Production and characterization of functionally graded NiTi shape memory alloys by Joule effect

Localized heat treatments via Joule effect were performed on cold-drawn NiTi strips to produce a functionally graded material (FGM). Three zones where locally heat treated at 300, 350, and 400 °C for 10 min followed by air cooling. Multiscale and multiphenomena characterization of the obtained FGM was performed through infrared temperature testing, four-point probe and eddy current testing, mechanical testing and synchrotron X-ray diffraction. The effect of these localized heat treatments is clearly observed by different techniques. The use of these short and localized heat treatments avoids the need of highly expensive manufacturing routes typically used to obtain the same effect on NiTi shape memory alloys, thus opening new possibilities for processing these advanced engineering alloys.