Nanostructure evolution and surface modification mechanism of Cr ion-implanted single-crystal iron: insights from molecular dynamics simulations

An advanced molecular dynamics (MD) model for Cr ion implantation of single-crystal iron was proposed, and its effectiveness was verified through SRIM calculations. The model systematically investigated the effects of Cr ion implantation energy and dose on surface morphology, ion distribution, surface damage, dislocation evolution and residual stress. The results clearly showed that the increment of implantation energy could significantly improve the surface roughness of the sample. Furthermore, the implantation energy proved crucial in determining the depth and extent of the modification layer. The escalation in implantation dose led to a progressive saturation of internal defects and the amorphous structure within the sample, with the saturation value being contingent upon the implantation energy. Thermal spike effects and recrystallization predominantly contribute to dynamic damage at elevated implantation energies. Conversely, in the context of low-energy implantation, a sufficiently high dose may facilitate the production of dislocations. Crucially, the underlying mechanism of dislocation loop evolution has been elucidated. Primarily, residual compressive stress arises from lattice distortion and phase transformation, with both its magnitude and penetration depth escalating in correlation with energy levels. Furthermore, annealing plays a pivotal role in diminishing residual compressive stress.