Atomistic mechanisms underlying plasticity and crack growth in ceramics: a case study of AlN/TiN superlattices

Interfaces between components of a material govern its mechanical strength and fracture resistance. While great number interfaces is present in nanolayered materials, such as superlattices, their fundamental role during loading lacks understanding. Here we combine ab initio classical molecular dynamics simulations, nanoindentation, transmission electron microscopy to reveal atomistic mechanisms underlying plasticity crack growth B1 AlN(001)/TiN(001) superlattices under loading. The system model for modern refractory ceramics used protective coatings. simulations demonstrate an anisotropic response uniaxial tensile deformation principal crystallographic directions due different strain-activated plastic mechanisms. Superlattices strained orthogonal (001) show modest cleave parallel AlN/TiN layers. Contrarily, B1-to-B3 or B1-to-B4(Bk) phase transformations AlN facilitate remarkable toughness enhancement upon in-plane [110] [100] elongation, respectively. We verify the predictions experimentally conclude that strain-induced growth—via loss interface coherency, dislocation-pinning at interfaces, layer interpenetration followed by formation slip bands—can be hindered controlling thicknesses superlattice components.