| Load-depth curves, elastic modulus, indentation morphology as well as the relationship between nanohardness and indent depth of (110) and (100) oriented iridium single crystals were investigated via nanoindentation technique and atomic force microscopy (AFM). The results indicate that the elastic modulus of Ir(100) and Ir(110) is 477 GPa and 493 GPa, respectively. The indentation size effect (ISE) is observed over the entire range of indentation depths 10~2500 nm, particularly for the depth in the range of 10~500 nm. Based on Nix-Gao model, the calculated nanohardness (H0) of Ir(100) and Ir(110) is 2.32 and 2.46 GPa, respectively, which is defined as the ISE disappeared. There is no ISE can be observed on Ir(100) and Ir(110) as the penetrating depth more than about 4910 and 5220 nm, respectively. By means of power law, the ISE factor (m) of Ir(110) and Ir(100) are calculated as 0.48 and 0.44, respectively, which are much greater than those of other metallic and semi-metallic materials. This anomaly may be associated with abnormally strong interactions between atoms of iridium. |
