Local influence of material processing on phase transitions in NiTi shape memory alloys investigated by IR thermography

Local variations of the phase transition temperatures are important for the functionality of actuators based on NiTi shape memory alloys. Mechanical distortions induced by process treatment can suppress the phase transition from the austenitic to the martensitic structure. In this work, local changes of the phase transition have been investigated by time-dependent IR thermography. For the quantitative interpretation of the thermographical measurements, information about the IR emissivity is important. In this work a new thermal wave method based on two detection techniques is presented, which can be used to measure both the IR emissivity and the thermal transport properties.