Assessing the superelastic properties of SPS NiTi alloy by nanoindentation

In this study, the mechanical properties of a superelastic Nitinol alloy synthesized by Spark Plasma Sintering (SPS) were investigated using nanoindentation, a technique that enables the evaluation of mechanical properties at the local scale. It was shown that using a spherical indenter allows better assessment of the material’s superelastic properties compared to a Berkovich tip because of the gradual increase of the strain under the spherical indenter. The elastic recovery measured during the single and multicycle indentations was compared with the results of the cyclic tensile tests, and both methods proved to be consistent. For the indentation loads not surpassing the superelastic plateau (below 100 mN), the recovery of the SPS sample was not load sensitive. It decreased from approximately 95 % in the first cycle to 80 % at the 20th cycle. For higher loads the recovery decreased, pointing at the development of the plasticity. For commercial sample, the recovery was load dependent at all loads indicating reduced superelastic capacity. It was demonstrated that the superelastic properties of SPS sample can be superior to that of the commercial sample, proving the SPS method as a very promising for the preparation of the superelastic materials. This study highlights nanoindentation as an effective and reliable method for characterizing the superelastic materials, making it a valuable tool for the rapid developpement of superelastic alloys produced via powder metallurgy techniques. • Nanoindentation was successfully used for characterization of superelastic properties of NiTi alloys. • Spherical indenter tip provides better assessment of superelastic materials than Berkovich tip. • Recovery from multicycle nanoindentation tests correlates well with the results of cyclic tensile tests. • SPS could be used for the preparation of NiTi material with superior superelastic properties.