Mechanism of coarsening and deformation behavior of nanoporous Cu with varying relative density
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Mechanism of coarsening and deformation behavior of nanoporous Cu with varying relative density Lijie He1, Muhammad Hadi2, Haomin Liu1, Niaz Abdolrahim1,2,3,a) 1
Materials Science Program, University of Rochester, Rochester, New York 14627, USA Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, USA 3 Materials Science Program, University of Rochester, Rochester, New York 14627, USA; and Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, USA a) Address all correspondence to this author. e-mail: [email protected] 2
Received: 17 October 2019; accepted: 9 March 2020
In this study, uniaxial tensile loading simulations were performed on several single crystalline copper nanoporous (NP) structures with varying relative density (RD) via molecular dynamics simulations. From the results, two distinctive deformation patterns were observed: structures with a low RD went through coarsening, and structures with a high RD did not. During coarsening, dislocations are nucleated because of the high surface stress induced by the thin ligaments. These dislocations drive the merging of ligaments as well as nodes and lead to an increase in the differences between the size of nodes and ligaments. The disproportional nodes and ligaments result in a lowered strength. In addition, larger nodes provide more favorable circumstances for the formation of sessile dislocations, which hinder the movement of other propagating Shockley partials and result in strain hardening. Subsequently, lower RD structures offer anomalously high strain-hardening potential, whereas high RD structures show better strength but poor deformability. These results help us in better understanding the plastic behavior of NP structures as a function of their RD.
Introduction Nanoporous (NP) structures have now for a decade proven to have unique and favorable physical, chemical, and mechanical properties. These properties have in turn attracted much attention in harnessing these structures for use in our lives, from using them as electrochemical actuators and sensors [1, 2, 3, 4] to making filters for fuel cells [5]. The possibilities continue to grow daily, but we first aim to understand these structures in a more comprehensive capacity to accurately predict their mechanical behavior in a multitude of cases. To achieve this, NP structures of a range of metals, such as gold [4, 6, 7, 8, 9, 10], aluminum [11], and even Cu@Ni core–shell structure [12, 13, 14, 15], have been subjected to a magnitude of experimental and simulation-based testings, to map their mechanical properties and behaviors under different types of loading conditions. From these studies, it is revealed to us that unlike their counterparts in macroscale porous materials, morphological properties such as ligament size [16, 17, 18] and topological properties such as genus [19, 20] have a significant impact on the mechanical properties of the
ª Materials Research Society 2020
structures. On the one hand, the high surf
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