Local deformation behavior of the surface layers of NiTi alloy in instrumented sharp indentation

The paper presents the analysis of the research data on the investigation of the local deformation behavior and mechanical properties of the surface layers of NiTi alloy depend on the shape of the indenter's tip (Vickers and Berkovich). Investigations of the mechanical properties (microhardness HOP, Young's modulus EOP, parameter of plasticity δh, and shape recovery ratio η) of the surface layers of NiTi alloy were held by the method of instrumented indentation test. The analysis of the experimental data shows, that at a maximum load Pmax from ∼5 up to ∼300 mN, the deformation behavior of the surface layers of the initial NiTi samples under instrumented sharp indentation with tips of different shapes are similar at a surface layer of ∼1 µm thickness. It means that, regardless of the shape of the indenter's tip, almost identical stress and strain states are created in the indentation zone and adjacent areas.