The microscopic superelastic behavior of a nickel-titanium (NiTi) alloy has been studied by instrumented indentation experiments using both spherical and pyramidal (e.g., Berkovich) diamond indenters. The indentation load–displacement curves for a superelastic NiTi and an annealed copper were obtained under a range of indentation conditions. We show that indentation-induced superelasticity exists under both spherical and pyramidal indenters, which may be exploited for many applications, ranging from microelectromechanical systems to surface engineering.

The thermally induced recovery of microscopic deformation in a nickel–titanium shape-memory alloy was examined. Surface deformation was simulated by indenting the alloy in the martensite phase at room temperature using both spherical and pyramidal indenters. We show that deformation in spherical microindents can be almost completely reversed by moderate heating. Partial recovery was observed for pyramidal impressions formed by a Vickers indenter and the recovery ratio was independent of the indentation depth. The observations were rationalized using the concept of representative strain and maximum stress under the spherical and pyramidal indenters.

Hardness and Young's modulus of high-quality cubic boron nitride films grown by chemical vapor deposition

No abstract