Dynamic characterization of shock response in crystalline-metallic glass nanolaminates

The dynamic response of crystalline Cu-amorphous Cu63Zr37 nanolaminates under shock loading has been investigated in the present study by atomistic simulations to provide an insight of their overall deformation behavior with respect to different grain structure in the crystalline region. The dynamic characterization of the structural evolution of the nanolaminates during shock loading has been carried out based on various techniques including common neighbor analysis, dislocation analysis, Voronoi cluster analysis, pressure profile, and kinetic energy maps. Pressure profiles of single crystalline Cu-circle divide Cu63Zr37 metallic glass (SC/MG) nanolaminate at relatively low shock velocity show the presence of an elastic precursor in the crystalline region owing to the plane-plane collision phenomenon. Increasing the shock velocities in the SC/MG specimen results in FCC to BCC phase transition in the crystalline region. In particular, the crystalline/amorphous interface causes the generation of reflected rarefaction wave back into the crystalline region which aids in the evolution and stabilization of the BCC phase. In the NC/MG specimen, the misalignment of planes across different grains reduces the intensity of elastic precursor at low shock velocity due to disruption in the plane-plane collision, whereas the grain boundaries act as nucleating region for the BCC phase during the high-velocity shock propagation. The coordination number of the Cu63Zr37 glass region has been found to increase during high-velocity shock loading which can be accounted by the formation of <0 4 4 6> and <0 4 4 7> indexed Voronoi polyhedra. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.