On the Characterization of Phase Transformation Temperatures in NiTi by DSC and BFR

Differential scanning calorimetry (DSC) and bend-free recovery (BFR) are two common techniques for measuring the phase transformation temperatures in NiTi shape memory alloys. The transformation temperatures measured from these techniques are not always in unison. The discrepancy in the measured transformation temperatures between the two techniques can be attributed to the role of R-phase, precipitates, and the stress-temperature equivalence. In the present study, varying compositions of shape memory and superelastic binary NiTi alloys are subjected to different heat treatments and their transformation temperatures compared from DSC and BFR measurements. The measured discrepancies are analyzed and compared with the alloy heat treatment. The transformation temperatures are also compared by measuring and comparing the work output from DSC and BFR.