Shape memory alloys (SMAs) are highly desirable for widespread utilization in biomedical implants and micro electro-mechanical systems (MEMS) due to their distinctive property of undergoing reversible martensitic phase transformation, which can be triggered either thermally or mechanically. However, the functionality of SMAs is a crucial property affecting the exploitation of these smart materials. Normally, their tensile reversibility degrades significantly within first a few cycles and is declined at smaller scales. Here, we studied the small-scale tensile superelasticity of a Cu-based shape memory alloy upon cycling. The tensile single-crystalline micro-samples were fabricated by the focused ion beam milling process. Due to the stress-induced martensitic transformation, the superelastic behavior of the micro-samples was investigated by in-situ micro-tension during large number of cycles followed by monitoring microstructural evolution upon cycling. The highly cycled micro-samples still exhibited a perfectly reproducible and completely recoverable superelastic behavior. To assist theoretical analysis of deformation, the orientation of the samples and crystal structure of austenite and martensite were also measured by electron-backscatter diffraction (EBSD) and synchrotron X-ray microdiffraction experiment, respectively.
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