Molecular Dynamics Simulation on the Initiation of Plastic Deformation by Nanoindentation

The mechanical properties of materials are fundamentally derived from the microscopic structures and their behavior, and nanoindentation testing is widely used in fundamental studies of microscopic plasticity in materials. However, it is difficult to capture the plastic deformation phenomena moment by moment in experiments. For this issue, molecular dynamics (MD) simulation is a useful tool for visualizing atomistic behavior in materials. To cultivate a better understanding the elementary process of microscopic plastic deformation, in this study, we conducted nanoindentation MD simulation for body-centered cubic (BCC) iron (Fe) and hexagonal close-packed (HCP) magnesium (Mg) and visualized the initiation of plastic deformation, that is, dislocation nucleation. Furthermore, displacement burst events, called “pop-in,” are observed in nanoindentation and well-known as catastrophic events which result from dislocation nucleation. Here, we also predicted the temperature dependency of first pop-in load based on nanoindentation MD simulation for HCP Mg. Compared to the prediction result for BCC Fe in our previous study, the temperature dependence for Mg is much smaller than that for Fe.