Atomistic Simulations of Elastic-Plastic Deformation in Nickel Single Crystal under Shock Loading

Shock-induced elastic-plastic deformation of nickel single crystal [001] is investigated by combining large scale molecular dynamics simulations with the Embedded Atom Method (EAM) potential. The shock-induced pressure is in a range of 30-110 GPa, and the temperature ranges from 600 to 6000 K. The shock front and its rear exhibit elastic, plastic, solid-solid phase transition, which largely depends on the pressure amplitude. Because of the thinness of simulated sample, the shock pressure directly associated with dislocation nucleation is adopted as the Hugoniot elastic limit (HEL), and on this basis, the shock-induced plastic behaviors of nickel single crystal are analyzed. The simulation results show that the shock wave parameters for the defect-free crystal are larger than the experimental values, and this difference is mainly due to that the real sample contains large concentrations of impurities, cavities defects and grain boundaries. The distribution of dislocations at different shock velocities are analyzed by use of dislocation extraction algorithm (DXA). Shock-induced Shockley dislocation appears first. As the shock strength increases, various dislocations gradually emerge. However, Shockley dislocation is always the main type.