Harmony of Self‐Similarity: Overcoming the Strength–Ductility Trade‐Off Through Harmonic Structure

Abstract

Within the new generation of structural materials having heterogeneous microarchitectures, one of the top performers is harmonic structure (HS). Herewith, the exciting discovery of self‐similarity in their stress–strain behavior is reported. HS materials consist of the 3D skeleton of ultrafine grains (UFG) encompassing coarse‐grained (CG) counterparts. Our discovery simplifies the mathematical description of such a system and helps unraveling hidden patterns. Specifically, it is demonstrated that overcoming the strength–ductility trade‐off in HS occurs since its components have a characteristic strengthening mechanism, which realizes the synergy of three factors: 1) hetero‐deformation‐induced (HDI) strengthening of the CG phase, the deformation of which increases with acceleration with respect to the deformation of the entire sample; 2) the transition of the CG phase to the strengthened to saturation UFG phase; and 3) the work of UFG phase deformation, which increases with acceleration when the sample is strained due to the rapidly growing value of and the factor (2).