Role of lithium atoms in modulating dynamic deformation and phase transition of iron-based single crystals under cylindrically shock

Cylindrical shock loading has significant effects on the plasticity and phase transition of iron-based alloys. However, due to the limitations of loading technology and detection methods in experiments, the plasticity and phase transition laws of alloys under cylindrical shock are unclear. In this work, large-scale nonequilibrium molecular dynamics (NEMD) simulation was applied to study the cylindrical shocking behavior of Fe-Li alloy. The results show that under cylindrically divergent shock, Li atoms cause significant shocking pressure attenuation, leading to a decrease in hexagonal close-packed (HCP) phase structure ratio and dislocation density. For cylindrically convergent shock, solute atoms induced obvious dislocation solid solution segregation, and the sharp increase in dislocation density led to plastic hardening in Fe-Li alloy. Notably, the critical concentration of Li atoms required for hardening is substantially reduced compared to planar shock (5 at% vs 10 at%) due to the energy concentration effects of cylindrically convergent shock. Furthermore, because of the synergistic interaction between multiaxial strain and anisotropic wavefront propagation, the Fe-Li alloy preferentially undergoes plastic hardening along [±110] direction. In planar shock, Li atoms significantly affect the diversity of HCP variants. In contrast, in cylindrical shock, Li atoms have a weak effect on the diversity of HCP variants, which is attributed to the dominance of energy/stress fluctuations caused by geometric constraints over solute induced disturbances.