Microstructure-Property Relations in the Tensile Behavior of Bimodal Nanostructured Metals

Bimodal nanostructured (NS) metals realize the superior strength due to the strengthening of nanograined (NG) matrix, whereas their high ductility arises from the toughening of coarse-grained (CG) inclusions. Their overall strength and ductility can be influenced by 1) the fracture properties of CG and NG phases, 2) the distribution of CG inclusions, and 3) interfaces. Herein, a 3D cohesive finite element framework is built up and three classes of cohesive elements are developed: 1) cohesive elements embedded into the CG phase, 2) those embedded at the CG—NG interfaces, and 3) those embedded into the NG phase, to examine the tensile fracture of the bimodal NS Cu. The results indicate that the cohesive strength of NG phase is decisive to the overall performances and it also affects the roles of both the cohesive strength of CG phase and the distribution of CG inclusions. When the CG inclusions are array-arranged in the interior of the entire microstructure, the best overall strength and ductility can be obtained. In addition to these, both the strength and ductility of the bimodal NS Cu get stabilized when the cohesive strength and the fracture energy of interfaces are larger than those of CG phase.