Role of void shape on shock responses of nanoporous metallic glasses via molecular dynamics simulation

The void shape significantly affects the mechanical properties of nanoporous metallic glasses (NPMGs) under conventional loading. However, how the shock responses of NPMGs depend on the void shape has been rarely studied. In this work, shock simulations of Cu₅₀Zr₅₀ NPMGs containing voids with different shapes are performed by molecular dynamics, aiming to investigate the roles of the void shape on plastic deformation, void collapse, and spallation. The results reveal that the void shape has a significant effect on the peak value of the atomic strain curve and the fraction of atoms participating in the plastic deformation. There is a very weak dependence of the void collapse mode on the void shape under the weak shocks, where the voids collapse perpendicularly to the shock direction. As the shock strength increases, the void collapse mechanism gradually transforms into an internal jet, and the void shape plays an important role in the jet formation. During spallation, the initial damages tend to concentrate in the void collapse regions and then coalesce into large damages. The void shape influences the coalescence degree of spall damage. The spall strength is positively correlated with strain rate and local five-fold symmetry, but negatively correlated with temperature on the spall plane. Additionally, the void influences the spall strength due to the different distribution of the above factors after voids collapse in nanoporous samples.