Molecular dynamics simulation on the relationship between strength and shear band of bimodal structure materials

Abstract

A bimodal structure material, in which coarse grain region is surrounded by fine crystal grain region, shows excellent mechanical properties of both high strength and high ductility. However, the mechanism has not been fully understood yet. In this study, we perform tensile deformation tests of bimodal structure models with different finer grain networks via molecular dynamics simulations to investigate the influence of the network on the formation of shear bands that strongly govern the strength and ductility of bimodal materials. Three types of the network are considered: the shapes of the network are squire lattice, triangle lattice, and honeycomb structure. Initial plastic deformation occurs in fine grain regions because of the stress concentration due to the bimodal structure. As plastic deformation progresses, the crystal slips in each finer grain gradually combine to form a shear band in the finer grain network regions when the coarse grain regions are not an extension of the propagation direction of the shear band. Therefore, it is found that the shape of the finer grain network is important factor to design excellent mechanical properties of bimodal structure materials.