Probing Residual Stresses and Dislocation Dynamics by Combining X-Ray Nano-Diffraction and Micropillar Compression Testing

Architecting materials for extreme environments requires a comprehensive understanding of their behavior under challenging conditions. This study introduces a novel approach that combines micropillar compression testing with X-ray nano diffraction to in-situ investigate strains within TiN-based physical vapor deposited (PVD) thin films during loading. The micropillar compression testing induces and moves dislocations within the coating material. The simultaneous X-ray nano diffraction with a focused beam of 250 nm in size allows to capture detailed information about changes in strain as well as structure. Nanocrystalline Ti-B-N coatings with boron contents up to 40 at.% and ceramic-metallic TiN-Nb multilayers with different modulations served as model systems. The nanocrystalline Ti-B-N exhibits significant differences in deformation and fracture behavior, depending on the amorphous grain boundary phase fraction. The stresses needed to move dislocations within the metallic Nb layers of the TiN-Nb multilayers, depend on the Nb layer thickness and varies between ~3 and 10 GPa.<br/><br/>These comprehensive investigations allow to extract information on the predominant strength, ductility, and failure mechanisms active in nanocomposite or multilayered PVD materials. Based on these, PVD thin films with exceptional resilience and damage tolerance, making them suitable for high-stress applications, can be designed.