Fabrication Processing of High TransitionTemperature Shape Memory Alloys

Shape memory alloy (SMA) actuators are finding application within defense and commercial markets, with SMA mechanisms being used on NASA's EO1 and Mighty Sat I spacecraft. Other applications include control surfaces that improve the lift-to-drag ratio foraircraft or modify engine inlet flow characteristics. The Navy has an interest in smart structures to modify wake signature or enhance control surface performance. Commercial interests include machine tool clamps and modification of the aerodynamicproperties of Formula-type racecars. Although work output, hysteresis, and cyclic stability are acceptable for conventional NiTi alloys, materials with similar capability at higher transition temperature are desired. The objective of this Phase I effortis to identify shape memory alloy compositions, such as binary NiTi alloy with additions of Pd or Pt, that have transition temperatures of 150C or higher. The ability to form these alloys into actuator shapes from wire, rod and sheet shall bedemonstrated. Data obtained during forming operations will be applied to deformation models that will enable scaling into a high volume production facility during Phase II. Actuator capabilities such as work output, hysteresis and creep will be evaluatedfor each alloy composition to ensure that defense application requirements are satisfied.Data obtained during forming operations in this program will be applied to deformation models to assist in fabrication scaling. Applications of high transitiontemperature SMA actuators include control surfaces for aircraft, engine inlet ducting, shape control of fin structures, antenna reflectors, vehicle aerosurfaces, and machine tool clamps.