nm, can be either single-phase nanocrystalline materials or multi-phase nanocomposite materials. Nanocrystalline materials can also be treated as nanocomposites with grain interior as matrix and grain boundary as secondary phase. The strengthening models of nanostructured materials resemble those strengthening models of conventional composite structures, but have substantial deviations from conventional strengthening mechanisms due to their distinctive nanoscale structure and the complex hierarchy of their nanoscale microstructure. This paper reviewed the current progress in developments of strengthening models for nanostructured materials with emphasis on single-phase nanocrystalline and multi-phase nanocomposite materials, which would help guide the design of new nanostructured materials and other similar nanoscale composite structures. Furthermore, practical large scale industrial applications of high strength nanostructured materials require these materials to possess decent formability, ductility or other functional properties to satisfy both structural and multifunctional applications. Therefore, the latest developments of novel nanostructured materials are discussed to highlight their potential of overcoming the strength ductility trade-off and strength-conductivity trade-off by various approaches. Their complex and distinctive nanoscale microstructure suggests the potential challenges and opportunities in developing new strengthening models for designing future advanced nanostructured materials with unprecedented properties.

Keywords: Nanostructured materials; strength; model; nanocomposite; interface; strength-ductility/conductivity trade-offs; size effect; nanoprecipitates and nanotubes; covetic materials; additive manufacturing

Article published in International Journal of Current Engineering and Technology, Vol.8, No.2 (March/April 2018)