Ni Nanoindentation at the Nanoscale: Atomic Rearrangements at the Ni–C Interface

As mechanical testing proceeds toward ever-decreasing length scales, the ultimate limit is the atomic scale. Here, we investigate the atomic-scale interactions that occur at the diamond–nickel interface during the earliest stages of a Ni nanoindentation measurement. Using molecular dynamics with a custom-designed empirical potential, we found that, irrespectively of the Ni orientation, the same Ni–C interfacial structure always formed between the substrate and the diamond indenter. As the indenter digs deeper into the specimen, the location of the Ni–C interface changes, but its structure never does. In addition, the local formation of this structure produces longer-range disorder that may affect the local stresses and activation barriers to dislocation nucleation. As this process requires relatively large atomic displacements of the Ni atoms for some Ni orientations, we used density functional theory calculations to validate and understand the process.