The nanohardness H of multilayer specimens TiC/VC@Si and TiC/VC@Sapphire prepared by Pulsed-Laser-Deposition is investigated to check the existence of a superlattice effect as known from TiN/VN multilayers. In the pre...The nanohardness H of multilayer specimens TiC/VC@Si and TiC/VC@Sapphire prepared by Pulsed-Laser-Deposition is investigated to check the existence of a superlattice effect as known from TiN/VN multilayers. In the present work the multilayer period thickness λ varies between 1.34 nm and 24.8 nm (total layer thickness t ≈ 200 nm). Unlike Young’s modulus E, H is enhanced, regardless of t, by covering Si as well as sapphire with a TiC/VC multilayer;the relative load carrying capacity being larger for Si. The maximum value of H obtained is 38 GPa for TiC/VC@Sapphire. It is observed for a multilayer thickness of λ ≈ 10 nm. Hardness of TiC/VC@Sapphire obeys, after annealing, a Hall-Petch relation H = 35.25 + 6.945 λ–0.5 (H in GPa und λ≥ 10 nm). From orientation dependent X-ray absorption fine structure and X-ray reflection records, short-range order and layer geometry are derived. These analyses reveal a continuous approach of interatomic distances Ti-C and V-C for deceasing multilayer periods. High-resolution transmission electron microscopy shows that multilayers are nanostructured, i.e., not only TiC/VC phase boundaries but also subgrains represent obstacles against plastic deformation. Dislocations play a major role as sources of internal stress and vehicles of plasticity.展开更多
基金thank the German Research Foundation(DFG)for financial support
文摘The nanohardness H of multilayer specimens TiC/VC@Si and TiC/VC@Sapphire prepared by Pulsed-Laser-Deposition is investigated to check the existence of a superlattice effect as known from TiN/VN multilayers. In the present work the multilayer period thickness λ varies between 1.34 nm and 24.8 nm (total layer thickness t ≈ 200 nm). Unlike Young’s modulus E, H is enhanced, regardless of t, by covering Si as well as sapphire with a TiC/VC multilayer;the relative load carrying capacity being larger for Si. The maximum value of H obtained is 38 GPa for TiC/VC@Sapphire. It is observed for a multilayer thickness of λ ≈ 10 nm. Hardness of TiC/VC@Sapphire obeys, after annealing, a Hall-Petch relation H = 35.25 + 6.945 λ–0.5 (H in GPa und λ≥ 10 nm). From orientation dependent X-ray absorption fine structure and X-ray reflection records, short-range order and layer geometry are derived. These analyses reveal a continuous approach of interatomic distances Ti-C and V-C for deceasing multilayer periods. High-resolution transmission electron microscopy shows that multilayers are nanostructured, i.e., not only TiC/VC phase boundaries but also subgrains represent obstacles against plastic deformation. Dislocations play a major role as sources of internal stress and vehicles of plasticity.
