Nanoindentation response of superelastic materials

摘要

Several nickel-titanium alloys have been mechanically tested over a range of temperature, such that superelastic deformation should or should not take place. Both conventional uniform loading (tension and compression) and nanoindentation (using a range of conditions) have been carried out. Indentation tests were conducted using either spherical or Berkovich tips, with either high or low load configurations. These experiments were conducted at various temperatures, corresponding to above A_f, below M_f,or at an intermediate temperature. Elastic constants, supcrelasticity parameters and plastic deformation characteristics obtained using conventional mechanical tests are compared with indentation responses and conclusions drawn about how best to identify superelastic deformation via nanoindentation data. In particular, it is concluded that use of spherical indenters facilitates such identification. Scale effects arc also discussed. These experimental investigations are supplemented by preliminary development of an ABAQUS finite element model suitable for study of the indentation response of superelastic material.