Deformation mechanisms and ductility enhancement in core-shell Cu@Ni nanoporous metals
LJ He and N Abdolrahim, COMPUTATIONAL MATERIALS SCIENCE, 150, 397-404 (2018).
In recent years, studies have shown that Nanoporous (NP) metals deform in a relatively brittle manner under tensile loading. We investigated the mechanical performance of NP structures under tensile loading using atomistic simulations. We compared the stress strain curves for two types of NP structures: a single crystal Cu NP structure and a core- shell Cu NP structure with a coating layer of Ni. Our results suggested that the core-shell structure exhibits increased Young's modulus and yield strength, probably due to the addition of the stiffer Ni atoms. The core-shell structure also exhibits an extensive enhancement in ductility with decreased strain-softening rate, reduced strain localization and delayed ultimate failure of the structure. Our simulations revealed that the enhancement of ductility could be attributed to three different mechanisms: the energy barrier of the coherent interface hindering dislocation movements, and increased accumulation of sessile dislocations as well as the nucleation and propagation of twin boundaries in connecting nodes in core-shell structure compared to single crystal Cu NP. All these mechanisms worked collectively and resulted in a stronger and more ductile NP metal.
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