G. Paul, F. Sczerzenie, SAES Smart Materials, New Hartford, NY
In the processing of nitinol, there are four main parameters that control the superelastic and shape memory properties: alloy composition, amount of cold work and time & temperature of thermal processing. Alloy composition and the degree of cold work have been reported in the past. To build on our knowledge, this paper aims to give a better understanding of the effect of heat treatment (time and temperature), on the mechanical and Temperature Transition Region (TTR) properties. Two binary, As of -15oC and +95oC, nitinol alloy wires were selected to be tested. Each wire tested had a diameter of 1mm and a cold work of 45%. These wires were then heat treated at various times (ranging from 1min to 1hr) and temperatures (ranging from 400oC to 700oC). A MTS tensile machine and a TA DSC were used to obtain the mechanical and temperature transition region properties. Metallographic analysis was used to evaluate any microstructure changes that resulted from the heat treatments.
