3D microstructure-based simulations of strength and ductility of bimodal nanostructured metals

Bimodal nanostructured (NS) metals composed of coarse-grained (CG) and nano-/ultrafine-grained phases possess high strength and good ductility. In this paper, three-dimensional (3D) microstructure-based numerical simulations via the mechanism-based strain gradient plasticity and the Johnson-Cook failure model are performed to study the effects of the shape and distribution of CG inclusions on the strength and ductility of bimodal NS Cu. Our results show that both the shape and distribution of CG inclusions significantly affect the overall ductility, while the former has more prominent influences than the latter. Spherical CG inclusions result in excellent overall ductility under all considered spatial distributions, while CG inclusions with sharp edges and corners facilitate microcrack initiation. However, the earlier microcrack initiation does not necessarily lead to a lower ductility since proper combinations of the shape and distribution of CG inclusions may retard microcrack propagation and thus enhance the overall ductility. These 3D microstructure-based simulations are helpful for the design of bimodal NS metals with improved mechanical properties.