Atomistic Modeling of Shock Loading in SiC Ceramics
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Atomistic Modeling of Shock Loading in SiC Ceramics Paulo S. Branicio and Jingyun Zhang Institute of High Performance Computing, Agency for Science, Technology and Research 1 Fusionopolis Way, 16-16 Connexis 138622, Singapore. ABSTRACT Large scale molecular-dynamics simulations of plane shock loading in SiC are performed to reveal the interplay between shock-induced compaction, structural phase transformation (SPT) and plastic deformation. The shock profile is calculated for a wide range of particle velocity from 0.1 km/s to 6.0 km/s. Single crystalline models indicate no induced plasticity or SPT for shock loading below 2.0 km/s. For intermediate particle velocity, between 2.0 km/s and 4.5 km/s the generated shock wave splits into an elastic precursor and a zinc blende to rocksalt structural transformation wave. That is induced by the increase in shock pressure to over 90 GPa and results in a steep increase of density from 3.21 g/cm3 to ~4.65 g/cm3. For particle velocity greater than 4.5 km/s a single overdriven transformation shock wave is generated. These simulation results provide an atomistic view of the dynamic effects of shock impact on single crystal highstrength ceramics. INTRODUCTION SiC is a high strength ceramic material with outstanding and intriguing mechanical properties and vast applications, e.g. such as in coatings for satellites, spacecrafts, vehicles, and armor. Shock loading by plate impact is a commonly used experimental technique to investigate the behavior of materials under extreme conditions. From the extensive literature on plate impact one can find pioneer studies of shock waves in metals, characterizing phenomena such as shockinduced plasticity in fcc crystals1 and shock induced structural phase transition from bcc to hcp in iron2. In particular shock experiments with SiC3, 4 have shown a complex material behavior with the generation of a multishock structure including the presence of a delayed failure wave. The Hugoniot compression of 6H-SiC measured up to 160 GPa5 showed the presence of a solidsolid phase transition at 105 GPa, in agreement with static high pressure experiments. The strength of SiC determined by the shear stress in the shock Hugoniot6 was shown to increased by about 50% at stresses of 50-75 GPa before diminishing on the approaching of the phase transformation. So far, the intriguing response of SiC to shock loading revealed by these experiments is not well understood and have not been described at the atomic level. Here we use large-scale molecular dynamics (MD) simulations with an accurate interatomic potential for SiC with the aim to provide such counterpart and shed light on the experimental findings listed above. METHODOLOGY Large scale, multi-million atom MD simulations are employed to investigate the response of 3CSiC, under mild to very strong planar shock waves. To model interactions between atoms we used an effective interatomic potential validated by a large set of relevant experimental properties including elastic constants, melting temperature, vibrational
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