Thermomechanical response of 50-7 at.-%Ni-Ti alloy in the pseudoelastic regime

The thermomechanical response of 50(.)7 at.-%Ni - Ti superelastic alloy has been investigated for a range of applied strains and strain rates. Parameters of interest include the critical stresses for nucleation and completion (a., and sigma(mf) respectively) of the stress induced martensite (SIM) transformation, as well as the magnitude of the endothermal and exothermal reactions as a function of the applied strain and rate of deformation. Novel techniques including infrared thermometry and laser extensometry have been utilised, and are found to be particularly suited to experimentation with nitinol. The transformation temperatures and values of entropy and enthalpy of formation have been determined using differential scanning calorimetry.