Enhancing the strength and ductility of pure metal via multi-scale and multitype composite heterostructuring

High strength and good ductility are essential for the engineering applications of structural materials, yet these two attributes often do not coexist. In the present study, a composite heterostructuring designed with multi-scale, lamellar, and bimodal was developed to deal with the trade-off between strength and ductility. This heterostructuring includes coarse-grain soft domains arranged in a lamellar structure within a matrix characterized by both fine and ultrafine grains arranged in a bimodal structure created through a straightforward thermo-mechanical process. The gradient in strength among various grain structures generates a gradient in strain during deformation. This promotes the generation of additional geometrically necessary dislocations (GNDs) in the soft domain, favouring strength enhancement. The ongoing and efficient accumulation and evolution of GNDs within the soft domains are further developed into the dislocation cells and subgrain boundaries, which, on the other hand, increase the strain hardening and, hence, the ductility.