Dynamic characterization of shock wave responses of bicontinuous nanoporous amorphous alloys: Microstructure effects

Abstract

Nanoporous amorphous alloys (NP-AAs) are of great interest due to their lightweight, enhanced plasticity, and high elastic limit. Here, we explore the shock responses of Cu50Zr50 NP-AAs with bicontinuous structure through non-equilibrium molecular dynamics (MD) simulations, focusing on the effects of shock velocity, ligament size, and solid fraction. Hugoniot jump conditions are used to verify our MD results. It is found that the shock behaviors of NP-AAs have strong solid fraction-dependence, but low sensitivity to ligament size. A higher solid fraction can promote the development of shear transformation zones, facilitating shock wave propagation. With increasing piston velocity, solid fraction, or decreasing ligament size, the shock wavefront becomes steeper. The quantitive analyses of the evolution of atomic shear strain and Voronoi polyhedra demonstrate that the damage of shock wave on the NP-AAs becomes more severe, with the decreasing solid fraction/ligament size or increasing piston velocity. Two modes of void collapse are revealed: the mutual extrusion of ligaments at low piston velocities, and the filling of jets and melt materials at high piston velocities. In addition, we observe that the internal jet causes the temperature distribution along the lateral directions to be heterogeneous and is more difficult to generate in NP-AAs with high solid fractions, because of the small pores and poor pore connectivity.