Investigation of point defect evolution and Voronoi cluster analysis for magnesium during nanoindentation

The present study investigates the effect of nanoindentation on single-crystal magnesium specimens using the embedded-atom method potential in molecular dynamics simulation. Analyses are done under dynamic loading where the load-bearing capacity and change in the structural configuration are studied on the basal (Z–direction) and two prismatic planes (X– and Y–directions) with varying indenter velocities. The investigation of structural evolution is done using atomic displacement analyses to measure the net magnitude of displacement, atomic strain analyses to evaluate the shear strain developed in the process, and Wigner–Seitz defect analyses to calculate the total vacancies at varied timesteps. Furthermore, Voronoi analyses are done when indented on the basal plane to identify the cluster distribution at different planar depths of the specimen. From the analyses, it has been observed that the load-bearing capacity of the specimen varies with the indentation velocity and the direction of indentation on the specimen. Additionally, it is seen that the observed shear and total atomic displacement in the Z–direction is the least in comparison to the other two axes. The partial dislocation 1/3<-12-10> is seen to be majorly present and the population of dislocation loops is more abundant for lower indenter velocities. Furthermore, clusters <0, 4, 4, 6> and <0, 6, 0, 8> are the major indices developed during nanoindentation on the basal plane where they exhibit symmetrical distribution as observed from the Z–direction.