Fabrication and Transformation Characteristics of Reversible Shape Memory Alloy Thin Film Actuators

This paper presents the fabrication process and transformation characteristics of reversible shape memory alloy thin film actuators which are useful for micromachines. Nickel ( Ni ) rich titanium-nickel alloy ( TiNi ) thin films were sputter deposited on rock salt plates or copper foils and heat processed with two steps which were crystallization ( 800 °C-10 min ) and shape memorization ( 400 °C-6 h ). Reversible shape memory effects of the actuators were shown between the room temperature ( R phase ) by natural radiation of heat and high temperature ( about 90 °C) ( Austenite phase ) by electric current heating. Their metallurgical properties were analyzed by ICP, DSC, XRD and TEM. It was found that precipitate, Ti 3 Ni 4 , played an important role as bias springs for the shape memory effect as the same as the bulk TiNi. Consequently, the relationship between the fabrication process and transformation characteristics of the actuators which is useful to realize reversible shape memory alloy thin film actuators for micromachines was obtained.