The Physical and Mechanical Properties of Nickel Titanium Shape Memory Alloys for High Temperature Actuators

Binary Nickel Titanium alloys with transformation temperature range (TTR) of 95oC are being used in high temperature shape memory effect actuators.  We have observed that higher TTR binary alloys have larger inclusion size and greater area fraction of inclusions than alloys that are superelastic at room temperature.  Actuator performance is affected by the response to cyclic strain and by variations in strain recovery. Historically, higher inclusion content has been correlated to reductions in strain recovery. This paper will present new data on the structure, physical properties and cyclic mechanical behavior of binary alloys with varying TTR and inclusion content.  We will compare TTR, active Af, static mechanical properties and cyclic strain recovery of these materials in both superelastic and shape memory strain recovery cycles.