Evaluation of the Superelastic Behavior at Nano-scale on Long-term Cycling in Cu-Al-Ni Micropillars Array

A 4x4 array of square cross-section micro-pillars was milled by focused ion beam technique on an [001] Cu-Al-Ni shape memory alloy single crystal. All pillars in the array were tested in nano-compression using an instrumented nanoindenter. The micro-pillars superelastic response was tested over hundreds cycles on all pillars and over thousands on two randomly selected pillars. Superelastic behavior was evaluated from its load-depth curves individually using the loss factor as evaluation parameter in the 200th cycle. Recoverable and reproducible superelastic behavior has been observed during the long-term cycling tests and the mean loss factor was 0.16. These results open the door for the design of devices that could be integrated in MEMS technology with a good reliability.