Atomistic Simulation of the Effect of Twins on the Indentation Behavior of BCC-Fe

The different nanoindentation deformation mechanisms are predicted based on the molecular dynamics (MD) method of single crystal (SC) and nano-twin (NT) BCC-Fe at different temperatures. The MD results indicate that the deformation behavior of SC BCC-Fe during indentation is primarily attributed to the propagation of the dislocation loop. The interaction between dislocations and twin boundaries (TBs) in NT BCC-Fe dominates plastic deformation. At the TBs, a new position for dislocation nucleation is formed leading to slip transfer. The hardness decreases as the twin thickness (δ) decreases, showing a similar inverse Hall–Petch effect. Additionally, both SC and NT-BCC-Fe exhibit a decrease in hardness with increasing temperature. This study provides theoretical guidance for understanding the plastic behavior of BCC metals and the development of high-performance BCC metal materials.