Modeling the thermodynamic behavior and shock response of Ti systems at the atomic scales and the mesoscales

Abstract

The ‘quasi-coarse-grained dynamics’ (QCGD) method is extended to model the thermodynamic behavior and the shock response of HCP Ti systems at the mesoscales by coarse-graining the atomistic microstructure using representative atoms (R-atoms) and scaled interatomic potentials. To demonstrate the capability of the QCGD method, the melting behavior of a single-crystal slab of HCP Ti and the dynamic failure (spallation) behavior of nanocrystalline systems under shock loading conditions are first investigated using molecular dynamics (MD) simulations using an embedded atom method interatomic potential for Ti. The melting simulation suggests an interplay between the nucleation and propagation of the surface-induced heterogeneous melting and the nucleation and propagation of bulk homogeneous melting of the system. In addition, the spall strengths calculated using MD at strain rates of 1010 s−1 allow the development of improved models for the strain rate dependence of the spall strength determined experimentally at 105 s−1. The QCGD method is observed to be capable of reproducing the MD-predicted kinetics of melting and the shock response and spall failure of nanocrystalline Ti systems using a coarse-grained microstructure comprising of representative atoms (R-atoms). The QCGD simulations demonstrate the ability to model the mesoscale behavior of Ti systems by modeling the shock deformation and failure due to spallation of a 1 µm × 1 µm × 2 µm sized system at strain rates of 108 s−1 to bridge the gap between MD simulations and experiments.