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Ni-n-Cu shape memory films were mixed-sputter deposited from separate nickel, titanium, and copper targets, providing increased compositional flexibility. Shape memory characteristics, examined for films with 7 at.% Cu and 41-51 at.% TI, were determined w i t h temperature controlled substrate currvature measurements, and microstructure was studied w i t h transmission electron microscopy. The Ni-Ti-Cu films were found to have shape memory properties comparable to bulk materials, with transformation temperatures between 20 and 62"C, a 10-13°C hysteresis, and up to 330 m a recoverable stress.

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Thin film shape memory alloys (SMAs) have the potential to become a primary actuating mechanism for mechanical devices with dimensions in the micron to millimeter range requiring large forces over long displacements. In this paper, the thermo-mechanical behavior of shape memory films is presented, techniques for characterizing Ni-Ti-based shape memory films are evaluated, and design issues for SMA microactuators are discussed. The substrate curvature method is used to investigate the response of Ni-Ti-Cu SMA films, revealing recoverable stresses up to 510 MPa, transformation temperatures above 32°C, and hysteresis widths between near 10°C. Fatigue data shows that for small strains, applied loads up to 350 MPa can be sustained for thousands of cycles.