Effect of nano-void on the phase transformation of single crystal iron under shock compression

Shock-induced phase transformation (body-centered cubic alpha phase to hexagonal close-packed epsilon phase) in single crystal iron has been investigated by means of molecular dynamics (MID) simulations using an embedded atom method (EAM) potential. By introducing a nano-void in the single crystal iron, the nucleation velocity and the nucleation sites are observed to be different from the perfect single crystal iron. The simulation results show that the void accelerates the nucleation velocity, which induces the new phase to nucleate more easily. At the same time, the void affects the nucleation sites; the initial homogeneous nucleation is observed near the leading front of the shock wave in the perfect single crystal iron, but they first occur around the edge of the void, and finally form a butterfly shaped transformation zone in the defect single crystal iron.