A phase-field model for shock-induced α-γ phase transition of RDX

A thermodynamically consistent continuum phase-field model has been developed to investigate the role of shock-induced solid-solid phase transformation in the deformation mechanisms of molecular single crystals. The effects of microstructural evolution and phase transformation are distinguished and modeled within a crystal plasticity framework that is developed for single crystals at high strain rate. When applied to 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) single crystal, the model predicts α-γ phase transition within the experimentally observed range of shock stresses. Phase-field simulations suggest that the α-γ phase transition requires finite time to occur, where plasticity tends to delay the transition. Phase transformation is associated with stress relaxation, and increased temperature rise and associated shock-sensitivity. The shock response of α-γ phase transition is orientation dependent.