Strength and toughness of micro- and nano-structured materials: unified influence of composition, grain size and structural dimension

Strength (or hardness) and toughness of micro- and nano-structured grained materials are analysed, assuming the key role played by the interfaces. A new fractal approach is developed to unify the influences on the mechanical properties of volumetric grain content, grain size and structural dimension. In particular, the finding of grain size effect on material strength represents an extension of the well-known empirical Hall-Petch law. A fractal structural parameter, representing an extension of the Gurland's structural parameter, is proposed to investigate, design and optimise new materials. An experimental comparison on Poly-Crystalline Diamond and WC/Co alloy concludes the paper.