Contact damage of machinable aluminum nitride/ boron nitride nanocomposites

AlN/BN nanocomposites indicated such a unique property as machinable with high fracture strength. In order to investigate the deformation mechanism of AlN/BN nanocomposites, Hertzian contact tests were performed on monolithic AlN, and nano-composite and microcomposite AlN/BN. The monolith and microcomposite comprised micro-sized grains of AlN and BN. In the microcomposite, plate-like BN particles preferentially oriented perpendicular to the hot-press direction. On the other hand, the nanocomposite showed a finer microstructure with fine BN particles and small matrix grains. These microstructural differences led to differences in the mechanism of contact damage. The damage of the monolithic AlN and the AlN/BN micro-composite exhibited collapsed Hertzian cone fracture and preferentially oriented large cracks perpendicular to the hot-press direction, whereas the damage observed in the nanocomposites appeared to be quasi-plastic deformation.