Atomistic simulations of shock compression of single crystal and core-shell Cu@Ni nanoporous metals

Abstract

We have performed systematic molecular dynamics simulations to study the deformation behavior of a single crystal structure and a core-shell Cu@Ni nanoporous (NP) structure under shock loading for a wide range of shock intensities. Our results suggest that the core-shell structure exhibits less volume compression than the single crystal NP structure by virtue of its enhanced mechanical strength and associated interfacial strain-hardening under shock loading. The core-shell NP structure also demonstrates an increased shock-energy absorption efficiency of around 10.5% larger than the single crystal NP structure because of its additional Cu/Ni interface. The mechanisms of shock-induced deformation are observed to vary greatly with shock intensity. Pores are observed to collapse partially in both NP structures at very low shock intensity, up≤0.15 km/s. Complete collapsing of the pores through plastic deformation followed by direct crushing and formation of internal jetting and hot-spot have been observed at higher shock intensities. The evolution of microstructure and the underlying mechanisms operating at different shock intensity regimes have been investigated in this article. At a shock pressure of ∼6.05 GPa, i.e., up=0.75 km/s, the shock-induced deformed microstructure of both NP structures recovered through dynamic recrystallization. The postshock dynamic recrystallization has been observed to be mediated through rapid relaxation of shear stress followed by atomic rearrangements.