The deformation behavior of BCC metal microstructures at high pressures has contributions from dislocation slip, deformation twinning, and phase transformation. The current efforts to investigate plasticity contributions in BCC metals are largely limited to real-time in situ x-ray diffraction (XRD) and single-crystal (sc) systems. However, the interpretations of the plasticity contributions from diffractograms are non-trivial, especially when multiple modes of deformation may be operating. Molecular dynamics (MD) simulations can successfully capture various deformation modes in metals and complement experiments using simulated diffractograms at various stages of evolution. MD simulations, however, are limited to time and length scales that are significantly smaller than experiments. The quasi-coarse-grained dynamics (QCGD) method is a new mesoscale method that extends MD simulations to larger length/time scales by coarse-graining an atomistic microstructure using representative atoms and scaling interatomic potentials to define their interactions. This talk will demonstrate the ability of QCGD simulations to model the evolution of microstructure and unravel the plasticity contributions from slip, twinning, and phase transformation behavior during the interaction of a shock wave with pre-existing porosity. Accurate modeling of this phenomenon at the mesoscales requires the ability to predict the nucleation and evolution of defects as well as the heat generation and dissipation mechanisms (hot spot formation) during void collapse. This talk will also discuss the use of virtual XRD to characterize the plasticity contributions in BCC Ta and Fe microstructures as predicted using MD simulations. The simulations suggest that the plasticity contributions and rates of void collapse as the wave interacts with the voids vary with shock pressures and void size, wherein larger void sizes and higher pressures result in increased temperatures (hot spots) and faster void collapse
2025-04-09 09:00:00
