Shock induced damage and fracture in SiC at elevated temperature and high strain rate

Large-scale molecular dynamics simulations are used to investigate shock-induced damage and fracture in 3CSiC single crystals at an elevated initial temperature of 2000 K and a high tensile strain rate of ∼10¹⁰ s⁻¹. Three crystal orientations have been evaluated: [001], [110] and [111]. A comprehensive comparison has been made between cases at 2000 K and at 300 K to address the effects of high temperature on the mechanical performance of SiC under shock loading. Results show that for shock compression, the high temperature decreases the longitude elastic wave speeds as well as the shock stresses. The shock-induced plasticity is mainly in the form of deformation twinning at 300 K, but twinning is absent at 2000 K. The high temperature decreases the structural phase transition threshold pressure in SiC from ∼90 GPa at 300 K (for all three orientations) to ∼75 GPa in [001], ∼57 GPa in [110] and ∼64 GPa in [111] at 2000 K, with corresponding particle velocities of 2.75 km/s, 2.0 km/s, and 2.25 km/s, respectively, in agreement with trends observed in recent experiments. The spall fracture behavior reveals that high temperature reduces the spall strength with an average spall strength of ∼20.7 GPa in [001], ∼21.4 GPa in [110] and ∼22.5 GPa in [111] at 2000 K in the classical spall regime, which are about 33% lower than strengths measured at 300 K. However, in the micro-spall regime the spall strengths are very similar at both temperatures. The corresponding thresholds of particle velocity to trigger spall decrease at elevated temperature except for [001] loading, as well as the thresholds for generating overdriven phase transition waves.