Mechanical response of nanoindentation and material strengthening mechanism of nt-cBN superhard materials based on molecular dynamics

In this paper, the mechanical response of nanoindentation process of nano-twinned cubic Boron Nitride (nt-cBN) materials is investigated by molecular dynamics method. The introduction of nano-twinned structure in cBN materials can lead to superior mechanical properties than those of single-crystal cBN (sc-cBN) materials. The mechanism of material strengthening is derived by studying the dislocation propagation during the indentation process. The limitation of dislocation propagation by nano-twinned layers leads to the accumulation of dislocations in the interlayer to form immovable dislocation multi-junctions, which leads to the increase of intracrystalline back stress and raises the yield stress of the material. In the high-pressure environment, dislocations can react with twin boundary layers and split into multiple dislocations, increasing the dislocation density and the number of dislocation multi-junctions in the material. The reaction between dislocations and twin-crystal plays an important role in twin-crystal strengthening.